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Suppose that you have an abstract for a scientific paper: we have used multi - epoch images from the infrared array camera on board the _ spitzer space telescope _ to search for substellar companions to stars in the solar neighborhood based on common proper motions . through this work
, we have discovered a faint companion to the white dwarf wd 0806 - 661 .
the comoving source has a projected separation of @xmath0 , corresponding to 2500 au at the distance of the primary ( 19.2 pc ) . if it is physically associated , then its absolute magnitude at 4.5 is @xmath1 mag fainter than the faintest known t dwarfs , making it a strong candidate for the coolest known brown dwarf .
the combination of @xmath2 and the age of the primary ( 1.5 gyr ) implies an effective temperature of @xmath3 k and a mass of @xmath4 @xmath5 according to theoretical evolutionary models .
the white dwarf s progenitor likely had a mass of @xmath6 @xmath7 , and thus could have been born with a circumstellar disk that was sufficiently massive to produce a companion with this mass .
therefore , the companion could be either a brown dwarf that formed like a binary star or a giant planet that was born within a disk and has been dynamically scattered to a larger orbit . .
And you have already written the first three sentences of the full article: the methane - bearing t dwarfs comprise the coolest known class of brown dwarfs ( * ? ? ?
* references therein ) .
these sources have atmospheres that are sufficiently cool for h@xmath8o and ch@xmath9 gases to form in abundance , resulting in distinct , planet - like spectra @xcite ..
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the similar masses and effective temperatures of t dwarfs as compared to
warm " exoplanets make them critical benchmarks for theoretical atmospheric and interior models of substellar objects @xcite .
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12,601 |
Suppose that you have an abstract for a scientific paper: we investigate the role of a suitable interaction between a matter fluid and a phantom field for the coincidence problem .
there exists a stationary scaling solution which is a stable attractor at late times .
furthermore , the cosmic doomsday is avoided in one region of the parameter space .
scalar field plays an important role in modern cosmology .
dark energy can be attributed to the dynamics of a scalar field , called quintessence @xcite , which convincingly realize the present accelerated expansion of the universe by using late - time attractor solutions in which the scalar field mimics the perfect fluid in a wide range of parameters . but regarded as dark energy , quintessence field with the state equation parameter @xmath0 may be not consistent with recent observation @xcite . in order to obtain @xmath1 , phantom field with reverse sign in its dynamical term
may be a simplest implementing and can be regarded as one of interesting possibilities describing dark energy @xcite .
the physical background for phantom type of matter with strongly negative pressure would be found in string theory @xcite .
phantom field may also arise from a bulk viscous stress due to particle production @xcite or in higher - order theories of gravity @xcite , brans - dicke and non - minimally coupled scalar field theories @xcite .
the cosmological models which allow for phantom matter appear naturally in the mirage cosmology of the braneworld scenario @xcite and in k - essence models @xcite . in spite of the fact that the field theory of phantom fields encounters the problem of stability which one could try to bypass by assuming them to be effective fields @xcite , it is nevertheless interesting to study their cosmological implication .
recently , there are many relevant studies of phantom energy @xcite .
the physical properties of phantom energy are rather weird , as they include violation of the dominant - energy condition , naive superluminal sound speed and increasing energy density....
And you have already written the first three sentences of the full article: it is a pleasure to acknowledge helpful discussions with winfried zimdahl .
this project was in part supported by national basic research program of china under grant no.2003cb716300 and also by nnsfc under grant no.10175070 .
99 b.ratra and p.j.e.peebles , phys.rev . *.
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d37 * ( 1988 ) 3406 ; c.wetterich , nucl.phys . *
b302 * ( 1988 ) 668 .
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12,602 |
Suppose that you have an abstract for a scientific paper: high intensity back - scattered laser beams will allow the efficient conversion of a substantial fraction of the incident lepton energy into high energy photons , thus significantly extending the physics capabilities of an @xmath0 linear collider .
the annihilation of two photons produces @xmath1 final states in virtually all angular momentum states .
an important physics measurement is the measurement of the higgs coupling to two photons .
the annihilation of polarized photons into the higgs boson determines its fundamental @xmath2 coupling as well as determining its parity .
other novel two - photon processes include the two - photon production of charged pairs @xmath3 @xmath4 , @xmath5 and supersymmetric squark and slepton pairs .
the one - loop box diagram leads to the production of pairs of neutral particles such as @xmath6 and @xmath7 at the next order one can study higgstrahlung processes , such as @xmath8 since each photon can be resolved into a @xmath4 pair , high energy photon - photon collisions can also provide a remarkably background - free laboratory for studying possibly anomalous @xmath9 collisions and annihilation . in the case of qcd , each photon can materialize as a quark anti - quark pair which interact via multiple gluon exchange .
the diffractive channels in photon - photon collisions allow a novel look at the qcd pomeron and odderon
. the @xmath10 odderon exchange contribution can be identified by looking at the heavy quark asymmetry . in the case of @xmath11 collisions
, one can measure the photon structure functions and its various components .
exclusive hadron production processes in photon - photon collisions provide important tests of qcd at the amplitude level , particularly as measures of hadron distribution amplitudes which are also important for the analysis of exclusive semi - leptonic and two - body hadronic @xmath12-decays .
slac - pub-10410 + april 2004 * high energy photon
photon + collisions at a linear collider * stanley j. brodsky +....
And you have already written the first three sentences of the full article: one of the important areas of investigation at the proposed high energy electron - positron linear collider will be the study of photon - photon collisions . since photons couple directly to all fundamental fields carrying the electromagnetic current
leptons , quarks , @xmath13 supersymmetric particles , etc.high energy @xmath14 collisions will provide a comprehensive laboratory for exploring virtually every aspect of the standard model and its extensions @xcite .
effective photon beams from virtual bremsstrahlung provide access to low energy quasi - real @xmath15 collisions @xcite ..
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a large number of studies have been performed at the 4 detectors at lep , at cesr , babar , belle , vepp-4 , vepp-2 , adone , and other @xmath16 storage rings .
the qed processes @xmath17 and @xmath18 have been studied at the l3 detector at lep at 161 gev @xmath19 209 gev .
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12,603 |
Suppose that you have an abstract for a scientific paper: the presence of a dipolar statistical anisotropy in the spectrum of cosmic microwave background ( cmb ) fluctuations was reported by the wilkinson microwave anisotropy probe ( wmap ) , and has recently been confirmed in the planck 2013 analysis of the temperature anisotropies . at the same time , the planck 2013 results report a stringent bound on the amplitude of the local - type non - gaussianity . we show that the non - linear effect of the dipolar anisotropy generates not only a quadrupole moment in the cmb but also a local - type non - gaussianity .
consequently , it is not easy to build models having a large dipolar modulation and at the same time a sufficiently small quadrupole and level of local bispectral anisotropy to agree with the present data .
in particular , most models proposed so far are almost excluded , or are at best marginally consistent with observational data .
we present a simple alternative scenario that may explain the dipolar statistical anisotropy while satisfying the observational bounds on both the quadrupole moment and local - type non - gaussianity . .
And you have already written the first three sentences of the full article: it was suggested by wmap that the amplitude of cosmic microwave background ( cmb ) anisotropies has a dipolar directional dependence @xcite .
this anomalous signature has been recently confirmed by planck @xcite .
although it is possible that this anisotropy is a foreground effect , it is an interesting question whether or not we can explain this feature consistently within the paradigm of the inflationary universe ..
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the basic issue is that a dipolar modulation of the amplitude of the curvature perturbation requires a seed dipolar perturbation .
this seed dipolar perturbation itself is known to produce quadrupole and octupole moments of cmb anisotropy , known as the grishchuk - zeldovich ( gz ) effect @xcite .
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Suppose that you have an abstract for a scientific paper: the macro detector was located in the hall b of the gran sasso underground laboratories under an average rock overburden of @xmath0 .
a transition radiation detector composed of three identical modules , covering a total horizontal area of @xmath1 , was installed inside the empty upper part of the detector in order to measure the residual energy of muons .
this paper presents the measurement of the residual energy of single and double muons crossing the apparatus .
our data show that double muons are more energetic than single ones .
this measurement is performed over a standard rock depth range from @xmath2 to @xmath3 . the macro collaboration + = 10000 , , , , , , , , , , , % authorc .
bloise@xmath4 , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , and .
+ 1
. dipartimento di fisica delluniversit di bari and infn , 70126 bari , italy + 2 .
dipartimento di fisica delluniversit di bologna and infn , 40126 bologna , italy + 3 .
physics department , boston university , boston , ma 02215 , usa + 4 .
california institute of technology , pasadena , ca 91125 , usa + 5 .
department of physics , drexel university , philadelphia , pa 19104 , usa + 6 .
laboratori nazionali di frascati dellinfn , 00044 frascati ( roma ) , italy + 7 .
laboratori nazionali del gran sasso dellinfn , 67010 assergi ( laquila ) , italy + 8 . depts . of physics and of astronomy , indiana university , bloomington , in 47405 , usa + 9 .
dipartimento di fisica delluniversit dellaquila and infn , 67100 laquila , italy + 10 .
dipartimento di fisica....
And you have already written the first three sentences of the full article: underground muons are the remnants of the air showers initiated by the collisions of primary cosmic rays with air nuclei
. these secondary cosmic ray muons can easily cross large amounts of matter and penetrate into underground laboratories .
the energy spectra of underground muons depend on the energy spectra and composition of primary cosmic rays , on their interactions with air nuclei and on the muon energy loss in the rock . in this paper the measurement of the energy spectra of underground single and double muons , performed with a @xmath1 transition radiation detector ( trd ) , that was installed in the empty upper part of the macro detector @xcite ,.
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is presented .
an analysis using part of the single muon data sample was already published @xcite .
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12,605 |
Suppose that you have an abstract for a scientific paper: in this paper , we propose systematic block markov superposition transmission of repetition ( bmst - r ) codes , which can support a wide range of code rates but maintain essentially the same encoding / decoding hardware structure .
the systematic bmst - r codes resemble the classical rate - compatible punctured convolutional ( rcpc ) codes , except that they are typically non - decodable by the viterbi algorithm due to the huge constraint length induced by the block - oriented encoding process .
the information sequence is partitioned equally into blocks and transmitted directly , while their replicas are interleaved and transmitted in a block markov superposition manner . by taking into account that the codes are systematic
, we derive both upper and lower bounds on the bit - error - rate ( ber ) under maximum _ a posteriori _ ( map ) decoding .
the derived lower bound reveals connections among ber , encoding memory and code rate , which provides a way to design good systematic bmst - r codes and also allows us to make trade - offs among efficiency , performance and complexity .
numerical results show that : 1 ) the proposed bounds are tight in the high signal - to - noise ratio ( snr ) region ; 2 ) systematic bmst - r codes perform well in a wide range of code rates ; and 3 ) systematic bmst - r codes outperform spatially coupled low - density parity - check ( sc - ldpc ) codes under an equal decoding latency constraint
. block markov superposition transmission ( bmst ) , lower bounds , maximum _ a posteriori _ ( map ) decoding , rate - compatible codes , upper bounds , sliding window decoding , systematic codes . .
And you have already written the first three sentences of the full article: since the invention of turbo codes @xcite and the rediscovery of low - density parity - check ( ldpc ) codes @xcite , constructing practical good codes has been being an active research topic in our field .
recent developments include the invention of polar codes @xcite and flourishment of spatially coupled ldpc ( sc - ldpc ) codes ( first introduced as ldpc convolutional codes @xcite and later recast as sc - ldpc codes @xcite ) , both of which are provable capacity - achieving @xcite over memoryless binary - input symmetric - output channels . despite this success in theory ,
more flexible constructions are still desired in practice ..
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especially , it is often desirable in practice to design codes that support a variety of code rates but maintain essentially the same encoding / decoding hardware structure .
one way to achieve this is the use of rate - compatible codes , which can be constructed from a mother code by using the puncturing and/or extending techniques .
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Suppose that you have an abstract for a scientific paper: we derive and discuss the strong dependence on metallicity of the co to @xmath0 conversion factor @xmath1/[h]$ ] appropriate to extragalactic objects , as well as the weaker dependence found for such objects from interferometer measurements . 2 2 # 1#1 0123456789 abcdef
@mtlplain@loaded = cmssi10 = cmssi10 = cmssi10 = cmmib10 = mtssi10 = mtssbx10 = mtssbi10 = mtmib10 @mtlplain@loaded .
And you have already written the first three sentences of the full article: the difficulty of directly observing molecular hydrogen ( @xmath0 ) , the major constituent of the interstellar medium in galaxies , and ways of doing so indirectly are reviewed elsewhere in this volume ( combes 2000 ) .
usually , @xmath0 cloud properties are derived by extrapolation from more easily conducted co observations .
for instance , observed co cloud sizes and velocity widths yield total molecular gas masses under the assumption of virial equilibrium ..
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however , in extragalactic systems especially , this method is beset by pitfalls ( see israel , 1997 , hereafter is97 ) and requires high linear resolutions ( i.e. use of interferometer arrays ) .
more seriously , _ the fundamental assumption of virialization appears to be false_. as individual components ( ` clumps ' ) have velocities of only a few km s@xmath2 and co complex sizes are 50100 pc , crossing times are comparable to co complex _ lifetimes _ of only a few times 10@xmath3 years or less ( leisawitz et al .
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Suppose that you have an abstract for a scientific paper: the first results of the k2k(kek to kamioka ) long - baseline neutrino oscillation experiment are presented in this talk . in 1999 7.2@xmath010@xmath1 protons on target were delivered to the experiment . during this period of running
there were 3 events fully contained in the super - kamiokande inner detector fiducial area which occurred during the beam spill timing window . in the case of no oscillations
the expected number of events during this period was 12.3@xmath2 .
the near detectors located at kek also have begun detailed measurements of neutrino interactions in water at around 1 gev . .
And you have already written the first three sentences of the full article: the atmospheric neutrino anomaly observed by super - kamiokande(sk ) and other recent underground experiments strongly suggests @xmath3 neutrino oscillation .
the allowed region of the oscillation parameters obtained by sk are in the range of @xmath4 ev@xmath5 and @xmath6 0.88 with 90% confidence level@xcite , where @xmath7 is the mass difference squared between two neutrino mass eigenstates and @xmath8 is the mixing angle between two neutrinos .
the principal goal of the k2k experiment is to confirm neutrino oscillation with a man - made neutrino beam and to measure the oscillation parameters ..
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[ fig1 ] is a schematic of the setup .
we use the 12 gev kek - ps as a neutrino source and sk as the far detector .
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12,608 |
Suppose that you have an abstract for a scientific paper: we consider two variations of the discrete car parking problem where at every vertex of @xmath0 a car arrives with rate one , now allowing for parking in two lines .
+ a ) the car parks in the first line whenever the vertex and all of its nearest neighbors are not occupied yet .
it can reach the first line if it is not obstructed by cars already parked in the second line ( `` screening '' ) .
+ b ) the car parks according to the same rules , but parking in the first line can not be obstructed by parked cars in the second line ( `` no screening '' ) . in both models ,
a car that can not park in the first line will attempt to park in the second line . if it is obstructed in the second line as well , the attempt is discarded .
+ we show that both models are solvable in terms of finite - dimensional odes .
we compare numerically the limits of first and second line densities , with time going to infinity .
while it is not surprising that model a ) exhibits an increase of the density in the second line from the first line , more remarkably this is also true for model b ) , albeit in a less pronounced way .
* ams 2000 subject classification : * 82c22 , 82c23 . car parking problem , random sequential adsorption , sequential frequency assignment process , particle systems . .
And you have already written the first three sentences of the full article: car parking , first considered in a mathematical way by rnyi @xcite in 1958 , gives rise to interesting models that in several variations have been applied in many fields of science . in the original car parking problem ,
unit length cars are appearing with constant rate in time and with constant density in space on the line where they try to park .
a new car is allowed to park only in case there is no intersection with previously parked cars . otherwise the attempt is rejected ..
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rnyi proved that the density of cars has the limit @xmath1 , the so - called parking constant . in the simplest discrete version of the car parking problem ,
cars of length @xmath2 try to park at their midpoints randomly on @xmath0 .
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Suppose that you have an abstract for a scientific paper: transport networks are found at the heart of myriad natural systems , yet are poorly understood , except for the case of river networks . the scheidegger model , in which rivers are convergent random walks , has been studied only in the case of flat topography , ignoring the variety of curved geometries found in nature .
embedding this model on a cone , we find a convergent and a divergent phase , corresponding to few , long basins and many , short basins , respectively , separated by a singularity , indicating a phase transition .
quantifying basin shape using hacks law @xmath0 gives distinct values for @xmath1 , providing a method of testing our hypotheses .
the generality of our model suggests implications for vascular morphology , in particular differing number and shapes of arterial and venous trees . .
And you have already written the first three sentences of the full article: transport networks occur in a vast variety of natural systems . from river basins to leaf venation , we observe a spectrum of solutions to the problem of optimal distribution through a landscape , given a set of constraints on the construction of links .
previous work on treelike networks originates in the study of river basins , which can be modeled as convergent random walks , or equivalently as flow through a linear slope field with additive noise .
this approach , the scheidegger model @xcite , does not incorporate the effects of convergent and divergent topologies , which occur both in geomorphology ( e.g. endorheic basins ) and in biologically relevant systems ..
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the vasculature of the retina , for instance , may be viewed as divergent for the arteries , which originate at the center , and convergent for the veins , which terminate there .
another example of this morphology occurs in the functional units of organs , such as the liver , have distinct zones where the arteries originate and the veins terminate , respectively . convergence and divergence in river networks originates in the presence of curvature in the underlying topography .
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Suppose that you have an abstract for a scientific paper: this work presents new results about the graviton massive spectrum in two - field thick branes . analyzing the massive spectra with a relative probability method we have firstly showed the presence of resonance structures and
obtained a connection between the thickness of the defect and the lifetimes of such resonances .
we obtain another interesting results considering the degenerate bloch brane solutions . in these thick brane models
, we have the emergence of a splitting effect controlled by a degeneracy parameter .
when the degeneracy constant tends to a critical value , we have found massive resonances to the gravitational field indicating the existence of modes highly coupled to the brane .
we also discussed the influence of the brane splitting effect over the resonance lifetimes . .
And you have already written the first three sentences of the full article: recently , it has been given much attention to the study of topological defects in the context of brane - world models , due to its property of allowing the localization of several different types of fields .
as extended defects in field theory the domain walls have been used in high - energy physics to represent brane scenarios with extra dimensions @xcite .
the bloch walls , which could be seen as chiral interfaces @xcite , are used in the context of extra dimensions to construct a @xmath0 model of two scalar fields coupled with gravity , the so called bloch brane @xcite ..
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the bloch brane model is generated dynamically and has internal structure .
the asymptotic bulk metric is a slice of a five - dimensional anti - de sitter ( ads ) spacetime , denoted by @xmath1 .
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12,611 |
Suppose that you have an abstract for a scientific paper: dust growth and settling considerably affect the spectral energy distributions ( seds ) of protoplanetary disks .
we investigated dust growth and settling in protoplanetary disks through numerical simulations to examine time - evolution of the disk optical thickness and seds . in the present paper
, we considered laminar disks as a first step of a series of papers . as a result of dust growth and settling , a dust layer forms around the mid - plane of a gaseous disk . after the formation of the dust layer , small dust grains remain floating above the layer .
although the surface density of the floating small grains is much less than that of the dust layer , they govern the disk optical thickness and the emission .
size distributions of the floating grains obtained from numerical simulations are well - described by an universal power - law distribution , which is independent of the disk temperature , the disk surface density , the radial position in the disk , etc .
the floating small grains settle onto the dust layer in a long time scale compared with the formation of the dust layer .
typically , it takes @xmath0yr for micron - sized grains . rapid grain growth in the inner part of disks makes the radial distribution of the disk optical thickness less steep than that of the disk surface density , @xmath1 .
for disks with @xmath2 , the radial distribution of the optical thickness is almost flat for all wavelengths at @xmath3yr . at @xmath4yr , the optical thickness of the inner disk ( @xmath5 a few au ) almost vanishes , which may correspond to disk inner holes observed by spitzer space telescope .
furthermore , we examined time - evolution of disk seds , using our numerical results and the two - layer model .
the grain growth and settling decrease the magnitude of the seds especially at @xmath6 m .
our results indicate that grain growth and settling can explain the decrease in observed energy fluxes at millimeter / sub - millimeter wavelengths with time scales of @xmath7yr without....
And you have already written the first three sentences of the full article: circumstellar disks surrounding t tauri and herbig ae / be stars are thought to the birth sites of planetary systems and they are called protoplanetary disks . the physical properties of the protoplanetary disks have been inferred from analyses of their spectral energy distributions ( seds ) .
analyses of observations at millimeter / sub - millimeter wavelengths suggest that the disks have masses of 0.001 - 0.1 @xmath8 and their life time is @xmath9yr ( e.g. , strom et al .
1989 ; beckwith et al . 1990 ; wyatt et al ..
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2003 ) .
recent observations with high - resolution at various wavelengths gave us much information on disk spatial structure ( e.g. , grady et al .
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Suppose that you have an abstract for a scientific paper: 0.2cmwe delineate the allowed parameter and mass range for a wino - like dark matter particle containing some higgsino admixture in the mssm by analysing the constraints from diffuse gamma - rays from the dwarf spheroidal galaxies , galactic cosmic rays , direct detection and cosmic microwave background anisotropies .
a complete calculation of the sommerfeld effect for the mixed - neutralino case is performed .
we find that the combination of direct and indirect searches poses significant restrictions on the thermally produced wino - higgsino dark matter with correct relic density .
for @xmath0 nearly the entire parameter space considered is excluded , while for @xmath1 a substantial region is still allowed , provided conservative assumptions on astrophysical uncertainties are adopted .
= 1 tum - hep-1065/16 + ftuam-16 - 38 + ift - uam / csic-16 - 106 + november 2 , 2016 * the last refuge of mixed wino - higgsino dark matter + * m. beneke@xmath2 , a. bharucha@xmath3 , a. hryczuk@xmath4 , + s. recksiegel@xmath2 , and p. ruiz - femena@xmath5 + _ @xmath6physik department t31 , + james - franck - strae 1 , technische universitt mnchen , + d85748 garching , germany + @xmath7 aix marseille univ , universit de toulon , cnrs , cpt , marseille , france + @xmath8department of physics , university of oslo , box 1048 , +
no-0371 oslo , norway + @xmath9national centre for nuclear research , + hoa 69 , 00 - 681 , warsaw , poland + @xmath10departamento de fsica terica and instituto de fsica terica uam - csic , + universidad autnoma de madrid , e-28049 madrid , spain _ .
And you have already written the first three sentences of the full article: many remaining regions in the parameter space of the minimal supersymmetric standard model ( mssm ) , which yield the observed thermal relic density for neutralino dark matter , rely on very specific mechanisms , such as higgs - resonant annihilation in the so - called funnel region , or sfermion co - annihilation . in @xcite
we identified new regions , where the dark matter particle is a mixed as opposed to pure wino , has mass in the tev region , and yields the observed relic density .
these new regions are driven to the correct relic abundance by the proximity of the resonance of the sommerfeld effect due to electroweak gauge boson exchange ..
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in such situations , the annihilation cross section is strongly velocity dependent , and the present - day annihilation cross section is expected to be relatively large , potentially leading to observable signals in indirect searches for dark matter ( dm ) . on the other hand
, a substantial higgsino fraction of a mixed dark matter particle leads to a large , potentially observable dark matter - nucleon scattering cross section . in this paper
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Suppose that you have an abstract for a scientific paper: particle - in - cell ( pic ) is the most used algorithm to perform self - consistent tracking of intense charged particle beams .
it is based on depositing macro - particles on a grid , and subsequently solving on it the poisson equation .
it is well known that pic algorithms occupy intrinsic limitations as they introduce numerical noise .
although not significant for short - term tracking , this becomes important in simulations for circular machines over millions of turns as it may induce artificial diffusion of the beam . in this work , we present a modeling of numerical noise induced by pic algorithms , and discuss its influence on particle dynamics .
the combined effect of particle tracking and noise created by pic algorithms leads to correlated or decorrelated numerical noise . for decorrelated numerical noise
we derive a scaling law for the simulation parameters , allowing an estimate of artificial emittance growth .
lastly , the effect of correlated numerical noise is discussed , and a mitigation strategy is proposed . .
And you have already written the first three sentences of the full article: it is well known that in operational scenarios requiring long - term storage , sources of noise in the machine can lead to detrimental effects on the beam .
examples include rf voltage noise , beam - beam interaction , ground motion , and feedback noise , which all have been subject of studies to mitigate or exploit their impact , as reported in refs .
@xcite recently , a similar concern has raised for numerical noise in self - consistent simulation of high intensity beams ..
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in fact , the study of space charge effects via self - consistent simulations has become important with the advent of new projects , like the future sis100 synchrotron of the fair project @xcite , and the liu project @xcite for the cern accelerator complex . in these projects
some scenarios require the storage of a high intensity bunched beam for seconds .
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Suppose that you have an abstract for a scientific paper: hard x - ray selection is the most efficient way to discriminate between accretion - powered sources , such as agn , from sources dominated by starlight .
hard x - rays are also less affected than other bands by obscuration .
we have then carried out the bepposax high energy large area survey ( hellas ) in the largely unexplored 5 - 10 kev band , finding 180 sources in @xmath0 deg@xmath1 of sky with flux @xmath2 .
after correction for the non uniform sky coverage this corresponds to resolving about 30 % of the hard cosmic x - ray background ( xrb ) .
here we report on a first optical spectroscopic identification campaign , finding 12 agn out of 14 x - ray error - boxes studied .
seven agn show evidence for obscuration in x - ray and optical bands , a fraction higher than in previous rosat or asca - rosat surveys ( at a 95 - 99 % and 90 % confidence level respectively ) , thus supporting the scenario in which a significant fraction of the xrb is made by obscured agn .
= -0.5 in x ray : selection background galaxies .
And you have already written the first three sentences of the full article: while it is now clear that the cosmic x - ray background ( xrb ) is made by the superposition of many discrete sources , and that the soft ( 0.52 kev ) xrb is mostly produced by agn ( hasinger et al .
1998 , schmidt et al . 1998 ) , the nature of the sources making the energetically dominant hard ( 250 kev ) xrb is still largely unknown .
this is due to the lack , until recent years , of sensitive imaging instruments above 23 kev ..
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thanks to asca and bepposax , the 2 - 10 kev band is now accessible to surveys ( boyle et al .
1998 , ueda et al .
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Suppose that you have an abstract for a scientific paper: we reexamine the spectroscopic underpinnings of recent suggestions that [ ] and [ ] lines from the orion region are produced in gas where the iron - carrying grains have been destroyed and the electron density is surprisingly high .
our new observations show that previous detections of [ ] 5577 were dominated by telluric emission .
our limits are consistent with a moderate density ( @xmath0 @xmath1 ) photoionized gas .
we show that a previously proposed model of the orion region reproduces the observed [ ] and [ ] spectrum .
these lines are fully consistent with formation in a dusty region of moderate density .
_ astrophysical journal letters _ , 1996 , in press .
And you have already written the first three sentences of the full article: the orion nebula is the defining blister region ( @xcite ; @xcite ) .
a star cluster ionizes the skin of the molecular cloud , causing an expansion away from the molecular cloud towards us .
the region is in photoionization equilibrium with a density in concert with that of the background photodissociation region ( @xcite ) , and both regions are dusty with high depletions of the refractory elements ( @xcite ) ..
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bautista , pradhan , & osterbrock ( 1994 ; hereafter bpo ) , bautista & pradhan ( 1995 ; hereafter bp95 ) , and bautista , peng , & pradhan ( 1996 ; hereafter bpp ) have recently suggested that [ ] and [ ] lines are produced by a warm ( @xmath2 k ) region with very high electron density ( @xmath3 @xmath1 ) and a solar iron abundance .
this would be surprising for such a dusty environment , but would have important implications for grain destruction mechanisms . here
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Suppose that you have an abstract for a scientific paper: the landau - pomeranchuk - migdal effects on photon emission from the quark gluon plasma have been studied as a function of photon mass , at a fixed temperature of the plasma .
the integral equations for the transverse vector function ( @xmath0 ) and the longitudinal function ( @xmath1 ) consisting of multiple scattering effects are solved by the self consistent iterations method and also by the variational method for the variable set \{@xmath2 } , considering the bremsstrahlung and the @xmath3 processes .
we define four new dynamical scaling variables , @xmath4 , @xmath5 , @xmath6 , @xmath7 , for bremsstrahlung and * aws * processes and analyse the transverse and longitudinal components as a function of \{@xmath2}. we generalize the concept of photon emission function and we define four new emission functions for massive photon emission represented by @xmath8 , @xmath9 , @xmath10 , @xmath11 .
these have been constructed using the exact numerical solutions of the integral equations .
these four emission functions have been parameterized by suitable simple empirical fits . in terms of these empirical emission functions ,
the virtual photon emission from quark gluon plasma reduces to one dimensional integrals that involve folding over the empirical @xmath12 functions with appropriate quark distribution functions and the kinematic factors . using this empirical emission functions , we calculated the imaginary part of the photon polarization tensor as a function of photon mass and energy .
quark gluon plasma ( qgp ) state is expected to be formed in the relativistic heavy ion collisions . in order to identify the plasma or a de - confined state
, one needs to study the physical processes in quark matter , that can distinctly and conclusively identify this state of matter , such as parton energy loss leading to jet suppression mechanism . in this context , electromagnetic processes such as photons and dilepton emission are also considered as important signals .
photons and dileptons are emitted....
And you have already written the first three sentences of the full article: the photon production rates from bremsstrahlung and the @xmath17 processes considering the lpm effects are estimated by using eq.[photrate ] @xcite .
@xmath18 \left[n_f(q_0+p_0 ) \right .
\nonumber \\ & & \left ..
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( 1-n_f(p_0))\right]~\int \frac{\bf d^2\tilde{p}_\perp}{(2\pi)^2 } 2{\bf \tilde{p}_\perp \cdot\re\tilde{f}(\tilde{p}_\perp ) } \label{photrate}\end{aligned}\ ] ] @xmath19 \label{amy}\end{aligned}\ ] ] @xmath20 \label{amydelta}\end{aligned}\ ] ] @xmath21\left[n_f(q_0+p_0 ) \right .
\nonumber \\ & & \left .
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12,617 |
Suppose that you have an abstract for a scientific paper: we have imaged a sample of 45 face - on spiral galaxies in the k - band , to determine the morphology of the old stellar population , which dominates the mass in the disk .
the k - band images of the spiral galaxies have been used to calculate different characteristics of the underlying density perturbation such as arm strengths , profiles and cross - sections , and spiral pitch angles .
contrary to expectations , no correlation was found between arm pitch angle and hubble type , and combined with previous results this leads us to conclude that the morphology of the old stellar population bears little resemblance to the optical morphology used to classify galaxies .
the arm properties of our galaxies seem inconsistent with predictions from the simplest density wave theories , and some observations , such as variations in pitch angle within galaxies , seem hard to reconcile even with more complex modal theories .
bars have no detectable effect on arm strengths for the present sample .
we have also obtained b - band images of three of the galaxies . for these galaxies
we have measured arm cross - sections and strengths , to investigate the effects of disk density perturbations on star formation in spiral disks .
we find that b - band arms lead k - band arms and are narrower than k - band arms , apparently supporting predictions made by the large scale shock scenario , although the effects of dust on b - band images may contribute towards these results .
galaxies : spiral - galaxies : structure - galaxies : fundamental parameters .
And you have already written the first three sentences of the full article: ever since the pioneering work of lin & shu ( 1964 , 1966 ) many theoretical models have been proposed to explain the existence of spiral structure in disk galaxies .
many are based upon the lin - shu hypothesis ( e.g. lin , yuan & shu 1969 ; roberts 1969 ; roberts , roberts & shu 1975 ) which describes spiral patterns as density waves , which cause compression of the gas component as it flows through the arms leading to subsequent star formation .
modal theories ( bertin et al ..
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1989a , 1989b ; bertin & lin 1996 ) are more complex density wave models , which describe disks of galaxies as resonant cavities within which density waves of different modes can co - exist and interfere to produce a range of observed phenomena .
tidal models ( toomre & toomre 1972 ; kormendy & norman 1979 ) set up spiral structure through transient density waves , which are caused by the tidal field of a nearby neighbour .
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Suppose that you have an abstract for a scientific paper: large scale features of a randomly isotropically forced incompressible and unbounded rotating fluid are examined in perturbation theory . at first order in both the random force amplitude and the angular velocity
we find two types of modifications to the fluid equation of motion .
the first correction transforms the molecular shear viscosity into a ( rotation independent ) effective viscosity .
the second perturbative correction leads to a new large scale non - dissipative force proportional to the fluid angular velocity in the slow rotation regime .
this effective force does no net work and alters the dispersion relation of inertial waves propagating in the fluid .
both dynamically generated corrections can be identified with certain components of the most general axisymmetric `` viscosity tensor '' for a newtonian fluid .
# 1 pacs : 47.27-i , 47.32.-y .
And you have already written the first three sentences of the full article: the special features of turbulence in the presence of rotation have attracted the interest of many authors @xcite . relying on some experiments ,
the methods of study used have ranged from analytic approaches to numerical simulations @xcite .
the central theme in rotating fluids is the effect of the coriolis force , which induces anisotropy ( there is a preferred direction , that of the rotation axis ) ..
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this anisotropy is extreme in the limit of fast rotation , which actually forces the flow to become two - dimensional ( proudman - taylor theorem ) @xcite . in this work
we apply perturbation theory to the randomly forced navier - stokes equation with coriolis force as a model for the turbulent regime of a rotating fluid .
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12,619 |
Suppose that you have an abstract for a scientific paper: we provide the first direct lifting of the mass / anisotropy degeneracy for a cluster of galaxies , by jointly fitting the line of sight velocity dispersion and kurtosis profiles of the coma cluster , assuming an nfw tracer density profile , a generalized - nfw dark matter profile and a constant anisotropy profile .
we find that the orbits in coma must be quasi - isotropic , and find a mass consistent with previous analyses , but a concentration parameter 50% higher than expected in cosmological @xmath0-body simulations .
we then test the accuracy of our method on realistic non - spherical systems with substructure and streaming motions , by applying it to the ten most massive structures in a cosmological @xmath0-body simulation .
we find that our method yields fairly accurate results on average ( within 20% ) , although with a wide variation ( factor 1.7 at 1@xmath1 ) for the concentration parameter , with decreased accuracy and efficiency when the projected mean velocity is not constant with radius . .
And you have already written the first three sentences of the full article: the kinematical ( `` jeans '' ) analyses of near - spherical structures using the spherical jeans equation for stationary systems : @xmath2 where @xmath3 is the 3d density distribution of the tracer population , suffer from the fact that this one equation involves two unknowns : the mass distribution @xmath4 and the velocity anisotropy @xmath5 ( we make use of the symmetry of spherical systems yielding @xmath6 ) . in some cases of simple anisotropy profiles
@xmath7 , the jeans equation can be inverted to yield the radial dispersion as a single integral over radii of @xmath8 times some kernel , and one can insert this solution into the equation that links the line - of - sight velocity dispersion to the radial one , to obtain after some algebra , the line - of - sight dispersion as a single integral over @xmath8 and some other kernel . in what follows , we attempt to lift the mass / anisotropy degeneracy by adding a second equation , namely the 4th order jeans equation for constant anisotropy ( okas 2002 ) @xmath9 where we express the line of sight _ kurtosis _ as a double integral over @xmath8 and @xmath10 and a third kernel ( the details are given in okas & mamon 2003 ) .
we apply our formalism to the nearby coma cluster , for which we ve extracted from ned the positions and line - of - sight velocities of 967 galaxies , among which 355 early - type galaxies whose kinematics we analyze here ( we omit spiral galaxies , which are expected to have a non negligible mean radial velocity caused by their infall and subsequent transformation at cluster pericenter ) . our mass model includes 1 ) a stellar component , which we find is well fit by an nfw ( navarro et al ..
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1996 ) model ; 2 ) a dark matter component , which we assume to be a generalized nfw model with arbitrary inner slope : @xmath11 where @xmath12 is the scale radius of the dark matter ( in general different from that of the luminous distribution ) , and @xmath13 for the nfw model .
the profiles differ by their inner slope @xmath14 but have a common outer limiting behavior of @xmath15 ; and 3 ) an isothermal gas component , taken from the rosat x - ray observations by briel et al .
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Suppose that you have an abstract for a scientific paper: getting agents in the internet , and in networks in general , to invest in and deploy security features and protocols is a challenge , in particular because of economic reasons arising from the presence of network externalities .
our goal in this paper is to model and investigate the impact of such externalities on security investments in a network . specifically , we study a network of interconnected agents subject to epidemic risks such as viruses and worms where agents can decide whether or not to invest some amount to deploy security solutions .
we consider both cases when the security solutions are strong ( they perfectly protect the agents deploying them ) and when they are weak .
we make three contributions in the paper .
first , we introduce a general model which combines an epidemic propagation model with an economic model for agents which captures network effects and externalities .
second , borrowing ideas and techniques used in statistical physics , we introduce a local mean field ( lmf ) model , which extends the standard mean - field approximation to take into account the correlation structure on local neighborhoods .
third , we solve the lmf model in a network with externalities , and we derive analytic solutions for sparse random graphs of agents , for which we obtain asymptotic results .
we find known phenomena such as free riders and tipping points .
we also observe counter - intuitive phenomena , such as increasing the quality of the security technology can result in a decreased adoption of that technology in the network . in general , we find that both situations with strong and weak protection exhibit externalities and that the equilibrium is not socially optimal - therefore there is a market failure . insurance is one mechanism to address this market failure . in related work
, we have shown that insurance is a very effective mechanism @xcite and argue that using insurance would increase the security in a network such as the internet . [ network problems ] [....
And you have already written the first three sentences of the full article: users and computers in the internet face a wide range of security risks . of particular concern ,
are _ epidemic risks _ , such as those propagated by worms and viruses .
epidemic risks depend on the behavior of other entities in the network , such as whether or not those entities invest in security solutions to minimize their likelihood of being infected ..
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our goal in this paper is to analyze the strategic behavior of agents facing such epidemic risks .
the propagation of worms and viruses @xcite , but also many other phenomena in the internet such as the propagation of alerts and patches @xcite or of routing updates @xcite , can be modeled using epidemic spreads through a network . as a result , there is now a vast body of literature on epidemic spreads over a network topology from an initial set of infected nodes to susceptible nodes .
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Suppose that you have an abstract for a scientific paper: we present the bolocam galactic plane survey ( bgps ) , a 1.1 mm continuum survey at 33 effective resolution of 170square degrees of the galactic plane visible from the northern hemisphere .
the bgps is one of the first large area , systematic surveys of the galactic plane in the millimeter continuum without pre - selected targets .
the survey is contiguous over the range @xmath0 , @xmath1 . towards the cygnus x spiral arm ,
the coverage was flared to @xmath2 for @xmath3 .
in addition , cross - cuts to @xmath2 were made at @xmath4 3 , 15 , 30 and 31 .
the total area of this section is 133 square degrees . with the exception of the increase in latitude ,
no pre - selection criteria were applied to the coverage in this region .
in addition to the contiguous region , four targeted regions in the outer galaxy were observed : ic1396 ( 9 square degrees , @xmath5 , @xmath6 ) , a region towards the perseus arm ( 4 square degrees centered on @xmath7 , @xmath8 near ngc7538 ) , w3/4/5 ( 18 square degrees , @xmath9 ) and gem ob1 ( 6 square degrees , @xmath10 ) . the survey has detected approximately 8400 clumps over the entire area to a limiting non - uniform 1-@xmath11 noise level in the range 11 to 53 mjy beam@xmath12 in the inner galaxy .
the bgps source catalog is presented in a companion paper @xcite .
this paper details the survey observations and data reduction methods for the images .
we discuss in detail the determination of astrometric and flux density calibration uncertainties and compare our results to the literature .
data processing algorithms that separate astronomical signals from time - variable atmospheric fluctuations in the data time - stream are presented .
these algorithms reproduce the structure of the astronomical sky over a limited range of angular scales and produce artifacts in the vicinity of bright sources . based on simulations
, we find that extended emission on scales larger than about 59 is nearly completely attenuated ( @xmath13 ) and the linear scale....
And you have already written the first three sentences of the full article: millimeter - wavelength continuum surveys of the galactic plane provide the most efficient way to find molecular clumps that are the likely formation sites of massive stars and star clusters .
the development of detector arrays has made blind surveys of large areas possible .
such surveys bypass the need for selection based on the presence of embedded stars or star clusters , infrared sources , masers , or radio continuum emission ..
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in particular , they can locate molecular clumps before stars form , providing vital information on the initial conditions of star formation .
these surveys can also provide valuable constraints on the physical properties of the clumps , especially masses and mean densities , when combined with distance information .
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Suppose that you have an abstract for a scientific paper: in this paper i provide simple and easily verifiable conditions under which a strong form of stochastic equicontinuity holds in a wide variety of modern time series models .
in contrast to most results currently available in the literature , my methods avoid mixing conditions .
i discuss several applications in detail . .
And you have already written the first three sentences of the full article: stochastic equicontinuity typically captures the key difficulty in weak convergence proofs of estimators with non - differentiable objective functions .
precise and elegant methods have been found to deal with cases where the data dependence structure can be described by mixing conditions ; see @xcite for an excellent summary
. mixing assumptions are convenient in this context because they measure how events generated by time series observations rather than the observations themselves relate to one another and therefore also measure dependence of functions of such time series ..
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the downside to these assumptions is that they can be hard to verify for a given application .
@xcite describes alternatives and considers parametric classes of functions that behave like mixingales , but his results come at the expense of lipschitz continuity conditions on these functions and rule out many applications of interest . in this paper
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12,623 |
Suppose that you have an abstract for a scientific paper: using first - principles methods we performed a theoretical study of carbon clusters in silicon carbide ( sic ) nanowires .
we examined small clusters with carbon interstitials and antisites in hydrogen - passivated sic nanowires growth along the [ 100 ] and [ 111 ] directions .
the formation energies of these clusters were calculated as a function of the carbon concentration .
we verified that the energetic stability of the carbon defects in sic nanowires depends strongly on the composition of the nanowire surface : the energetically most favorable configuration in carbon - coated [ 100 ] sic nanowire is not expected to occur in silicon - coated [ 100 ] sic nanowire .
the binding energies of some aggregates were also obtained , and they indicate that the formation of carbon clusters in sic nanowires is energetically favored . .
And you have already written the first three sentences of the full article: silicon carbide ( sic ) is a wide - band - gap semiconductor with excellent physical , electronic and mechanical properties@xcite such as high thermal conductivity , high breakdown field , low density , high saturation velocity , high mechanical strength , and stability at high temperature .
these exceptional features make sic a promising candidate to replace silicon in electronic devices operating in high - power , high - frequency , and high - temperature regimes.@xcite in the last years , sic nanostructures ( like nanospheres,@xcite nanosprings,@xcite nanowires@xcite and nanotubes@xcite ) have been successfully synthesized , and several theoretical and experimental works @xcite have been performed to investigate their structural and electronic properties .
the unique features of sic combined with quantum - size effects make the sic nanostructures interesting materials for nanotechnology applications ..
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for instance , sic nanowires and nanotubes have been considered as candidates for hydrogen storage nanodevices@xcite and for building blocks in molecular electronic applications.@xcite in particular , silicon carbide nanowires ( sic nws ) have excellent field emission properties,@xcite high mechanical stability and high electrical conductance,@xcite and could be used as nanoscale field emitters or nanocontacts in harsh environments .
some optical and electronic properties of semiconductors may be modified by the presence of defects .
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Suppose that you have an abstract for a scientific paper: we present simulations modeling closed regions of the solar corona threaded by a strong magnetic field where localized photospheric vortical motions twist the coronal field lines .
the linear and nonlinear dynamics are investigated in the reduced magnetohydrodynamic regime in cartesian geometry . initially the magnetic field lines get twisted and the system becomes unstable to the internal kink mode , confirming and extending previous results . as typical in this kind of investigations , where initial conditions implement smooth fields and flux - tubes ,
we have neglected fluctuations and the fields are laminar until the instability sets in . but previous investigations indicate that fluctuations , excited by photospheric motions and coronal dynamics , are naturally present at all scales in the coronal fields .
thus , in order to understand the effect of a photospheric vortex on a more realistic corona , we continue the simulations after kink instability sets in , when turbulent fluctuations have already developed in the corona . in the nonlinear stage
the system never returns to the simple initial state with ordered twisted field lines , and kink instability does not occur again
. nevertheless field lines get twisted , but in a disordered way , and energy accumulates at large scales through an inverse cascade .
this energy can subsequently be released in micro - flares or larger flares , when interaction with neighboring structures occurs or via other mechanisms . the impact on coronal dynamics and cmes initiation
is discussed . .
And you have already written the first three sentences of the full article: photospheric convection and the coronal magnetic field play a key role in heating the solar corona . for the magnetically confined ( closed ) regions of the corona
it has long been suggested that small heating events , dubbed _ nanoflares _ , continuously deposit energy at the small scales and can contribute a substantial fraction of the total heating @xcite . the slow photospheric motions ( with a timescale @xmath0 8 minutes , magnitude @xmath1 , and correlation scale @xmath2 ) transfer energy from the photosphere into the corona shuffling the footpoints of the magnetic field lines . the work done by the denser photospheric plasma on the magnetic field lines footpoints injects energy into the corona , mostly as magnetic energy .
the perturbations generated at the photospheric level propagate along the loop at the alfvn speed . in a coronal loop.
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the alfvn velocity associated to the strong axial magnetic field @xmath3 is @xmath4 ( @xmath5 is the average mass density ) , and considering a typical loop length @xmath6 we obtain for the alfvn crossing time @xmath7 . the crossing time is therefore significantly smaller than the photospheric timescale : @xmath8 .
furthermore as magnetic pressure largely exceeds plasma pressure the plasma @xmath9 is small ( @xmath10 ) .
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Suppose that you have an abstract for a scientific paper: we discuss the technique of wide - field imaging as it applies to very long baseline interferometry ( vlbi ) . in the past vlbi data sets
were usually averaged so severely that the field - of - view was typically restricted to regions extending a few hundred milliarcseconds from the phase centre of the field .
recent advances in data analysis techniques , together with increasing data storage capabilities , and enhanced computer processing power , now permit vlbi images to be made whose angular size represents a significant fraction of an individual antenna s primary beam .
this technique has recently been successfully applied to several large separation gravitational lens systems , compact supernova remnants in the starburst galaxy m82 , and two faint radio sources located within the same vla first field .
it seems likely that other vlbi observing programmes might benefit from this wide - field approach to vlbi data analysis . with the raw sensitivity of global vlbi set to improve by a factor 4 - 5 over the coming few years
, the number of sources that can be detected in a given field will rise considerably .
in addition , a continued progression in vlbi s ability to image relatively faint and extended low brightness temperature features ( such as hot - spots in large - scale astrophysical jets ) is also to be expected .
as vlbi sensitivity approaches the @xmath0jy level , a wide - field approach to data analysis becomes inevitable .
techniques : interferometric , image processing , , methods : data analysis 95.75.-z , 95.75.mn , 98.58.mj .
And you have already written the first three sentences of the full article: the undistorted field of view of a given vlbi data set is usually limited by two main effects : bandwidth smearing and time - average smearing @xcite
. the narrower the individual frequency channels and the smaller the integration time , the larger the unaberrated field of view .
data generated by vlbi correlators are comprised of a set of measurements of the complex visibility as a function of frequency ( or delay ) and time ..
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most continuum vlbi data sets are delivered to the astronomer with relatively narrow frequency channels ( @xmath1 mhz ) and short integration times ( @xmath2 secs ) .
for example , a typical @xmath3 cm evn data set , in its original form , boasts a field - of - view , @xmath4 , in excess of @xmath5 arcminute .
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Suppose that you have an abstract for a scientific paper: we report on the generation of an indistinguishable heralded single - photon state , using highly nondegenerate spontaneous parametric downconversion ( spdc ) .
spectrally factorable photon pairs can be generated by incorporating a broadband pump pulse and a group - velocity matching ( gvm ) condition in a periodically - poled potassium titanyl phosphate ( ppktp ) crystal .
the heralding photon is in the near ir , close to the peak detection efficiency of off - the - shelf si single - photon detectors ; meanwhile , the heralded photon is in the telecom l - band where fiber losses are at a minimum .
we observe spectral factorability of the spdc source and consequently high purity ( 90% ) of the produced heralded single photons by several different techniques . because this source can also realize a high heralding efficiency ( @xmath0% )
, it would be suitable for time - multiplexing techniques , enabling a pseudo - deterministic single - photon source , a critical resource for optical quantum information and communication technology . .
And you have already written the first three sentences of the full article: single - photon sources are critical resources for quantum - enhanced technologies , such as quantum metrology @xcite , quantum communications @xcite , and photonic quantum computation @xcite .
heralded single - photon sources ( hspss ) , first demonstrated by hong and mandel @xcite in 1986 , have been of great interest in quantum information applications .
heralded single photons may be created by a photon - pair producing nonlinear optical process such as spontaneous parametric downconversion ( spdc ) or spontaneous four - wave mixing ( sfwm ) ; a single photon s presence is `` heralded '' by the detection of its twin photon . although hspss are not on - demand sources due to the probabilistic nature of the pair generation process , they are easier to design and implement compared to single emitter sources @xcite such as single atoms , ions , and semiconductor devices , which typically require vacuum and/or cryogenic systems . moreover , it is possible to improve a hsps to be pseudo - on - demand by using temporal or spatial multiplexing techniques @xcite . in the context of quantum information applications , there are essentially three key metrics for an hsps : indistinguishability , heralding efficiency , and source brightness ..
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indistinguishable photons , i.e. , pure and identical photons , are desirable because they can exhibit multi - photon interference @xcite that is central to many quantum information applications . in order to permit heralding of pure single photons , the spdc or sfwm
two - photon state source must be factorable .
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Suppose that you have an abstract for a scientific paper: we present multi - wavelength observations of the unusual nova v1535 sco throughout its outburst in 2015 .
early radio observations were consistent with synchrotron emission , and early x - ray observations revealed the presence of high - energy ( > 1 kev ) photons .
these indicated that strong shocks were present during the first @xmath02 weeks of the nova s evolution .
the radio spectral energy distribution was consistent with thermal emission from week 2 to week 6 .
starting in week 7 , the radio emission again showed evidence of synchrotron emission and there was an increase in x - ray emission , indicating a second shock event .
the optical spectra show evidence for at least two separate outflows , with the faster outflow possibly having a bipolar morphology .
the optical and near infrared light curves and the x - ray n@xmath1 measurements indicated that the companion star is likely a k giant . .
And you have already written the first three sentences of the full article: a nova eruption occurs when a white dwarf has accreted enough material from a companion star to trigger thermonuclear runaway on its surface ( e.g. , starrfield et al .
observations with modern telescopes have revealed the presence of strong shocks in nova systems . in particular , the discovery of gev @xmath2-rays from v407 cyg indicated that in at least some systems , the shocks were strong enough to accelerate particles to very high energies ( abdo et al . 2010 ) . in the case of v407 cyg ,
the shocks were the result of the nova ejecta colliding with a dense stellar wind from a mira variable companion ( abdo et al ..
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much to the surprise of the nova community , further observations with the _ fermi gamma - ray space telescope _ discovered @xmath2-ray emission from systems with main sequence companions ( e.g. , ackermann et al . 2014 ) . while observations across the electromagnetic spectrum have contributed to the discovery of shocks in novae ,
radio observations have proven to be particularly valuable . resolved radio images
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Suppose that you have an abstract for a scientific paper: models for majorana neutrino masses can be classified according to the level in perturbation theory at which the effective dimension five operator @xmath0 is realized .
the possibilities range from the tree - level up to the three - loop level realizations .
we discuss some general aspects of this approach and speculate about a model independent classification of the possible cases . among all the realizations , those in which the effective operator is induced by radiative corrections open the possibility for lepton number violation near -or at- the electroweak scale .
we discuss some phenomenological aspects of two generic radiative realizations : the babu - zee model and supersymmetric models with bilinear r - parity violation . .
And you have already written the first three sentences of the full article: neutrino experiments have firmly demonstrated neutrinos are massive and have non - vanishing mixing angles among the different generations @xcite . since in the standard model neutrinos are massless this experimental results are a clear evidence of beyond standard model physics . from a general point of view majorana neutrino masses can be generated by adding to the standard model lagrangian the non - renormalizable effective lagrangian @xcite @xmath1 where @xmath2 and @xmath3 are the lepton and higgs electroweak doublets .
the presence of the effective lagrangian in ( [ eq : eff - op ] ) guarantees that after electroweak symmetry breaking neutrinos acquire majorana masses .
extensions of the standard model in which neutrinos have majorana masses realize the effective operator @xmath4 in different ways . however , among all these possibilities there are subsets that have a common feature , namely the order in perturbation theory at which the operator is realized . as will be discussed in sec ..
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[ sec : o5realizations ] a rather general classification of neutrino mass models can be done by gathering together these different subsets . making an exhaustive list of possible realizations of @xmath4 and their corresponding phenomenology is far out of the scope of the present discussion .
thus , instead of using this approach we will discuss two classes of generic models : models in which neutrino masses are generated radiatively at the 2-loop level and supersymmetric models with broken r - parity . in the former case we will stick to the babu - zee model @xcite , while for the latter we will discuss bilinear r - parity breaking models with a neutralino lsp @xcite .
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Suppose that you have an abstract for a scientific paper: in the recent controversy about the role of tp - agb stars in evolutionary population synthesis ( eps ) models of galaxies , one particular aspect is puzzling : tp - agb models aimed at reproducing the lifetimes and integrated fluxes of the tp - agb phase in magellanic cloud ( mc ) clusters , when incorporated into eps models , are found to overestimate , to various extents , the tp - agb contribution in resolved star counts and integrated spectra of galaxies . in this paper , we call attention to a particular evolutionary aspect , linked to the physics of stellar interiors , that in all probability is the main cause of this conundrum . as soon as stellar populations intercept the ages at which rgb stars first appear , a sudden and abrupt change in the lifetime of the core he - burning phase causes a temporary `` boost '' in the production rate of subsequent evolutionary phases , including the tp - agb . for a timespan of about 0.1 gyr ,
triple tp - agb branches develop at slightly different initial masses , causing their frequency and contribution to the integrated luminosity of the stellar population to increase by a factor of @xmath0 .
the boost occurs for turn - off masses of @xmath1 , just in the proximity of the expected peak in the tp - agb lifetimes ( for mc metallicities ) , and for ages of @xmath2 gyr .
coincidently , this relatively narrow age interval happens to contain the few very massive mc clusters that host most of the tp - agb stars used to constrain stellar evolution and eps models .
this concomitance makes the agb - boosting particularly insidious in the context of present eps models .
as we discuss in this paper , the identification of this evolutionary effect brings about three main consequences .
first , we claim that present estimates of the tp - agb contribution to the integrated light of galaxies derived from mc clusters , are biased towards too large values .
second , the relative tp - agb contribution of single - burst populations falling in this critical age range....
And you have already written the first three sentences of the full article: it is well established that a sizable fraction of the integrated light of stellar populations comes from the thermally pulsing asymptotic giant branch ( tp - agb ) phase @xcite . however , the size of this fraction has been subject of much discussion in the recent literature , with evolutionary population synthesis ( eps ) models of galaxies favouring either `` heavy '' @xcite or `` light '' @xcite flux contributions from tp - agb stars .
efforts to account for the tp - agb contribution to the integrated light of galaxies are based on two different techniques : \1 ) eps models based on the isochrone method @xcite start by adopting the best - available sets of evolutionary tracks and isochrones including the tp - agb phase . since this phase is notoriously challenging to model due to difficulties and uncertainties in the description of mixing , energy transport by convection , mass loss , and numerical aspects at present
there is no set of widely - accepted tp - agb model grids in the literature ..
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therefore , in general , the choice falls on models which at least try to reproduce basic observables of tp - agb stars in the magellanic clouds ( mcs ; e.g. * ? ? ?
* ; * ? ? ?
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Suppose that you have an abstract for a scientific paper: we present the first optical ( 590890 nm ) imaging polarimetry observations of the pre - transitional protoplanetary disk around the young solar analog lkca 15 , addressing a number of open questions raised by previous studies .
we detect the previously unseen far side of the disk gap , confirm the highly off - centered scattered - light gap shape that was postulated from near - infrared imaging , at odds with the symmetric gap inferred from millimeter interferometry .
furthermore , we resolve the inner disk for the first time and trace it out to 30au .
this new source of scattered light may contribute to the near - infrared interferometric signal attributed to the protoplanet candidate lkca 15 b , which lies embedded in the outer regions of the inner disk .
finally , we present a new model for the system architecture of lkca 15 that ties these new findings together . these observations were taken during science verification of sphere zimpol and demonstrate this facility s performance for faint guide stars under adverse observing conditions .
= 1 .
And you have already written the first three sentences of the full article: transitional disks are protoplanetary disks with heavily depleted gaps or cavities in their inner regions ( e.g. * ? ? ?
* ; * ? ? ?
they are thought to represent a transitional state in disk evolution , in which the gas - rich primordial disk gradually disperses due to planet formation or other effects ( e.g. * ? ? ?.
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* ; * ? ? ?
* ; * ? ? ?
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Suppose that you have an abstract for a scientific paper: we analyse numerically manifestations of the radiative amplitude zero ( raz ) effect in single leptoquark production associated with hard photon emission .
we present some quantitative conclusions on the possibility to distinguish leptoquark charges produced in @xmath0 collisions taking account of three - body final state subprocesses and of proton structure functions . applying this method to hera and possible lep+lhc experiments we show that the raz analysis can serve as a tool to determine the leptoquark electric charge up to large leptoquark masses .
-2 cm -1 cm inp msu preprint-95 - 12/376 + qmw - ph-95 - 13 + hep - ph / yymmnn + 17-may-1995 * * v. ilyin , a. pukhov , v. savrin , a. semenov , + _ institute of nuclear physics of moscow state university , 119899 moscow , russia _ + and + w. von schlippe + _ queen mary & westfield college , london , england _
( to be submitted to physics letters ) .
And you have already written the first three sentences of the full article: in paper @xcite we have proposed a method for distinguishing the charges of leptoquarks collisions is considered . ] ( lq ) produced in the reaction @xmath1 the idea is based on the radiative amplitude zero ( raz ) effect , i.e. the absence of photon emission at some directions depending on the leptoquark electric charges . in this paper we give a detailed numerical analysis of this method applying it to hera and possible lep+lhc experiments . in ref .
@xcite we have derived the analytical formulas for the unpolarized cross sections of the hard subprocesses @xmath2 we have shown that they are proportional to a factor @xmath3 .
so , at some photon emission angles where this factor vanishes the cross sections have exact zeros whose positions are completely determined by the electron ( positron ) and quark charges , @xmath4 and @xmath5 , respectively . of course in reality the leptoquarks decay into two fermions ..
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considering the electron decay channel we have got the following clear signature : the hard photon , the electron ( or positron ) and a hard ( quark ) jet with complete kinematical reconstruction of the subprocess : @xmath6 in this paper we analyse numerically the manifestations of the raz effect for the case of this three - body final state subprocess .
we make some quantitative conclusions on a possibility to distinguish the charges of leptoquarks produced in @xmath0 collisions taking account of the proton structure functions .
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Suppose that you have an abstract for a scientific paper: we discuss a constant contribution to meson correlators at finite temperature . in the deconfinement phase of qcd
, a colored single quark state is allowed as a finite energy state , which yields to a contribution of wraparound quark propagation to temporal meson correlators .
we investigate the effects in the free quark case and quenched qcd at finite temperature .
the `` scattering '' contribution causes a constant mode in meson correlators with zero spatial momentum and degenerate quark masses , which can dominate the correlators in the region of large imaginary times . in the free spectral function ,
the contribution yields a term proportional to @xmath0 . therefore this contribution is related to transport phenomena in the quark gluon plasma .
it is possible to distinguish the constant contribution from the other part using several analysis methods proposed in this paper . as a result of the analyses
, we find that drastic changes in charmonium correlators for @xmath1 states just above the deconfinement transition are due to the constant contribution .
the other differences in the @xmath1 states are small
. it may indicate the survival of @xmath1 states after the deconfinement transition until , at least , @xmath2 . .
And you have already written the first three sentences of the full article: in the imaginary time formalism of finite temperature field theory , temporal correlators are related to several dynamical properties through a prescription of analytical continuation .
especially the imaginary time correlator can be described by the same spectral function as that of retarded and advanced green functions .
therefore the spectral functions extracted from the imaginary time correlators , which are able to be calculated in lattice qcd , enable us to investigate important physics at finite temperature , e.g. dilepton rates @xcite , light mesons @xcite , heavy quarkonia @xcite , glueballs @xcite , transport coefficients @xcite ..
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one of the most important quantities at finite temperature qcd is the spectral function of heavy quarkonium , which plays the key role for understanding the quark gluon plasma ( qgp ) formation in heavy ion collision experiments e.g. the rhic experiment at brookhaven national laboratory .
recent studies on the spectral function of charmonium above @xmath3 suggest that hadronic excitations corresponding to @xmath4 may survive in the deconfinement phase till relatively high temperature @xcite .
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Suppose that you have an abstract for a scientific paper: high redshift dla systems suggest that the relative abundances of elements might be roughly solar , although with absolute abundances of more than two orders of magnitude below solar .
the result comes from observations of the [ sii / znii ] ratio , which is a reliable diagnostic of the true abundance , and from dla absorbers with small dust depletion and negligible hii contamination .
in particular , in two dla systems nitrogen is detected and at remarkably high levels ( vladilo et al .
1995 , molaro et al .
1995 , green et al .
1995 , kulkarni et al .
1996 ) .
here we compare the predictions from chemical evolution models of galaxies of different morphological type with the abundances and abundance ratios derived for such systems .
we conclude that solar ratios and relatively high nitrogen abundances can be obtained in the framework of a chemical evolution model assuming short but intense bursts of star formation , which in turn trigger enriched galactic winds , and a primary origin for nitrogen in massive stars .
such a model is the most successful in describing the chemical abundances of dwarf irregular galaxies and in particular of the peculiar galaxy izw18 .
thus , solar ratios at very low absolute abundances , if confirmed , seem to favour dwarf galaxies rather than spirals as the progenitors of at least some of the dla systems . .
And you have already written the first three sentences of the full article: absorption line systems detected in the spectra of quasi stellar objects ( qso ) originate in intervening galaxies or protogalaxies . among the different classes of absorbers , the damped lyman @xmath0 systems ( dla ) are those characterized by n(hi )
@xmath1 10@xmath2 @xmath3 and by showing many low ionization species such as feii , siii , crii , znii and oi , which are in their dominant ionization stage for a hi region .
the high accuracy in the hydrogen column density determination derived from the damped wings and the absence of significant ionization corrections allow accurate absolute abundance determinations of the gas phase elements . since dla systems are observable up to the highest redshift they provide a unique tool for the study of the cosmic chemical history of the early universe ..
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such observations are complementary to the hubble deep field ones ( mobasher et al . 1996 ) which show that high redshift galaxies have a large variety of morphological types including many peculiar objects with traces of interaction and merging : interestingly , a large fraction are starburst galaxies , as suggested by their colors .
the relative elemental abundances rather than absolute ones are a valuable diagnostic of the first elemental buildup .
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Suppose that you have an abstract for a scientific paper: manifestly invariant renormalization scheme for supersymmetric gauge theories is proposed .
this scheme is applied to supersymmetric quantum electrodynamics . 6.1 in 8.70 in .03 in .03 in .03 in = -12pt .
And you have already written the first three sentences of the full article: this paper addresses the problem of a manifestly invariant renormalization procedure for supersymmetric ( susy ) gauge theories .
a peculiar feature of supersymmetric gauge theories is nonpolynomial structure of the action .
the only possibility to reduce the action to a polynomial form is to use the wess - zumino gauge ..
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however in this case the manifest supersymmetry is lost and the powerful superdiagram technique can not be used . in supersymmetric gauges an infinite number of primitively divergent diagrams is present , which makes the theory formally nonrenormalizable .
nevertheless it can be shown that supersymmetry and gauge invariance reduce the number of independent counterterms , and the usual charge and wave functions renormalizations are sufficient .
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Suppose that you have an abstract for a scientific paper: although the radio emission from most quasars appears to be associated with star forming activity in the host galaxy , about ten percent of optically selected quasars have very luminous relativistic jets apparently powered by a smbh which is located at the base of the jet .
when these jets are pointed close to the line of sight their apparent luminosity is enhanced by doppler boosting and appears highly variable .
high resolution radio interferometry shows directly the outflow of relativistic plasma jets from the smbh .
apparent transverse velocities in these so - called `` blazars '' are typically about 7c but reach as much as 50c indicating true velocities within one percent of the speed of light .
the jets appear to be collimated and accelerated in regions as much as a hundred parsecs downstream from the smbh .
measurements made with earth to space interferometers indicate apparent brightness temperatures of @xmath0 k or more .
this is well in excess of the limits imposed by inverse compton cooling .
the modest doppler factors deduced from the observed ejection speeds appear to be inadequate to explain the high observed brightness temperatures in terms of relativistic boosting . .
And you have already written the first three sentences of the full article: historically the first speculations about the existence of active galactic nuclei ( agn ) and super massive black holes ( smbhs ) came from the huge energy requirements implied by the discovery of distant powerful radio galaxies and quasars . today
, radio observations remain crucial to understanding the role of smbhs in astrophysics . only at radio wavelengths
is it possible to image the region immediately surrounding the smbh central engine and the relativistic jets which apparently originate with the smbh ..
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typical resolution obtained with very long baseline interferometer ( vlbi ) observations at centimeter wavelengths is of the order of 0.001 arccsecond ( 1 milliarcsec ) .
thus , for nearby sources such as those located in the virgo cluster , a linear resolution of 1 milliarcsec corresponds to only about 0.1 parsec or about 100 schwartzchild radii for the smbh located in the nucleus of m87 .
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Suppose that you have an abstract for a scientific paper: it is well known that if the power spectral density of a continuous time stationary stochastic process does not have a compact support , data sampled from that process at any uniform sampling rate leads to biased and inconsistent spectrum estimators . in a recent paper
, the authors showed that the smoothed periodogram estimator can be consistent , if the sampling interval is allowed to shrink to zero at a suitable rate as the sample size goes to infinity . in this paper ,
this ` shrinking asymptotics ' approach is used to obtain the limiting distribution of the smoothed periodogram estimator of spectra and cross - spectra .
it is shown that , under suitable conditions , the scaling that ensures weak convergence of the estimator to a limiting normal random vector can range from cube - root of the sample size to square - root of the sample size , depending on the strength of the assumption made .
the results are used to construct asymptotic confidence intervals for spectra and cross spectra .
it is shown through a monte - carlo simulation study that these intervals have appropriate empirical coverage probabilities at moderate sample sizes .
_ keywords : _ power spectral density , spectrum estimation , smoothed periodogram , shrinking asymptotics , asymptotic confidence interval . .
And you have already written the first three sentences of the full article: estimation of power spectral density ( spectrum ) of a continuous time , mean square continuous , stationary stochastic process is a classical problem . generally the estimation is based on finitely many samples of the process .
it is well known that if the spectrum is compactly supported ( bandlimited ) , then it can be estimated from uniformly spaced samples , provided the sampling is done at the nyquist rate or faster ( kay , 1999 ) . for sampled non - bandlimited processes , or bandlimited processes sampled at sub - nyquist rate ,
the problem of aliasing leads to biased estimation ..
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for this reason , it is sometimes argued that a non - bandlimited spectrum can never be estimated consistently from uniformly spaced samples at any fixed sampling rate ( shapiro and silverman , 1960 ; masry , 1978 ) .
consequently , some researchers have turned to non - uniform sampling schemes such as stochastic sampling and periodic non - uniform sampling .
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Suppose that you have an abstract for a scientific paper: we study index - coding problems ( one sender broadcasting messages to multiple receivers ) where each message is requested by one receiver , and each receiver may know some messages a priori .
this type of index - coding problems can be fully described by directed graphs .
the aim is to find the minimum codelength that the sender needs to transmit in order to simultaneously satisfy all receivers requests .
for any directed graph , we show that if a maximum acyclic induced subgraph ( mais ) is obtained by removing two or fewer vertices from the graph , then the minimum codelength ( i.e. , the solution to the index - coding problem ) equals the number of vertices in the mais , and linear codes are optimal for this index - coding problem .
our result increases the set of index - coding problems for which linear index codes are proven to be optimal . .
And you have already written the first three sentences of the full article: we consider index - coding problems , first introduced by birk and kol @xcite , where a sender communicates with multiple receivers simultaneously through a shared broadcast medium .
the aim is to find the shortest codeword that the sender needs to broadcast in order for each receiver , knowing some of the messages broadcast by the sender a priori , to obtain its requested message .
index - coding problems have been receiving much attention lately due to its equivalence to network - coding problems @xcite ..
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each index - coding problem instance can be fully described by a directed or an undirected graph .
bar - yossef et al .
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Suppose that you have an abstract for a scientific paper: we develop a systematic coarse graining procedure for systems of @xmath0 qubits .
we exploit the underlying geometrical structures of the associated discrete phase space to produce a coarse - grained version with reduced effective size .
our coarse - grained spaces inherit key properties of the original ones .
in particular , our procedure naturally yields a subset of the original measurement operators , which can be used to construct a coarse discrete wigner function .
these operators also constitute a systematic choice of incomplete measurements for the tomographer wishing to probe an intractably large system .
= 1 .
And you have already written the first three sentences of the full article: recently , the understanding of many - body quantum systems has dramatically progressed .
nowadays we are achieving an amazing degree of control over larger and larger systems @xcite .
therefore , verification during each stage of experimental procedures is of utmost importance ; quantum tomography is the appropriate tool for that purpose ..
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the goal of quantum tomography is to reconstruct the state of a system by performing multiple measurements on identically prepared copies of the system .
once the experimental data are extracted , a numerical procedure determines which density matrix fits best the measurements .
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Suppose that you have an abstract for a scientific paper: we construct one - parameter families of right - angled hexagons in the hyperbolic plane such that each right - angled hexagon belongs to such a family , and between each pair of hexagons in the same family we describe a lipschitz map that realizes the best lipschitz constant in its homotopy class relative to the boundary .
this produces new geodesics for the arc metric on teichmller spaces of hyperbolic surfaces with nonempty boundary and as a by - product , we get new geodesics for thurston s metric on teichmller spaces of hyperbolic surfaces without boundary .
the results generalize results obtained in the two papers @xcite and @xcite .
ams mathematics subject classification : 32g15 ; 30f30 ; 30f60 ; 53a35 .
keywords : teichmller space ; arc metric ; thurston s metric ; deforming hyperbolic hexagons . .
And you have already written the first three sentences of the full article: the teichmller space of a surface admits several natural metrics , starting with the teichmller metric introduced by teichmller in 1939 , followed by the weil - petersson metric introduced by weil in 1958 , and by many others .
it is probable that the third most active subject in the metric theory of teichmller space is now that of the metric introduced by thurston in 1985 and which is called now thurston s metric .
the three metrics w mentioned , along with several others defined on teichmller space are extremely interesting and they were studied from various points of view : the infinitesimal structure ( finsler or riemannian ) , the geodesics , the convexity properties , the boundary structure , etc ..
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some difficult questions concerning these properties were solved and others remain open and make the subject a living one . in the present paper ,
when we consider the theory for surfaces with boundary , we mean the non - reduced theory , that is , the homotopies that we consider , in the definition of the equivalence relation defining teichmller spaces , do not fix the boundary of the surface pointwise .
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Suppose that you have an abstract for a scientific paper: many present - day galaxies are known to harbor supermassive , @xmath0 @xmath1 , black holes .
these central black holes must have grown through accretion from less massive seeds in the early universe .
the molecules co and h@xmath2 can be used to trace this young population of accreting massive black holes through the x - ray irradiation of ambient gas .
the x - rays drive a low - metallicity ion - molecule chemistry that leads to the formation and excitation of co and h@xmath2 in @xmath3 k gas .
h@xmath2 traces very low metallicity gas , @xmath4 solar or less , while some pollution by metals , @xmath5 solar or more , must have taken place to form co. strong co @xmath6 and h@xmath2 s(0 ) & s(1 ) emission is found that allows one to constrain ambient conditions .
comparable line strengths can not be produced by fuv or cosmic ray irradiation .
weak , but perhaps detectable , h@xmath7 ( 2,2)@xmath8(1,1 ) emission is found and discussed .
the models predict that black hole masses larger than @xmath9 @xmath1 can be detected with alma , over a redshift range of 5 - 20 , provided that the black holes radiate close to eddington . .
And you have already written the first three sentences of the full article: central to the study of galaxy evolution is the formation and evolution of the supermassive black holes in their nuclei .
accretion onto these black holes can provide the energy source for active galactic nuclei , which in turn impact the evolution of galaxies ( silk 2005 ) .
the processes believed to play a role in the formation of seed black holes , from which large black holes may form through accretion , involve 1 ) dynamical friction and collision processes in dense young stellar clusters ( portegies zwart et al ..
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2004 ) ; 2 ) seeds as the remnants of popiii stars ( e.g. , bromm et al . 1999 , abel et al .
2000 , yoshida et al .
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Suppose that you have an abstract for a scientific paper: we explore the nature of unresolved x - ray emission in a broad sample of galaxies of all morphological types based on archival _ chandra _ data . after removing bright compact sources , we study @xmath0 luminosity ratios of unresolved emission , and compare them with the solar neighborhood values .
we conclude that unresolved emission is determined by four main components , three of which were known before : ( i ) the population of faint unresolved sources associated with old stellar population . in early - type galaxies , their @xmath1 kev band luminosity scales with the stellar mass with @xmath2 ; ( ii ) the ism with @xmath3 kev present in galaxies of all types . because of the large dispersion in the gas content of galaxies , the size of our sample is insufficient to obtain reliable scaling law for this component ; ( iii ) the population of unresolved young stars and young stellar objects in late - type galaxies .
their @xmath1 kev band luminosity scales with the star - formation rate with @xmath4sfr @xmath5 ; ( iv ) in four old and massive virgo ellipticals ( m49 , m60 , m84 , ngc4636 ) we find anomalously high x - ray emission in the @xmath1 kev band .
its presence has not been recognized before and its nature is unclear .
although it appears to be stronger in galaxies having stronger ism component , its existence can not be explained in terms of an extrapolation of the warm ism spectrum .
association with virgo cluster of galaxies suggests that the excess emission may be due to intracluster gas accreted in the gravitational well of a massive galaxy .
we investigate this and other possibilities .
galaxies : elliptical and lenticular , cd galaxies : irregular galaxies : spiral x - rays : galaxies x - rays : stars x - rays : ism .
And you have already written the first three sentences of the full article: the x - ray appearance of most nearby ( @xmath6 mpc ) galaxies is determined by bright x - ray binaries @xcite , such as high - mass x - ray binaries ( hmxbs ) and low - mass x - ray binaries ( lmxbs ) .
because of their high x - ray luminosity ( @xmath7 ) notable fraction of them can be resolved with moderately deep _
chandra _ exposures , and hence hence they can be studied in full particulars ( e.g. * ? ? ?.
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* ; * ? ? ?
* ; * ? ? ?
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Suppose that you have an abstract for a scientific paper: a class of methods based on multichannel linear prediction ( mclp ) can achieve effective blind _
dereverberation _ of a source , when the source is observed with a microphone array .
we propose an inventive use of mclp as a pre - processing step for blind _ source separation _ with a microphone array .
we show theoretically that , under certain assumptions , such pre - processing reduces the original blind reverberant source separation problem to a non - reverberant one , which in turn can be effectively tackled using existing methods .
we demonstrate our claims using real recordings obtained with an eight - microphone circular array in reverberant environments .
microphone array , source separation , blind dereverberation , multichannel linear prediction , beamforming , post - filtering . .
And you have already written the first three sentences of the full article: in anechoic environments , audio source separation with a microphone array can be achieved by beamforming and post - filtering @xcite . on the other hand , in reverberant environments , reverberation causes significant degradation in the quality and intelligibility of the beamformer output , especially if the room impulse responses ( rir ) are not taken into account or are not known precisely .
this is a serious limitation because in practice , rirs are usually not known with precision and they can vary wildly with respect to the positions of the microphone / source pair .
a related problem addressing reverberation without explicit rir knowledge is called blind dereverberation @xcite . a successful class of methods for blind dereverberation fall under the framework of multi - channel linear prediction ( mclp ) @xcite ..
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these methods require a microphone array and employ linear prediction to extract information about the properties of reverberation . in this paper
, we propose to employ mclp , which is primarily used for single source dereverberation , as a pre - processing step in source separation .
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Suppose that you have an abstract for a scientific paper: the diluted kondo lattice model is investigated at strong antiferromagnetic local exchange couplings @xmath0 , where almost local kondo clouds drastically restrict the motion of conduction electrons , giving rise to the possibility of quantum localization of conduction electrons for certain geometries of impurity spins .
this localization may lead to the formation of local magnetic moments in the conduction - electron system , and the inverse indirect magnetic exchange ( iime ) , provided by virtual excitations of the kondo singlets , couples those local moments to the remaining electrons .
exemplarily , we study the one - dimensional two - impurity kondo model with impurity spins near the chain ends , which supports the formation of conduction - electron magnetic moments at the edges of the chain for sufficiently strong @xmath0 . employing degenerate perturbation theory as well as analyzing spin gaps numerically by means of the density - matrix renormalization group , it is shown that the low - energy physics of the model can be well captured within an effective antiferromagnetic rkky - like two - spin model ( `` rkky from iime '' ) or within an effective central - spin model , depending on edge - spin distance and system size . .
And you have already written the first three sentences of the full article: it has recently been suggested @xcite that fermionic alkaline - earth atoms @xcite can be used to efficiently simulate condensed - matter systems with spin and orbital degrees of freedom .
one of those many - body systems is the one - dimensional kondo - lattice model @xcite with its intricate interplay between kondo screening and magnetic order @xcite .
particularly , the regime of strong antiferromagnetic local exchange coupling @xmath0 is accessible to the experiment @xcite . the purpose of the present paper is to demonstrate that quantum confinement effects resulting from strong @xmath0 in a _ spin - diluted _ system can effectively result in a _.
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weak _ indirect magnetic rkky @xcite interaction .
this is achieved by exploiting the characteristics of a novel `` inverse '' indirect magnetic exchange ( iime ) mechanism that has been proposed recently @xcite .
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Suppose that you have an abstract for a scientific paper: [ sec : abstract ] natural landslides exhibit scaling properties revealed by power law relationships .
these relationships include the frequency of the size ( e.g. , area , volume ) of the landslides , and the rainfall conditions responsible for slope failures in a region .
reasons for the scaling behavior of landslides are poorly known .
we investigate the possibility of using the transient rainfall infiltration and grid - based regional slope - stability analysis code ( trigrs ) , a consolidated , physically - based , numerical model that describes the stability / instability conditions of natural slopes forced by rainfall , to determine the frequency statistics of the area of the unstable slopes and the rainfall intensity @xmath0
duration @xmath1 conditions that result in landslides in a region .
we apply trigrs in a portion of the upper tiber river basin , central italy .
the spatially distributed model predicts the stability / instability conditions of individual grid cells , given the local terrain and rainfall conditions .
we run trigrs using multiple , synthetic rainfall histories , and we compare the modeling results with empirical evidences of the area of landslides and of the rainfall conditions that have caused landslides in the study area .
our findings revealed that trigrs is capable of reproducing the frequency of the size of the patches of terrain predicted as unstable by the model , which match the frequency size statistics of landslides in the study area , and the mean rainfall @xmath2 conditions that result in unstable slopes in the study area , which match rainfall @xmath3 thresholds for possible landslide occurrence .
our results are a step towards understanding the mechanisms that give rise to landslide scaling properties . .
And you have already written the first three sentences of the full article: there is accumulating evidence that natural landslides exhibit scaling properties @xcite , including the area and volume of the slope failures @xcite , and the amount of rainfall required for the initiation of landslides in a region @xcite .
the scaling properties of landslides are revealed by power law dependencies , and are considered evidence of the critical state of landscape systems dominated by slope wasting phenomena @xcite it is known that , regardless of the physiographic or the climatic settings , the probability ( or frequency ) density of event landslides increases with the area of the landslide up to a maximum value , known as the rollover " , after which the density decays along a power law @xcite . the length scale for the rollover , and the rapid decay along a power law , are conditioned by the mechanical and structural properties of the soil and bedrock where the landslides occur @xcite , and are independent of the landslide trigger @xcite .
the probability ( or frequency ) density of the landslide volume obeys a negative power - law , with a scaling controlled by the type of the landslides @xcite ..
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the dependence of landslide volume on landslide area was also shown to obey a distinct scaling behavior over more than eight orders of magnitude @xcite .
rainfall is a recognized trigger of landslides , and early investigators have recognized that empirical rainfall thresholds can be established to determine the amount of rainfall required to initiate landslides in a region @xcite .
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Suppose that you have an abstract for a scientific paper: we demonstrate tunable frequency - converted light mediated by a @xmath0 nonlinear photonic crystal nanocavity .
the wavelength - scale inp - based cavity supports two closely - spaced localized modes near 1550 nm which are resonantly excited by a 130 fs laser pulse .
the cavity is simultaneously irradiated with a non - resonant probe beam , giving rise to rich second - order scattering spectra reflecting nonlinear mixing of the different resonant and non - resonant components . in particular , we highlight the radiation at the sum frequencies of the probe beam and the respective cavity modes .
this would be a useful , minimally - invasive monitor of the joint occupancy state of multiple cavities in an integrated optical circuit .
to realize all - optical logic on an integrated semiconductor chip , it is necessary to develop a toolkit of logical operations ( gates ) which can manipulate optical signals .
these operations serve to generate , condition , and detect optical signals , and are most naturally applied in cavities , where photons can be localized for many optical cycles .
recent work has demonstrated that photonic crystal nanocavities can be fabricated with @xmath1 factors greater than @xmath2 , and are thus capable of storing photons for more than 1 nanosecond @xcite and realizing one - bit delays in bit streams of data @xcite .
cavities can also serve as channel drop filters to transfer a signal from one waveguide to another @xcite . in both classical and quantum optical protocols
, the ability to perform conditional logic requires nonlinear functionality @xcite .
recent advances on this front include all - optical switching via bistability and free - carrier tuning @xcite , dynamic @xmath1 factor control for the release of photons on demand @xcite , and adiabatic frequency conversion through the perturbation of cavity modes @xcite .
the latter approach is effective for generating small frequency shifts in an optical mode , but for larger shifts , the nonlinearity....
And you have already written the first three sentences of the full article: the authors wish to acknowledge the financial support of the natural sciences and engineering research council of canada , the canadian institute for advanced research , the canadian foundation for innovation , and the canadian institute for photonic innovations ..
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Suppose that you have an abstract for a scientific paper: the object of this paper is to introduce a new and fascinating method of solving large linear equations , based on cramer s rule or gaussian elimination but employing sylvester s determinant identity in its computation process .
in addition , a scheme suitable for parallel computing is presented for this kind of generalized chi s determinant condensation processes , which makes this new method have a property of natural parallelism .
finally , some numerical experiments also confirm our theoretical analysis .
_ keywords _ : sylvester s determinant identity ; cramer s rule ; chi s method ; parallel process . .
And you have already written the first three sentences of the full article: as is well - known , how to solve effectively linear systems is a very important problem in scientific and engineering fields .
many of linear solvers have been researched such as gaussian elimination @xcite , relaxation methods @xcite , row - action iteration schemes @xcite and ( block ) krylov subspace @xcite .
recently , a low communication condensation - based linear system solver utilizing cramer s rule is presented in @xcite . as the authors stated that unique combination between cramer s rule and matrix condensation techniques yields an elegant parallel computing architectures , by constructing a binary , tree - based data flow in which the algorithm mirrors the matrix at critical points during the condensation process ..
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moreover , the accuracy and computational complexity of the proposed algorithm are similar to lu - decomposition @xcite . in this paper , we will continue research this kind of parallel algorithms and give some theoretical analysis and a generalized chi s determinant condensation process , which perfect the corresponding conclusions .
this paper is organized as follows . in second 2
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Suppose that you have an abstract for a scientific paper: a recent micromegas manufacturing technique , so called microbulk , has been developed , improving the uniformity and stability of this kind of detectors .
excellent energy resolutions have been obtained , reaching values as low as 11% fwhm at 5.9 kev in ar+5%ic@xmath0h@xmath1 .
this detector has other advantages like its flexible structure , low material budget and high radio - purity .
two microbulk detectors with gaps of 50 and 25 @xmath2 m have been characterized in argon- and neon - based mixtures with ethane , isobutane and cyclohexane .
the results will be presented and discussed .
the gain curves have been fitted to the rose - korff gain model and dependences of the electron mean free path and the threshold energy for ionization have been obtained . the possible relation between these two parameters and the energy resolution
will be also discussed . .
And you have already written the first three sentences of the full article: micromegas ( for micro mesh gaseous structure ) is a parallel - plate detector invented by i. giomataris in 1995 @xcite .
it consists of a thin metallic grid ( commonly called mesh ) and an anode plane , separated by insullated pillars .
both structures define a small gap ( between 20 and 300 @xmath2 m ) , where primary electrons generated in the conversion volume are amplified , applying moderate voltages at the cathode and the mesh . this technology has proven to have many advantages like its high granularity , good energy and time resolution , easy construction , little mass and gain stability ..
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the first detectors were built by screwing two different frames : the anode plane and the metallic grid , under which the insullated pillars were electroformed . by applying voltages to both structures ,
the intense electric field pulled down the mesh and the flatness was thus defined by the height of the pillars , with an accuracy better than 10 @xmath2 m . the good flatness and parallelism between the anode and the mesh
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Suppose that you have an abstract for a scientific paper: we discuss results of analyzing a time series of selected photospheric - optical spectra of core collapse supernovae ( ccsne ) .
this is accomplished by means of the parameterized supernovae synthetic spectrum ( ssp ) code `` synow '' .
special attention is addressed to traces of hydrogen at early phases , especially for the stripped - envelope sne ( i.e. sne ib - c ) .
a thin low mass hydrogen layer extending to very high ejection velocities above the helium shell , is found to be the most likely scenario for type ib sne .
address = osservatorio astronomico di trieste , via g.b.tiepolo 11 - i-34131 trieste - italy address=<common address for author1 and author2 > address= department of physics and astronomy , university of oklahoma , norman , ok 73019 , usa address=
european southern observatory , karl - schwarzschild - strasse 2 .
d-85478 , graching - germany .
And you have already written the first three sentences of the full article: our main goals are to identify traces of hydrogen , helium and oxygen in type ib - c sne , and to identify any systematic similarities and differences correlating with other physical properties in the ccsne family .
we have selected a sample of 45 photospheric spectra of 20 ccsne objects . in the present paper
we show results for a few objects . a detailed analysis for the complete sample has been presented recently in elmhamdi et al ..
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2006 @xcite . for the purpose of our analysis
we make use of the parameterized supernova synthetic spectrum code `` synow '' .
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Suppose that you have an abstract for a scientific paper: a brief introduction to the projector augmented wave method is given and recent developments are reviewed .
the projector augmented wave method is an all - electron method for efficient ab - initio molecular dynamics simulations with full wave functions .
it extends and combines the traditions of existing augmented wave methods and the pseudopotential approach . without sacrificing efficiency ,
the paw method avoids transferability problems of the pseudopotential approach and it has been valuable to predict properties that depend on the full wave functions . .
And you have already written the first three sentences of the full article: the main goal of electronic structure methods is to solve the schrdinger equation for the electrons in a molecule or solid , to evaluate the resulting total energies , forces , response functions and other quantities of interest . in this paper
we review the projector augmented wave ( paw ) method @xcite , an electronic structure method for ab - initio molecular dynamics with full wave functions .
the main goal of this paper is not to provide a particularly complete or detailed account of the methodology , but rather to lay out the underlying ideas ..
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a more rigorous description can be found in the original paper @xcite . density functional theory @xcite maps a description for interacting electrons onto one of non - interacting electrons in an effective potential .
the remaining one - electron schrdinger equation still poses substantial numerical difficulties : ( 1 ) in the atomic region near the nucleus , the kinetic energy of the electrons is large , resulting in rapid oscillations of the wave function that require fine grids for an accurate numerical representation . on the other hand ,
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Suppose that you have an abstract for a scientific paper: the paper examines the geometrical properties of a six - dimensional kaluza - klein type model .
they may have an impact on the model of the structure of a neutron and its excited states in the realm of one particle physics .
the statistical reason for the six - dimensionality and the stability of the solution is given .
the derivation of the weak limit approximation of the general wave mechanical ( quantum mechanical ) approach , defined in the context of losing its self - consistency ( here gravitational ) , is presented . the non self - consistent case for the klein - gordon equation
is defined .
the derivation of the energy of states and the analysis of the spin origin of the analyzed fields configuration is presented as the manifestation of both the geometry of the internal two - dimensional space and kinematics of fields inside it .
the problem of the departure from the ( gravitational ) self - consistent calculations of the metric tensor and of other fields of the configuration is discussed .
the implementation of the model for the description of a neutron and its excited states , including their spins and energies , is given .
the informational reason for the existence of the internal extra space dimensions is proposed .
example.eps gsave newpath 20 20 moveto 20 220 lineto 220 220 lineto 220 20 lineto closepath 2 setlinewidth gsave .4 setgray fill grestore stroke grestore .
And you have already written the first three sentences of the full article: the paper presents the model of an elementary particle and particularly the model of the neutral nucleon and its excited states .
since the model is atomic - like i will give a concise reminder both of the history of the models of an atom and of a neutron which still overlap until the present day .
possibly the first model of an atom in the 20-th century was kelvin s static one @xcite of a sphere of uniformly distributed positive electricity with embedded discrete electrons , followed closely by the thomson s model of `` the pudding with raisin muffins in it '' @xcite ..
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models also appeared at the end of the 19-th century , stimulated by empirical facts suggesting the complexity of the structure of the atom and its composition from smaller components @xcite .
as a result , both the theoretical intuition and the empirical indications prompted the sense of the electron to thomson .
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Suppose that you have an abstract for a scientific paper: the last few years have been witness to a proliferation of new results concerning heavy exotic hadrons .
experimentally , many new signals have been discovered that could be pointing towards the existence of tetraquarks , pentaquarks , and other exotic configurations of quarks and gluons .
theoretically , advances in lattice field theory techniques place us at the cusp of understanding complex coupled - channel phenomena , modelling grows more sophisticated , and effective field theories are being applied to an ever greater range of situations .
it is thus an opportune time to evaluate the status of the field . in the following
, a series of high priority experimental and theoretical issues concerning heavy exotic hadrons is presented . .
And you have already written the first three sentences of the full article: in 2007 the belle collaboration claimed the discovery of the z(4430 ) .
this state attracted considerable attention because it is charged and couples to charmonium , implying that the most economical interpretation of its quark content is @xmath0 .
the recent high statistics confirmation of the @xmath1 by the lhcb collaboration , and the startling demonstration of phase motion , has brought sharp focus on exotic hadronic matter ..
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indeed , the @xmath2 joins a long list of other putative exotic states , several of which have been reported within the past year : _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ @xmath3 multiquarks : : + x(3872 ) , z@xmath4(3900 ) , y(3940 ) , z@xmath4(4020 ) , z@xmath5(4050 ) , z@xmath6(4250 ) , y(4140 ) @xmath7 multiquarks : : + z@xmath8(10610 ) , z@xmath8(10650 ) other unusual states : : + d@xmath9(2317 ) , h dibaryon , y(2175 ) , y(4260 ) , y(4660 ) , y@xmath8(10888 ) , @xmath10 , @xmath11 , @xmath12 . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ although hadronic exotics such as glueballs , hybrids , and multiquark states have been long expected , the understanding of these states is primarily at the level of conjecture .
certainly , if the confirmation of the @xmath2 marks the beginning of the exploration of a new sector of matter , the current phenomenology concerning quark interactions will need to be radically overhauled .
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Suppose that you have an abstract for a scientific paper: superbubbles that result from the stellar winds and supernovae of ob associations probably play a fundamental role in the structure and energetics of the ism in star - forming galaxies .
their influence may also dominate the relationship between the different interstellar gas phases .
how do superbubbles form and evolve ? how do they affect the local and global ism ?
the magellanic clouds provide a superior opportunity to study this shell - forming activity , since both stellar content and gaseous structure can be examined in detail . here , the results of recent studies of superbubbles in the magellanic clouds are reviewed .
# 1to 0pt#1 .
And you have already written the first three sentences of the full article: it is now well - established that the kinetic feedback from massive stars creates shell structures in the interstellar medium ( ism ) .
indeed , studies of these objects in the magellanic clouds provide the best empirical understanding of this phenomenon .
these types of shells can be roughly classified into three categories ( chu 1996 ; meaburn 1980 ) , which are summarized in table 1 : `` bubbles '' and supernova remnants ( snrs ) , which result from stellar winds and supernovae ( sne ) of individual massive stars ; `` superbubbles , '' which result from the action of a few , to hundreds of , ob star winds and sne clustered in an ob association ; and `` supergiant shells , '' which have sizes of order @xmath0 kpc or more ..
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if the supergiant shells are analogously created by massive star feedback , they must be associated with starburst phenomena having total wind and sn energies of @xmath1 erg .
this review will focus on recent ( 1990 s ) studies of superbubbles in the magellanic clouds , with also a brief look at supergiant shells .
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Suppose that you have an abstract for a scientific paper: using highly efficient gpu - based simulations of the tight - binding bogoliubov - de gennes equations we solve self - consistently for the pair correlation in rhombohedral ( abc ) and bernal ( aba ) multilayer graphene by considering a finite intrinsic s - wave pairing potential .
we find that the two different stacking configurations have opposite bulk / surface behavior for the order parameter .
surface superconductivity is robust for abc stacked multilayer graphene even at very low pairing potentials for which the bulk order parameter vanishes , in agreement with a recent analytical approach . in contrast , for bernal stacked multilayer graphene , we find that the order parameter is always suppressed at the surface and that there exists a critical value for the pairing potential below which no superconducting order is achieved .
we considered different doping scenarios and find that homogeneous doping strongly suppresses surface superconductivity while non - homogeneous field - induced doping has a much weaker effect on the superconducting order parameter . for multilayer structures with hybrid stacking ( abc and aba )
we find that when the thickness of each region is small ( few layers ) , high - temperature surface superconductivity survives throughout the bulk due to the proximity effect between abc / aba interfaces where the order parameter is enhanced . .
And you have already written the first three sentences of the full article: superconducting correlations in graphene - based structures have been the focus of intensive theoretical and experimental research even before graphene became one of the most important topics in condensed matter physics .
following last decade experimental evidences reporting hints of superconductivity behavior in graphite @xcite and graphite intercalated compounds @xcite , a considerable amount of theoretical studies have been devoted to provide a clear understanding about possible mechanisms that could induce intrinsic superconducting states in single and multilayer graphene @xcite .
more recently experimental investigations have reported intriguing traces of high - temperature superconducting behavior in highly oriented pyrolytic graphite ( hopg ) samples @xcite , feeding speculations about the existence of intrinsic superconducting correlations in graphite and graphite - based compounds . despite the fact that most of these experimental evidence suggests that superconductivity in graphite compounds appears due to external causes , several theoretical studies reveal the possibility of inducing superconductivity in graphite by considering unconventional symmetry of the order parameter @xcite ..
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however , these calculations show that superconductivity becomes stable after considering disorder @xcite or high doping in the graphene layers @xcite while surface superconductivity appears to be stable in clean rhombohedral graphite in the absence of external doping @xcite .
considering that most of these calculations are based on a reduced hamiltonian or are performed within two - dimensional models , by ignoring the interplanar hopping , a numerical description of the superconducting correlation in multilayer graphene is urgently needed .
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Suppose that you have an abstract for a scientific paper: recently , it was predicted theoretically and verified experimentally that a pair of delayed and cross - polarized short laser pulses can create molecular ensembles with a well defined sense of rotation ( clockwise or counterclockwise ) .
here we provide a comparative study of the classical and quantum aspects of the underlying mechanism for linear molecules and for symmetric tops , like benzene molecules , that were used for the first experimental demonstration of the effect .
very good quantitative agreement is found between the classical description of the process and the rigorous quantum mechanical analysis at the relevant experimental conditions .
both approaches predict the same optimal values for the delay between pulses and the angle between them , and deliver the same magnitude of the induced oriented angular momentum of the molecular ensemble .
as expected , quantum and classical analysis substantially deviate when the delay between pulses is comparable with the period of quantum rotational revivals .
however , time - averaged characteristics of the excited molecular ensemble are equally good described by the these two approaches .
this is illustrated by calculating the anisotropic time - averaged angular distribution of the double - pulse excited molecules , which reflects persistent confinement of the molecular axes to the rotation plane defined by two polarization vectors of the pulses . .
And you have already written the first three sentences of the full article: laser control of molecular rotation , alignment and orientation has received significant attention in recent years ( for a review , see e. g. @xcite ) .
interest in the field has increased , mainly due to the improved capabilities to manipulate characteristics of the laser pulses ( such as time duration and temporal shape ) , which in turn leads to potential applications offered by controlling the angular distribution of molecules . since the typical rotational motion is slow ( @xmath0 ) with respect to the typical short pulse ( @xmath1 ) , effective rotational control and manipulation are in reach . during the last decade ,
temporal rotational dynamics of pulse - excited molecules was studied @xcite , and multiple pulse sequences giving rise to the enhanced alignment were suggested @xcite and realized @xcite ..
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further manipulations such as optical molecular centrifuge and alignment - dependent strong field ionization of molecules were demonstrated @xcite .
selective rotational excitation in bimolecular mixtures was suggested and demonstrated in the mixtures of molecular isotopes @xcite and molecular spin isomers @xcite .
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Suppose that you have an abstract for a scientific paper: the large majority of egret point sources remain without an identified low - energy counterpart , and a large fraction of these sources are most likely extragalactic .
whatever the nature of the extragalactic egret unidentified sources , faint unresolved objects of the same class must have a contribution to the diffuse extragalactic gamma - ray background ( egrb ) .
understanding this component of the egrb , along with other guaranteed contributions from known sources , is essential if we are to use this emission to constrain exotic high - energy physics . here , we follow an empirical approach to estimate whether a potential contribution of unidentified sources to the egrb is likely to be important , and we find that it is .
additionally , we show how upcoming glast observations of egret unidentified sources , as well as of their fainter counterparts , can be combined with glast observations of the galactic and extragalactic diffuse backgrounds to shed light on the nature of the egret unidentified sources even without any positional association of such sources with low - energy counterparts . .
And you have already written the first three sentences of the full article: the origin of the isotropic diffuse emission ( sreekumar et al .
1998 ) in energies between @xmath0 and @xmath1 , detected by the _
energetic gamma - ray experiment telescope _ ( egret ) aboard the _ compton gamma - ray observatory _.
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, remains one of the great unknowns of gev - energy astrophysics .
there are two major questions that still remain unanswered
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Suppose that you have an abstract for a scientific paper: since may 2011 the ams-02 experiment is installed on the international space station and is observing cosmic radiation .
it consists of several state - of - the - art sub - detectors , which redundantly measure charge and energy of traversing particles . due to the long exposure time of ams-02 of many years the measurement of momentum for protons and ions
is limited systematically by the spatial resolution and magnetic field strength of the silicon tracker .
the maximum detectable rigidity for protons is about 1.8 tv , for helium about 3.6 tv .
we investigate the possibility to extend the range of the energy measurement for heavy nuclei ( @xmath0 ) with the transition radiation detector ( trd ) .
the response function of the trd shows a steep increase in signal from the level of ionization at a lorentz factor @xmath1 of about 500 to @xmath2 , where the transition radiation signal saturates . for heavy ions the signal fluctuations in the trd are sufficiently small to allow an energy measurement with the trd beyond the limitations of the tracker .
the energy resolution of the trd is determined and reaches a level of about 20% for boron ( @xmath3 ) . after adjusting the operational parameters of the trd
a measurement of boron and carbon could be possible up to 5 tev / nucleon .
transition radiation , proportional tubes , space - borne detector , cosmic rays 29.40.cs , 98.70.sa , 07.87.+v = 0.5 cm .
And you have already written the first three sentences of the full article: transition radiation detectors ( trds ) have a long tradition in direct cosmic - ray measurements .
they have been utilized as threshold detectors already by e.g. @xcite and @xcite , recently by heat @xcite , and now by the ams-02 @xcite experiment .
they have been used to measure the energy of highly relativistic cosmic - ray nuclei in several other experiments : crn @xcite , tracer @xcite , and cream @xcite ..
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the light weight per area and signal response at very high energies make transition radiation detectors valuable for the direct observation of cosmic radiation on balloon - borne or space - based experiments . transition radiation ( tr )
is emitted as x - ray photons @xcite by particles with lorentz factors @xmath1 above about 1000 , when they traverse boundaries of different dielectric constants . above the threshold the tr yield increases with lorentz factor , until it reaches saturation usually above @xmath4 .
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Suppose that you have an abstract for a scientific paper: we present a 60 ks _ chandra _ acis - s observation of the thermal composite supernova remnant 3c 391 .
the southeast - northwest elongated morphology is similar to that previously found in radio and x - ray studies .
this observation unveils a highly clumpy structure of the remnant .
detailed spatially resolved spectral analysis for the small - scale features reveals that the interior gas is generally of normal metal abundance and has approached or basically reached ionization equilibrium .
the hydrogen column density increases from southeast to northwest .
three mechanisms , radiative rim , thermal conduction , and cloudlet evaporation , may all play roles in the x - ray appearance of 3c 391 as a thermal composite " remnant , but there are difficulties with each of them in explaining some physical properties .
comparatively , the cloudlet evaporation model is favored by the main characteristics such as the highly clumpy structure and the uniform temperature and density distribution over most of the remnant .
the directly measured postshock temperature also implies a young age , @xmath0 , for the remnant . the postshock gas pressure derived from the ne and sw rims , which harbor maser spots , is consistent with the estimate for the maser regions .
an unresolved x - ray source is observed on the northwest border and its spectrum is best fitted by a power - law . .
And you have already written the first three sentences of the full article: 3c 391 ( g31.9 + 0.0 ) , a supernova remnant ( snr ) with irregular morphology , has been observed in several electromagnetic bands .
radio observations with the vla reveal an elongated structure extending from the northwest ( nw ) to the southeast ( se ) , surrounded by a shell except on the se border , where it appears that the snr has broken out of a dense region into an adjacent region of lower density ( reynolds & moffett 1993 ) . in x - rays , both _ einstein _
( wang & seward 1984 ) and _ rosat _ ( rho & petre 1996 ) observations show that the centroid of the soft x - ray emission sits in the se region ..
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the _ asca _
observation reveals a hard x - ray enhancement in the nw region , and confirms the decrease in hydrogen column density across the remnant from nw to se ( chen & slane 2001 ) .
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Suppose that you have an abstract for a scientific paper: we consider the effects of an outflow on radiation escaping from the infalling envelope around a massive protostar . using numerical radiative transfer calculations , we show that outflows with properties comparable to those observed around massive stars lead to significant anisotropy in the stellar radiation field , which greatly reduces the radiation pressure experienced by gas in the infalling envelope .
this means that radiation pressure is a much less significant barrier to massive star formation than has previously been thought . .
And you have already written the first three sentences of the full article: stars with masses @xmath0 have short kelvin times that enable them to reach the main sequence while they are still accreting @xcite .
the resulting nuclear burning leads to a huge luminosity , which produces a correspondingly large radiation pressure force on dust grains suspended in the incoming gas .
this force can exceed the star s gravitational pull , possibly halting accretion and setting an upper limit on the star s final mass ..
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early spherically symmetric calculations suggested that this phenomenon sets an upper limit on stellar masses of @xmath1 , @xcite for typical galactic metallicities .
more recent non - spherical calculations have loosened that constraint by considering the role of accretion disks @xcite .
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Suppose that you have an abstract for a scientific paper: we analyse and numerically simulate the full many - body quantum dynamics of a spin-1 condensate in the single spatial mode approximation .
initially , the condensate is in a `` ferromagnetic '' state with all spins aligned along the @xmath0 axis and the magnetic field pointing along the @xmath1 axis .
in the course of evolution the spinor condensate undergoes a characteristic change of symmetry , which in a real experiment could be a signature of spin - mixing many - body interactions .
the results of our simulations are conveniently visualised within the picture of irreducible tensor operators .
cold atoms , trapped atoms , bose condensate , spinor condensate , nonequilibrium dynamics , many body theory 03.75.fi , 05.30.jp , 67.40.db , 05.70.ln .
And you have already written the first three sentences of the full article: this paper is a tribute to bruce shore s role in establishing the concept of atomic coherence and the related techniques of irreducible tensor operators @xcite .
we demonstate that this viewpoint emerges quite naturally when describing the evolution of a spinor condensate . during the past decade
condensed bose gases have energed as flexible test system to explore the rich structure of many - body physics ..
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a systematic introduction into cold gases in general and spinor condensates in particular may be found , e.g. , in the book by pethick and smith @xcite . with the development of purely optical traps @xcite
, we are in the position to hold atoms with their complete hyperfine submanifold , thus entering the regime of spinor physics @xcite .
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Suppose that you have an abstract for a scientific paper: theoretical models that describe oscillations in biological systems are often either a _ limit cycle oscillator _ , where the deterministic nonlinear dynamics gives sustained periodic oscillations , or a _ noise - induced oscillator _ , where a fixed point is linearly stable with complex eigenvalues and addition of noise gives oscillations around the fixed point with fluctuating amplitude .
we investigate how each class of model behaves under the external periodic forcing , taking the well - studied van der pol equation as an example .
we find that , when the forcing is additive , the noise - induced oscillator can show only one - to - one entrainment to the external frequency , in contrast to the limit cycle oscillator which is known to entrain to any ratio .
when the external forcing is multiplicative , on the other hand , the noise - induced oscillator can show entrainment to a few ratios other than one - to - one , while the limit cycle oscillator shows entrain to any ratio .
the noise blurs the entrainment in general , but clear entrainment regions for limit cycles can be identified as long as the noise is not too strong . * biological systems present us with a wide range of oscillators , which include cell cycles , circadian rhythms , calcium oscillations , pace maker cells , and protein responses , but it is often a challenging task to identify the minimal models behind these oscillations .
the proposed models are typically categorized into two classes : ( i ) _ limit cycle oscillator _
, where fixed points are linearly unstable and the oscillations are described by stable limit cycles sustained by nonlinearities of the system which are deterministic .
noise can be added on the top of the deterministic oscillations .
( ii ) _ noise - induced oscillator _
, where the fixed point is linearly stable for the system without noise and the system relaxes to the fixed point with damped oscillations when temporally perturbed .
addition of noise to this type of system is known to show....
And you have already written the first three sentences of the full article: biological systems present us with a bewildering fauna of oscillators : cell cycles @xcite , circadian rhythms @xcite , calcium oscillations @xcite , pace maker cells @xcite , protein responses @xcite , and so on .
sometimes , however , it is hard to see what are the minimal models behind these oscillations .
typically , the models are categorized into two classes : ( i ) _ limit cycle oscillator _ :.
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the fixed point is linearly unstable and the oscillations are described by stable limit cycles sustained by nonlinearity of the system in the deterministic case @xcite .
noise ( e.g. molecular noise due to limited number of copy numbers ) can be added on the top of the deterministic oscillations .
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Suppose that you have an abstract for a scientific paper: effects of ion mobility and positron fraction on solitary waves of envelop of laser field and potential of electrostatic field in weak relativistic electron - positron - ion plasma are investigated .
the parameter region for the existence of solitary waves is obtained analytically , and the reasonable choice of parameters is clarified . both cases of mobile and immobile ions
are considered .
it is found that the amplitudes of solitary waves in the former case are larger compared to the latter case . for small plasma density ,
the localized solitary wave solutions in terms of approximate perturbation analytical method are consistent well with that by exact numerical calculations .
however as the plasma density increases the analytical method loses its validity more and more .
the influence of the positron fraction on the amplitudes of solitary waves shows a monotonous increasing relation .
implication of our results to the particle acceleration is also discussed briefly . .
And you have already written the first three sentences of the full article: since the relativistic laser - plasma interaction was first investigated by akhiezer and polovin @xcite , many nonlinear phenomena have been found , such as solitons , vortices , double layers and so on .
in particular the discovery of electromagnetic solitary waves have attracted the attention of many people due to its robust and resilient behaviors @xcite . in past decades
many works have been performed in conventional electron - ion ( ei ) plasma @xcite . on the other hand , there exists also electron - positron - ion ( epi ) plasma in most astrophysical environments and in the laboratory @xcite , for example , in the pulsar magnetosphere @xcite , the active galactic nuclei @xcite , and the early universe @xcite ..
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recently the studies of nonlinear waves in the intense laser field interacting with epi plasma have revealed some new features @xcite .
usually the epi plasma is very different from the conventional ei plasma and also different from the pure electron - positron ( ep ) plasma @xcite .
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Suppose that you have an abstract for a scientific paper: very recently , pamela collaboration has formally reported two sets of data on positron and antiproton flux measurements done at very high energies and with unprecedented accuracy .
the reports reveal a puzzle of great topical interest and importance : it is decisively found that there is a sharp smooth rise of the positron fraction , whereas for antiproton production no such rises occur ; rather the fraction either flattens , or shows signs of falling off gradually with increasing energies .
the present work is just an attempt to decipher the riddle with the help of a host of radically new ideas about the particle - structure , the multiparticle - production mechanisms and the concept of nucleon break - downs into the constituent partons .
the application of these ideas found remarkable successes in the past ; exactly similar or more striking are the findings by the present study .
keywords : cosmic - ray interactions with the earth , positron emission , cosmic - rays high energy interactions , dark matter .
+ pacs nos . : 94.94 . , 79.20.mb .
, 13.85.tp .
, 95.35.+d
. = currsize = currsize .
And you have already written the first three sentences of the full article: since the end of october 2008 , there has been a tremendous surge of interest and excitement , and then a consequent flurry of activity among the astroparticle and high energy physicists .
the two works that shook the world of astroparticle and cosmic ray physics in the last one fortnight are the startling revelations made by adriani et al in two consecutive reports@xcite : ( i ) the pamela satellite experiment by adriani et al@xcite observed and convincingly demonstrated a sharply rising ratio of the positron flux measurements upto the studied 10 - 100gev range of ( secondary ) energy ; ( ii ) conversely , the findings on the antiproton - to - proton flux showed no such similar behaviour ; rather the ratio - values showed strong tendencies of flattening in the range of 80 - 100gev secondary energy@xcite .
this striking contrast in the nature of antiparticle - to - particle ratios poses a serious puzzle to the theorists and occupies the centre - stage of astroparticle physics domain today , stimulating more than two dozens of works within a very very short span @xcite-@xcite ..
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in fact , some previous studies@xcite had already given very careful but strong hints to the possibilities of such discoveries finally reported only very recently , for which the paradox , once formally reported , instantly caught such a large number of physicists to a feverish pitch compelling them to act .
in the domain of astroparticle physics , particularly with regard to the studies on dark matter ( dm ) and the weakly interacting massive particles ( wimps ) , searches for antimatter cosmic rays comprising positrons and antiprotons constitute a very important corner .
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Suppose that you have an abstract for a scientific paper: we present results for the momentum - resolved single - particle spectral function of the low - dimensional system tiocl in the insulating state , obtained by a combination of _ ab initio _ density functional theory ( dft ) and variational cluster ( vca ) calculations .
this approach allows to combine a realistic band structure and a thorough treatment of the strong correlations .
we show that it is important to include a realistic _ two - dimensional _ band structure of tiocl into the effective strongly - correlated models in order to explain the spectral weight behavior seen in angle - resolved photoemission ( arpes ) experiments .
in particular , we observe that the effect of the interchain couplings is a considerable redistribution of the spectral weight around the @xmath0 point from higher to lower binding energies as compared to a purely one - dimensional model treatment .
hence , our results support a description of tiocl as a two - dimensional compound with strong anisotropy and also set a benchmark on the spectral features of correlated coupled - chain systems . .
And you have already written the first three sentences of the full article: in recent years a significant amount of research has been dedicated to strongly - correlated materials with reduced dimensionality since they exhibit a large variety of fascinating dimension - related properties .
an example is the layered quantum spin system tiocl , where bilayers of ti - o are separated by cl@xmath1 ions .
this system was originally thought to be a possible candidate for a rvb superconductor upon doping@xcite because of its frustrated triangular lattice geometry ..
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later on , various experimental measurements@xcite revealed that tiocl shows in fact an anomalous spin - peierls behavior with two consecutive phase transitions .
magnetic susceptibility was initially described in terms of a one - dimensional spin-1/2 heisenberg model with a large intra - chain coupling constant @xmath2k.@xcite .
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Suppose that you have an abstract for a scientific paper: we investigate the uv continuum slope @xmath0 of a large quasar sample from sdss dr7 . by using specific continuum windows , we build two samples at lower ( @xmath1 ) and higher ( @xmath2 ) redshifts , which correspond to the continuum slopes at longer ( nuv ) and shorter ( fuv ) rest wavelength ranges respectively . overall , the average continuum slopes are @xmath3 and @xmath4 for @xmath5 and @xmath6 with similar dispersions @xmath7 . for both samples ,
we confirm the luminosity dependence of the continuum slope , i.e. , fainter quasars have redder spectra .
we further find that both @xmath5 and @xmath6 have a common upper limit ( @xmath8 ) which is almost independent of the quasar luminosity @xmath9 .
this finding implies that the intrinsic quasar continuum ( or the bluest quasar ) , at any luminosity , obey the standard thin disk model .
we propose that the other quasars with redder @xmath0 are caused by the reddening from the dust _
locally_. with this assumption , we employ the dust extinction scenario to model the observed @xmath10 relation .
we find that , a typical value of @xmath11 to @xmath12 mag ( depending on the types of extinction curve ) of the quasar _ local _ dust is enough to explain the discrepancy of @xmath0 between the observation ( @xmath13 ) and the standard accretion disk model prediction ( @xmath8 ) . .
And you have already written the first three sentences of the full article: quasar continuum in the uv - opt band is powered by the thermal energy of the accretion disk and typically written as a power - law relation @xmath14 , where @xmath0 is the continuum slope and a larger @xmath0 means bluer / flatter continuum .
the standard thin disk ( std ) model predicts a constant value @xmath15 of the slope in the uv - opt band @xcite .
however , in observation , the average @xmath0 of this band is about @xmath16 @xcite , which is far more redder than the theoretical prediction @xcite ..
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although more sophisticated disk models do predict redder / softer slopes when they include more details such as the comptonization in the disk atmosphere , the deviation from local thermodynamic equilibrium and so on , they are still not as red as the observations ( e.g. , * ? ? ?
* ) . to alleviate the discrepancy between model prediction and observations , several other explanations , e.g. ,
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Suppose that you have an abstract for a scientific paper: we investigate the effect of assisted hopping in the anderson impurity model .
we use the flow equation method , which , by means of unitary transformations , generates a sequence of hamiltonians in order to eliminate the assisted hopping terms .
this approach yields a renormalized on - site energy @xmath0 , a renormalized correlation energy @xmath1 , and other terms , which include pair hopping . for some parameter values , the initial hamiltonian flows towards an attractive anderson model .
we argue that this result implies a tendency towards local pairing fluctuations . .
And you have already written the first three sentences of the full article: the properties of magnetic impurities in metals , and of small dots attached to metallic leads share many characteristics , due to the similar role played by electron electron interactions .
the electrostatic repulsion leads to the formation of local moments@xcite , which are quenched at sufficiently low temperatures .
quantum dots are more complicated structures@xcite and an effective kondo hamiltonian can only be defined in the limit of large spacing between the electronic levels within the dot ..
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then , the main physical processes at low temperatures are due to the changes of the occupancy of the level closest to the fermi energy of the leads .
even if we assume this restriction , terms beyond the kondo hamiltonian can arise due to the finite extension and inhomogeneities of the electron states inside a mesoscopic quantum dot .
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Suppose that you have an abstract for a scientific paper: we report on the spectral analysis of circinus x1 observed by the asca satellite in march 1998 along one orbital period .
the luminosity of the source ( in the 0.1100 kev band ) ranges from @xmath0 erg s@xmath1 at the periastron ( orbital phase @xmath2 ) to @xmath3 erg s@xmath1 at orbital phase @xmath4 . from the spectral analysis and the lightcurve
we argue that cir x1 shows three states along the orbital evolution .
the first state is at the orbital phase interval 0.970.3 : the luminosity becames super eddington and a strong flaring activity is present . in this state
a shock could form in the inner region of the system due to the super eddington accretion rate , producing an outflow of ionized matter whose observational signature could be the prominent absorption edge at @xmath5 kev observed in the energy spectrum at these phases . in the second state ,
corresponding to the orbital phase interval between 0.3 and 0.7 , the accretion rate is sub eddington and we observe a weaker outflow , with smaller hydrogen column : the absorption edge is now at @xmath6 kev with an optical depth a factor of 2.5 to 6 smaller .
the third state corresponds to the orbital phase interval 0.780.97 . in this state the best fit model to the spectrum requires the presence of a partial covering component , indicating that the emission from the compact object is partially absorbed by neutral matter , probably the atmosphere of the companion star and/or the accreting matter from the companion . .
And you have already written the first three sentences of the full article: circinus x1 ( cir x1 ) is a puzzling x ray binary .
because of its rapid variability a black hole was supposed to be the compact object in this system ( toor , 1977 ) , until type i x ray bursts were detected ( tennant et _ al .
_ , 1986 a , b ) , suggesting that the compact object is a neutron star ..
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a modulation with a period of 16.6 days was observed at several wavelengths in the emission of the source .
the high stability of this period was a strong indication that it is the orbital period of cir x1 .
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12,667 |
Suppose that you have an abstract for a scientific paper: photon colliders ( , ) are based on backward compton scattering of laser light off the high energy electrons in linear colliders .
all projects of linear colliders include this option . in this paper physics motivation , possible parameters and some interaction region aspects of photon colliders
are discussed .
pacs : 29.17.+w , 41.75.ht , 41.75.lx , 13.60.fz photon collider ; linear collider ; photon photon ; gamma gamma ; electron photon ; photon electron ; compton scattering ; backscattering ; .
And you have already written the first three sentences of the full article: linear colliders , lc , at the center of mass energy from 100 gev up to several tev will be one of the central instruments in experimental high energy physics in the next 2 to 3 decades .
four projects are being developed : nlc @xcite , tesla @xcite , jlc @xcite , and clic @xcite .
tesla team has published in march 2001 the technical design of the superconductiing linear collider on the energy 90800 gev @xcite ..
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the unique feature of the @xmath0 linear colliders is the possibility to construct on its basis a photon collider using the process of the compton backscattering of laser light off the high energy electrons @xcite .
this option is considered now for all linear colliders projects : nlc @xcite ; tesla @xcite ; jlc @xcite ; clic @xcite . in the following
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12,668 |
Suppose that you have an abstract for a scientific paper: gamma rays with energy above 10 gev interact with optical - uv photons resulting in pair production .
therefore , a large sample of high redshift sources of these gamma rays can be used to probe the extragalactic background starlight ( ebl ) by examining the redshift dependence of the attenuation of the flux above 10 gev .
glast , the next generation high - energy gamma - ray telescope , will have the unique capability to detect thousands of gamma - ray blazars to redshifts of at least @xmath0 , with sufficient angular resolution to allow identification of a large fraction of their optical counterparts . by combining established models of the gamma - ray blazar luminosity function , two different calculations of the high energy gamma - ray opacity due to ebl absorption , and the expected glast instrument performance to produce simulated fluxes and redshifts for the blazars that glast would detect ,
we demonstrate that these gamma - ray blazars have the potential to be a highly effective probe of the optical - uv ebl . .
And you have already written the first three sentences of the full article: in the last few years the study of galaxy formation and evolution has seen tremendous progress .
instruments at many different wavelengths have begun to penetrate to the relevant redshifts .
one important prediction of models of galaxy formation and evolution is the nature of the radiation field produced by star formation ..
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one way to probe the resulting extragalactic background light ( ebl ) is to measure the attenuation through pair production of gamma rays from distant sources .
however , without a large sample of sources distributed across a wide redshift range , it is difficult to distinguish between extragalactic absorption and characteristics peculiar to individual sources . the large area telescope ( lat ) instrument on the gamma - ray large area space telescope ( glast ) will observe gamma rays with energies from 20 mev to @xmath1 gev .
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Suppose that you have an abstract for a scientific paper: fitting models for non - poisson point processes is complicated by the lack of tractable models for much of the data . by using large samples of independent and identically distributed realizations and statistical learning ,
it is possible to identify absence of fit through finding a classification rule that can efficiently identify single realizations of each type .
the method requires a much wider range of descriptive statistics than are currently in use , and a new concept of model fitting which is derive from how physical laws are judged to fit data . .
And you have already written the first three sentences of the full article: the statistical analysis of point processes is well understood , provided that the data is modeled by a homogeneous or inhomogeneous poisson point process .
if there are interactions among the points , the models become more complicated and so does the inference . in the case of many sets of data , using tests to see if probabilistically defined models fit is very difficult , both in terms of finding models to fit and tests which are sensible . in the absence of either , there is little that can be done using existing theory . taking a more experimental approach based on statistical learning has the potential to circumvent these difficulties . for the most part
, the non - poisson point processes will be assumed to be regular point processes , in which no two points can be any closer than some distance @xmath0 ..
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the methods developed here could be applied to any point process that defies modeling by a straightforward probabilistic model .
the methods discussed in this paper could be applied to four different types of problem in point process inference . 1
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Suppose that you have an abstract for a scientific paper: we calculate the grand canonical partition function at the one - loop level for scalar quantum electrodynamics at finite temperature and chemical potential .
a classical background charge density with a charge opposite that of the scalars ensures the neutrality of the system . for low density systems we find evidence of a first order phase transition .
we find upper and lower bounds on the transition temperature below which the charged scalars form a condensate .
a first order phase transition may have consequences for helium - core white dwarf stars in which it has been argued that such a condensate of charged helium-4 nuclei could exist .
0.9 cm * phase transitions of charged scalars * * at finite temperature and chemical potential * 0.7 cm rachel a. rosen _ oskar klein centre for cosmoparticle physics , department of physics _ _ stockholm university , albanova se-10691 , stockholm , sweden _ 0.5 cm .
And you have already written the first three sentences of the full article: there are two ways in which bosons can condense : via bose - einstein condensation or via spontaneous symmetry breaking .
bose - einstein condensation occurs due to a conserved current associated with the bosons . since the total number of particles ( or other conserved quantity )
can then be fixed , at low temperatures and high densities energy levels become overcrowded . " as a result the charge of the system must be stored the zero - momentum ground state . in theories with spontaneous symmetry breaking , a conserved current is not responsible for the condensation . instead , the interactions of the bosons make it energetically favorable for them to condense . in this paper.
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we consider the first mechanism , bose - einstein condensation , in the case that there is both a global @xmath0 symmetry corresponding to a conserved scalar number density as well as a local gauge symmetry .
in particular , we consider scalar quantum electrodynamics in which the conserved scalar current allows us to introduce a nonzero chemical potential for the scalars . to ensure the neutrality of the system we consider scalars that reside in a constant background charge density of the opposite charge .
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Suppose that you have an abstract for a scientific paper: we consider a point particle moving in a random distribution of obstacles described by a potential barrier .
we show that , in a weak - coupling regime , under a diffusion limit suggested by the potential itself , the probability distribution of the particle converges to the solution of the heat equation .
the diffusion coefficient is given by the green - kubo formula associated to the generator of the diffusion process dictated by the linear landau equation . .
And you have already written the first three sentences of the full article: the evolution of the density of a test particle moving in a configuration of obstacles is described at mesoscopic level by linear kinetic equations .
they are obtained from the microscopic hamiltonian dynamics under a kinetic scaling of space and time , namely @xmath0 , @xmath1 and a suitable rescaling of the density of the obstacles and the intensity of the interaction . accordingly to the resulting frequency of collisions , the mean free path of the particle can have or not macroscopic length and different kinetic equations arise .
typical examples are the linear boltzmann equation and the linear landau equation.
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. the first rigorous result appeared in 1969 in the paper of gallavotti @xcite , who derived a linear boltzmann equation starting from a random distribution of fixed hard scatterers in the boltzmann - grad limit ( low density ) , namely when the number of collisions is small , thus the mean free path of the particle is macroscopic .
the result was improved by spohn @xcite . in the weak - coupling regime ,
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Suppose that you have an abstract for a scientific paper: proton stability is guaranteed in the mssm by assuming a discrete symmetry , r - parity . however , there are additional r - parity conserving higher dimensional operators which violate lepton and baryon numbers and induce fast proton decay . here
we study the possibility that all renormalizable , as well as the most dangerous non - renormalizable , r - parity violating operators are forbidden by a flavor symmetry , providing a common origin for fermion mixing and proton and dark matter stability .
we propose a specific model based on the @xmath0 discrete symmetry . .
And you have already written the first three sentences of the full article: in july 2012 , the atlas @xcite and cms @xcite collaborations announced the discovery of a new boson , with a mass in the @xmath1 gev ballpark .
although detailed studies of its properties need to be done in order to confirm its identity , one is tempted to interpret this new particle in terms of the long - awaited higgs boson . in any case , this constitutes a decisive breakthrough in high energy physics that , once correctly understood , will surely shed light on the dynamics of the electroweak scale .
the discovery of the higgs boson , and the measurement of its mass , reminds us a long - standing theoretical problem in particle physics : the famous hierarchy problem @xcite ..
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this can be expressed as the high sensitivity that fundamental scalars have to physics at high energies .
unless one accepts a very precise fine - tuning of the parameters of the theory , the higgs mass is naturally pushed to those high energies , distabilizing the electroweak scale .
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Suppose that you have an abstract for a scientific paper: let @xmath0 be the total gain in @xmath1 repeated st .
petersburg games .
it is known that @xmath2 converges in distribution to a random element @xmath3 along subsequences of the form @xmath4 with @xmath5 and @xmath6 $ ] .
we determine the hausdorff and box - counting dimension of the range and the graph for almost all sample paths of the stochastic process @xmath7}$ ] .
the results are compared to the fractal dimension of the corresponding limiting objects when gains are given by a deterministic sequence initiated by hugo steinhaus . .
And you have already written the first three sentences of the full article: the famous st . petersburg game is easily formulated as a simple coin tossing game .
the player s gain @xmath8 in a single game can be expressed by means of the stopping time @xmath9 of repeated independent tosses @xmath10 of a fair coin until it first lands heads . for a sequence of gains
@xmath11 in independent st ..
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petersburg games the partial sum @xmath12 denotes the total gain in the first @xmath1 games . to find a fair entrance fee for playing the game
is commonly called the st .
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Suppose that you have an abstract for a scientific paper: binary and multiple systems constitute more than half of the total stellar population in the solar neighborhood @xcite .
their frequent occurrence as well as the fact that more than 70 @xcite planets have already been discovered in such configurations - most noteably the telluric companion of @xmath0 cen b @xcite - make them interesting targets in the search for habitable worlds .
recent studies @xcite have shown , that despite the variations in gravitational and radiative environment , there are indeed circumstellar regions where planets can stay within habitable insolation limits on secular dynamical timescales . in this article
we provide habitable zones for 19 near s - type binary systems from the hipparchos and wds catalogues with semimajor axes between 1 and 100 au .
hereby , we accounted for the combined dynamical and radiative influence of the second star on the earth - like planet . out of the 19 systems presented , 17 offer dynamically stable habitable zones around at least one component .
the 17 potentially habitable systems contain 5 f , 3 g , 7 k and 16 m class stars .
as their proximity to the solar system ( @xmath1 pc ) makes the selected binary stars exquisite targets for observational campaigns , we offer estimates on radial velocity , astrometric and transit signatures produced by habitable earth - like planets in eccentric circumstellar orbits .
[ firstpage ] astrobiology habitable zones binaries .
And you have already written the first three sentences of the full article: the discovery and confirmation of terrestrial bodies orbiting other stars ( e.g. @xcite ) has generated enormous public as well as scientific interest .
it has shown that after a mere two decades of exoplanetary research finding potentially habitable worlds around other stars seems to be almost within our grasp .
close - by stars and stellar systems are thereby premium targets , as they tend to offer reasonable signal to noise ratios ( snrs ) for photometry and radial velocity as well as comparatively large astrometric amplitudes @xcite . as more than half of the stars in the solar neighborhood are members of binary or multiple systems @xcite , it is not surprising that more than 70 planets in or around binary - stars have been discovered @xcite despite the current observational focus on single star systems . even - though nasa s _ kepler _ mission has been quite successful in finding circumbinary planets ( e.g. @xcite ) we will focus on binary - star systems with potential _.
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habitable zones ( hzs ) in this study .
in fact , most of the planets discovered in double stars are in these so - called s - type configurations @xcite , where the planet orbits one star only .
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Suppose that you have an abstract for a scientific paper: we have developed a grid of chemical evolution models applied to dwarf isolated galaxies , using @xcite yields .
the input data enclose different star formation efficiencies , galaxy mass and collapse time values .
the result is a wide collection of solutions that vary from objects with low metallicity and great amount of gas , to those with little gas and high metallicity .
no environmental effects like tidal or galactic winds have been treated , so these objects are expected to be close to field dwarf galaxies , more than cluster ones .
we have studied the time evolution of the abundance of oxygen and nitrogen and the amount of gas , related to their star formation history , as well as the possibility of gas losses by sn winds . .
And you have already written the first three sentences of the full article: according to the hierarchical model , dwarf galaxies are the building blocks of larger structures , consequently their study is crucial to understand galaxy formation and evolution .
although dwarf galaxies are the most numerous objects in the universe , there are some questions that remain apparently unresolved . in fact three of them deal with the same idea about their evolution .
the first question is related to observed mass metallicity relation : do these objects have a metallicity according to what we can expect ? ..
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in other words : why less massive objects have lower metallicity ?
since @xcite many efforts have been devoted to explain it .
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12,676 |
Suppose that you have an abstract for a scientific paper: a distinguishable and observable physical property of naked singular regions of the spacetime formed during a gravitational collapse has important implications for both experimental and theoretical relativity . we examine here whether energy can escape physically from naked singular regions to reach either a local or a distant observer within the framework of general relativity .
we find that in case of imploding null dust collapse scenarios field outgoing singular null geodesics including the cauchy horizon can be immersed between two vaidya spacetimes as null boundary layers with non vanishing positive energy density .
thus energy can transported from the naked singularity to either a local or a distant observer . and
example illustrating that similar considerations can be applied to dust models is given . .
And you have already written the first three sentences of the full article: a star with sufficient remnant mass ( @xmath0 ) , on completion of its nuclear fuel cycle , must enter the phase of a continuous gravitational collapse . once the nuclear fuel is exhausted gravitational forces become all powerful and hence star s internal pressure can not sustain the equilibrium resulting in a continued collapse @xcite . in the late stages of collapse
the gravitational forces become dominant and the physics of collapse is determined mainly by the theory of general relativity . under quite general and physical situations general relativity predicts that such a collapse must end in a singularity , i.e. , a region of spacetime with extreme curvatures @xcite .
physically one could describe singularity as a region of space with vanishing volume and unbounded gravitational forces ..
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general relativity , however , does not say anything about the nature or physical properties of such a singularity .
this is partially due to the fact that mathematical structure breaks down preventing analysis at and beyond the singularity .
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Suppose that you have an abstract for a scientific paper: we propose a setup comprising an arbitrarily large array of static qubits ( sqs ) , which interact with a flying qubit ( fq ) .
the sqs work as a quantum register , which can be written or read - out by means of the fq through quantum state transfer ( qst ) .
the entire system , including the fq s motional degrees of freedom , behaves quantum mechanically .
we demonstrate a strategy allowing for selective qst between the fq and a single sq chosen from the register .
this is achieved through a perfect mirror located beyond the sqs and suitable modulation of the inter - sq distances . .
And you have already written the first three sentences of the full article: a prominent paradigm in quantum information processing ( qip ) @xcite is to employ flying qubits ( fqs ) and static qubits ( sqs ) as carriers and registers of quantum information , respectively @xcite .
key to such idea is the ability to write and read - out the information content of a sq by means of a fq . by this , here we mean that efficient quantum state transfer ( qst ) between these two types of qubits must be possible on demand . in this picture
, _ control over memory allocation _ appears a desirable if not indispensable requirement ..
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for instance , one can envisage the situation where only one or a few sqs are available , e.g. because the remaining ones are encoding some information to save . on the other hand , one may need to carry away only the information saved in certain specific sqs .
alternatively , only a restricted area of the register of sqs may be interfaced with some external processing network where one would like to eventually convey information or from which output data are to be received . in such cases , the ability of _ selecting _ the exact location where the information content of the fq should be uploaded or downloaded is demanded . ideally , according to the schematics in fig .
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Suppose that you have an abstract for a scientific paper: two numbers are spectral equivalent if they have the same length spectrum .
we show how to compute the equivalence classes of this relation .
moreover , we show that these classes can only have either @xmath0 or infinitely many elements . .
And you have already written the first three sentences of the full article: some numbers can be written as a sum of consecutive integers , for example , @xmath1 but some can not , for example , @xmath2 .
the following is a beautiful characterization of this phenomenon : [ th : po2 ] a number is a sum of consecutive integers if and only if it is not a power of 2 .
proofs of theorem [ th : po2 ] can be found in @xcite . to simplify the subsequent discussion ,.
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let us call a sequence of consecutive natural numbers a * decomposition of @xmath3 * if its terms sum to @xmath4 .
the * length * of a decomposition is the number of terms in the decomposition and the * parity * of a decomposition is the parity of its length . a * trivial * decomposition is a decomposition of length @xmath5 .
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Suppose that you have an abstract for a scientific paper: the capacity of classical channels is convex .
this is not the case for the quantum capacity of a channel : the capacity of a mixture of different quantum channels exceeds the mixture of the individual capacities and thus is non - convex . here
we show that this effect goes beyond the quantum capacity and holds for the private and classical environment - assisted capacities of quantum channels . .
And you have already written the first three sentences of the full article: classical information theory was laid down by shannon in the nineteen forties to characterize the ultimate rate at which one could hope to transmit classical information over a classical communication channel : the channel capacity .
surprisingly in retrospective , not only it achieved its purpose but the capacity of classical channels turned out to comply with all the properties that one could expect for such a quantity : it can be efficiently computed @xcite and it gauges the usefulness of the channel in the presence of any additional contextual channel .
it is a natural consequence of additivity and convexity of the capacity in the set of channels . with quantum channels complemented by various auxiliary resources ,.
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a whole new range of communication tasks became feasible .
notably , they allow for the transmission of quantum and private classical communication tasks beyond the reach of classical channels . for most of these tasks ,
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Suppose that you have an abstract for a scientific paper: we have investigated the evolution of the shell structure of nuclei in going from the r - process path to the neutron drip line within the framework of the relativistic hartree - bogoliubov ( rhb ) theory . by introducing the quartic self - coupling of @xmath0 meson in the rhb theory in addition to the non - linear scalar coupling of @xmath1 meson ,
we reproduce the available data on the shell effects about the waiting - point nucleus @xmath2zn . with this approach
, it is shown that the shell effects at @xmath3 in the inaccessible region of the r - process path become milder as compared to the lagrangian with the scalar self - coupling only .
however , the shell effects remain stronger as compared to the quenching exhibited by the hfb+skp approach .
it is also shown that in reaching out to the extreme point at the neutron drip line , a terminal situation arises where the shell structure at the magic number is washed out significantly .
= 10000 .
And you have already written the first three sentences of the full article: a knowledge of the shell effects near the r - process path is important to discerning astrophysical scenario of nucleosynthesis @xcite .
the question whether the shell effects near the drip lines are strong or do quench has become crucial to understanding the nucleosynthesis of heavy nuclei .
the @xmath3 nuclei at the r - process path are assumed to play a significant role in providing nuclear abundances about @xmath4 . since nuclei contributing to this peak are extremely neutron - rich and are not accessible experimentally , it has not been possible to ascertain the nature of the shell effects in the vicinity of the r - process path ..
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due to the lack of experimental data , there prevail conflicting view points @xcite on the strength of the shell effects near the r - process path . in ref .
@xcite the shell effects in the region of the r - process path at @xmath3 were studied on the basis of the relativistic mean - field ( rmf ) theory using a successful nuclear interaction .
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Suppose that you have an abstract for a scientific paper: the mit and cxc acis teams have explored a number of measures to ameliorate the effects of radiation damage suffered by the acis fi ccds .
one of these measures is a novel ccd read - out method called `` squeegee mode '' .
a variety of different implementations of the squeegee mode have now been tested on the i0 ccd . our results for
the fitted fwhm at al - k@xmath0 and mn - k@xmath0 clearly demonstrate that all the squeegee modes provide improved performance in terms of reducing cti and improving spectral resolution .
our analysis of the detection efficiency shows that the so - called squeegee modes `` vanilla '' and `` maximum observing efficiency '' provide the same detection efficiency as the standard clocking , once the decay in the intensity of the radioactive source has been taken into account .
the squeegee modes which utilize the slow parallel transfer ( `` maximum spectral resolution '' , `` maximum angular resolution '' , and `` sub - array '' ) show a significantly lower detection efficiency than the standard clocking . the slow parallel transfer squeegee modes exhibit severe grade migration from flight grade 0 to flight grade 64 and a smaller migration into asca g7 .
the latter effect can explain some of the drop in detection efficiency .
there are a few observational penalities to consider in using a squeegee mode . utilizing
any squeegee mode causes a loss of fov near the aimpoint ( 4 to 16@xmath1 strips along the full length of the ccds ) , as well as the attendant dead - time increase .
secondly , the cost of the software implementation and its testing will be significant .
lastly , each squeegee mode `` flavor '' would require lengthy , mode - specific calibration observations .
therefore , since an efficacious , ground - based cti corrector algorithm is now available ( see paper by plucinsky , townsley , _ et al . _ in this proceedings ) , a scientific judgment will have to be made to determine which , if any , squeegee modes should be developed and calibrated....
And you have already written the first three sentences of the full article: the acis operations team , combining elements from the cxc and the acis mit@xmath2ipi team , has been developing and testing the new squeegee modes since the spring of 2000 . in squeegee mode ,
charge is collected in the top few rows of the ccd and then swept across the imaging array once per readout , thus filling some of the radiation - induced electron traps that cause degraded performance .
the development of a novel method of reading out the acis ccds was first developed and tested on ground ccds that are similar to flight ccds ( see prigozhin , _ et al . _.
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2000 for a characterization of the radiation damage of acis ccds ) .
this new mode ameliorates some of the effects caused by the radiation damage suffered early in the mission by the fi ccds . for a more comprehensive discussion on the design and clocking method of squeegee mode , see bautz and kissel ( 2000 ) .
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Suppose that you have an abstract for a scientific paper: rare event simulation and estimation for systems in equilibrium are among the most challenging topics in molecular dynamics . as was shown by jarzynski and others , nonequilibrium forcing can theoretically be used to obtain equilibrium rare event statistics .
the advantage seems to be that the external force can speed up the sampling of the rare events by biasing the equilibrium distribution towards a distribution under which the rare events is no longer rare . yet algorithmic methods based on jarzynski s and related results often fail to be efficient because they are based on sampling in path space .
we present a new method that replaces the path sampling problem by minimization of a cross - entropy - like functional which boils down to finding the optimal nonequilibrium forcing .
we show how to solve the related optimization problem in an efficient way by using an iterative strategy based on milestoning . .
And you have already written the first three sentences of the full article: molecular dynamics ( md ) simulations allow for analysis and understanding of the dynamical behaviour of molecular systems .
however realistic simulations on timescales beyond microseconds are still infeasible even on the most powerful general purpose computers , which renders the md - based analysis of many biological equilibrium processes , that are often rare compared to the characteristic time scale of the system and hence require prohibitively long simulations , impossible .
the hallmark of these rare events is that the average waiting time between the events is orders of magnitude longer than the timescale of the switching event itself ..
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thus rare event simulation and estimation are among the most challenging topics in molecular dynamics .
the molecular dynamics literature on rare event simulations is rich . since direct numerical equilibrium simulation
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Suppose that you have an abstract for a scientific paper: we consider the energy release associated with first - order transition by gibbs construction and present such energy release as an accumulation of a series of tiny binding energy differences between over - compressed states and stable ones .
universal formulae for the energy release from one homogeneous phase to the other is given .
we find the energy release per converted particle varies with number density . as an example , the deconfinement phase transition at supranuclear densities is discussed in detail .
the mean energy release per converted baryon is of order 0.1mev in rmf theory and mit bag descriptions for hadronic matter and strange quark matter for a wider parameter region .
pacs numbers : 97.60.jd , 05.70.fh , 12.38.mh , 64.60.-i .
And you have already written the first three sentences of the full article: glendenning@xcite had realized the essentially different character of a first - order transition in simple system possessing a single conserved quantity and complex one having more than one conserved charge .
one of the most remarkable features of a simple system is the constancy of the pressure during the transition from one homogeneous phase to the other .
such phase transition is the typical description of first - order one in textbook ..
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the properties of the transition are quite different in complex .
the pressure varies continuously with the proportion of two pure phases in equilibrium .
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Suppose that you have an abstract for a scientific paper: a low - dispersion keck i spectrum of sn 1980k taken in august 1995 ( t = 14.8 yr after explosion ) and a november 1997 mdm spectrum ( t = 17.0 yr ) show broad 5500 km s@xmath0 emission lines of h@xmath1 , [ o i ] 6300,6364 , and [ o ii ] 7319,7330 .
weaker but similarly broad lines detected include [ fe ii ] 7155 , [ s ii ] 4068,4072 , and a blend of [ fe ii ] lines at 50505400 .
the presence of strong [ s ii ] 4068,4072 emission but a lack of [ s ii ] 6716,6731 emission suggests electron densities of 10@xmath2 @xmath3 . from the 1997 spectra
, we estimate an h@xmath1 flux of @xmath4 erg @xmath5 s@xmath0 indicating a 25% decline from 19871992 levels during the period 1994 to 1997 , possibly related to a reported decrease in its nonthermal radio emission .
a may 1993 mmt spectrum of sn 1979c ( t = 14.0 yr ) shows a somewhat different spectrum from that of sn 1980k .
broad , 6000 km s@xmath0 emission lines are also seen but with weaker h@xmath1 , stronger [ o iii ] 4959,5007 , more highly clumped [ o i ] and [ o ii ] line profiles , no detectable [ fe ii ] 7155 emission , and a faint but very broad emission feature near 5750 .
a 1997 _ hst _ faint object spectrograph , near - uv spectrum ( 2200 4500 ) shows strong lines of c ii ] 2324,2325 , [ o ii ] 2470 , and mg ii 2796,2803 along with weak [ ne iii ] 3969 , [ s ii ] 4068,4072 and [ o iii ] 4363 emissions .
the uv emission lines show a double - peak profile with the blueward peak substantially stronger than the red , suggesting dust extinction within the expanding ejecta ( e[b v ] = @xmath6 mag ) .
the lack of detectable [ o ii ] 3726,3729 emission together with [ o iii ] ( 4959 + 5007)/4363 @xmath7 4 imply electron densities 10@xmath8 @xmath3 .
these new sne ii - l spectra show general agreement with the lines expected in a circumstellar interaction model , but the specific models that are available show several differences with the observations .
high electron densities ( 10@xmath9....
And you have already written the first three sentences of the full article: the type ii linear supernova ( sn ii - l ) sn 1980k in ngc 6946 reached a peak brightness of v = 11.4 in november 1980 ( see barbon , ciatti , & rosino 1982 ; @xcite and references therein ) . despite a steadily declining flux through 1982 ( @xcite ) , faint h@xmath1 emission from sn 1980k was detected in 1987 through narrow passband imaging ( @xcite , hereafter fb90 ) .
low - disperson optical spectra obtained in 1988 and 1989 showed broad , 6000 km s@xmath0 h@xmath1 and [ o i ] 6300,6364 emission , along with weaker line emission from [ ca ii ] 7291,7324 and/or [ o ii ] 7319,7330 , [ o iii ] 4959,5007 , and [ fe ii ] 7155 ( fb90 ; @xcite ; leibundgut et al .
monitoring of its optical flux from 1988 through 1992 indicated a nearly constant luminosity ( leibundgut , kirshner , & porter 1993 ; fesen , & matonick 1994 , hereafter fm94 ) ..
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following the optical recovery of sn 1980k , a handful of other sne ii - l have been optically detected 7 25 yr after maximum light .
these include sn 1986e in ngc 4302 ( @xcite ) , sn 1979c in m100 ( @xcite ) , and sn 1970
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Suppose that you have an abstract for a scientific paper: we use a new telescope concept , the dragonfly telephoto array , to study the low surface brightness outskirts of the spiral galaxy m101 .
the radial surface brightness profile is measured down to @xmath0magarcsec@xmath1 , a depth that approaches the sensitivity of star count studies in the local group .
we convert surface brightness to surface mass density using the radial @xmath2 color profile .
the mass density profile shows no significant upturn at large radius and is well - approximated by a simple bulge + disk model out to @xmath3kpc , corresponding to 18 disk scale lengths . fitting a bulge + disk + halo model we find that the best - fitting halo mass @xmath4 .
the total stellar mass of m101 is @xmath5 , and we infer that the halo mass fraction @xmath6 . this mass fraction is lower than that of the milky way ( @xmath7 ) and m31 ( @xmath8 ) .
all three galaxies fall below the @xmath9 @xmath10 relation predicted by recent cosmological simulations that trace the light of disrupted satellites , with m101 s halo mass a factor of @xmath11 below the median expectation . however , the predicted scatter in this relation is large , and more galaxies are needed to better quantify this possible tension with galaxy formation models .
dragonfly is well suited for this project : as integrated - light surface brightness is independent of distance , large numbers of galaxies can be studied in a uniform way . .
And you have already written the first three sentences of the full article: star counts in the direction of the andromeda galaxy ( m31 ) have shown that it is embedded in a large , complex stellar halo with significant substructure ( ibata et al .
2001 ; mcconnachie et al .
such halos are thought to be comprised of the debris of shredded satellite galaxies ( searle & zinn 1978 ; newberg et al . 2002 ; mcconnachie et al ..
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2009 ) , and their existence around luminous spiral galaxies is a central prediction of galaxy formation models ( bullock & johnston 2005 ; abadi , navarro , & steinmetz 2006 ; purcell , bullock , & zentner 2008 ; johnston et al .
2008 ; cooper et al . 2010
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Suppose that you have an abstract for a scientific paper: we investigate the electric and thermal transport properties in a disordered weyl ferromagnet on an equal footing by using the keldysh formalism in curved spacetime .
in particular , we calculate the anomalous thermal hall conductivity , which consists of the kubo formula and the heat magnetization , without relying on the wiedemann - franz law .
we take nonmagnetic impurities into account within the self - consistent @xmath0-matrix approximation and reproduce the wiedemann - franz law for the extrinsic fermi - surface and intrinsic fermi - sea terms , respectively .
this is the first step towards a unified theory of the anomalous hall effect at finite temperature , where we should take into account both disorder and interactions . .
And you have already written the first three sentences of the full article: the thermal hall effect ( the ) is a heat analog of the hall effect , namely , the heat current flows perpendicular to a temperature gradient when the time - reversal symmetry is broken .
recently , the the has been experimentally studied in ferromagnetic metals @xcite , ferromagnetic insulators @xcite , and frustrated magnets in a magnetic field @xcite . in ferromagnetic metals @xcite ,
the the is utilized in order to investigate effects of inelastic scattering on the anomalous hall effect ( ahe ) . according to the wiedemann - franz law , the lorenz ratio @xmath1 coincides with the universal lorenz number @xmath2 at @xmath3 , but decreases as temperature increases and inelastic scattering dominates elastic scattering . here.
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@xmath4 and @xmath5 are the electric and thermal ( hall ) conductivities , respectively , and @xmath0 is temperature . therefore the lorenz ratio is a quantitative indicator of inelastic scattering . in ferromagnetic insulators @xcite and frustrated magnets @xcite ,
the the is a powerful probe of chargeless spin excitations .
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Suppose that you have an abstract for a scientific paper: we present first results on the ca isotopic abundances derived from the high resolution mass time - of - flight ( mtof ) spectrometer of the charge , element , and isotope analysis system ( celias ) experiment on board the solar and heliospheric observatory ( soho ) .
we obtain isotopic ratios @xmath0ca/@xmath1ca @xmath2 ( @xmath3 ) and @xmath0ca/@xmath4ca @xmath2 ( @xmath5 ) , consistent with terrestrial values .
this is the first in situ determination of the solar wind calcium isotopic composition and is important for studies of stellar modeling and solar system formation since the present - day solar ca isotopic abundances are unchanged from their original isotopic composition in the solar nebula . .
And you have already written the first three sentences of the full article: the main motivation to study solar wind composition is to obtain information on the isotopic composition of elements in the sun .
this is important because the sun constitutes @xmath6 of solar system matter , and for most elements the solar composition could provide the most reliable information on the composition of the primordial solar nebula .
because nowhere in the sun have temperatures ever been high enough to alter isotopic abundances of heavy elements by nuclear reactions , solar ca is thought to reflect the original isotopic composition in the solar nebula . yet , most of what is known of solar isotopic abundances is inferred from terrestrial and from meteoritic abundances with a few exceptions : recently , the isotopic composition of solar wind magnesium , the first analysis of the isotopic abundances of a refractive element in solar matter measured in situ with the spacecraft borne mass spectrometer wind / mass , has been reported ( @xcite ) ..
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the solar isotopic composition of the volatile noble gases helium and neon have been determined in situ with the apollo foil experiments ( @xcite ) . in situ measurements with celias / mtof ( @xcite ) on board soho
have confirmed that the solar neon isotopic composition differs significantly from the terrestrial and meteoritic abundances .
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Suppose that you have an abstract for a scientific paper: from a coarse - grained perspective the motif of a self - activating species , activating a second species which acts as its own repressor , is widely found in biological systems , in particular in genetic systems with inherent oscillatory behavior .
here we consider a specific realization of this motif as a genetic circuit , in which genes are described as directly producing proteins , leaving out the intermediate step of mrna production .
we focus on the effect that inherent time scales on the underlying fine - grained scale can have on the bifurcation patterns on a coarser scale in time .
time scales are set by the binding and unbinding rates of the transcription factors to the promoter regions of the genes .
depending on the ratio of these rates to the decay times of the proteins , the appropriate averaging procedure for obtaining a coarse - grained description changes and leads to sets of deterministic equations , which differ in their bifurcation structure .
in particular the desired intermediate range of regular limit cycles fades away when the binding rates of genes are of the same order or less than the decay time of at least one of the proteins .
our analysis illustrates that the common topology of the widely found motif alone does not necessarily imply universal features in the dynamics . .
And you have already written the first three sentences of the full article: [ intro_sec ] a frequently found motif in biological networks , in particular in genetic networks , is the combination of a positive feedback loop in which one species ( @xmath0 ) activates itself , and a negative feedback loop , in which the first species activates its own repressor , the second species ( @xmath1 ) . in connection with genetic systems
such motifs are realized in the camp signalling system in the slime mold dictyosthelium discoideum @xcite , in the embryonic division control system @xcite , the mapk - cascade @xcite , or in the circadian clock @xcite . from the viewpoint of theoretical physics one
is interested in dynamical features that are in common to the many different dynamical realizations of this motif ..
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one common feature is certainly the occurrence of regular oscillations and the possibility of excitable behavior for an appropriate choice of parameters , and these features are captured already by a deterministic description in form of the bistable frustrated unit , considered in @xcite and references therein
. it should be emphasized , however , that the different realizations do not only differ by the biological systems in which they are realized , but also by the degree in which this representation as two coupled loops as shown in fig .
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Suppose that you have an abstract for a scientific paper: we present the analysis of the mean switching time and its standard deviation of short overdamped josephson junctions , driven by a direct current and a periodic signal .
the effect of noise enhanced stability is investigated .
it is shown that fluctuations may both decrease and increase the switching time . .
And you have already written the first three sentences of the full article: the investigation of nonlinear properties of josephson junctions ( jjs ) is very important due to their broad applications in logic devices .
recently , a lot of attention was payed to josephson logic devices with high damping . in papers [ rylyakov @xmath0 likharev , 1999 ; bunyk _ et al . _ ,
2001 ] a description and analysis of the entire system of single flux quantum logic elements are presented ..
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the noise properties of systems consisting of many elements may be well understood from the noise properties of a single jj .
the processes occurring in such devices are based on a reproduction of quantum pulses due to @xmath1 spasmodic change of the phase difference of the overdamped jjs .
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Suppose that you have an abstract for a scientific paper: we review status and perspectives of the search for the light eta - mesic nuclei using cosy-11 , wasa - at - cosy and cosy - tof detector systems . .
And you have already written the first three sentences of the full article: the negatively charged pions and kaons can be trapped in the coulomb potential of atomic nucleus forming so called pionic ( kaonic ) atoms .
observations of such atoms allows for studies of strong interaction of pions and kaons with atomic nuclei on the basis of shifts and widths of the energy levels @xcite .
it is also conceivable that a neutral meson could be bound to a nucleus . in this case.
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the binding is exclusively due to the strong interaction and hence such object can be called a _
mesic nucleus_. here the most promising candidate is the @xmath0-mesic nucleus since the @xmath0n interaction is strongly attractive . as discussed in the contribution by wycech @xcite the nuclear states of @xmath0
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Suppose that you have an abstract for a scientific paper: we present a theoretical study related to a recent experiment on the coalescence of sessile drops .
the study deals with the kinetics of relaxation towards equilibrium , under the action of surface tension , of a spheroidal drop on a flat surface .
for such a non - spherical drop under partial wetting conditions , the dynamic contact angle varies along the contact line .
we propose a new non - local approach to the wetting dynamics , where the contact line velocity depends on the geometry of the whole drop .
we compare our results to those of the conventional approach in which the contact line velocity depends only on the local value of the dynamic contact angle . the influence on drop dynamics of the pinning of the contact line by surface defects
is also discussed . .
And you have already written the first three sentences of the full article: at first glance , the motion of the gas - liquid interface along the solid surface is a purely hydrodynamic problem .
however , it attracted significant attention from the physicists since the work @xcite , which showed an unphysical divergence that appears in the hydrodynamic treatment if a motion of a wedge - shaped liquid slides along the solid surface .
the reason for this divergence lies in the no - slip condition ( i.e. zero liquid velocity ) at the solid surface ..
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being so common in hydrodynamics , this boundary condition is questionable in the vicinity of the contact line along which the gas - liquid interface joins the solid . in the absence of mass transfer between the gas and the liquid ,
the no - slip condition requires zero velocity for the contact line that is supposed to be formed of the liquid molecules in the contact with the solid .
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Suppose that you have an abstract for a scientific paper: we study the effects of a vertical electric field on the electronic band structure and transport in multilayer phosphorene and its nanoribbons .
we find a massive - to - massless dirac fermion transition along the armchair direction at a critical field @xmath0 at which the gap closes .
this transition is observable in quantum hall measurements , as the power - law dependence of the landau - level energy on the magnetic field goes from @xmath1 below @xmath0 , to @xmath2^{2/3}$ ] at @xmath0 , to @xmath2^{1/2}$ ] above @xmath0 .
multilayer phosphorene nanoribbons ( pnrs ) have edge states that govern electrical conduction .
we propose a dual - edge - gate pnr structure that works as a quantum switch . .
And you have already written the first three sentences of the full article: black phosphorus ( bp ) is a thermodynamically stable allotrope of phosphorus with a layered structure .
the layers of covalently bonded atoms are held together by the van der waals interaction .
similar to obtaining graphene from graphite by mechanical exfoliation , bp can be isolated to a few layers @xcite ..
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the resulting structure is a recent addition to the family of two - dimensional ( 2d ) materials called multilayer phosphorene .
monolayer phosphorene has a direct band gap of 1.45 ev @xcite . in multilayer phosphorene ,
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Suppose that you have an abstract for a scientific paper: wavefront shaping has revolutionized imaging deep in scattering media @xcite , being able to spatially @xcite and temporally @xcite refocus light through or inside the medium . however , wavefront shaping is not compatible yet with polarization - resolved microscopy given the need of polarizing optics to refocus light with a controlled polarization state . here , we show that wavefront shaping is not only able to restore a focus , but it can also recover the injected polarization state without using any polarizing optics at the detection . this counter - intuitive effect occurs up to several transport mean free path thick samples , which exhibit a speckle with a completely scrambled state @xcite .
remarkably , an arbitrary rotation of the input polarization does not degrade the quality of the focus . this unsupervised re - polarization out of the originally scrambled polarization state paves the way for polarization - resolved structural microscopy @xcite at unprecedented depths .
we exploit this phenomenon and demonstrate second harmonic generation ( shg ) structural imaging of collagen fibers in tendon tissues behind a scattering medium .
+ accessing the structural organization of molecular assemblies is an important aspect of biological imaging .
for instance , this organization determines important functions such as the formation of bio - filaments , but also contributes to disorders such as in the formation of amyloids in neurodegenerative diseases .
polarization - resolved microscopies are able to provide molecular structural insights beyond the diffraction - limited scale @xcite , and , being non - invasive and non - destructive , could in principle be used for deep _ in - vivo _ structural imaging .
unfortunately , light propagation through multiply scattering media , like thick biological tissues , inherently scrambles polarization states .
after injection of a well - defined polarization state and wavevector direction , each successive scattering event rotates the....
And you have already written the first three sentences of the full article: * optical set - up*. ultrashort pulses ( 130 fs , 800 nm , 76 mhz repetition rate , mira , coherent ) are steered onto a @xmath19 pixels reflective slm ( boulder nonlinear systems ) .
the slm is imaged on the back focal plane of the focusing lens ( achromatic lens , f=19 mm , ac127 - 019-b - ml , thorlabs ) with the scattering medium placed after it .
the nanoktp crystals are imaged by an objective ( 40x , 0.75 na , nikon ) on a 12-bit cmos camera ( flea3 , point grey ) and on a large area photon counting pmt ( mp 953 , perkinelmer ) ..
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the shg signal is spectrally separated with suitable dichroic mirror ( 560 nm longpass , ahf analysentechnik ) , shortpass ( 700 nm , fesh0700 , thorlabs ) and bandpass ( 400 @xmath20 10 nm , chroma technology ) filters .
additionally , a longpass filter ( 650 nm , felh0650 , thorlabs ) and a zero - order half - wave plate ( 46 - 555 , edmund optics ) placed in a motorized rotation stage are used for the excitation beam before the focusing lens .
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Suppose that you have an abstract for a scientific paper: chimera is a relatively new emerging phenomenon where coexistence of synchronous and asynchronous state is observed in symmetrically coupled dynamical units .
we report observation of the chimera state in multiplex networks where individual layer is represented by 1-d lattice with non - local interactions . while , multiplexing does not change the type of the chimera state and retains the multi - chimera state displayed by the isolated networks , it changes the regions of the incoherence .
we investigate emergence of coherent - incoherent bifurcation upon varying the control parameters , namely , the coupling strength and the network size .
additionally , we investigate the effect of initial condition on the dynamics of the chimera state . using a measure based on the differences between the neighboring nodes which distinguishes smooth and non - smooth spatial profile , we find the critical coupling strength for the transition to the chimera state . observing chimera in a multiplex network with one to one inter layer coupling is important to gain insight to many real world complex systems which inherently posses multilayer architecture . * emergence of chimera in multiplex network * + * saptarshi ghosh@xmath0 , sarika jalan@xmath1 , + _ @xmath2 complex systems lab , discipline of physics , indian institute of technology indore , khandwa road , simrol , indore 452020 , india + _ @xmath3 centre for biosciences and biomedical engineering , indian institute of technology indore , khandwa road , simrol , indore 452020 ,
india + @xmath4 email : [email protected] + @xmath5 email : [email protected] ( corresponding author ) _ _ * .
And you have already written the first three sentences of the full article: in past few decades , network science has discovered a plethora of novel phenomena while trying to mimic real world systems in a better manner .
one of such discovery is an observation of the chimera state .
it was first reported by kuramato et ..
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al . in 2002 while investigating non locally coupled identical oscillators in a ring network @xcite .
later , it was analyzed and christened by abrams and strogatz in 2006 as chimera state @xcite .
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Suppose that you have an abstract for a scientific paper: our aim is to compile a catalog of white dwarfs within 40 parsecs of the sun , in which newly discovered objects would significantly increase the completeness of the current census .
white dwarf candidates are identified from the superblink proper motion database ( @xcite ) , which allows us to investigate stars down to a proper motion limit as low as 40 @xmath0 .
the selection criteria and distance estimates are based on a combination of color - magnitude and reduced proper motion diagrams .
candidates with distances less than 50 parsecs are selected for spectroscopic follow - up .
we present our preliminary sample of spectroscopically confirmed white dwarfs , as well as their atmospheric parameters .
these parameters are obtained using the spectroscopic technique developed in @xcite for da stars .
db , dq , and dz stars are also analyzed spectroscopically . for featureless spectra as well as those showing only @xmath1 , we perform a detailed photometric analysis of their energy distribution . address = dpartement de physique , universit de montral , c.p .
6128 , succ .
centre - ville , montral , qubec h3c 3j7 , canada address = dpartement de physique , universit de montral , c.p . 6128 , succ .
centre - ville , montral , qubec h3c 3j7 , canada , address = department of astrophysics , division of physical sciences , american museum of natural history , central park west at 79th street , new york , ny 10024 , .
And you have already written the first three sentences of the full article: the current census of nearby white dwarfs is complete to within 20 parsecs from the sun , and contains 126 white dwarfs @xcite . since it represents a sample too small for detailed statistical analysis ,
there is a need to extend the complete sample of white dwarfs to a larger volume .
nearby white dwarfs have been traditionally found in catalogs of stars with large proper motions . in order to improve the statistics of the local white dwarf population.
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, we have been hunting for white dwarfs in the superblink catalog .
+ the superblink proper motion database @xcite is based on a re - analysis of the poss - i and poss - ii plates of the digitized sky survey ( 20 - 45 yr baseline ) .
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Suppose that you have an abstract for a scientific paper: we review the noncommutative gravity of wess et al .
@xcite and discuss its physical applications .
we define noncommutative symmetry reduction and construct deformed symmetric solutions of the noncommutative einstein equations .
we apply our framework to find explicit deformed cosmological and black hole solutions and discuss their phenomenology .
this article is based on a joint work with thorsten ohl @xcite . .
And you have already written the first three sentences of the full article: despite the great success of einstein s general theory of relativity , it is generally believed that it has to be modified at small distances , incorporating quantum effects of spacetime . to achieve this goal and arrive at a consistent theory of quantum gravity ,
a number of different approaches have been proposed , including string theory and loop quantum gravity as best known examples . for another prominent approach ,
see the contributions on causal dynamical triangulations to this proceedings ..
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the aim of these models is to provide a microscopic description of quantum spacetime subsequently to make contact to more macroscopic phenomena , like e.g. our universe . in doing
so it turns out that it is quite hard to connect the very small length scales on which these models are defined with the large scales on which observable physics takes place , e.g. cosmic inflation or particle physics .
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Suppose that you have an abstract for a scientific paper: the universe should be dark at energies exceeding @xmath0 ev .
this simple but solid prediction of our best known particle physics is not confirmed by observations , that seem to suggest a quite different picture .
numerous events have in fact been detected in this energy region , with spectra and anisotropy features that defy many conventional and unconventional explanations .
is there a problem with known physics or is this a result of astrophysical uncertainties ?
here we try to answer these questions , in the light of present observations , while discussing which information future observations may provide on this puzzling issue .
= 11.6pt .
And you have already written the first three sentences of the full article: one of the major goals of cosmic ray physics has always been the discovery and understanding of the _ end of the cosmic ray spectrum_. until the end of the 60s , this search was mainly aimed to understand the limits to the acceleration processes and nature of the sources responsible for the production of the particles with the highest energies .
however , after the discovery of the cosmic microwave background ( cmb ) , it became soon clear that the observed spectrum of the cosmic radiation had to be cut off at a `` natural '' energy , even if an ideal class of sources existed , able to accelerate particles to infinite energy .
in fact , if the sources are distributed homogenously in the universe , the photopion production in the scattering of particles off the cmb photons imply a cutoff in the observed spectrum of the cosmic rays at an energy @xmath1 ev , close to the kinematic threshold for that process @xcite . this cutoff has become known as the _ gzk cutoff _ and particles with @xmath2.
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are usually named ultra - high energy cosmic rays ( uhecrs ) .
several experiments have been operating to detect the flux of uhecrs , starting with volcano ranch @xcite and continuing with haverah park @xcite and yakutsk @xcite to the more recent experiments like agasa @xcite , fly s eye @xcite and hires @xcite .
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Suppose that you have an abstract for a scientific paper: a detailed comparison of faddeev and variational wave functions for @xmath0h , calculated with realistic nuclear forces , has been made to study the form of three - body correlations in few - body nuclei .
three new three - body correlations for use in variational wave functions have been identified , which substantially reduce the difference with the faddeev wave function .
the difference between the variational upper bound and the faddeev binding energy is reduced by half , to typically @xmath1 .
these three - body correlations also produce a significant lowering of the variational binding energy for @xmath2he and larger nuclei .
= 10000 .
And you have already written the first three sentences of the full article: quantum monte carlo methods , adopted for nuclei in the last decade , have proven to be very useful in obtaining exact solutions of the nuclear schrdinger equation for the ground and low - energy excited states of up to six nucleons @xcite , and it is likely that many states of seven and eight nucleons will be exactly calculated with realistic nuclear forces in the near future . a variational approximation , @xmath3 , to the lowest - energy state of the desired spin , parity , and isospin , @xmath4 , is first obtained by a variational monte carlo ( vmc ) calculation @xcite . the exact eigenstate , @xmath5 , belonging to the lowest - energy eigenvalue , @xmath6 , for that @xmath4 is then projected out using @xmath7 |\psi_v\rangle\ ] ] with the green s function monte carlo ( gfmc ) method @xcite .
the computation yields a population of configurations @xmath8 , where @xmath9 specifies the positions of all the nucleons and @xmath10 labels the configurations , distributed with the probability @xmath11 \psi_v({\bf r})| \ .\ ] ] mixed estimates , defined as : @xmath12_m = \frac { \langle\psi_v| o exp[-(h - e_0)\tau ] |\psi_v\rangle } { \langle\psi_v| exp[-(h - e_0)\tau ] |\psi_v\rangle } \ , \ ] ] are then calculated from this population .
obviously @xmath13_m$ ] converges to the eigenvalue @xmath6 in the limit @xmath14 , however , the variance of @xmath13_m$ ] depends primarily on that of the local variational energy : @xmath15 expectation values of operators other than h are generally calculated only up to first order in the difference @xmath16 from @xmath17_m - \frac { \langle\psi_v| o |\psi_v\rangle } { \langle\psi_v|\psi_v\rangle } \ .\ ] ] it is clear that accurate variational wave functions are needed for the success of this approach ..
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the variance of @xmath18 decreases and the terms neglected in eq.(5 ) become smaller as @xmath19 .
state - of - the - art variational wave functions @xcite of few - body nuclei have the form : @xmath20 |\psi_p\rangle \\ ] ] with the pair wave function @xmath21 given by : @xmath22 |\psi_{j}\rangle \ .\ ] ] the @xmath23 represents a symmetrized product , and the jastrow wave function , @xmath24 , is given by : @xmath25 |\phi\rangle \ .\ ] ] here @xmath26 is an antisymmetric product of single - particle wave functions with the desired @xmath4 , the @xmath27 is a two - body central correlation , and the operator @xmath28 is defined as : @xmath29 u_p(r_{ij } ) o^p_{ij } \ , \ ] ] @xmath30\otimes [ 1 , \tau_i\cdot\tau_j ] \ .\ ] ] the @xmath27 and @xmath28 correlations are generated by the static parts of the two - nucleon interaction .
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Suppose that you have an abstract for a scientific paper: in the general context of scalar - tensor theories , we consider a model in which a scalar field coupled to the ricci scalar in the gravitational sector of the lagrangian , is also playing the role of an `` extended quintessence '' field , dominating the energy content of the universe at the present time . in this framework , we study the linear evolution of the perturbations in the quintessence energy density , showing that a new phenomenon , named here `` gravitational dragging '' , can enhance the scalar field density perturbations as much as they reach the non - linear regime . the possibility of dark energy clumps formation is thus discussed . .
And you have already written the first three sentences of the full article: the recent growing evidences for a vacuum energy component in the universe @xcite have lead to the development of a number of models , most of which tend to alleviate the theoretical difficulties of the well known `` cosmological constant problem '' ( see @xcite for a review ) .
all these models are replacing the cosmological constant with a `` dynamical vacuum energy '' provided by an evolving scalar field , often named `` quintessence '' .
this field should provide the present cosmic accelerating phase through its negative equation of state ..
Please generate the next two sentences of the article
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such `` dark energy '' component has also been modeled in the general framework of scalar - tensor theories of gravity : in these `` extended quintessence '' ( eq ) scenarios @xcite-@xcite , the quintessence scalar field is directly coupled to the ricci scalar @xmath0 in the lagrangian of the theory : the canonical ricci scalar term @xmath1 , with @xmath2 , is replaced by @xmath3 , where @xmath4 is a function of the quintessence field @xmath5 . here
, @xmath6 is a `` bare '' gravitational constant , generally different from the newton s constant g as it is measured by cavendish - type experiments @xcite . in eq models ,
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