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10,400 |
Suppose that you have an abstract for a scientific paper: the prediction made by l. o. chua 45 + years ago ( see : ieee trans . circuit theory ( 1971 )
18:507 - 519 and also : proc .
ieee ( 2012 ) 100:1920 - 1927 ) about the existence of a passive circuit element ( called memristor ) that links the charge and flux variables has been confirmed by the hp lab group in its report ( see : nature ( 2008 ) 453:80 - 83 ) on a successful construction of such an element .
this sparked an enormous interest in mem - elements , analysis of their unusual dynamical properties ( i.e. pinched hysteresis loops , memory effects , etc . ) and construction of their emulators .
such topics are also of interest in mechanical engineering where memdampers ( or memory dampers ) play the role equivalent to memristors in electronic circuits . in this paper
we discuss certain properties of the oscillatory memristive circuits , including those with mixed - mode oscillations .
mathematical models of such circuits can be linked to the newton s law @xmath0 , with @xmath1 denoting the flux or charge variables , @xmath2 is a positive constant and the nonlinear non - autonomous function @xmath3 contains memory terms .
this leads further to scalar fourth - order odes called the jounce newtonian equations .
the jounce equations are used to construct the @xmath4+op - amp simulation circuits in spice .
also , the linear parallel @xmath5-@xmath6 and series @xmath7-@xmath8 circuits with sinusoidal inputs are derived to match the _ rms _ values of the memristive periodic circuits .
* keywords : * memristors , oscillatory circuits , action and coaction , newton s second law , jounce equations , spice * mathematics subject classification ( 2000 ) : * 34c15 , 34c25 , 70g60 .
And you have already written the first three sentences of the full article: [ [ historical - perspective - the - fourth - missing - element ] ] historical perspective : the fourth missing element + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + in 1971 l. o. chua predicted existence of a passive circuit element that links the flux and charge variables @xcite . the missing element marked by the question mark in fig.[fourth_element ] completes , together with the three well - known other passive elements ( resistor , inductor and capacitor ) , the fourth side of the square diagram @xcite . in total , there are six relationships between the four variables of voltage @xmath9 , current @xmath10 , charge @xmath11 and flux @xmath1 as the two diagonal relationships are the well - known time - derivatives .
it was not until 2008 when a group of researchers at the hewllet - packard lab has announced : _
the missing element has been found _ @xcite . after the announcement a rather large number of results dealing with memristors.
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have been reported in the literature ( cf .
[ 4 - 10 ] and references therein ) .
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10,401 |
Suppose that you have an abstract for a scientific paper: the - uv spectrum of mg@xmath0 has been investigated with high resolution employing fourier - transform spectroscopy and laser excitation . computer simulation and fit of line positions to the overlapping structures in the spectra yield precise transition frequencies . starting with the well characterized ground state @xmath1 from former work we derived excited energy levels and report on the evaluation of the @xmath2 excited state , which is found to interact with another electronic state , which we identify as the lower part of the ( 1)@xmath3 state .
a coupled channels fit to the level energies of the upper state yields a reliable potential energy curve for the for the range of vibrational levels 1 @xmath4 @xmath5 @xmath4 46 .
a potential energy curve for the ( 1)@xmath3 state is proposed , but the ( 1)@xmath3 state is only characterized by its coupling to the a state , and no direct transition to a level of the ( 1)@xmath3 could be uniquely identified due to the overlapping spectral structures . .
And you have already written the first three sentences of the full article: recently we reported on new investigations of the mg@xmath0 uv - absorption spectrum @xcite .
major motivation of the experimental efforts was a reliable characterization of the cold collision properties of ground state atoms by the molecular ground state , which were derived from the long range behaviour of the potential energy curve ( pec ) and given in the form of scattering lengths . with the new data , incorporating also data from former spectroscopic work @xcite
as much as possible , paper @xcite exclusively handles the properties of the molecular ground state and concentrates on different mathematical forms to represent the pec ..
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the spectroscopic data on the upper state level structure is more complex , and its evaluation will be reported in the present paper . due to the better precision compared to @xcite and the computer aided evaluation of the spectral structures , perturbations manifesting themselves by shifts of the observed spectral lines
could be identified .
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10,402 |
Suppose that you have an abstract for a scientific paper: motivated by analogue models of classical and quantum field theory in curved spacetimes and their recent experimental realizations , we consider wave scattering processes of dispersive fields exhibiting two extra scattering channels .
in particular , we investigate how standard superradiant scattering processes are affected by subluminal or superluminal modifications of the dispersion relation .
we analyze simple 1 + 1-dimensional toy - models based on fourth - order corrections to the standard second order wave equation and show that low - frequency waves impinging on generic scattering potentials can be amplified during the process . in specific cases , by assuming a simple step potential , we determine quantitatively the deviations in the amplification spectrum that arise due to dispersion , and demonstrate that the amplification can be further enhanced due to the presence of extra scattering channels .
we also consider dispersive scattering processes in which the medium where the scattering takes place is moving with respect to the observer and show that superradiance can also be manifest in such situations . .
And you have already written the first three sentences of the full article: experimental realizations of analogue black holes @xcite and their associated effects have drawn a lot of attention in the past few years @xcite .
probably the most discussed results have been the first observation of the classical analogue of hawking radiation in an open channel flow @xcite and the still controversial observation of radiation in ultrashort laser pulse filaments @xcite . even though it remains an open question whether or not real black holes emit hawking radiation , calculations involving analogue black holes suggest that the emission process is most probably unaffected by transplanckian effects that could , in principle , alter or even exclude the radiation process @xcite .
superradiance @xcite is another typical phenomenon of black hole physics @xcite which is also manifest in analogue models of gravity @xcite . in standard scattering processes ,.
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the ratio between the reflected and the incident particle number currents @xcite ( i.e. the reflection coefficient ) is smaller than one .
this is directly encoded by the fact that the amplitude of the reflected wave is usually smaller than the amplitude of the incident one in non - dispersive normalized scattering processes . however , in some special situations ( e.g. wave scattering in a kerr black hole spacetime ) , low - frequency incident waves can be amplified in the scattering process . this amplification effect , known as superradiance ,
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10,403 |
Suppose that you have an abstract for a scientific paper: the mechanical properties , electronic structure and phonon dispersion of ground state tho@xmath0 as well as the structure behavior up to 240 gpa are studied by using first - principles density - functional theory .
our calculated elastic constants indicate that both the ground state fluorite structure and high pressure cotunnite structure of tho@xmath0 are mechanically stable .
the bulk modulus , shear modulus , and young s modulus of cotunnite tho@xmath0 are all smaller by approximately 25% compared with those of fluorite tho@xmath0
. the poisson s ratios of both structures are approximately equal to 0.3 and the hardness of fluorite tho@xmath0 is 27.33 gpa .
the electronic structure and bonding nature of fluorite tho@xmath0 are fully analyzed , which show that the th - o bond displays a mixed ionic / covalent character .
the valence of th and o ions in fluorite tho@xmath0 can be represented as th@xmath1 and o@xmath2 .
the phase transition from the fluorite to cotunnite structure is calculated to be at the pressure of 26.5 gpa , consistent with recent experimental measurement by idiri _ et al_. @xcite . for the cotunnite phase it is further predicted that an isostructural transition takes place in the pressure region of 80 to 130 gpa . .
And you have already written the first three sentences of the full article: besides uranium and plutonium , thorium is also one kind of important nuclear materials .
metal thorium and its compounds have been widely investigated both experimentally and theoretically since metal thorium was found in 1828 . among thorium compounds , thorium dioxide tho@xmath0 , which is a stable diamagnetic transparent insulating solid ,
has attracted special attention ..
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in addition to its usage as an important nuclear fuel material , thorium dioxide has also been used as a solid - state electrolyte . in particular ,
due to its prominent hardness , tho@xmath0 has potential interests as an optical component material and laser host .
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10,404 |
Suppose that you have an abstract for a scientific paper: over the last two decades , the hera collider has provided a large amount of new information about qcd dynamics at high energy . while the most appreciated are the measurements of the proton structure functions in a wide range of parton momentum @xmath0 and virtuality @xmath1 , it is hard to believe that some of the observations at hera which do not fit the simple picture of dglap dynamics would not get amplified at the lhc , possibly rendering certain approaches to searches beyond the standard model inadequate . .
And you have already written the first three sentences of the full article: progress in the next decade ( and most probably even longer ) in high energy physics will be totally overshadowed by the results expected from the large hadron collider ( lhc ) at cern ( geneva ) where high energy protons will collide at an unprecedented center of mass energy of 14 tev , any time soon .
for quite some time , theorists claim that the success of the standard model ( sm ) of the unified electroweak interactions and of strong interactions can not be understood , unless it is a low energy realization of a more sophisticated construct , which should manifest itself already at tev scales .
it still remains to be seen whether the standard model higgs , whose mass is constrained by precision electroweak measurements @xcite , is realized in nature ..
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a low mass of the sm higgs , about 120 gev , creates the so - called hierarchy problem , that is the need at high energy for a tremendous fine - tuning of quantum - loop corrections to keep the higgs mass light enough for it to be relevant for electroweak symmetry breaking .
the favored candidates for the new horizon are supersymmetric ( susy ) theories and/or theories with universal extra - dimensions ( ued ) .
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10,405 |
Suppose that you have an abstract for a scientific paper: using three particles model without external environments , it is found that decisions of respective state of three particles by decoherence are not simultaneous .
furthermore , in this model , wave function of total three body system collapses spontaneously without any external environments .
therefore we may able to insist that a wavefunction of our universe has already collapsed spontaneously without any external observer , because of the same mechanism with this model . .
And you have already written the first three sentences of the full article: decoherence is that interference among different quantum states disappear because of dissipation - fluctuation from environments[1,2 ] .
it is said that decoherence makes a quantum system classical .
because when interference vanishes , an object can not go to other quantum states ..
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it means the object gets classicality . in quantum mechanics
, an object can be in some contradictory states at the same time .
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10,406 |
Suppose that you have an abstract for a scientific paper: high - magnetic - field radio pulsars are important transition objects for understanding the connection between magnetars and conventional radio pulsars .
we present a detailed study of the young radio pulsar j1119@xmath06127 , which has a characteristic age of 1900yr and a spin - down - inferred magnetic field of @xmath1 g , and its associated supernova remnant [email protected] , using deep _ xmm - newton _ and _ chandra x - ray observatory _ exposures of over 120ks from each telescope .
the pulsar emission shows strong modulation below 2.5kev , with a single - peaked profile and a large pulsed fraction of @xmath2 . employing a magnetic , partially ionized hydrogen atmosphere model
, we find that the observed pulse profile can be produced by a single hot spot of temperature 0.13kev covering about one third of the stellar surface , and we place an upper limit of 0.08kev for an antipodal hot spot with the same area
. the nonuniform surface temperature distribution could be the result of anisotropic heat conduction under a strong magnetic field , and a single - peaked profile seems common among high-@xmath3 radio pulsars .
for the associated remnant [email protected] , its large diameter could be attributed to fast expansion in a low - density wind cavity , likely formed by a wolf - rayet progenitor , similar to two other high-@xmath3 radio pulsars . .
And you have already written the first three sentences of the full article: over the past two decades , our understanding of neutron stars has been revolutionized due to discoveries of several new classes of objects ( see * ? ? ? * for a review ) .
an extreme class is magnetars , which typically have high spin - down - inferred magnetic fields - field can be estimated by @xmath4 g , where @xmath5 is the spin period in second and @xmath6 is the spin - down rate .
] of @xmath7@xmath8 g and show violent bursting activities ( see * ? ? ?.
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* ; * ? ? ?
* ; * ? ? ?
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10,407 |
Suppose that you have an abstract for a scientific paper: here we report on the significant role of a so far overlooked dynamical aspect , namely a secular resonance between the dwarf planet ceres and other asteroids .
we demonstrate that this type of secular resonance can be the dominant dynamical factor in certain regions of the main asteroid belt .
specifically , we performed a dynamical analysis of the asteroids belonging to the ( 1726 ) hoffmeister family .
to identify which dynamical mechanisms are actually at work in this part of the main asteroid belt , i.e. to isolate the main perturber(s ) , we study the evolution of this family in time .
the study is accomplished using numerical integrations of test particles performed within different dynamical models .
the obtained results reveal that the post - impact evolution of the hoffmeister asteroid family is a direct consequence of the nodal secular resonance with ceres .
this leads us to the conclusion that similar effects must exist in other parts of the asteroid belt . in this respect ,
the obtained results shed light on an important and entirely new aspect of the long - term dynamics of small bodies .
ceres fingerprint in asteroid dynamics , expressed through the discovered secular resonance effect , completely changes our understanding of the way in which perturbations by ceres - like objects affect the orbits of nearby bodies . .
And you have already written the first three sentences of the full article: orbital resonances exist everywhere in the solar system , and play an essential role in the dynamics of small bodies .
the synergy of fast and slow orbital angles produces a great assortment of resonant phenomena @xcite . over the years
numerous methods and models have been developed to interpret the complex dynamical environment of the main asteroid belt ..
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it is well known that this region is sculpted by a web of mean - motion and secular resonances coupled with subtle non - gravitational forces @xcite .
the implications of these effects on a large number of examples with unique dynamical characteristics have already been successfully described by existing dynamical models .
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10,408 |
Suppose that you have an abstract for a scientific paper: in this paper , we report a systematic study of the heaviest nuclei within the relativistic mean field ( rmf ) model . by comparing our results with those of the hartree - fock - bogoliubov method ( hfb ) and the finite range droplet model ( frdm ) , the stability and the shape of the heaviest nuclei
are discussed .
the theoretical predictions as well as the existing experimental data indicate that the experimentally synthesized superheavy nuclei are in between the fission stability line , the line connecting the nucleus with maximum binding energy per nucleon in each isotopic chain , and the @xmath0-stability line , the line connecting the nucleus with maximum binding energy per nucleon in each isobaric chain .
it is shown that both the fission stability line and the @xmath0-stability line tend to be more proton rich in the superheavy region . meanwhile ,
all the three theoretical models predict most synthesized superheavy nuclei to be deformed . .
And you have already written the first three sentences of the full article: recent claims of successful syntheses of superheavy elements 115 and 113 @xcite have aroused new enthusiasm about studies of superheavy nuclei in the nuclear physics community ( see refs . @xcite and references therein ) . for a review of recent experimental progress of this subject , we refer the reader to refs . @xcite . conventional liquid drop models of finite nuclei forbid the existence of any nuclei with a proton number larger than 100 , i.e. superheavy nuclei , due to the destructive coulomb force . however , shell effects are found to be able to stabilize these nuclei , and therefore explain their very existences @xcite .
it has long been predicted that there exist a large number of relatively long - lived superheavy nuclei , the so - called superheavy island , which is separated in neutron and proton numbers from the known heavy elements by a region of much higher instability .
although the experimentally - synthesized superheavy nuclei are indeed very heavy , it is generally believed that they are not examples of the originally sought island of superheavy elements . on the theoretical side , a lot of efforts have been made to interpret the experimental results and make various predictions ..
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a short review of the theoretical activities can be found in ref .
@xcite . nowadays
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10,409 |
Suppose that you have an abstract for a scientific paper: we study the optical bistability of an optomechanical system in which the position of a mechanical oscillator modulates the cavity frequency .
the steady - state mean - field equation of the optical mode is identical to the one for a kerr medium , and thus we expect it to have the same characteristic behavior with a lower , a middle , and an upper branch
. however , the presence of position fluctuations of the mechanical resonator leads to a new feature : the upper branch will become unstable at sufficiently strong driving in certain parameter regimes .
we identify the appropriate parameter regime for the upper branch to be stable , and we confirm , by numerical investigation of the quantum steady state , that the mechanical mode indeed acts as a kerr nonlinearity for the optical mode in the low - temperature limit .
this equivalence of the optomechanical system and the kerr medium will be important for future applications of cavity optomechanics in quantum nonlinear optics and quantum information science . .
And you have already written the first three sentences of the full article: photons are ideal carriers of quantum information @xcite
. they can propagate large distances in optical fibers before being absorbed , and their polarization has been used for quantum communication and quantum information applications .
however , photons barely interact , and thus it is difficult to implement the quantum two - qubit gates needed for universal quantum computation @xcite ..
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this situation changes in an optical medium where the photons can inherit an effective interaction , often modeled as a kerr nonlinearity .
this is why so - called kerr media are important for quantum technology based on photons @xcite .
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10,410 |
Suppose that you have an abstract for a scientific paper: we present an analytic theory of the diffraction of ( matter ) waves by a lattice in the quasi - bragg " regime , by which we mean the transition region between the long - interaction bragg and channelling " regimes and the short - interaction raman - nath regime .
the schrdinger equation is solved by _
adiabatic expansion _ , using the conventional adiabatic approximation as a starting point , and re - inserting the result into the schrdinger equation to yield a second order correction .
closed expressions for arbitrary pulse shapes and diffraction orders are obtained and the losses of the population to output states otherwise forbidden by the bragg condition are derived .
we consider the phase shift due to couplings of the desired output to these states that depends on the interaction strength and duration and show how these can be kept negligible by a choice of smooth ( e.g. , gaussian ) envelope functions even in situations that substantially violate the adiabaticity condition .
we also give an efficient method for calculating the effective rabi frequency ( which is related to the eigenvalues of mathieu functions ) in the quasi - bragg regime . .
And you have already written the first three sentences of the full article: diffraction by a point scatters light or matter waves into all directions .
a two - dimensional grating produces a few diffraction orders at those angles where the scatter from all of the grating adds coherently .
bragg diffraction by an infinite three - dimensional lattice can produce a single diffraction order , which happens when the scatter from all layers adds constructively , as described by the bragg condition ..
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when this happens for a higher scattering order ( high - order bragg diffraction " ) virtually all incident radiation can be scattered into this high order , in contrast to the two - dimensional case . by _
quasi - bragg diffraction _
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10,411 |
Suppose that you have an abstract for a scientific paper: we analyze the electronic transport through a quantum dot that contains a magnetic impurity .
the coherent transport of electrons is governed by the quantum confinement inside the dot , but is also influenced by the exchange interaction with the impurity .
the interplay between the two gives raise to the singlet - triplet splitting of the energy levels available for the tunneling electron . in this paper
, we focus on the charge fluctuations and , more precisely , the height of the conductance peaks .
we show that the conductance peaks corresponding to the triplet levels are three times higher than those corresponding to singlet levels , if electronic correlations are neglected ( for non - interacting dots , when an exact solution can be obtained ) .
next , we consider the coulomb repulsion and the many - body correlations . in this case , the singlet / triplet peak height ratio has a complex behavior .
usually the highest peak corresponds to the state that is lowest in energy ( ground state ) , regardless if it is singlet or triplet . in the end
, we get an insight on the kondo regime for such a system , and show the formation of three kondo peaks .
we use the equation of motion method with appropriate decoupling .
keywords : quantum dots , exchange interaction , quantum transport .
And you have already written the first three sentences of the full article: the quantum dots are zero - dimensional structures ( so called artificial atoms ) that are possible to be experimentally obtained and investigated individually , for some years now .
an incoming electron may tunnel through a quantum dot only if its energy matches a dot energy level , so we have a single electron transistor @xcite .
another interesting potential application is quantum computing using the spin of the quantum dot as information carrier @xcite ..
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the parameters that influence transmittance through a quantum dot ( like the size of the dot or the hybridization with the leads ) are much more easy to control comparing to the parameters of a bulk system , so one can test quantum theories in a way that was not possible before .
we give as example the observation of the two - channel kondo effect , described theoretically many years ago @xcite , but realized experimentally only very recently , in a double - dot system @xcite . in the last years , people have started to address the problem of quantum dots with magnetic impurities @xcite , which is also the subject of the present paper .
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10,412 |
Suppose that you have an abstract for a scientific paper: in recent studies , the production rate of photons or lepton pairs by a quark gluon plasma has been found to be enhanced due to collinear singularities .
this enhancement pattern is very dependent on rather strict collinearity conditions between the photon and the quark momenta .
it was estimated by neglecting the collisional width of quasi - particles . in this paper
, we study the modifications of this collinear enhancement when we take into account the possibility for the quarks to have a finite mean free path . assuming a
mean free path of order @xmath0 , we find that only low invariant mass photons are affected .
the region where collision effects are important can be interpreted as the region where the landau - pomeranchuk - migdal effect plays a role in thermal photon production by bremsstrahlung .
it is found that this effect modifies the spectrum of very energetic photons as well .
based on these results and on a previous work on infrared singularities , we end this paper by a reasonable physical picture for photon production by a quark gluon plasma , that should be useful to set directions for future technical developments . 1 . laboratoire de physique thorique lapth , + umr 5108 du cnrs , associe luniversit de savoie , + bp110 , f-74941 , annecy le vieux cedex , france 2
. brookhaven national laboratory , + physics department , nuclear theory , + upton , ny-11973 , usa lapth790/2000 , bnl - nt00/11 .
And you have already written the first three sentences of the full article: the photon production rate is thought to be a quantity of phenomenological interest in heavy ions collisions , possibly enabling one to detect the formation of a quark - gluon plasma .
part of the interest in this electromagnetic observable comes from the fact that photons are relatively weakly coupled to nuclear matter ( @xmath1 ) .
given the typical size of the system in such collisions ( much smaller than the mean free path of a photon ) , they do not re - interact between their production and their observation . as a consequence , photons ( real photons , or virtual photons decaying eventually into a lepton pair ).
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can provide information on the state of the system at the time they were produced . in order to calculate the photon yield from a hot quark - gluon plasma ,
thermal field theory is the tool of choice since its feynman rules automatically take into account the presence of a thermal bath with the appropriate distributions of partons .
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10,413 |
Suppose that you have an abstract for a scientific paper: atacama large millimeter / submillimeter array ( alma ) @xmath0co(j=1 - 0 ) observations are used to study the cold molecular ism of the cartwheel ring galaxy and its relation to hi and massive star formation ( sf ) .
co moment maps find @xmath1 m@xmath2 of h@xmath3 associated with the inner ring ( @xmath4 ) and nucleus ( @xmath5 ) for a galactic @xmath6-to-@xmath7 conversion factor ( @xmath8 ) .
the spokes and disk are not detected .
analysis of the inner ring s
co kinematics show it to be expanding ( @xmath9 km s@xmath10 ) implying an @xmath11 myr age .
stack averaging reveals co emission in the starburst outer ring for the first time , but only where hi surface density ( @xmath12 ) is high , representing @xmath13 m@xmath2 for a metallicity appropriate @xmath8 , giving small @xmath14 ( @xmath15 m@xmath2 pc@xmath16 ) , molecular fraction ( @xmath17 ) , and h@xmath3 depletion timescales ( @xmath18 myr ) . elsewhere in the outer ring @xmath19 m@xmath2 pc@xmath16 , @xmath20 and @xmath21 myr ( all @xmath22 ) .
the inner ring and nucleus are h@xmath3-dominated and are consistent with local spiral sf laws .
@xmath23 in the outer ring appears independent of @xmath14 , @xmath12 or @xmath24 .
the ism s long confinement in the robustly star forming rings of the cartwheel and am0644 - 741 may result in either a large diffuse h@xmath3 component or an abundance of co - faint low column density molecular clouds .
the h@xmath3 content of evolved starburst rings may therefore be substantially larger . due to its lower
@xmath23 and age the cartwheel s inner ring has yet to reach this state .
alternately , the outer ring may trigger efficient sf in an hi - dominated ism . .
And you have already written the first three sentences of the full article: gravitational interactions play a fundamental role in galaxy evolution , from their assembly at high-@xmath25 @xcite to much of their subsequent chemical and luminosity evolution @xcite . detailed studies of local interacting galaxies can provide important insights into these processes , particularly if the dynamical history can be reconstructed to allow detailed modeling .
ring galaxies , created in the passage of a companion through a spiral s disk , provide excellent examples .
the interaction generates one or more outwardly traveling orbit - crowded rings that `` snow - plow '' the disk s ism as they propagate @xcite and trigger star formation ( sf ) via large - scale gravitational instabilities ( * ? ? ?.
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* ; * ? ? ?
* hereafter hhr ) .
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10,414 |
Suppose that you have an abstract for a scientific paper: experimental data on total and differential elastic cross sections for @xmath0 , @xmath1 , @xmath2 , @xmath3 , @xmath4 starting from energy 3.5 gev in cms are used to determine parameters of vacuum contribution and parameters of basic non vacuum reggeons : @xmath5 , @xmath6 , @xmath7 and @xmath8 .
it is argued that non vacuum contributions to proton - proton and proton - neutron collisions correspond to spectrum in which baryon number is moved from the fragmentation region to central region in rapidity space . in this case
it is possible that chemical potential is increased in central region of spectrum of nucleus - nucleus interaction at low energies .
this effect might be important for facilities fair and nica . * nucleus - nucleus collisions at low energies .
the effects from non vacuum exchange * n.v .
radchenko@xmath9 , a.v .
dmitriev@xmath10 + @xmath11 _ e - mail : [email protected]_ + @xmath12 _ e - mail : [email protected]_ .
And you have already written the first three sentences of the full article: processes with multiple production at high energies are intensively studied both experimentally and theoretically . at that time behavior of multiple processes at low energies
@xmath13 gev is known much less .
multiple processes at low energies are dominated by contributions of non vacuum reggeons ..
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while `` pomeron physics '' is considerably well explored basing on qcd ( @xcite @xcite , also see @xcite and references therein ) clear qcd based picture of multiple processes , associated with non vacuum reggeons is still missing
. at low energies ( @xmath14 gev in center - of - mass system ) non vacuum exchange can give up to half of total cross sections value in @xmath15 and @xmath16 interactions .
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10,415 |
Suppose that you have an abstract for a scientific paper: the evolution of halos consisting of weakly self - interacting dark matter particles is summarized .
the halos initially contain a central density cusp as predicted by cosmological models .
weak self - interaction leads to the formation of an isothermal , low - density core which is in agreement with published data on the rotation curves of dwarf galaxies .
however , subsequently , core collapse leads to an even steeper central density cusp . in order to explain the observed dark matter rotation curves by weak interaction
, the cross section must be in a narrow range around @xmath0 . .
And you have already written the first three sentences of the full article: standard cosmological models predict that structure formation in the universe is dominated by a collisionless , gravitationally interacting , cold dark matter ( cdm ) component .
this theory has been very successfull in explaining the observed large - scale structures which might not be very surprising given the fact that large - scale structure formation is dominated by the initial power spectrum which to some extent can be fine - tuned . a more stringent test of the cdm scenario
are non - linear dark matter structures , that is dark matter halos on galactic scales which have decoupled from the expansion of the universe and have achieved a quasi - static virial equilibrium state ..
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the internal structure of virialized dark matter halos is a result of the collisionless gravitation interaction of dark matter particles which go through a phase of violent relaxation during the merging epoch .
cold dark matter halos therefore provide interesting insight into the nature of dark matter and its interactions and are to a lesser extent affected by the initial power spectrum .
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10,416 |
Suppose that you have an abstract for a scientific paper: a method is proposed for the calculation of diffusion constants for one - dimensional maps exhibiting deterministic diffusion .
the procedure is based on harmonic inversion and uses a known relation between the diffusion constant and the periodic orbits of a map .
the method is tested on an example map for which results calculated by different other techniques are available for comparison . .
And you have already written the first three sentences of the full article: deterministic diffusion plays an important rle in a variety of physical phenomena and applications , e.g. particle confinement in magnetic fields @xcite , conductivity in metals @xcite , etc .
a general theory of diffusion for systems with continuous time is presented in @xcite . in systems with periodic phase - space structure , diffusion may be induced by chaotic dynamics inside the elementary cells , causing an irregular jumping between the cells .
the investigation of deterministic diffusion is an interesting task both from the theoretical point of view , concerning the question of how the typical stochastic properties arise from a purely deterministic dynamics , as well as with regard to its various applications in different physical contexts ..
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it has been observed that even the simplest model systems one - dimensional maps which exhibit deterministic diffusion are capable of explaining the behaviour of relevant physical systems @xcite . for such maps , it has been demonstrated that the diffusive properties are related to the periodic orbits of the map restricted to an elementary cell @xcite . in particular , the diffusion constant characterizing the diffusive spreading can be obtained from the leading zero of a zeta function consisting of a product over contributions from all periodic orbits of the reduced map .
similar to the dynamical zeta functions which appear in semiclassical quantization problems , this product usually does not converge . in former work
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10,417 |
Suppose that you have an abstract for a scientific paper: we study brownian motion and the associated langevin equation in ads / cft .
the brownian particle is realized in the bulk spacetime as a probe fundamental string in an asymptotically ads black hole background , stretching between the ads boundary and the horizon .
the modes on the string are excited by the thermal black hole environment and consequently the string endpoint at the boundary undergoes an erratic motion , which is identified with an external quark in the boundary cft exhibiting brownian motion .
semiclassically , the modes on the string are thermally excited due to hawking radiation , which translates into the random force appearing in the boundary langevin equation , while the friction in the langevin equation corresponds to the excitation on the string being absorbed by the black hole .
we give a bulk proof of the fluctuation - dissipation theorem relating the random force and friction .
this work can be regarded as a step toward understanding the quantum microphysics underlying the fluid - gravity correspondence .
we also initiate a study of the properties of the effective membrane or stretched horizon picture of black holes using our bulk description of brownian motion .
( 0,0)(0,0 ) ( 350,300)itfa-2008 - 51 ( 350,285)dcpt-08/71 .
And you have already written the first three sentences of the full article: one of the interesting problems in statistical mechanics concerns the understanding of the origin of macroscopic dissipation and the approach to thermal equilibrium from microscopical point of view .
conventionally , given a statistical system in the thermodynamic or hydrodynamic limit , we imagine the collisions between the microscopic constituents of our system as being responsible for both of these macroscopic phenomena .
this kinetic theory based picture is firmly anchored on the basic idea of brownian motion in 1827 , the botanist robert brown observed @xcite under a microscope that tiny pollen particles suspended in water undergo incessant irregular motion , which became known as the brownian motion . as is well - known now , this peculiar motion is due to collisions with the fluid particles in random thermal motion ..
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therefore , any particle immersed in fluid at finite temperature exhibits such brownian motion , from a small pendulum suspended in a dilute gas @xcite to a heavy particle in quark - gluon plasma .
this universal phenomenon suggests that the interaction with microscopic constituents is responsible for dissipation and thermalization on macroscopic scales . since its advent
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Suppose that you have an abstract for a scientific paper: the linear model , in which a set of observations is assumed to be given by a linear combination of columns of a matrix ( often termed a dictionary ) , has long been the mainstay of the statistics and signal processing literature .
one particular challenge for inference under linear models is understanding the conditions on the dictionary under which reliable inference is possible .
this challenge has attracted renewed attention in recent years since many modern inference problems ( e.g. , high - dimensional statistics , compressed sensing ) deal with the `` underdetermined '' setting , in which the number of observations is much smaller than the number of columns in the dictionary .
this paper makes several contributions for this setting when the set of observations is given by a linear combination of a small number of _ groups of columns _ of the dictionary , termed the `` block - sparse '' case .
first , it specifies conditions on the dictionary under which most block submatrices of the dictionary ( often termed block subdictionaries ) are well conditioned .
this result is fundamentally different from prior work on block - sparse inference because ( @xmath0 ) it provides conditions that can be explicitly computed in polynomial time , ( @xmath1 ) the given conditions translate into near - optimal scaling of the number of columns of the block subdictionaries as a function of the number of observations for a large class of dictionaries , and ( @xmath2 ) it suggests that the spectral norm , rather than the column / block coherences , of the dictionary fundamentally limits the scaling of dimensions of the well - conditioned block subdictionaries .
second , in order to help understand the significance of this result in the context of block - sparse inference , this paper investigates the problems of block - sparse recovery and block - sparse regression in underdetermined settings . in both of these problems ,
this paper utilizes its result concerning conditioning of block subdictionaries and....
And you have already written the first three sentences of the full article: consider the classical linear forward model @xmath3 , which relates a parameter vector @xmath4 to an observation vector @xmath5 through a linear transformation ( henceforth referred to as a _ dictionary _ ) @xmath6 .
this forward model , despite its apparent simplicity , provides a reasonable mathematical approximation of reality in a surprisingly large number of application areas and scientific disciplines @xcite .
while the operational significance of this linear ( forward ) model varies from one application to another , the fundamental purpose of it in all applications stays the same : _ given knowledge of @xmath7 and @xmath8 , make an inference about @xmath9 ..
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_ however , before one attempts to solve an inference problem using the linear model , it is important to understand the conditions under which doing so is even feasible .
for instance , inferring anything about @xmath9 will be a moot point if the nullspace of @xmath8 were to contain @xmath9 .
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Suppose that you have an abstract for a scientific paper: we calculate the trispectrum of the primordial curvature perturbation generated by an epoch of slow - roll inflation in the early universe , and demonstrate that the non - gaussian signature imprinted at horizon crossing is unobservably small , of order @xmath0 , where @xmath1 is the tensor - to - scalar ratio . therefore any primordial non - gaussianity observed in future microwave background experiments is likely to have been synthesized by gravitational effects on superhorizon scales .
we discuss the application of maldacena s consistency condition to the trispectrum .
* keywords * : inflation , cosmological perturbation theory , physics of the early universe . .
And you have already written the first three sentences of the full article: in the inflationary scenario @xcite , the primordial curvature perturbation , @xmath2 , is generated via the vacuum fluctuations of one or more light scalar fields @xcite .
it is the only relevant perturbation in the simplest class of single - field models .
more generally , however , @xmath2 is sensitive to the model under consideration ..
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it may be accompanied by correlated or uncorrelated isocurvature perturbations @xcite which source its evolution , or it may be generated after the end of inflation by the decay of another field @xcite . it has recently become clear that interesting information about the particle physics that drove inflation is encoded in the non - gaussian features of the curvature perturbation @xcite .
although observations of the cosmic microwave background ( cmb ) anisotropy constrain the spectrum of perturbations to be close to scale - invariance with very nearly gaussian statistics @xcite , some non - gaussianity is inevitable due to the universal coupling of all matter fields to gravity @xcite .
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Suppose that you have an abstract for a scientific paper: we investigate a spectrum oligopoly market where each primary seeks to sell its idle channel to a secondary . transmission rate of a channel evolves randomly .
each primary needs to select a price depending on the transmission rate of its channel .
each secondary selects a channel depending on the price and the transmission rate of the channel . we formulate the above problem as a non - cooperative game .
we show that there exists a unique nash equilibrium ( ne ) and explicitly compute it . under the ne strategy profile a primary prices its channel to render the channel which provides high transmission rate more preferable ; this negates the perception that prices ought to be selected to render channels equally preferable to the secondary regardless of their transmission rates.we show the loss of revenue in the asymptotic limit due to the non co - operation of primaries . in the repeated version of the game ,
we characterize a subgame perfect ne where a primary can attain a payoff arbitrarily close to the payoff it would obtain when primaries co - operate . .
And you have already written the first three sentences of the full article: to accommodate the ever increasing traffic in wireless spectrum , fcc has legalized the unlicensed access of a part of the licensed spectrum band- which is known as _
secondary access_. however , secondary access will only proliferate when it is rendered profitable to license holders ( primaries ) .
we devise a framework to enable primaries to decide price they would charge unlicensed users ( secondaries ) ..
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the price will depend on the transmission rate which evolves randomly owing to usage of subscribers of primaries and fading .
a secondary receives a payoff from a channel depending on the transmission rate offered by the channel and the price quoted by the primary .
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Suppose that you have an abstract for a scientific paper: there exist natural generalizations of the real moduli space of riemann spheres based on manipulations of coxeter complexes .
these novel spaces inherit a tiling by the graph - associahedra convex polytopes .
we obtain explicit configuration space models for the classical infinite families of finite and affine weyl groups using particles on lines and circles .
a fulton - macpherson compactification of these spaces is described and this is used to define the coxeter operad . a complete classification of the building sets of these complexes
is also given , along with a computation of their euler characteristics .
[ section ] [ thm]proposition [ thm]corollary [ thm]lemma [ thm]conjecture [ thm]definition [ thm]example .
And you have already written the first three sentences of the full article: [ [ section ] ] a configuration space of @xmath0 ordered , distinct particles on a variety @xmath1 is @xmath2 over the past decade , there has been an increased interest in the configuration space of @xmath0 labeled particles on the projective line . the focus is on a quotient of this space by @xmath3 , the affine automorphisms on @xmath4 .
the resulting variety is the moduli space of riemann spheres with @xmath0 punctures @xmath5 there is a compactification @xmath6 of this space , a smooth variety of complex dimension @xmath7 , coming from geometric invariant theory @xcite . the space @xmath6 plays a crucial role as a fundamental building block in the theory of gromov - witten invariants , also appearing in symplectic geometry and quantum cohomology @xcite .
our work is motivated by the _.
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real _ points @xmath8 of this space , the set of points fixed under complex conjugation .
these real moduli spaces have importance in their own right , appearing in areas such as @xmath9-motives of goncharov and manin @xcite and lagrangian floer theory of fukaya @xcite .
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Suppose that you have an abstract for a scientific paper: whether technological societies remain small and planet - bound like our own , or ultimately span across galaxies is an open question in the search for extraterrestrial intelligence .
societies that engineer on a galactic scale are classified as type iii on kardashev s scale .
i argue that type iii societies can take the form of blackboxes , entire galaxies veiled in an opaque screen .
a blackbox has a temperature that is just above that of the cosmic microwave background , for the maximum possible thermodynamic efficiency .
the screen can be made from artificial dust pervading the galaxy , establishing feedback on the diffuse interstellar medium itself .
i show that there is enough material in galaxies to build blackboxes if the dust is fashioned into dipole antennas , especially if they are made of carbon nanotubes .
the thermal emission of a blackbox makes it a bright microwave source .
i examine the _ planck _ catalog of compact sources ( pccs2 ) to constrain the abundance of blackboxes .
none of the 100 ghz sources has the spectrum expected of a blackbox .
the null result rules out shrouded galaxy clusters out to @xmath0 and shrouded milky ways out to ( comoving ) 700 mpc .
the reach of the results includes 3 million galaxies containing an estimated 300 quadrillion terrestrial planets , as well as tens of thousands of galaxy clusters .
a more detailed search of the pccs2 can find or rule out blackboxes in 30 million galaxies , and the south pole telescope sunyaev - zeldovich survey can search another 20 million galaxies .
combined with the null results from other searches for type iii societies , i conclude that they are so rare that they basically do not exist within the observable universe .
a hypothesis of `` cosmic pessimism '' is discussed , in which we are alone , our long - term chances for survival are slim , and if we do survive , our future history will be checkered .
our loneliness is suggested by the lack of type iii societies .
i discuss the remaining....
And you have already written the first three sentences of the full article: what are the limits to technological achievement ? that question has always been implicit in discussions for the search for extraterrestrial intelligence ( seti ) . as far as we can tell
, the universe as a whole is pristine and natural . if it s easy for technological societies to engineer whole sections of the cosmos , then the simplest explanation seems to be that we are alone .
if such `` cosmic engineering '' is difficult or impossible , then there may be a menagerie of societies out there that are too subtle to detect yet ..
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interstellar travel , which has not yet been achieved by humans , is one possible limit to technology .
the apparent lack of starfarers in the local universe leads to fermi s paradox , which is the observation that the galaxy is old enough for even fairly slow starfarers , traveling at a few percent of @xmath1 , to spread across entirely ( @xcite and @xcite review possible solutions and implications ) .
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Suppose that you have an abstract for a scientific paper: we show a method for implementing universal quantum computing using of a singlet and triplets of nanowire double quantum dots coupled to a one - dimensional transmission line resonator .
this method is attractive for both quantum computing and quantum control with inhibition of spontaneous emission , enhanced spin qubit lifetime , strong coupling and quantum nondemolition measurements of spin qubits .
we analyze the performance and stability of all required operations and emphasize that all techniques are feasible with current experimental technology . .
And you have already written the first three sentences of the full article: a quantum computer comprising many two - level systems qubits , exhibits coherent superpositions and entanglement . quantum computing , which is based on these features , enables some computational problems to be solved faster than would ever be possible with a classical computer @xcite , and exponentially speeds up solutions to other problems over the best known classical algorithms @xcite , is currently attracting enormous interests . among the promising candidates for quantum computing , solid - state implementations such as spin qubits in quantum dots @xcite and bulk silicon @xcite , and charge qubits in bulk silicon @xcite and in superconducting josephson junctions @xcite , are especially attractive because of stability and expected scalability of solid - state systems ; of these competing technologies , semiconductor double quantum dots ( dqds ) are particularly important because of the combination spin and charge manipulations to take advantage of long memory times associated with spin states and at the same time to enable efficient readout and coherent manipulation of charge states .
our goal is to develop a realizable architecture for semiconductor quantum computation .
the qubit is manifested as a nanowire ( nw ) quantum dot pair such that each having an electron and thus the singlet and one of the triplets of two - electron states correspond to the logical state @xmath0 and the orthogonal state @xmath1 ..
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the resonator - assisted interaction between dqds and a microwave transmission line resonator ( tlr ) is used to implement a universal set of quantum gates and readout of the qubits . from two points ,
we show the advantages of our scheme compared to the previous proposals on semiconductor quantum computation .
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Suppose that you have an abstract for a scientific paper: we show that simply connected projective manifolds in characteristic @xmath0 have no nontrivial stratified bundles .
this gives a positive answer to a conjecture by d. gieseker ( 1975 ) .
the proof uses hrushovski s theorem on periodic points . .
And you have already written the first three sentences of the full article: let @xmath1 be a smooth complex variety .
the category of bundles with integrable connections on @xmath1 is the full subcategory of the category of coherent @xmath2-modules which are @xmath3-coherent as well .
it is a @xmath4-linear abelian rigid category . if @xmath1 is projective or if we restrict to connections which are regular singular at infinity , then it is equivalent by the riemann - hilbert correspondence to the @xmath4-linear abelian rigid category of local systems of complex vector spaces ( @xcite ) . upon neutralizing those categories by the choice of a point @xmath5.
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, the riemann - hilbert correspondence translates via the tannaka formalism into an isomorphism between the proalgebraic completion of the topological fundamental group @xmath6 and the tannaka pro - algebraic group @xmath7 of flat bundles .
malcev ( @xcite ) and grothendieck ( @xcite ) showed that if the tale fundamental group @xmath8 is trivial , that is if @xmath1 does not have any nontrivial connected finite tale covering , then @xmath7 is trivial as well , thus there are no nontrivial flat bundles .
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Suppose that you have an abstract for a scientific paper: the dynamics of a phase - separated two - component bose - einstein condensate are investigated , in which a bubble of one component moves through the other component .
numerical simulations of the gross pitaevskii equation reveal a variety of dynamics associated with the creation of quantized vortices . in two dimensions , a circular bubble deforms into an ellipse and splits into fragments with vortices , which undergo the magnus effect .
the bnard
von krmn vortex street is also generated . in three dimensions , a spherical bubble deforms into toruses with vortex rings .
when two rings are formed , they exhibit leapfrogging dynamics . .
And you have already written the first three sentences of the full article: a droplet of ink falling into water deforms from a sphere to a toroidal shape due to the formation of a vortex ring @xcite .
an air bubble rising in water exhibits complicated dynamics such as zigzag and spiral motion @xcite .
such phenomena are caused by the interaction between the droplet ( ink ) or the bubble ( air ) with the medium ( water ) , where the former moves through the latter ..
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the subject of the present paper is the dynamics of phase - separated two - component superfluids in similar situations , that is , a bubble of one component moving through the other component . a variety of dynamical properties have been observed in two - component bose
einstein condensates ( bec ) @xcite .
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Suppose that you have an abstract for a scientific paper: neglected tropical diseases ( ntd ) , particularly vector - borne diseases ( vbd ) , account for a large proportion of the global disease burden , and their control faces several challenges including diminishing human and financial resources for those distressed from such diseases .
visceral leishmaniasis ( vl ) , the second - largest parasitic killer in the world ( after malaria ) affects poor populations in endemic countries and causes considerable cost to the affected individuals and their society .
mathematical models can serve as a critical tool for understanding the driving mechanisms of a ntd such as vl .
the who promotes integrated control programs for vl but this policy is not well supported by systematic quantitative and dynamic evidence and so potential benefits of the policy are limited . moreover , mathematical models can be readily developed and used to understand the functioning of the vl system cheaply and systematically .
the focus of this research is three - fold : ( i ) to identify non - traditional but critical mechanisms for ongoing vl transmission in resource limited regions , ( ii ) to review mathematical models used for other infectious diseases that have the potential to capture identified factors of vl , and ( iii ) to suggest novel quantitative models for understanding vl dynamics and for evaluating control programs in such frameworks for achieveing vl elimination goals . .
And you have already written the first three sentences of the full article: visceral leishmaniasis ( vl ) is a neglected vector - borne infectious disease that is transmitted to humans by infected sandflies and is the second - largest parasitic killer in the world after malaria @xcite .
if left untreated , most cases result in death within two to three years of clinical manifestation .
most of the new cases ( approximately 90% ) occur in bangladesh , brazil , ethiopia , india , nepal , south sudan , and sudan ..
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vl is identified as a neglected tropical disease by the who because it is endemic in several poverty stricken regions of the world , although preventive measures and successful treatment is common in most developed countries .
many people living in these impoverished regions are daily - wage workers , for whom infection with a disease like vl restricts the bread - winners ability to provide livelihood for their families .
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Suppose that you have an abstract for a scientific paper: the cluster of ultra - high - energy cosmic rays observed by the agasa , hires and yakutsk experiments is studied with respect to possible deflections of particles in regular magnetic fields .
best - fit positions of a potential source of these clustered particles are found , with account of the errors in energy estimation , both in the frameworks of particular models of the galactic magnetic field and treating the direction and the amount of deflection as free parameters .
the study suggests that an unknown regular component of either galactic or extragalactic magnetic field may dominate over modelled components in the direction of the cluster .
possible sources of the cosmic rays in that direction are considered . .
And you have already written the first three sentences of the full article: clustering of arrival directions of the cosmic rays with energies exceeding @xmath0 ev , evidence to which was originally found @xcite on the basis of the early agasa data , was subject to numerous tests and reanalises both with the updated agasa event list and with the event sets of other experiments @xcite .
all statistically significant positive results were obtained by making use of the sets of cosmic rays which included the original list of ref .
@xcite , the one used to formulate the conjecture without these 36 events , the cosmic - ray samples were simply depleted statistically at these high energies ..
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recently , the world data set was supplemented by the events detected by the hires experiment in the stereoscopic mode .
the arrival directions were determined with unprecedented accuracy and , by themselves , did not exhibit any significant clustering @xcite .
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Suppose that you have an abstract for a scientific paper: for an oriented surface link @xmath0 , we can take a satellite construction called a 2-dimensional braid over @xmath0 , which is a surface link in the form of a covering over @xmath0 .
we demonstrate that 2-dimensional braids over surface links are useful for showing the distinctness of surface links .
we investigate non - trivial examples of surface links with free abelian group of rank two , concluding that their link types are infinitely many . .
And you have already written the first three sentences of the full article: a _ surface link _ is the image of a smooth embedding of a closed surface into euclidean space @xmath1 .
two surface links are _ equivalent _ if there is an orientation - preserving self - diffeomorphism of @xmath1 carrying one to the other . in this paper , we assume that surface links are oriented . in @xcite , we investigated a satellite construction called a 2-dimensional braid over an oriented surface link , and introduced its graphical presentation called an @xmath2-chart on a surface diagram .
a 2-dimensional braid over a surface link @xmath0 is a surface link in the form of a covering over @xmath0 , and can be regarded as an analog to a double of a classical link ..
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one of expected applications of the notion of a 2-dimensional braid is that it will provide us with a method for showing the distinctness of surface links .
the aim of this paper is to demonstrate such use for 2-dimensional braids .
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Suppose that you have an abstract for a scientific paper: quantum systems with sublevel structures prevent full population inversion from one manifold of sublevels to the other using strong ultrafast resonant pulses . in this work
we explain the mechanism by which this population transfer is blocked .
we then develop a novel concept of geometric control , assuming full or partial coherent manipulation within the manifolds and show that by preparing specific coherent superpositions in the initial manifold , full population inversion or full population blockade , _
i.e _ laser - induced transparency , can be achieved . in particular , by parallel population transfer we show how population inversion between the manifolds can be obtained with minimal pulse area . as the number of sublevels increases ,
population inversion can overcome the pulse area theorem at the expense of full control over the initial manifold of sublevels .
in this work we are concerned with intrinsic properties of the dynamics of systems with manifolds of sublevels , described by two ( or more ) quantum numbers , that hereafter will be generically called quantum structures . from the point of view of controlling the system dynamics ,
quantum structures pose several interesting problems .
quantum control@xcite typically implies the ability to manipulate interfering pathways , which increases with the number of levels that participate in the dynamics as long as the system is _ controllable _ @xcite .
a multi - level structure would therefore offer more control opportunities at the expense of the ability to manipulate within the substructures .
our general goal is to investigate whether quantum structures limit , or conversely help , in controlling the system . in this paper
we will be concerned with coarse - grained goals , where the objective of the control will be the state of the manifold given by the first quantum number , not the detailed state of the sublevels . in finding the best possible controls we will _ assume _ that the substructure is partially controllable ,
....
And you have already written the first three sentences of the full article: this work was supported by the nrf grant funded by the korean government ( 2007 - 0056343 ) , the international cooperation program ( nrf-2013k2a1a2054518 ) , the basic science research program ( nrf-2013r1a1a2061898 ) , the edison project ( 2012m3c1a6035358 ) , and the micinn project ctq2012 - 36184 .
rice and m. zhao , optical control of molecular dynamics ( john wiley & sons , new york , 2000 ) .
m. shapiro and p. brumer , quantum control of molecular processes ( wiley - vch , 2012 ) ..
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d. dalessandro , introduction to quantum control and dynamics ( chapman & hall , 2007 ) . c. brif ,
r. chakrabarti and h. rabitz , adv .
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Suppose that you have an abstract for a scientific paper: i discuss the current status of efforts to constrain the strangeness - conserving weak hadronic interaction , which can be isolated in nuclear systems because of the associated parity violation . .
And you have already written the first three sentences of the full article: in this talk i will discuss the weak nucleon - nucleon ( nn ) interaction : the experiments that have been done , the strategies theorists have developed to interpret measurements , and the puzzles that remain to be resolved .
while the weak interaction can be observed in flavor - changing hadronic decays , the neutral current contribution to such decays is suppressed by the gim mechanism and thus unobservable .
the nn and nuclear systems are thus the only practical laboratories for studying the hadronic weak interaction in all of its aspects @xcite . as the weak contribution to the nn interaction.
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is many orders of magnitude smaller than the strong and electromagnetic contributions ( the suppression relative to the strong interaction is @xmath0 ) , parity violation must be exploited to isolate weak observables .
the most common observables are pseudoscalars arising from the interference of the weak and strong / electromagnetic interactions , e.g. , the circular polarization of @xmath1 rays emitted from an unpolarized excited nuclear state , or the @xmath1 ray asymmetry if the nuclear state can be polarized .
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Suppose that you have an abstract for a scientific paper: we give descriptions of metrizable topological spaces that are images of the sorgenfrey line under continuous maps of different types ( open , closed , quotient and others ) .
to obtain this descriptions , we introduce the notion of a lusin @xmath0-base ; the sorgenfrey line and the baire space have lusin @xmath0-bases , and if a space @xmath1 has a lusin @xmath0-base , then for each nonempty polish space @xmath2 there exists a continuous open map @xmath3 .
And you have already written the first three sentences of the full article: the sorgenfrey line is the real line with topology whose base consists of all half - open intervals of the form @xmath4 where @xmath5 we study questions of the following form : + _ let @xmath6 be a class of continuous maps and suppose @xmath7 is a map from the sorgenfrey line onto a metrizable space @xmath8 what can we say about @xmath1 ? _
the answers to this questions for some classes @xmath6 are presented in table 1 ; all proofs are given in this paper ( see the third column in table 1 ) .
& & + & & + ' '' '' all maps & & + ' '' '' quotient maps&nonempty analytic & + ' '' '' pseudo - open maps&spaces & + ' '' '' biquotient maps&&corollary [ s8 . ].
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+ & ' '' '' nonempty absolute borel spaces & + one - to - one maps & in which every nonempty & + & ' '' '' open subset is uncountable & + ' '' '' open maps & ' '' '' nonempty polish spaces&corollary [ s14 . ]
+ ' '' '' closed maps & ' '' '' nonempty at most countable&corollary [ s23 . ] + ' '' '' closed - open maps & ' '' '' polish spaces & + ' '' '' open countable - to - one maps&&corollary [ s17 . ]
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Suppose that you have an abstract for a scientific paper: the inner structure of neutron star is considered from theoretical point of view and is compared with the observed data .
we have proposed a form of an equation of state relating pressure with matter density which indicates the stiff equation of state of neutron stars . from our study
we have calculated mass(m ) , compactness(u ) and surface red - shift(@xmath0 ) for the neutron stars namely psr j1614 - 2230 , psr j1903 + 327 , cen x-3 , smc x-1 , vela x-1 , her x-1 and compared with the recent observational data .
we have also indicated the possible radii of the different stars which needs further study .
finally we have examined the stability for such type of theoretical structure . .
And you have already written the first three sentences of the full article: study of compact objects like star takes much attention to the astrophysicists for the last few decades .
it plays the crucial role like a bridge among astrophysics , nuclear physics and particle physics .
one of the possible existing compact objects in our universe is neutron star ( or strange star ) ..
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neutron stars are the most acceptable and known compact objects for the study of dense matter physics . in general , neutron stars
are composed almost entirely of neutrons , while strange stars are made from strange quark matter(sqm ) .
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Suppose that you have an abstract for a scientific paper: we consider a compact riemann surface with a holomorphic involution , two marked fixed points of the involution and a divisor obeying an equation up to linear equivalence of divisors involving all this data .
examples of such data are fermi curves of @xmath0-dimensional periodic schrdinger operators .
we show that the equation has a solution if and only if the two marked points are the only fixed points of the involution . .
And you have already written the first three sentences of the full article: let @xmath1 be a compact riemann surface of genus @xmath2 and @xmath3 a holomorphic involution with two fixed points @xmath4 and @xmath5
. then the linear equivalence @xmath6 is solvable by a divisor @xmath7 of degree @xmath8 if and only if @xmath4 and @xmath5 are the only fixed points of @xmath9 .
it is known that on fermi curves of @xmath0-dimensional periodic schrdinger operators , there exists a holomorphic involution @xmath9 with two fixed points such that the pole divisor of the corresponding normalized eigenfunctions obeys this linear equivalence , see @xcite ..
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it was remarked in @xcite without proof that i.r .
shafarevich and v. v. shokurov pointed out that @xmath6 can hold if and only if @xmath4 and @xmath5 are the only fixed points of @xmath9 .
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Suppose that you have an abstract for a scientific paper: the purpose of this article is to show the continuity of the value function of the sparse optimal ( or @xmath0-optimal ) control problem .
the sparse optimal control is a control whose support is minimum among all admissible controls . under the normality assumption
, it is known that a sparse optimal control is given by @xmath1 optimal control .
furthermore , the value function of the sparse optimal control problem is identical with that of the @xmath1-optimal control problem . from these properties ,
we prove the continuity of the value function of the sparse optimal control problem by verifying that of the @xmath1-optimal control problem . .
And you have already written the first three sentences of the full article: in this article , we consider the _ sparse optimal control _ , also known as the _ maximum hands - off control _ @xcite . a sparse control is defined as a control that has a much shorter support than the horizon length .
a sparse optimal control is a control witch has the minimum support among all admissible controls , i.e. , a sparse optimal control maximizes the time interval where the control value is exactly zero . on such a time interval , we can stop actuators . in automobiles , for example , we can reduce @xmath2 emissions , fuel consumption , traffic noise and so on if we can stop actuators for long periods of time .
therefore the sparse optimal control has prospects for solving the environmental problems @xcite ..
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this optimal control problem is however hard to solve since the cost function is neither convex nor continuous . to overcome this difficulty
, one can adopt @xmath1 optimality as a convex approximation of the problem .
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Suppose that you have an abstract for a scientific paper: grover s database search algorithm , although discovered in the context of quantum computation , can be implemented using any physical system that allows superposition of states .
a physical realization of this algorithm is described using coupled simple harmonic oscillators , which can be exactly solved in both classical and quantum domains .
classical wave algorithms are far more stable against decoherence compared to their quantum counterparts . in addition to providing convenient demonstration models , they may have a role in practical situations , such as catalysis .
address = centre for high energy physics and supercomputer education and research centre + indian institute of science , bangalore-560012 , india .
And you have already written the first three sentences of the full article: any physical system with some initial state , some final state , and some interaction in between is a candidate for processing information .
one only needs to construct a suitable map between physical properties of the system and abstract mathematical variables .
most of the development in computer algorithms has been in the framework of particle - like " discrete digital languages ..
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it is known that wave - like " analogue computation can also be carried out ( e.g. using rlc circuits ) , but that has not been explored as intensively .
the obvious reason is that discrete variables allow a degree of precision , by implementation of error correction procedures , that continuous variables can not provide .
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Suppose that you have an abstract for a scientific paper: we report on the progress of the development of cvcat , an interactive catalogue on cataclysmic variables , which is the first application based on astrocat , a general framework for the installation and maintenance of web - based interactive astronomical databases .
registered users can contribute directly to the catalogue content by adding new objects , object properties , literature references , and annotations .
the scientific quality control of the catalogue is carried out by a distributed editorial team .
searches in cvcat can be performed by object name , classification , certain properties or property ranges , and coordinates .
search results can be retrieved in several output formats , including xml .
old database states can be restored in order to ensure the citability of the catalogue .
furthermore , cvcat is designed to serve as a repository for reduced data from publications .
future prospects include the integration of astrocat - based catalogues in the international network of virtual observatories . .
And you have already written the first three sentences of the full article: traditionally , in astronomy the availability of online digital information is excellent with respect to scientific publications ( nasa s _ astrophysics data system _ , _ arxiv.org _ preprint server ) and raw observational data . with the development of the _ astrocat _ software
we intend to fill the gap between these two categories by enabling astronomers to set up _ interactive _ astronomical catalogues for reduced and inferred data ( fig . 1 ) .
_ astrocat _ is a software framework for the implementation of a new type of web - based interactive astronomical catalogues . _.
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astrocat_-based catalogues are intended to hold information on the physical properties of astronomical objects of a specific class .
we provide the possibility to account for fine - grained hierarchical sub - classifications of the selected objects .
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Suppose that you have an abstract for a scientific paper: heavy quarks , i.e. charm and beauty , are considered calibrated probes for the strongly interacting deconfined medium ( quark gluon plasma , qgp ) formed in heavy - ion collisions .
produced in hard scattering processes in the initial stages of the collision , they interact with the medium , lose energy and , depending on the coupling strength to the medium , take part in the collective motion of the qcd matter .
alice measured the production of @xmath0 , @xmath1 , @xmath2 and @xmath3 mesons at central rapidity in pp , p pb and pb pb collisions at the lhc .
the study of the modification of the transverse momentum differential yields of charm particles in pb
pb collisions with respect to pp collisions , quantified by the nuclear modification factor ( @xmath4 ) , can unravel details of the energy loss mechanism , such as its dependence on the quark mass and on the path length the parton travels through the medium .
a similar comparison between pp and p pb collision data ( @xmath5 ) is fundamental to disentangle effects related to the presence of the hot medium from cold nuclear matter effects .
the degree of thermalization and coupling to the medium is investigated in semi - peripheral pb - pb collisions by measuring the elliptic flow coefficient ( @xmath6 ) at low @xmath7 . at high @xmath7
, @xmath6 is sensitive to the path - length dependence of the energy loss .
results on the transverse momentum and centrality dependence of the d - meson elliptic flow and @xmath4 will be presented .
the comparison with the @xmath4 of non - prompt @xmath8 from b - meson decays measured with cms will be discussed .
the preliminary results on d - meson @xmath5 and the dependence of d - meson yields on rapidity in p
pb collisions will be shown . as an outlook , the analysis and the preliminary results on the azimuthal correlations of d - mesons and charged hadrons in pp collisions will be described .
qgp , charm , heavy flavour , alice , energy loss , elliptic flow .
And you have already written the first three sentences of the full article: the comparison of open heavy - flavour hadron production in proton - proton , proton - pb and pb pb collisions at the lhc offers the opportunity to investigate the properties of the high - density colour - deconfined state of strongly - interacting matter ( quark gluon plasma , qgp ) that is expected to be produced in high - energy collisions of heavy nuclei @xcite . due to their large mass , charm and beauty quarks
are created at the initial stage of the collision in hard - scattering processes with high virtuality ( @xmath9}^{2}$ ] ) involving partons of the incident nuclei .
they interact with the medium and lose energy via both inelastic ( medium - induced gluon radiation , or radiative energy loss ) @xcite and elastic ( collisional energy loss ) @xcite processes ..
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the loss of energy , sensitive to the medium energy density and size , is expected to depend on the quark mass and be smaller for heavy quarks than for light quarks and gluons for most of the mechanisms considered in theoretical models . in particular
, the parton and mass dependence of radiative energy loss derives from the smaller colour coupling factor of quarks with respect to gluons , and from the ` dead - cone effect ' , which reduces small - angle gluon radiation for heavy quarks with moderate energy - over - mass values @xcite . a sensitive observable is the nuclear modification factor , defined as @xmath10 , where @xmath11 is the yield measured in heavy - ion collisions , @xmath12 is the average nuclear overlap function calculated with the glauber model @xcite in the considered centrality range , and @xmath13 is the production cross section in pp collisions
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Suppose that you have an abstract for a scientific paper: we show that rotation strongly affects the nature of the supernova progenitor ( blue / red supergiant or wolf rayet star ) , and thus the supernova types .
in particular our models well reproduce the variations of the number ratio snib / ic to snii with metallicity .
rotation also produces envelope enrichments of the n / c ratio , and increases the size of the co cores .
we show the evolution of the specific angular momentum up to the presn stage and make comparison with neutron stars .
we suggest that the rare wo stars , preferentially formed at low metallicity , are the progenitors of grb . .
And you have already written the first three sentences of the full article: models taking account of the effects of rotation for massive stars can reproduce the observed surface enrichments ( @xcite @xcite ; @xcite @xcite ) , they can explain the great number of red supergiants observed in the smc @xcite . in both cases , non rotating models fail to fit these observed features .
rotation also favours the formation of wr stars ( @xcite @xcite ; @xcite @xcite ; @xcite @xcite , @xcite ) .
let us recall that for a star to be considered as a wr star , at least two conditions must be fullfilled : first , the star must be in the blue part of the hr diagram ( typically @xmath0 ) and secondly , the mass fraction of hydrogen at the surface @xmath1 must be inferior to @xmath20.4 . in the case of.
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non rotating models , the decrease of the h abundance at the surface can only result from the uncovering of the outer layers by stellar winds . in rotating models , it results from the action of both the stellar winds and the rotational mixing .
rotation thus adds its effects to that of mass loss and makes easier the entry into the wr phase .
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Suppose that you have an abstract for a scientific paper: we investigate the cosmological dynamics in teleparallel gravity with nonminimal coupling .
we analytically extract several asymptotic solutions and we numerically study the exact phase - space behavior . comparing the obtained results with the corresponding behavior of nonminimal scalar - curvature theory , we find significant differences , such is the rare stability and the frequent presence of oscillatory behavior . .
And you have already written the first three sentences of the full article: gravitational modification is one of the main directions one can follow in order to describe the late - time universe acceleration and/or the early - time inflationary stage ( see for instance @xcite ) , which has the potential advantage of avoiding introducing exotic fields and the concept of dark energy ( see @xcite and references therein ) . definitely one should note that , apart from the different physical interpretation , one can transform from one approach to the other , partially or completely , keeping track only of the number of extra degrees of freedom @xcite .
thus , one can have various combined scenarios , with nonminimal couplings between gravity and scalar fields being the most used class .
speaking of modified gravity , a natural question arises , namely what formulation of gravity to use as a basis of modification ..
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the usual approach on the literature is to start from the standard curvature gravitational formulation , that is from the einstein - hilbert action of general relativity , and extend it in various ways @xcite .
however , a different but still very interesting class of modified gravity could arise starting from torsional formulations of general relativity ( gr ) . in particular , it is well known that einstein also constructed the `` teleparallel equivalent of general relativity '' ( tegr ) , where gravity is described not by the curvature tensor but by the torsion one @xcite .
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Suppose that you have an abstract for a scientific paper: this paper presents some results about the combinatorial properties of the glued semigroups and gives a combinatorial characterization of them .
some classical results for affine glued semigroups are generalized to finitely generated commutative reduced cancellative and with zero element glued semigroups . in addition , some algorithms to construct this kind of semigroups with different properties are given . .
And you have already written the first three sentences of the full article: let @xmath0 be a finitely generated commutative semigroup with zero element such that it is reduced ( i.e. @xmath1 ) .
we suppose that @xmath2 is cancellative , that is to say , if @xmath3 with @xmath4 then @xmath5 with these conditions , we may assume that @xmath2 is a subsemigroup of a non necessarily torsion - free group .
if @xmath2 is torsion - free , then @xmath2 is an affine semigroup . from now on.
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, we assume that all the semigroups appearing in this work are finitely generated , commutative and reduced , thus in the sequel we omit these adjectives .
let @xmath6 be a field and @xmath7 $ ] the polynomial ring in @xmath8 indeterminates .
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Suppose that you have an abstract for a scientific paper: we present _ xmm - newton _ observations of ngc891 , a nearby edge - on spiral galaxy .
we analyse the extent of the diffuse emission emitted from the disk of the galaxy , and find that it has a single temperature profile with best fitting temperature of 0.26 kev , though the fit of a dual - temperature plasma with temperatures of 0.08 and 0.30 kev is also an acceptable fit .
there is a considerable amount of diffuse x - ray emission protruding from the disk in the nw direction out to approximately 6 kpc .
we analyse the point source population using a _ chandra _ observation , using a maximum likelihood method to find that the slope of the cumulative luminosity function of point sources in the galaxy is @xmath0 . using a sample of other local galaxies , we compare the x - ray and infrared properties of ngc891 with those of normal and starburst spiral galaxies , and
conclude that ngc891 is most likely a starburst galaxy in a quiescent state .
we establish that the diffuse x - ray luminosity of spirals scales with the far infra - red luminosity as @xmath1 , except for extreme starbursts , and ngc891 does not fall in the latter category .
we study the supernova sn1986j in both _
xmm - newton _ and _ chandra _ observations , and find that the x - ray luminosity has been declining with time more steeply than expected ( @xmath2 ) .
[ firstpage ] galaxies : individual : ngc891 x - rays : diffuse emission galaxies : starburst supernovae : individual : sn1986j x - rays : galaxies .
And you have already written the first three sentences of the full article: the environment of a spiral galaxy can influence its evolution in many ways .
close interactions with nearby galaxies have been shown to trigger inspire star formation , and thus alter the interstellar medium ( ism ) of the galaxy .
properties of the ism could also be affected by direct infall of material from the intergalactic medium ( igm ) , or , if the galaxy is in a group or cluster , by the ram pressure stripping by the igm . however , in certain , outflows into the igm could be a significant mode of the interaction of a galaxy with its surroundings ..
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bursts of star formation in the galaxy can , if sufficiently strong , lead to the outflow of matter , which will be predominantly visible at h@xmath3 and x - ray wavelengths @xcite .
these outflows can be strong enough to escape the visible extent of the galaxy , but still be retained by the halo of the galaxy . in some of these cases ,
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Suppose that you have an abstract for a scientific paper: we consider the subdiffusion reaction process with reactions of a type @xmath0 ( in which particles @xmath1 are assumed to be mobile whereas @xmath2 static ) in comparison to the subdiffusion
reaction process with @xmath3 reactions which was studied by i.m .
sokolov , m.g.w .
schmidt , and f. sagus in _ phys .
rev .
e _ * 73 * , 031102 ( 2006 ) . in both processes
a rule that reactions can only occur between particles which continue to exist is taken into account .
although in both processes a probability of the vanishing of particle @xmath1 due to a reaction is independent of both time and space variables ( assuming that in the system with the @xmath0 reactions , particles @xmath2 are distributed homogeneously ) we show that subdiffusion reaction equations describing these processes as well as their greens functions are qualitatively different .
the reason for this difference is as follows . in the case of the former reaction , particles @xmath1 and @xmath2 have to meet with some probability before the reaction occurs in contradiction with the case of the latter reaction . for the subdiffusion process with the @xmath0 reactions we consider three models which differ in some details concerning a description of the reactions .
we base the method considered in this paper on a random walk model in a system with both discrete time and space variables .
then , the system with discrete variables is transformed into a system with both continuous time and space variables .
such a method seems to be convenient in analysing subdiffusion reaction processes with partially absorbing or partially reflecting walls .
the reason is that within this method we can determine greens functions without a necessity of solving a fractional differential subdiffusion reaction equation with boundary conditions at the walls .
as an example we use the model to find the greens functions for a subdiffusive reaction system ( with the reactions mentioned above ) , which is bounded by a partially absorbing wall....
And you have already written the first three sentences of the full article: the process of subdiffusion can occur in media in which particles movement is strongly hindered due to the internal structure of a medium .
subdiffusion is usually defined as a random walk process in which @xmath4 , where @xmath5 is a mean square displacement of a random walker , @xmath6 is a subdiffusion parameter ( @xmath7 ) , @xmath8 is a subdiffusion coefficient and @xmath9 denotes the gamma function ; for normal diffusion there is @xmath10 .
subdiffusion is mostly described by means of subdiffusion equations with a fractional time derivative derived from the continuous time random walk formalism @xcite ..
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when the subdiffusion process is extended to a subdiffusion reaction process then the form and the position of the reaction term within the subdiffusion
reaction equation is not clear .
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Suppose that you have an abstract for a scientific paper: we find that the viability of a cosmological model that incorporates 2 sterile neutrinos with masses around 1 ev each , as favored by global neutrino oscillation analyses including short baseline results , is significantly dependent on the choice of datasets included in the analysis and the ability to control the systematic uncertainties associated with these datasets .
our analysis includes a variety of cosmological probes including the cosmic microwave background ( wmap7+spt ) , hubble constant ( hst ) , galaxy power spectrum ( sdss - dr7 ) , and supernova distances ( sdss and union2 compilations ) . in the joint observational analysis ,
our sterile neutrino model is equally favored as a @xmath0cdm model when using the mlcs light curve fitter for the supernova measurements , and strongly disfavored by the data at @xmath1 when using the salt2 fitter .
when excluding the supernova measurements , the sterile neutrino model is disfavored by the other datasets at @xmath2 , and at best becomes mildly disfavored at @xmath3 when allowing for curvature , evolving dark energy , additional relativistic species , running of the spectral index , and freedom in the primordial helium abundance .
no single additional parameter accounts for most of this effect . therefore , if laboratory experiments continue to favor a scenario with roughly ev mass sterile neutrinos , and if this becomes decisively disfavored by cosmology , then a more exotic cosmological model than explored here may become necessary . .
And you have already written the first three sentences of the full article: the standard models of particle physics and cosmology do not yet fully describe the neutrino sector , with open questions related to the mass - generation mechanism of the neutrinos , any sterile neutrino partners of the active neutrinos , and their potential relation to the number of relativistic degrees of freedom inferred from cosmology . in recent years
, there has been some experimental evidence pointing towards the existence of additional light ( effectively massless ) degrees of freedom .
in particular , a combined analysis of cosmic microwave background ( cmb ) data from wmap7 , baryon acoustic oscillation ( bao ) distances from sdss+2df , and hubble constant from hst yields a weak preference for additional light degrees of freedom ( @xmath4 ) @xcite ..
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when moreover including small - scale cmb data from act or spt , this preference mildly increases to the @xmath5 level ( @xmath6 with addition of act @xcite and @xmath7 with addition of spt @xcite ) .
these constraints on @xmath8 explicitly assume that the additional particles are massless , and have sparked further work @xcite .
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Suppose that you have an abstract for a scientific paper: a recently developed analytical method for systematic improvement of the convergence of path integrals is used to derive a generalization of euler s summation formula for path integrals .
the first @xmath0 terms in this formula improve convergence of path integrals to the continuum limit from @xmath1 to @xmath2 , where @xmath3 is the coarseness of the discretization .
monte carlo simulations performed on several different models show that the analytically derived speedup holds . ,
, path integral , quantum theory , effective action 05.30.-d , 05.10.ln , 03.65.db .
And you have already written the first three sentences of the full article: feynman s path integrals @xcite represent a compact and rich formalism for dealing with quantum theories .
they have proved to be powerful tools for investigating symmetries , deriving non - perturbative results , delineating connections between different theories and different sectors of theories .
their flexibility and intuitive appeal have allowed us to generalize quantization to ever more complicated systems and have led to a rich cross fertilization of ideas between high energy and condensed matter physics @xcite ..
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today , they are used both analytically and numerically @xcite in many other areas of physics , in chemistry and materials science , as well as in quantitative finance @xcite .
unfortunately we still have very little knowledge of the precise mathematical properties of path integrals . as a result
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Suppose that you have an abstract for a scientific paper: we present a study of the reciprocity of human behaviour based on mobile phone usage records .
the underlying question is whether human relationships are mutual , in the sense that both are equally active in keeping up the relationship , or is it on the contrary typical that relationships are lopsided , with one party being significantly more active than the other .
we study this question with the help of a mobile phone data set consisting of all mobile phone calls between 5.3 million customers of a single mobile phone operator .
it turns out that lopsided relations are indeed quite common , to the extent that the variation can not be explained by simple random deviations or by variations in personal activity .
we also show that there is no non - trivial correlation between reciprocity and local network density .
= 1 .
And you have already written the first three sentences of the full article: representing collections of social relations as networks has become a standard practice not only in sociology but also in the study of complex systems . a social network @xmath0 is defined by the set of @xmath1 nodes , @xmath2 , which correspond to individuals , and by the set of edges ( or links ) @xmath3 , which correspond to some associations between the individuals .
even though it is common to assume the associations to be symmetric ( i.e. @xmath4 ) @xcite , for our purposes the edges are always directed , meaning that @xmath5 is independent of @xmath6 . in a _
weighted _ network each edge is also assigned a weight ..
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we consider the edge weights as proxies for the strength of a relationship , and therefore the weights are strictly positive . in our notation
@xmath7 is the weight of a directed edge from node @xmath8 to @xmath9 , and @xmath10 is equivalent to saying that there is no edge from @xmath8 to @xmath9 .
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Suppose that you have an abstract for a scientific paper: charged - pion decay offers many opportunities to study lorentz violation . using an effective field theory approach
, we study lorentz violation in the lepton , @xmath0-boson , and quark sectors and derive the differential pion - decay rate , including muon polarization . using coordinate redefinitions we are able to relate the first - generation quark sector , in which no bounds were previously reported , to the lepton and @xmath0-boson sector .
this facilitates a tractable calculation , enabling us to place bounds on the level of @xmath1 on first - generation quark parameters .
our expression for the pion - decay rate can be used to constrain lorentz violation in future experiments . .
And you have already written the first three sentences of the full article: many quantum - gravity theories predict scenarios in which lorentz symmetry is ( spontaneously ) broken @xcite .
this breakdown of lorentz symmetry is often studied in the context of the standard - model extension ( sme ) @xcite .
the sme is an effective field theory containing all possible lorentz - violating terms that are singlets under the gauge group of the standard model ( sm ) of particle physics ..
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these terms are built out of sm fields contracted with tensor coefficients that parametrize lorentz violation .
many of these sme coefficients have been constrained with high precision @xcite , but weak decays still offer interesting possibilities to obtain new bounds , or to improve existing bounds @xcite .
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Suppose that you have an abstract for a scientific paper: superfluid phases of @xmath0he are quantuim liquids with the interacting fermionic and bosonic fields . in many respects
they can simulate the interacting quantum fields in the phyiscal vacuum .
one can observe analogs of such phenomena as axial anomaly , vacuum polarization , zero - charge effect , fermionic charge of the vacuum , baryogenesis , ergoregion , vacuum instability , etc .
we discuss some topics on example of several linear defects in @xmath1he - a : ( 1 ) disgyration , which simulates the extremely massive cosmic string : ( 2 ) singular vortex , which is analogous to the spinning cosmic string ; and ( 3 ) continuous vortex , which motion causes the `` momentogenesis '' which is the analog of baryogenesis in early universe . the production of the fermionic momentum by the vortex motion ( the counterpart of the electroweak baryogenesis ) has been recently measured in manchester experiments on rotating superfluid @xmath1he - a and @xmath1he - b . to simulate the other phenomena one needs rather low temperature and high homogeneity , which probably can be reached under microgravity conditions . .
And you have already written the first three sentences of the full article: here we demonstrate several of numerous examples of analogy between high energy physics and superfluid @xmath1he .
we consider 3 types of topologically stable linear defects in @xmath1he - a , which exhibit the properties of different types of cosmic strings .
the `` gravity '' and the axial anomaly in the presence of such defects are discussed ..
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the quasiparticles in @xmath1he - a are chiral and massless fermions . close to the gap nodes , ie at @xmath2 ( @xmath3 is unit vector in the direction of the gap nodes in the momentum space ) the energy spectrum @xmath4 of the gapless a - phase fermions are `` relativistic '' @xcite : @xmath5 here the `` vector potential '' @xmath6 is dynamical : @xmath7 ; @xmath8 ; and the metric tensor is @xmath9 where @xmath10 and @xmath11 ( with @xmath12 ) are `` speeds of light '' propagating transverse to @xmath3 and along @xmath3 correspondingly ; @xmath13 is the fermi momentum ; @xmath14 is the fermi velocity ; @xmath15 is the mass of @xmath1he atom ; @xmath16 is the gap amplitude in @xmath1he - a . in the presence of superflow with the superfluid velocity @xmath17 the following term
is added to the energy @xmath4 : @xmath18 the second term corresponds to the scalar potential @xmath19 of the `` electromagnetic field '' , while the first one leads to the nonzero element @xmath20 of the metric tensor . as a result the eq.(1.1 ) transforms to @xmath21 with @xmath22 , @xmath23 and the metric tensor @xmath24
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Suppose that you have an abstract for a scientific paper: in this paper , we propose successive optimization non - linear precoding strategies for physical - layer security in wireless networks .
we also investigate different precoding techniques for multi - user mimo systems under various conditions of channel state information ( csi ) between the access point and the users and the eavesdroppers . a non - linear precoding technique based on successive optimization tomlinson - harashima precoding ( so - thp ) and simplified generalized matrix inversion (
s - gmi ) technique is proposed along with a strategy for injecting artificial noise prior to transmission .
simulation results show that the proposed so - thp+s - gmi precoding technique outperforms existing non - linear and linear precoding algorithms in terms of ber and secrecy rate performances .
+ physical - layer security techniques , precoding , transmit processing . .
And you have already written the first three sentences of the full article: data security in wireless systems has been dominated in the past by encryption methods like data encryption standard ( des ) and advanced encryption standard ( aes ) which have played very important roles in the security aspects of data transmission .
however , these encryption algorithms suffer from high complexity and latency .
this has motivated the investigation of novel secrecy techniques which can be implemented in the physical layer and which are under consideration to provide secure wireless transmission . in the 1970s , wyner posed the alice - bob - eve problem and proposed the wire - tap transmission system in @xcite ..
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the wire - tap transmission system gives a basic description on how to achieve the secrecy in the physical layer with better gaussian channels between users than the gaussian wire - tap channel .
later on another study reported in @xcite showed that secrecy transmission is possible even when the eavesdropper has a better channel to the transmitter in a statistical sense than the receiver with confidential messages . the secrecy capacity @xcite for different kinds of channels , such as the gaussian wire - tap channel , the mimo wire - tap channels have been studied in @xcite and @xcite . in some later works @xcite , @xcite , it has been found that by adding artificial noise to the system the secrecy of the transmission can be further enhanced . in recent years , precoding techniques have been widely applied to multi - user mimo systems .
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Suppose that you have an abstract for a scientific paper: we consider the relativistic scattering of unequal - mass scalar particles through graviton exchange in the small - angle high - energy regime and calculate the scattering amplitude up to the next - to - leading eikonal correction , including gravitational effects of the same order .
we find that these power corrections are consistent with the exponentiation of a corrected phase in impact parameter space , once all possible graviton exchanges are summed .
the leading power correction is suppressed by a single power of the ratio of momentum transfer to the energy of the light particle in the rest frame of the heavy particle , independent of the heavy particle mass . for large enough heavy - particle mass ,
the saddle point for the impact parameter is modified compared to the leading order by a multiple of the schwarzschild radius determined by the mass of the heavy particle , independent of the energy of the light particle . .
And you have already written the first three sentences of the full article: there has been a renewed interest in perturbative quantum gravity in part due to recent developments illuminating a relationship between gravity and gauge theory amplitudes @xcite and also because of its relevance in high energy , small angle scattering @xcite .
the long distance regime of this theory is particularly interesting as quantum gravity has a simpler infrared structure than gauge theories .
for instance , there is a cancellation of collinear divergences in the former theory but not the latter @xcite and the logarithmically divergent soft amplitudes have a ladder like structure . since the infrared behavior of perturbative quantum gravity is tractable , it is important to look for observables for which long distance effects are particularly important ..
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a fundamentally infrared dominated physical quantity of note in perturbative quantum gravity is the eikonal phase that has been calculated for small - angle high - energy scattering processes .
an eloquent overview of the eikonal regime for this type of scattering is given in a set of lectures by giddings @xcite .
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Suppose that you have an abstract for a scientific paper: in this paper , we calculate the contribution of the littlest higgs(lh ) model to the process @xmath0 at the future high energy @xmath1 collider(@xmath2 ) .
the results show that , within the parameter spaces preferred by the electroweak precision , the deviation of the total cross sections from its @xmath3 value varies from a few percent to tens percent .
the correction of the lh model to the process might be detected at the future @xmath2 experiments in the favorable parameter space .
on the other hand , we find that the correction of the lh model is sensitive to the trilinear higgs coupling in some case and the process can also provide us a chance to probe such coupling in the lh model .
pacs number(s ) : 12.60cn , 14.80.mz , 12.15.lk , 14.80.cp .
And you have already written the first three sentences of the full article: + the standard model(sm)provides an excellent effective field theory description of almost all particle physics experiments .
but in the sm the higgs boson mass suffers from an instability under radiative corrections .
the naturalness argument suggests that the cutoff scale of the sm is not much above the electroweak scale : new physics will appear around tev energies . among the extended models beyond the sm , the little higgs model offers a very promising solution to the hierarchy problem in which the higgs boson is naturally light as a result of nonlinearly realized symmetry @xcite ..
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the key feature of this kind of models is that the higgs boson is a pseudo - goldstone boson of an approximate global symmetry which is spontaneously broken by a vacuum expectation value(vev ) at a scale of a few tev and thus is naturally light . + the most economical little higgs model is the littlest higgs(lh ) model , which is based on the @xmath4 nonlinear sigma model @xcite .
it consists of a @xmath5 global symmetry , which is spontaneously broken down to @xmath6 by a vacuum condensate @xmath7 . in the lh model , a set of new heavy gauge bosons@xmath8 and a new heavy - vector - like quark(t )
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Suppose that you have an abstract for a scientific paper: we report the experimental study of resonant rayleigh scattering in gaas - algaas superlattices with ordered and intentionally disordered potential profiles ( correlated and uncorrelated ) in the growth direction @xmath0 .
we show that the intentional disorder along @xmath0 modify markedly the energy dispersion of the dephasing rates of the excitons .
the application of an external magnetic field in the same direction allows the continuous tuning of the in plane exciton localization and to study the interplay between the in plane and vertical disorder .
= 10000 .
And you have already written the first three sentences of the full article: in recent years , a large number of studies has been devoted to explore the general properties of disordered systems through the investigation of the optical response and transport properties of semiconductor nanostructures .
an important topic in the physics of disordered systems is to understand the influence of an intentionally disordered potential profile along the growth axis @xmath0 in semiconductor superlattices ( sl s ) on quantum interference and carrier localization @xcite .
sl s are excellent candidates to perform such a study since the advances achieved in molecular beam epitaxy ( mbe ) allow the fabrication sl s tailored with desired conduction- and valence - band profiles . in this way it is possible to design a great variety of one dimensional potentials with intentional disordered in the growth direction @xmath0 ( vertical disorder ) which coexists with the in plane disorder due to unintentional growth islands ..
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the global result is an anisotropic disorder which effect on the quantum interference has become an interesting subject of recent experimental studies . as an example , magneto - transport measurements in doped semiconductor superlattices recently allowed the study of the effects of the anisotropy on the phase - breaking time of the electrons @xcite . in the present work we measure simultaneously the continuous wave resonant rayleigh scattering ( rrs ) , the photoluminescence(pl ) and photoluminescence excitation ( ple ) spectra of semiconductor sl s in a magnetic field to study the influence of the vertically correlated and uncorrelated anisotropic disorder on the coherence relaxation and exciton localization .
we use this technique since rrs has access to information on the effective localization and on the spectral dispersion of the dephasing @xcite while the photoluminescence(pl ) and photoluminescence excitation ( ple ) spectra in magnetic field are valid techniques to study the exciton delocalization along @xmath0 @xcite . at the same time
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Suppose that you have an abstract for a scientific paper: the qcd sum rule for the pentaquark @xmath0 , first analyzed by sugiyama , doi and oka , is reanalyzed with a phenomenological side that explicitly includes the contribution from the two - particle reducible kaon - nucleon intermediate state .
the magnitude for the overlap of the @xmath0 interpolating current with the kaon - nucleon state is obtained by using soft - kaon theorem and a separate sum rule for the ground state nucleon with the pentaquark nucleon interpolating current .
it is found that the k - n intermediate state constitutes only 10% of the sum rule so that the original claim that the parity of @xmath0 is negative remains valid . .
And you have already written the first three sentences of the full article: the discovery of the @xmath0 baryon by leps collaboration at spring-8 @xcite and subsequent confirmation in the other experiments @xcite have spurred a lot of works in the field of exotic hadrons .
so far , not much is known about the properties of the @xmath0 except its mass , which is about 1540 mev , and its small decay width , which is smaller than the experimental resolutions of around @xmath1 mev .
thus , to determine the quantum numbers as well as other properties of @xmath0 , various production mechanisms have been proposed @xcite ..
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the @xmath0 baryon , being a strangeness + 1 state , is exotic since its minimal quark content should be @xmath2 .
other states that have positive strangeness but different charges are not observed , which suggests that the @xmath0 is an isosinglet .
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Suppose that you have an abstract for a scientific paper: in the present work we study a dark energy model in which a non - linear scalar field ( tachyon ) with a born - infeld type of action is responsible for the observed cosmic acceleration . the potential of the tachyon is well - motivated since it comes from open string theory and the model is subjected to various cosmological constraints with data coming from supernovae as well as from microwave background radiation .
our analysis shows that in the particular model under study the tachyon can be an excellent candidate for dark energy in the universe , as the model agrees with a series of observational data and for a wide range of the parameters of the model . * cosmological constraints on a dark energy * * model with a non - linear scalar field * g. panotopoulos department of physics , university of crete , 0.2 cm heraklion , crete , greece 0.2 cm email:[email protected]_ .
And you have already written the first three sentences of the full article: perhaps the most dramatic discovery in modern cosmology is the observational fact that the present universe undergoes an accelerating phase . during the last ten years or
so a remarkable progress in technology has allowed us to witness extraordinary precision measurements in cosmology .
a plethora of observational data are now available , which show that we live in a flat universe that expands with an accelerating rate and that the dominant component in the energy budget of the universe is an unusual material , the nature of which still remains unknown ..
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identifying the origin and nature of dark energy is one of the great challenges in modern theoretical cosmology .
the simplest candidate for dark energy is the cosmological constant , which corresponds to a perfect fluid with parameter @xmath0 .
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Suppose that you have an abstract for a scientific paper: i review the basics of perturbative qcd , including infrared divergences and safety , collinear and @xmath0 factorization theorems , and various evolution equations and resummation techniques for single- and double - logarithmic corrections .
i then elaborate its applications to studies of jet substructures and hadronic two - body heavy - quark decays . .
And you have already written the first three sentences of the full article: one of the important missions of the large hadron collider ( lhc ) is to search for new physics beyond the standard model .
the identification of new physics signals usually requires precise understanding of standard - model background , whose contributions mainly arise from quantum chromodynamics ( qcd ) .
many theoretical approaches have been developed based on qcd , which are appropriate for studies of processes in different kinematic regions and involving different hadronic systems ..
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the theoretical framework for high - energy hadron collisions is known as the perturbative qcd ( pqcd ) .
i will focus on pqcd below , introducing its fundamental ingredients and applications to lhc physics .
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Suppose that you have an abstract for a scientific paper: we present a detailed theoretical study of scanning tunneling imaging and spectroscopy of c@xmath0 on silver and gold surfaces , motivated by the recent experiments and discussion by x. lu et al .
[ prl * 90*,096802(2003 ) and prb * 70*,115418(2004 ) ] .
the surface / sample / tip system is described within a self consistent dft based tight binding model .
the topographic and conductance images are computed at constant current from a full self consistent transport theory based on nonequilibrium green s functions and compared with those simulated from the local density of states .
the molecular orbitals of c@xmath0 are clearly identified in the energy resolved maps , in close correspondence with the experimental results .
we show how the tip structure and orientation can affect the images .
in particular , we consider the effects of truncated tips on the energy resolved maps . .
And you have already written the first three sentences of the full article: scanning tunneling microscopy ( stm ) was introduced to image surface structures in real space @xcite , and is nowadays used to obtain more complete information on the local electronic properties with the scanning tunneling spectroscopy ( sts ) technique .
its operation is based on the measurement of the tiny tunneling current flowing from a very sharp conducting tip to the surface when a bias voltage is applied .
images are obtained by recording the vertical displacement of the tip as it is moved across the surface , while keeping the tunneling current constant with a precise feedback mechanism . if the current increases due to a protrusion on the surface , the tip is lifted to bring the current back to the set value , therefore revealing the topography of the substrate ..
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tersoff and hamann @xcite have shown how the images do not only reflect the geometric structure of the surface , but also depend on the electronic density of states of the sample , which is identified , to a first approximation , with the differential conductance .
this observation has opened the way to spectroscopic measurements with a spatial resolution which is by far not accessible by other surface science techniques .
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Suppose that you have an abstract for a scientific paper: as is well - known , the requirement that gamma ray bursts be optically thin to high energy photons yields a lower limit on the lorentz factor ( @xmath0 ) of the expansion . in this paper , we provide a simple derivation of the lower limit on @xmath0 due to the annihilation of photon pairs , and correct the errors in some of the previous calculations of this limit .
we also derive a second limit on @xmath0 due to scattering of photons by pair - created electrons and positrons .
for some bursts , this limit is the more stringent .
in addition , we show that a third limit on @xmath0 , which is obtained by considering the scattering of photons by electrons which accompany baryons , is nearly always less important than the second limit .
finally , we evaluate these limits for a number of bursts . .
And you have already written the first three sentences of the full article: many gamma ray bursts ( grb s ) emit photons with very high observed energies ( @xmath1 1 mev ) .
if the expansions of the bursts were non - relativistic , then the optical depth to the high energy photons would be so large that these photons could not be observed .
this is the `` compactness problem '' ( e.g. @xcite ) ..
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three basic processes contribute to the optical depth of high energy photons : ( a ) annihilation of pairs of photons into @xmath2 pairs ; ( b ) scattering of photons by either the @xmath3 or the @xmath4 created by the annihilation of photon pairs ; ( c ) scattering of photons by the electrons which are associated with baryons that may be present in the exploding ejecta . since the optical depth from each of these three processes decreases with increasing lorentz factor ( @xmath0 ) of the expansion , the requirement that the burst be optically thin yields a lower limit on @xmath0 .
in the following sections , we calculate the appropriate lower limits on @xmath0 .
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Suppose that you have an abstract for a scientific paper: a simple question of celestial mechanics is investigated : in what regions of phase space near a binary system can planets persist for long times ? the planets are taken to be test particles moving in the field of an eccentric binary system . a range of values of the binary eccentricity and mass ratio is studied , and both the case of planets orbiting close to one of the stars , and that of planets outside the binary orbiting the system s center of mass , are examined . from the results ,
empirical expressions are developed for both @xmath0 the largest orbit around each of the stars , and @xmath1 the smallest orbit around the binary system as a whole , in which test particles survive the length of the integration ( @xmath2 binary periods ) .
the empirical expressions developed , which are roughly linear in both the mass ratio @xmath3 and the binary eccentricity @xmath4 , are determined for the range @xmath5-@xmath6 and @xmath7 in both regions , and can be used to guide searches for planets in binary systems . after considering the case of a single low - mass planet in binary systems , the stability of a mutually - interacting system of planets orbiting one star of a binary system is examined , though in less detail .
# 1 .
And you have already written the first three sentences of the full article: the long - standing question of whether planets can form and then persist in binary star systems appears to have been answered observationally .
planets have been detected about 55 @xmath8 cancri , @xmath9 bootis and 16 cygni b , all of which have companion stars ( butler et al .
1997 ; cochran et al ..
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1997 ) . given that this basic question has been answered , one might now wonder what types of binary systems can harbor planets . rather than addressing the more difficult issue of how planets are formed in binary systems , a simple question of celestial mechanics
is asked : in what regions of phase space near a binary system could low - mass planets persist for long times ?
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Suppose that you have an abstract for a scientific paper: i set the stage for discussion of the stellar populations in interacting galaxies by looking back over the slow development of our understanding of these systems . from early anecdotal collections , to systematic cataloging , and finally to increasingly sophisticated @xmath0-body calculations , we have seen how gravity in distributed systems can produce the stunning variety of structures we see . at the same time , measures across the spectrum have made it clear that galaxy interactions are linked to star formation , albeit with the physical mechanisms much less clear . improved data sets , including hst imaging , deep ir data , and large samples with well - defined selection criteria , have started to reveal correlations with dynamical parameters pointing to detailed histories of starbirth during collisions .
the merger hypothesis for elliptical galaxies has broadened into seeing interactions and mergers as important parts of the overall evolution of galaxies .
the connection becomes more important as we look to higher redshift , where more frequent interactions can drive the evolution of galaxies in multiple ways .
links between the properties of central black holes and surrounding galaxies makes it important likewise to understand the connections between agn and interactions , which has remained more ambiguous due to the strong role of sample selection .
finally , contemporary data reach deep enough to show that most galaxies have interacted in the observable past ; we must consider these events to be a normal part of galaxy history . .
And you have already written the first three sentences of the full article: with hindsight , astronomers knew that galaxies interact before understanding what galaxies are .
the famous depiction of the whirlpool galaxy m51 and its companion by the earl of rosse , from 1845 , marks not only the clear discovery of spiral structure in galaxies , but indicates a connection of the spiral pattern to the companion object . within 20 years , foucault s improvements ( notably silver coating of glass mirrors ) allowed jean chacornac to depict considerably more detailed structure , including the dust patches seen against the companion , with the much smaller paris 0.8 m reflector ( @xcite ) .
many astronomers attention was drawn to the remarkable variety of forms taken by interacting galaxies on viewing the atlases produced by @xcite , with its extension by @xcite , and especially the @xcite atlas ..
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vorontsov - velyaminov s work was somewhat neglected in the west , owing at least partly to its publication in a very small photographically - reproduced edition with images reproduced from the palomar sky survey .
in contrast , arp s images , many taken with the palomar 5 m telescope and using considerable care in acquisition and reproduction , were especially striking .
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Suppose that you have an abstract for a scientific paper: the thermal history of the universe before the epoch of nucleosynthesis is unknown .
the maximum temperature in the radiation - dominated era , which we will refer to as the reheat temperature , may have been as low as 0.7 mev . in this paper
we show that a low reheat temperature has important implications for many topics in cosmology .
we show that weakly interacting massive particles ( wimps ) may be produced even if the reheat temperature is much smaller than the freeze - out temperature of the wimp , and that the dependence of the present abundance on the mass and the annihilation cross section of the wimp differs drastically from familiar results .
we revisit predictions of the relic abundance and resulting model constraints of supersymmetric dark matter , axions , massive neutrinos , and other dark matter candidates , nucleosynthesis constraints on decaying particles , and leptogenesis by decay of superheavy particles .
we find that the allowed parameter space of supersymmetric models is altered , removing the usual bounds on the mass spectrum ; the cosmological bound on massive neutrinos is drastically changed , ruling out dirac ( majorana ) neutrino masses @xmath0 only in the range 33 kev @xmath1 6 ( 5 ) mev , which is significantly smaller from the the standard disallowed range 94 ev @xmath2 2 gev ( this implies that massive neutrinos may still play the role of either warm or cold dark matter ) ; the cosmological upper bound on the peccei - quinn scale may be significantly increased to @xmath3gev from the usually cited limit of about @xmath4gev ; and that efficient out - of - equilibrium gut baryogenesis and/or leptogenesis can take place even if the reheat temperature is much smaller than the mass of the decaying superheavy particle . 0.0 in epsf # 1#2 .
And you have already written the first three sentences of the full article: the initiation of the radiation - dominated era of the universe is believed to result from the decay of coherent oscillations of a scalar field whose energy dominated the universe before decay .
the decay of the coherent oscillations of the scalar field and the subsequent thermalization of the decay products is known as reheating . , where @xmath5 is the friedmann
robertson walker scale factor ..
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one could just as easily imagine that the universe is dominated by some unstable massive particle species , rather than coherent oscillations of a scalar field . ]
the reheat process is often associated with the final stage of inflation . however , reheating could have been episodic , with several reheat events after inflation .
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Suppose that you have an abstract for a scientific paper: when dealing with certain kind of complex phenomena the theoretician may face some difficulties typically a failure to have access to information for properly characterize the system for applying the full power of the standard approach to the well established , physically and logically sound , boltzmann - gibbs statistics .
to circumvent such difficulties , in order to make predictions on properties of the system and looking for an understanding of the physics involved ( for example in analyzing the technological characteristics of fractal - structured devices ) can be introduced large families of auxiliary statistics .
we present here a systematization of these different styles in what can be termed as unconventional statistical mechanics , accompanied of an analysis of the construction and a clarification of its scope and interpretation .
as illustrations are derived heterotypical bose - einstein , fermi - dirac and maxwell - boltzmann distributions , and several applications including studies of experimental works are briefly described . .
And you have already written the first three sentences of the full article: over twenty years ago montroll and shlesinger wrote that _ in the world of investigation of complex phenomena that requires statistical modeling and interpretation , several competing styles have been emerging _ , each with its own champions @xcite . lately a large amount of efforts with a flood of papers related to one particular case has been given to the topic .
what is at play consists in that in the study of certain physicochemical systems we may face difficulties when handling situations involving fractal - like structures , correlations ( spatial and temporal ) with some type of scaling , turbulent and chaotic motion , small size ( nanometer scale ) system with eventually a low number of degrees of freedom and complicate boundary conditions , generalized hydrodynamics , and so on .
the interest on them has been recently enhanced as a consequence that such situations are present in electronic and opto - electronic devices of the nowadays point - first technologies and also in technological areas involving the use of disordered systems , polymeric solutions , conducting glasses , the case of microbatteries , and others ..
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the question is that these difficulties consist , as a rule , in that the theoretician can not properly satisfy _ fisher s criteria of efficiency and sufficiency _ @xcite in the conventional , well established , physically and logically sound boltzmann - gibbs statistics , meaning an impairment to correctly include the presence of large fluctuations ( and eventually higher - order variances ) and to account for the relevant and proper characteristics of the system , respectively .
then , just out of necessity and convenience and to be able to make predictions and in the way providing an understanding , even partial , of the physics of the system of interest , for example in analyzing technological characteristic of physico - chemical systems as illustrated in sect .
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Suppose that you have an abstract for a scientific paper: in a central nucleus - nucleus collision at high - energies , medium partons kicked by a near - side jet acquire a momentum along the jet direction and subsequently materialize as the observed ridge particles .
they carry direct information on the early parton momentum distribution which can be extracted by using the ridge data for central auau collisions at @xmath0 gev .
the extracted parton momentum distribution has a thermal - like transverse momentum distribution but a non - gaussian , relatively flat rapidity distribution at mid - rapidity with sharp kinematic boundaries at large rapidities that depend on the transverse momentum . in central high - energy heavy - ion collisions ,
the state of the parton medium during the early stage of a nucleus - nucleus collision is an important physical quantity .
it furnishes information for the investigation of the mechanism of parton production in the early stages of the collision of two heavy nuclei .
it also provides the initial data for the evolution of the system toward the state of quark - gluon plasma .
not much is know about the early state of the partons from direct experimental measurements .
recently , the star collaboration observed a @xmath1-@xmath2 correlation of particles associated with a near - side jet in central auau collisions at @xmath0 gev at rhic , where @xmath1 and @xmath3 are the azimuthal angle and pseudorapidity differences relative to a high-@xmath4 trigger particle @xcite .
the near - side correlations can be decomposed into a `` jet '' component with fragmentation and radiation products at @xmath5@xmath6(0,0 ) , and a `` ridge '' component at @xmath7@xmath80 with a ridge structure in @xmath3 .
while many theoretical models have been proposed @xcite , a momentum kick model was presented to describe the ridge phenomenon @xcite .
the model assumes that a near - side jet occurs near the surface and it kicks medium partons , loses energy along its way , and fragments into the trigger particle and other....
And you have already written the first three sentences of the full article: 40 j. bielcikova ( star collaboration ) , j. phys . *
g74 * , s929 ( 2007 ) ; l. molnar ( star collaboration ) , j. phys . *
g74 * , s592 ( 2007 ) ; b. abelev ( star collaboration ) , arxiv:0705.3371 ; c. nattrass ( star collaboration ) , proceedings of quark matter conference , jaipur , india , feb . 4 - 10 , 2008 ..
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r. c. hwa , arxiv:0708.1508 ; p. romatschke , phys .
rev . c*75 * 014901 ( 2007 ) ; s. a. voloshin , nucl .
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Suppose that you have an abstract for a scientific paper: the search for planets orbiting two stars ( spots ) survey aims to study the formation and distribution of planets in binary systems by detecting and characterizing circumbinary planets and their formation environments through direct imaging . with the sphere extreme adaptive optics instrument
, a good contrast can be achieved even at small ( @xmath0300 mas ) separations from bright stars , which enables studies of planets and disks in a separation range that was previously inaccessible . here , we report the discovery of resolved scattered light emission from the circumbinary disk around the well - studied young double star ak sco , at projected separations in the @xmath11340 au range .
the sharp morphology of the imaged feature is surprising , given the smooth appearance of the disk in its spectral energy distribution .
we show that the observed morphology can be represented either as a highly eccentric ring around ak sco , or as two separate spiral arms in the disk , wound in opposite directions .
the relative merits of these interpretations are discussed , as well as whether these features may have been caused by one or several circumbinary planets interacting with the disk . .
And you have already written the first three sentences of the full article: ak sco is a spectroscopic f5+f5 binary in the upper centaurus lupus ( ucl ) association with an estimated age of @xmath11020 myr ( e.g. * ? ? ?
* ; * ? ? ?
its distance is relatively uncertain , with the original hipparcos catalogue @xcite giving a value of 145@xmath2 pc while the newer @xcite reduction gives a value of 102@xmath3 pc ..
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however , interferometric measurements have independently provided a distance estimate of 141@xmath47 pc @xcite , hence we use this latter value here .
the system is classified as a haebe disk system from infrared excess ( e.g. * ? ? ?
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Suppose that you have an abstract for a scientific paper: we report _ chandra _ observations of the dwarf nova wx hyi in quiescence .
the x - ray spectrum displays strong and narrow emission lines of n , o , mg , ne , si , s and fe .
the various ionization states implied by the lines suggest that the emission is produced within a flow spanning a wide temperature range , from @xmath0 k to @xmath1 k. line diagnostics indicate that most of the radiation originates from a very dense region , with @xmath2 @xmath3 .
the _ chandra _
data allow the first tests of specific models proposed in the literature for the x - ray emission in quiescent dwarf novae .
we have computed the spectra for a set of models ranging from hot boundary layers , to hot settling flows solutions , to x - ray emitting coronae .
wx hyi differs from other dwarf novae observed at minimum in having much stronger low temperature lines , which prove difficult to fit with existing models , and possibly a very strong , broad o vii line , perhaps produced in a wind moving at a few @xmath4 @xmath5 .
the accretion rate inferred from the x - rays is lower than the value inferred from the uv .
the presence of high - velocity mass ejection could account for this discrepancy while at the same time explaining the presence of the broad o vii line .
if this interpretation is correct , it would provide the first detection of a wind from a dwarf nova in quiescence . .
And you have already written the first three sentences of the full article: cataclysmic variables ( cvs ) are a class of interacting binaries in which a donor star transfers mass onto a white dwarf ( wd ) accretor ( see warner 1995 for a comprehensive review ) .
the characteristics of the accretion flow depend mostly on the rate of accretion onto the wd and on the wd magnetic field strength . in non - magnetic systems
( @xmath6 g ) , accretion from the donor proceeds through an undisturbed accretion disk , which connects to the wd through a boundary layer ( patterson & raymond 1985 ) ..
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when the wd is more strongly magnetized , the accreting material is forced to follow the topology of the field lines before it hits the surface ( aizu 1973 ) . as a dwarf nova of the su uma type , wx hyi ( discovered by luyten 1932 ) belongs to the class of non - magnetic cvs .
its orbital period is 0.0748134 days , and because it does not show eclipses , only an estimated inclination angle of @xmath7 is available ( schoembs & vogt 1981 ) .
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Suppose that you have an abstract for a scientific paper: the capture numbers entering the rate equations ( re ) for submonolayer film growth are determined from extensive kinetic monte carlo ( kmc ) simulations for simple representative growth models yielding point , compact , and fractal island morphologies .
the full dependence of the capture numbers @xmath0 on island size @xmath1 , and on both the coverage @xmath2 and the @xmath3 ratio between the adatom diffusion coefficient @xmath4 and deposition rate @xmath5 is determined .
based on this information , the re are solved to give the re island size distribution ( re - isd ) , as quantified by the number @xmath6 of islands of size @xmath1 per unit area . the re - isds are shown to agree well with the corresponding kmc - isds for all island morphologies . for compact morphologies , however , this agreement is only present for coverages smaller than @xmath7 due to a significantly increased coalescence rate compared to fractal morphologies . as found earlier , the scaled kmc - isds @xmath8 as a function of scaled island size @xmath9 approach , for fixed @xmath2 , a limiting curve @xmath10 for @xmath11 .
our findings provide evidence that the limiting curve is independent of @xmath2 for point islands , while the results for compact and fractal island morphologies indicate a dependence on @xmath2 . .
And you have already written the first three sentences of the full article: the kinetics of submonolayer nucleation and island growth during the initial stage of epitaxial thin film growth has been studied intensively both experimentally and theoretically for more than three decades ( for reviews , see refs . , and references therein ) .
important aspects of the growth kinetics in the submonolayer growth regime can be described by the rate equations ( re ) approach.@xcite this approach has proven to be very valuable in inorganic thin film growth .
interestingly , many of the theoretical concepts developed for thin film growth kinetics of inorganic materials , have shown recently to be very valuable also for applications in organic thin film growth.@xcite this is due to the fact that these concepts often are not specifically referring to particular materials . instead , they take into account the key mechanisms involved in the complex interplay of deposition , evaporation , diffusion , aggregation and dissociation from a general viewpoint ..
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parameters entering the re are the capture numbers @xmath0 , which describe the strength of islands of size @xmath1 to capture adatoms at a coverage @xmath2 and ratio @xmath12 of the adatom diffusion coefficient @xmath4 and deposition flux @xmath5 .
the dependence of the capture numbers on @xmath1 has been studied for various @xmath13 but only for one or a few @xmath2 values . in this work
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Suppose that you have an abstract for a scientific paper: we consider numeration systems where digits are integers and the base is an algebraic number @xmath0 such that @xmath1 and @xmath0 satisfies a polynomial where one coefficient is dominant in a certain sense .
for this class of bases @xmath0 , we can find an alphabet of signed - digits on which addition is realizable by a parallel algorithm in constant time .
this algorithm is a kind of generalization of the one of avizienis .
we also discuss the question of cardinality of the used alphabet , and we are able to modify our algorithm in order to work with a smaller alphabet .
we then prove that @xmath0 satisfies this dominance condition if and only if it has no conjugate of modulus @xmath2 . when the base @xmath0 is the golden mean , we further refine the construction to obtain a parallel algorithm on the alphabet @xmath3 .
this alphabet can not be reduced any more .
numeration , addition , parallel algorithm , golden mean .
And you have already written the first three sentences of the full article: a positional numeration system is given by a base and by a set of digits .
the base @xmath0 is a real or complex number such that @xmath1 , and the digit set @xmath4 is a finite alphabet of real or complex digits .
the most studied numeration systems are of course the usual ones , where the base is a positive integer ..
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but there have been also numerous studies where the base is an irrational real number ( the so - called _ @xmath0-expansions _ ) , a complex number , or a non - integer rational number , _ etc_. some surveys can be found in ( * ? ? ?
* chapter 7 ) and ( * ? ? ? * chapter 2 ) . in this work ,
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Suppose that you have an abstract for a scientific paper: the study has been carried out on the prospects of probing the sterile neutrino mixing with the magnetized iron calorimeter ( ical ) at the india - based neutrino observatory ( ino ) , using atmospheric neutrinos as a source .
the so - called 3 @xmath0 1 scenario is considered for active - sterile neutrino mixing and lead to projected exclusion curves in the sterile neutrino mass and mixing angle plane .
the analysis is performed using the neutrino event generator nuance , modified for ical , and folded with the detector resolutions obtained by the ino collaboration from a full geant4 based detector simulation .
a comparison has been made between the results obtained from the analysis considering only the energy and zenith angle of the muon and combined with the hadron energy due to the neutrino induced event .
a small improvement has been observed with the addition of the hadron information to the muon . in the analysis
we consider neutrinos coming from all zenith angles and the earth matter effects are also included .
the inclusion of events from all zenith angles improves the sensitivity to sterile neutrino mixing by about 35@xmath1 over the result obtained using only down - going events .
the improvement mainly stems from the impact of earth matter effects on active - sterile mixing .
the expected precision of ical on the active - sterile mixing is explored and allowed confidence level ( c.l . )
contours presented . at the assumed true value of @xmath2 for the sterile mixing angles and marginalization over @xmath3 and the sterile mixing angles , the upper bound at 90% c.l .
( from 2 parameter plots ) is around @xmath4 for @xmath5 and @xmath6 , and about @xmath7 for @xmath8 . .
And you have already written the first three sentences of the full article: a series of measurements using neutrinos from different sources _
viz_. solar @xcite , atmospheric , @xcite reactor @xcite , and accelerator @xcite , have established the phenomenon of neutrino oscillations .
the discovery of neutrino oscillations represents today one of the main experimental evidences of new physics beyond the standard model ..
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results from these experiments led us to the current standard three - neutrino mixing paradigm , in which the three active neutrinos @xmath9 , @xmath10 , @xmath11 are superposition of three massive neutrinos @xmath12 , @xmath13 , @xmath14 with masses @xmath15 , @xmath16 and @xmath17 , respectively . the experimental results given by solar neutrino oscillations correspond to @xmath18 7.5 @xmath19 10@xmath20 ev@xmath21 and atmospheric neutrino oscillations correspond to @xmath22 @xmath19 10@xmath23 ev@xmath21 , where @xmath24 and @xmath25 with @xmath261 , 2 , 3 . two mixing angles , which are important in the solar neutrino and atmospheric neutrino sectors , have been measured to be large ( @xmath27 and @xmath28 , respectively ) while the third mixing angle which connects the two sectors has been recently measured @xmath29 @xcite .
while data from all of the above mentioned experiments fit nicely into the standard three generation picture , there are indications ( sometimes referred as anomalies ) from other neutrino experiments which provide a motivation to extend the three generation paradigm to include a fourth neutrino mixed with the three standard neutrinos .
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Suppose that you have an abstract for a scientific paper: a possibility to measure @xmath0 using reactor neutrinos is examined in detail .
it is shown that the sensitivity @xmath1 can be reached with data by placing identical chooz - like detectors at near and far distances from a giant nuclear power plant whose total thermal energy is .
it is emphasized that this measurement is free from the parameter degeneracies which occur in accelerator appearance experiments , and therefore the reactor measurement plays a role complementary to accelerator experiments .
it is also shown that the reactor measurement may be able to resolve the degeneracy in @xmath2 if @xmath0 and @xmath3 are relatively large .
1.4 cm .
And you have already written the first three sentences of the full article: despite the accumulating knowledges of neutrino masses and the lepton flavor mixing by the atmospheric @xcite , the solar @xcite , and the accelerator @xcite neutrino experiments , the ( 1 - 3 ) sector of the maki - nakagawa - sakata ( mns ) matrix @xcite is still in the dark . at the moment , we only know that @xmath4 is small , @xmath5 , by the bound imposed by the chooz reactor experiment @xcite . in this paper
we assume that the light neutrino sector consists of three active neutrinos only .
one of the challenging goals in an attempt to explore the full structure of lepton flavor mixing would be measuring the leptonic cp or t violating phase @xmath6 in the mns matrix ..
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if kamland @xcite confirms the large - mixing - angle ( lma ) mikheev - smirnov - wolfenstein ( msw ) @xcite solution of the solar neutrino problem , the most favored one by the recent analyses of solar neutrino data @xcite , we will have an open route toward the goal .
yet , there might still exist the last impasse , namely the possibility of too small value of @xmath7 .
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10,468 |
Suppose that you have an abstract for a scientific paper: near - ultraviolet spectroscopic data obtained with the hst stis instrument on the dme flare star yz canis minoris ( yz cmi ) were analyzed .
flare and quiet intervals were identified from the broadband near - uv light curve , and the spectrum of each flare was separately extracted .
mg ii and fe ii line profiles show similar behavior during the flares .
two large flares allowed time - resolved spectra to be analyzed , revealing a very broad component to the mg ii k line profile in at least one flare spectrum ( f9b ) . if interpreted as a velocity , this component requires chromospheric material to be moving with fwhm @xmath0 250 km sec@xmath1 , implying kinetic energy far in excess of the radiative energy .
the mg ii k flare line profiles were compared to recent radiative hydrodynamic models of flare atmospheres undergoing electron beam heating .
the models successfully predict red enhancements in the line profile with typical velocity of a few km sec@xmath1 , but do not reproduce the flares showing blue enhancements , or the strongly broadened line observed in flare f9b .
a more complete calculation of redistribution into the line wings , including the effect of collisions with the electron beam , may resolve the origin of the excess line broadening . .
And you have already written the first three sentences of the full article: spectroscopic signatures of flares on m dwarfs have been sporadically explored , mostly at optical wavelengths , since the pioneering observations of uv ceti by joy & humason ( 1949 ) .
principal features observed during flares include strong continuum radiation rising toward the blue and near - ultraviolet ; broad , enhanced hydrogen balmer series emission lines ; enhanced emission in high temperature lines such as he i , he ii , c iv , n v , si iv ; enhanced xray emission ; and bursts of radio emission ( e.g. kunkel 1967 , jackson et al .
1989 , hawley & pettersen 1991 , eason et al ..
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1992 , osten et al . 2005 ) . yz canis minoris ( yz cmi , also known as gliese 285 ) , an active dm4.5e star with v=11.1 and d=6pc ( perryman et al .
1997 ) , has been a popular target for flare monitoring campaigns , due to its proximity and strong activity , which improves the chances of observing a flare .
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10,469 |
Suppose that you have an abstract for a scientific paper: the oxidized ag(111 ) surface has been studied by a combination of experimental and theoretical methods , scanning tunneling microscopy ( stm ) , x - ray photoelectron spectroscopy ( xps ) , and density functional theory ( dft ) .
a large variety of different surface structures is found , depending on the detailed preparation conditions .
the observed structures fall into four classes : ( a ) individually chemisorbed atomic oxygen atoms , ( b ) three different oxygen overlayer structures , including the well - known @xmath0 phase , formed from the same ag@xmath1 and ag@xmath2 building blocks , ( c ) a @xmath3 structure not previously observed , and ( d ) at higher oxygen coverages structures characterized by stripes along the high - symmetry directions of the ag(111 ) substrate .
our analysis provides a detailed explanation of the atomic - scale geometry of the ag@xmath1/ag@xmath2 building block structures , and the @xmath3 and stripe structures are discussed in detail .
the observation of many different and co - existing structures implies that the o / ag(111 ) system is characterized by a significantly larger degree of complexity than previously anticipated , and this will impact our understanding of oxidation catalysis processes on ag catalysts . .
And you have already written the first three sentences of the full article: ( color online ) coexistence of phases .
@xmath4 stm image of a ag(111 ) sample exposed to @xmath5 torr atomic oxygen for 40 min at 500 k sample temperature ( -0.44 na ,
-55.8 mv).,width=325 ] the oxidation of the ag(111 ) surface is a fascinating example of how a seemingly simple system can escape a detailed understanding for decades , in spite of repeated and thorough efforts ..
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the history of surface science investigations of the oxidation of ag(111 ) , briefly reviewed recently,@xcite started back in the sixties and early seventies with a couple of single crystal studies@xcite and took a serious upswing with the investigations by rovida _
_ in the seventies,@xcite who , in particular , reported on the now renowned @xmath0 phase . in the following much of the effort
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10,470 |
Suppose that you have an abstract for a scientific paper: the maximum mass limits of neutron stars in scalar - tensor gravity is discussed and compared with the limits set by general relativity .
the limit is parametrized with respect to the combination of the nuclear saturation parameters and the maximum sound velocity in the core .
it is shown that , for smaller values of the sound velocity in the core , the maximum mass limit of the scalarized neutron stars is larger than that of in general relativity . however
, for stiff equations of state with sound velocity higher than @xmath0 of the velocity of light , the maximum mass limit in general relativity is larger than that of in scalar - tensor gravity .
the results suggest that future observations of massive neutron stars , may constrain the maximum sound velocity as well as the coupling parameter in scalar - tensor gravity . .
And you have already written the first three sentences of the full article: general relativity ( gr ) is the prevailing theory for gravity . for hundred years
has been tested in various astrophysical scenarios and its agreement with experiments and observations is remarkable .
still , most of gr s tests have been performed in the weak - field regime , e.g. in our solar system . moreover , there exist phenomena , such as dark matter and dark energy ( accelerated expansion of the universe ) which do no fit well in the standard gr framework . at smaller scales ,.
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it is not yet clear if gravitational field is described by gr in the strong - field regime , for example around / inside a compact object .
thus , one might probe and/or verify the gravitational theory in strong - field regime via the astronomical observations of the phenomena associated with compact objects .
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10,471 |
Suppose that you have an abstract for a scientific paper: coulomb interaction effects have pronounced consequences in carbon nanotubes due to their 1d nature . in particular , correlations imply the breakdown of fermi liquid theory and typically lead to luttinger liquid behavior characterized by pronounced power - law suppression of the transport current and the density of states , and spin - charge separation .
this paper provides a review of the current understanding of non - fermi liquid effects in metallic single - wall nanotubes ( swnts ) .
we provide a self - contained theoretical discussion of electron - electron interaction effects and show that the tunneling density of states exhibits power - law behavior .
the power - law exponent depends on the interaction strength parameter @xmath0 and on the geometry of the setup .
we then show that these features are observed experimentally by measuring the tunneling conductance of swnts as a function of temperature and voltage .
these tunneling experiments are obtained by contacting metallic swnts to two nanofabricated gold electrodes .
electrostatic force microscopy ( efm ) measurements show that the measured resistance is due to the contact resistance from the transport barrier formed at the electrode / nanotube junction .
these efm measurements show also the ballistic nature of transport in these swnts . while charge transport can be nicely attributed to luttinger liquid behavior , spin - charge separation has not been observed so far .
we briefly describe a transport experiment that could provide direct evidence for spin - charge separation . .
And you have already written the first three sentences of the full article: the electronic properties of one - dimensional ( 1d ) metals have attracted considerable attention for fifty years by now . starting with the work of tomonaga in 1950 @xcite and later by luttinger @xcite ,
it has become clear that the electron - electron interaction destroys the sharp fermi surface and leads to a breakdown of the ubiquituous fermi liquid theory pioneered by landau @xcite .
this breakdown is signalled by a vanishing quasiparticle weight @xmath1 in the presence of arbitrarily weak interactions ..
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the resulting non - fermi liquid state is commonly called luttinger liquid ( ll ) , or sometimes tomonaga - luttinger liquid .
the name `` luttinger liquid '' was coined by haldane @xcite to describe the universal low - energy properties of one - dimensional conductors .
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Suppose that you have an abstract for a scientific paper: for given computational resources , the accuracy of plasma simulations using particles is mainly held back by the noise due to limited statistical sampling in the reconstruction of the particle distribution function . a method based on wavelet analysis
is proposed and tested to reduce this noise .
the method , known as wavelet based density estimation ( wbde ) , was previously introduced in the statistical literature to estimate probability densities given a finite number of independent measurements .
its novel application to plasma simulations can be viewed as a natural extension of the finite size particles ( fsp ) approach , with the advantage of estimating more accurately distribution functions that have localized sharp features .
the proposed method preserves the moments of the particle distribution function to a good level of accuracy , has no constraints on the dimensionality of the system , does not require an a priori selection of a global smoothing scale , and its able to adapt locally to the smoothness of the density based on the given discrete particle data .
most importantly , the computational cost of the denoising stage is of the same order as one time step of a fsp simulation .
the method is compared with a recently proposed proper orthogonal decomposition based method , and it is tested with three particle data sets that involve different levels of collisionality and interaction with external and self - consistent fields . .
And you have already written the first three sentences of the full article: particle - based numerical methods are routinely used in plasma physics calculations @xcite . in many cases these methods are more efficient and simpler to implement than the corresponding continuum eulerian methods . however , particle methods face the well known statistical sampling limitation of attempting to simulate a physical system containing @xmath0 particles using @xmath1 computational particles .
particle methods do not seek to reproduce the exact individual behavior of the particles , but rather to approximate statistical macroscopic quantities like density , current , and temperature .
these quantities are determined from the particle distribution function ..
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therefore , a problem of relevance for the success of particle - based simulations is the reconstruction of the particle distribution function from discrete particle data .
the difference between the distribution function reconstructed from a simulation using @xmath2 particles and the exact distribution function gives rise to a discretization error generically known as `` particle noise '' due to its random - like character .
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10,473 |
Suppose that you have an abstract for a scientific paper: at the end of july 2006 , the blazar pks @xmath0 ( @xmath1 ) underwent a strong outburst observed at tev energies by hess ( up to @xmath2 crab flux level at @xmath3 gev ) .
the _ swift _ satellite followed the evolution of the source for about one month .
the data analysis reported in another paper has shown that , despite the violent activity at tev energies , the synchrotron energy distribution increased in normalization , but only with a small shift in frequency . in the present work
, we fit the broad - band spectrum with a log - parabolic model , to search for indications of intrinsic curvature , which in turn is usually interpreted as a signature of energy - dependent acceleration mechanisms of electrons .
address = inaf / iasf - bologna , via gobetti 101 , 40129 , bologna ( italy ) address = inaf / osservatorio astronomico di brera , via brera 28 , 20121 milano ( italy ) address = inaf / osservatorio astronomico di brera , via brera 28 , 20121 milano ( italy ) address = dipartimento di scienze , universit dellinsubria , via vallegio 11 , 22100 como ( italy ) address = inaf / osservatorio astronomico di brera , via brera 28 , 20121 milano ( italy ) address = george mason university , department of physics and astronomy , school of computational sciences , mail stop 3f3 , 4400 university drive , fairfax , va 22030 , usa address = inaf / osservatorio astronomico di torino , via osservatorio 20 , 10025 pino torinese ( italy ) address = inaf / osservatorio astronomico di torino , via osservatorio 20 , 10025 pino torinese ( italy ) address = inaf / osservatorio astronomico di trieste , via g.b .
tiepolo 11 , 34131 trieste ( italy ) address = inaf / osservatorio astronomico di brera , via brera 28 , 20121 milano ( italy ) address = osservatorio astronomico , universit di perugia , via b. bonfigli , 06126 perugia ( italy ) address = nasa / goddard space flight center , code 661 , greenbelt , md 20771 , usa address = inaf / iasf - bologna , via....
And you have already written the first three sentences of the full article: the hess cerenkov telescope alerted the astronomical community on july 27 , 2006 about an increase of activity of the blazar pks @xmath0 ( z=0.116 ) in the tev energy range @xcite .
the same night the blazar displayed flares up to 17 crab ( e > 200 gev ) on time scales of 5 minutes @xcite .
an immediate x - ray / uv / optical follow - up with the _ swift _ satellite was activated and the analysis of data is reported in @xcite . a prompt increase of the x - ray flux without large spectral changes was revealed ..
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interestingly , the frequency of the synchrotron peak remained at values similar to those observed in the past , with low tev activity @xcite .
further details can be found in @xcite .
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10,474 |
Suppose that you have an abstract for a scientific paper: it has been found in _ in vitro _
experiments that cytoskeletal filaments driven by molecular motors show finite diffusion in sliding motion even in the long filament limit [ y. imafuku _ et al .
_ , biophys
. j. 70 ( 1996 ) 878 - 886 ; n. noda _ et al . _ ,
biophys . 1 ( 2005 )
45 - 53 ] .
this anomalous fluctuation can be an evidence for cooperativity among the motors in action because fluctuation should be averaged out for a long filament if the action of each motor is independent . in order to understand the nature of the fluctuation in molecular motors , we perform numerical simulations and analyse velocity correlation in three existing models that are known to show some kind of cooperativity and/or large diffusion coefficient , i.e. sekimoto - tawada model [ k. sekimoto and k. tawada , phys . rev . lett .
75 ( 1995 ) 180 ] , prost model [ j. prost _
et al . _ ,
phys . rev .
lett .
72 ( 1994 ) 2652 ] , and duke model [ t. duke , proc .
natl .
acad .
sci .
usa , 96 ( 1999 ) 2770 ] .
it is shown that prost model and duke model do not give a finite diffusion in the long filament limit in spite of collective action of motors .
on the other hand , sekimoto - tawada model has been shown to give the diffusion coefficient that is independent of filament length , but it comes from the long time correlation whose time scale is proportional to filament length , and our simulations show that such a long correlation time conflicts with the experimental time scales .
we conclude that none of the three models do not represent experimental findings . in order to explain the observed anomalous diffusion
, we have to seek for the mechanism that should allow both the amplitude and the time scale of the velocity correlation to be independent of the filament length . * anomalous fluctuations in sliding motion of cytoskeletal filament driven by molecular motors : model simulations * 2ex * yasuhiro@xmath0 imafuku , namiko mitarai@xmath1 , katsuhisa tawada@xmath0 , and hiizu....
And you have already written the first three sentences of the full article: one of the outstanding problems in molecular processes in living systems has been how they achieve reliable action under the influence of overwhelming thermal and/or statistical fluctuations . in the case of muscle contraction ,
huxley@xcite has already noticed , in his original work , that collective action of many motors produces smooth sliding motion even though action of individual motor is highly stochastic .
recently , imafuku and co - workers have done series of experiments on filament motion driven by many molecular motors ; focusing on the _ fluctuation _ rather than the average motion , they have revealed an intriguing aspect of co - operativity in the collective action@xcite ..
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they performed the _ in vitro _
motility assay on an unloaded filament of length @xmath2 , measured the displacement @xmath3 over the time interval between @xmath4 and @xmath5 , and evaluated the diffusion coefficient @xmath6 in the sliding motion defined by @xmath7 where @xmath8 denotes the average over initial time @xmath4 and samples .
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10,475 |
Suppose that you have an abstract for a scientific paper: a comprehensive study on compactness has been carried out on the 2df galaxy group catalogue constructed by merchn & zandivarez .
the compactness indexes defined in this work take into account different geometrical constraints in order to explore a wide range of possibilities .
our results show that there is no clear distinction between groups with high and low level of compactness when considering particular properties as the radial velocity dispersion , the relative fraction of galaxies per spectral type and luminosity functions of their galaxy members .
studying the trend of the fraction of galaxies per spectral type as a function of the dimensionless crossing time some signs of dynamical evolution are observed . from the comparison with previous works on compactness
we realize that special care should be taken into account for some compactness criteria definitions in order to avoid possible biases in the identification .
a & a galaxies : clusters : general - galaxies : statistics . .
And you have already written the first three sentences of the full article: compact groups ( cgs ) are small systems of a few galaxies which are in close proximity one another .
their are excellent laboratories for studying galaxy interactions and , in particular , merging processes . given their high galaxy density ( equivalent to those at the centers of rich clusters ) and small velocity dispersion ( @xmath0 ) ,
cg members are expected to finally merge into one giant elliptical galaxy within a few short crossing times . historically , cgs were of interest because of the obvious distortion of many of their member galaxies . the first systematic seek for cgs.
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was pioneered by rose ( 1977 ) , using a surface number density contrast procedure .
the most widely analysed samples are the hickson compact groups ( hcgs ) ( hickson 1982 , hickson 1997 ) , which have been selected on the basis of population , isolation ( avoiding cores of rich clusters ) and compactness .
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10,476 |
Suppose that you have an abstract for a scientific paper: for crucial tests between theory and experiment , ab initio close coupling calculations are carried out for photoionization of several oxgyen ions : o ii , o iii , o iv , o v. the relativistic fine structure and resonance effects are studied using the r - matrix and its relativistic variant the breit pauli r - matrix ( bprm ) approximations .
extremely detailed comparison is made with high resolution experimental measurements carried out in three different set - ups : advanced light source at berkeley , synchrotron radiation experiment with a new modulator at university of aarhs , and synchrotron radiation experiment at university of paris - sud .
the comparisons illustrate physical effects in photoionization such as ( i ) fine structure , ( ii ) resolution , and ( iii ) metastable components .
photoionization cross sections @xmath0 of the ground and a few low lying excited states of these ions obtained in the experimental spectrum include combined features of these states .
the general features of the measured @xmath0 were predicted in the earlier calculations in ls coupling .
however , due to higher resolution achievement in the recent experiments , the theoretically calculated resonances need to be resolved with much finer energy mesh for precise comparison .
in addition , prominent resonant features are observed in the measured spectra that can form from transitions allowed with relativistic fine structure , but not in ls coupling .
present results include calculations from both ls coupling and the relativistic bprm method to decipher the features in photoionization spectra .
@xmath0 are obtained for ground and metastable ( i ) @xmath1 states of o ii , ( ii ) @xmath2 and @xmath3 states of o iii , ( iii ) @xmath4 and @xmath5 levels of o iv , and ( iv ) @xmath6 and @xmath7 states of o v. most of the computed theoretical resonance structures are seen experimentally , although there are some discrepancies .
one of the main conclusions of the present study is that resonances in....
And you have already written the first three sentences of the full article: photoionization cross sections of many atoms and ions were studied in detail with resonance structures for ground and many excited states under the opacity project ( op , @xcite ) .
the close coupling ( cc ) r - matrix method , as employed under the op , accurately considers the numerous autoionizing resonances in cross sections along interacting ( overlapping ) rydberg series .
the study under the op resulted in new features in the cross sections , such as prominent pec ( photo - excitation of core ) resonances ..
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the radiative work under the op has been extened to collisional and radiative processes under the iron project ( ip , @xcite ) with inclusion of relativistic effects using the bprm method .
however , while the methods used are state - of - the - art , possible deficiencies are : ( i ) the resonance structures in the op / ip cross sections are not always fully resolved , and ( ii ) the important near - threshold resonances may not be accurate owing to inadequate eigenfunction expansions . a prime need therefore is to benchmark the vast amount of theoretical op / ip data that is now being utilized for global applications such as calculation of stellar opacities , photoionization rates in astrophysical models . on the experimental side ,
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10,477 |
Suppose that you have an abstract for a scientific paper: we introduce a non - hermitian approximation of bloch optical equations .
this approximation provides a complete description of the excitation , relaxation and decoherence dynamics of ensembles of coupled quantum systems in weak laser fields , taking into account collective effects and dephasing . in the proposed method one
propagates the wave function of the system instead of a complete density matrix . relaxation and dephasing are taken into account via automatically - adjusted time - dependent gain and decay rates . as an application
, we compute the numerical wave packet solution of a time - dependent non - hermitian schrdinger equation describing the interaction of electromagnetic radiation with a quantum nano - structure and compare the calculated transmission , reflection , and absorption spectra with those obtained from the numerical solution of the liouville- von - neumann equation .
it is shown that the proposed wave packet scheme is significantly faster than the propagation of the full density matrix while maintaining small error .
we provide the key ingredients for easy - to - use implementation of the proposed scheme and identify the limits and error scaling of this approximation . .
And you have already written the first three sentences of the full article: optics of nanoscale materials has attracted considerable attention in the past several years @xcite due to various important applications @xcite .
exploring electrodynamics of near - fields associated with subwavelength systems , researchers are now truly dwelling into nanoscale @xcite . owing to both new materials processing techniques @xcite and continuous progress in laser physics @xcite the research in nano - optics is currently transitioning from linear systems , where materials and their relative arrangement control optical properties @xcite , to the nonlinear regime @xcite .
the latter expands optical control capabilities far beyond conventional linear optics as in the case of active plasmonic materials @xcite , for instance , combining highly localized electromagnetic ( em ) radiation driven by surface plasmon - polaritons ( spp ) with non - linear materials @xcite ..
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yet another promising research direction , namely optics of highly coupled exciton - polariton systems , is emerging @xcite .
it basically reincarnates a part of research in semiconductors @xcite , bringing it to nanoscale via deposition of ensembles of quantum emitters ( molecules @xcite , quantum dots @xcite ) directly on to plasmonic materials . even in the linear regime , when the external em radiation is not significantly exciting the quantum sub - system , spp near - fields can be strongly coupled to quantum emitters .
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10,478 |
Suppose that you have an abstract for a scientific paper: in this work , a one - dimensional model of crystalline solids based on the dirac comb limit of the krnig - penney model is considered . from the wave functions of the valence electrons , we calculate a statistical measure of complexity and the fisher - shannon information for the lower energy electronic bands appearing in the system .
all these magnitudes present an extremal value for the case of solids having half - filled bands , a configuration where in general a high conductivity is attained in real solids , such as it happens with the monovalent metals .
and crystalline solid models ; electronic band structure ; statistical indicators the application of information theory measures to quantum systems is a subject of interest in the last years @xcite
. some relevant properties of the hierarchical organization of atoms @xcite and nuclei @xcite are revealed when these indicators are calculated on these many - body systems . on the one hand
, they display an increasing trend with the number of particles , electrons or nucleons . on the other hand
, they take extremal values on the closure of shells . moreover , in the case of nuclei , the trace of magic numbers is displayed by these entropic products such as the fisher - shannon information @xcite and a statistical complexity measure @xcite .
also these statistical quantifiers have revealed a connection with physical measures , such as the ionization potential and the static dipole polarizability @xcite in atomic physics .
all of them , theoretical and physical magnitudes , are capable of unveiling the shell structure of atoms , specifically the closure of shells in the noble gases .
a strategy to calculate these indicators is to quantify the discrete hierarchical organization of these multiparticle systems through the fractional occupation probabilities .
these probabilities capture the filling of the shell structure of these systems . from them ,
the different statistical magnitudes are derived .
the metallic clusters is....
And you have already written the first three sentences of the full article: the authors acknowledge some financial support from the spanish project dgicyt - fis2009 - 13364-c02 - 01 .
also thanks to the consejera de economa , comercio e innovacin of the junta de extremadura ( spain ) for financial support , project ref . gru09011 ..
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10,479 |
Suppose that you have an abstract for a scientific paper: the motion of molecules on solid surfaces is of interest for technological applications , but it is also a theoretical challenge .
we study the deterministic and thermal diffusive dynamics of a dimer moving on a periodic substrate .
the deterministic motion of the dimer displays strongly nonlinear features and chaotic behavior .
the dimer thermal diffusive dynamics deviates from simple arrhenius behavior , due to the coupling between vibrational and translational degrees of freedom . in the low - temperature limit
the dimer diffusion can become orders of magnitude larger than that of a single atom , as also found experimentally .
the relation between chaotic deterministic dynamics and stochastic thermal diffusion is discussed .
epsf keywords : surface , molecules , molecular dynamics 2 .
And you have already written the first three sentences of the full article: the surface diffusion of single adatoms has been intensively studied over the last decades , @xcite due to its importance in thin film and crystal growth .
@xcite once individual atoms are adsorbed on a surface they can meet , thus forming larger clusters .
however , the diffusion of even the simplest cluster , a dimer , on a surface is by far not yet understood ..
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@xcite the diffusion dynamics can be strongly affected by the coupling of the intramolecular motion to the translational motion of the centre of mass ( cm ) of the cluster .
@xcite herein , we present a simple , one - dimensional model for studying the hamiltonian and diffusive dynamics of a dimer , which is relevant to systems where quasi - one - dimensional motion takes place .
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10,480 |
Suppose that you have an abstract for a scientific paper: we have made the first map of co(j=3 - 2 ) emission covering the disk of the edge - on galaxy , ngc 4631 , which is known for its spectacular gaseous halo .
the strongest emission , which we model with a gaussian ring , occurs within a radius of 5 kpc .
weaker disk emission is detected out to radii of 12 kpc , the most extensive molecular component yet seen in this galaxy . from comparisons with infrared data
, we find that co(j=3 - 2 ) emission more closely follows the hot dust component , rather than the cold dust , consistent with it being a good tracer of star formation .
the first maps of @xmath0 , h@xmath1 mass surface density and sfe have been made for the inner 2.4 kpc radius region .
only 20% of the sf occurs in this region and excitation conditions are typical of galaxy disks , rather than of central starbursts .
the sfe suggests long gas consumption timescales ( @xmath2 @xmath3 yr ) .
the velocity field is dominated by a steeply rising rotation curve in the region of the central molecular ring followed by a flatter curve in the disk .
a very steep gradient in the rotation curve is observed at the nucleus , providing the first evidence for a central concentration of mass : m@xmath4 m@xmath5 within a radius of 282 pc .
the velocity field shows anomalous features indicating the presence of molecular outflows ; one of them is associated with a previously observed co(j=1 - 0 ) expanding shell .
consistent with these outflows is the presence of a thick ( @xmath6 up to @xmath7 kpc ) co(j=3 - 2 ) disk .
we suggest that the interaction between ngc 4631 and its companion(s ) has agitated the disk and also initiated star formation which was likely higher in the past than it is now .
these may be necessary conditions for seeing prominent halos .
[ firstpage ] galaxies : individual ( ngc 4631 ) , galaxies : halos , ism : bubbles , ism : molecules , galaxies : ism , ism : structure .
And you have already written the first three sentences of the full article: ngc 4631 ( fig .
[ fig : mom0_optical ] , table [ tab : galaxy_params ] ) is an edge - on . ]
galaxy that is known for a spectacular multi - phase halo kpc . ] ..
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this galaxy is one of the targets of the james clerk maxwell telescope ( jcmt ) nearby galaxies legacy survey ( ngls ) @xcite whose goals include searching for molecular gas and dust in nearby galaxies and comparing the global properties of such systems .
in addition , the spatial and spectral coverage of the 325 - 375 ghz band presented by the new heterodyne array receiver programme - b - band ( harp - b ) detector together with the wide - band auto - correlation spectrometer imaging system ( acsis ) has also made it possible to study individual galaxies in the sample in some detail .
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10,481 |
Suppose that you have an abstract for a scientific paper: we give an explicitly computable lower bound for the arithmetic self - intersection number @xmath0 of the dualizing sheaf on a large class of arithmetic surfaces .
if some technical conditions are satisfied , then this lower bound is positive . in particular ,
these technical conditions are always satisfied for minimal arithmetic surfaces with simple multiplicities and at least one reducible fiber , but we have also used our techniques to obtain lower bounds for some arithmetic surfaces with non - reduced fibers . .
And you have already written the first three sentences of the full article: let @xmath1 be a number field , let @xmath2 denote the ring of integers of @xmath1 .
let @xmath3 denote a smooth , projective , geometrically irreducible curve of genus @xmath4 , let @xmath5 be a proper regular model of @xmath6 and let @xmath7 denote the relative dualizing sheaf on @xmath8 over @xmath9 , equipped with the arakelov metric .
the arithmetic self - intersection @xmath0 is one of the most fundamental objects in arithmetic intersection theory ; see for instance @xcite for a discussion . in this note.
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we show how to effectively compute lower bounds on @xmath0 in many situations including , but not limited to , semistable @xmath8 . to each @xmath10-divisor @xmath11 of degree one
we attach in definiton [ lddef ] a hermitian line bundle @xmath12 .
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Suppose that you have an abstract for a scientific paper: we compute and present the distribution in mass of single and binary neutron stars , strange stars , and black holes .
the calculations were performed using a stellar population synthesis code .
we follow evolution of massive single stars as well as binaries with high mass primaries
. the final product of the latter evolution can be either a binary composed of a white dwarf and a compact object ( neutron star , black hole , strange star ) , two compact objects in a binary , or two single stars if the system was disrupted .
we find in binaries a population of black holes which are more massive than single black holes which are a product of either binary or single evolution .
we also find that if quark stars exist at all , their population can be as large as the population of black holes . .
And you have already written the first three sentences of the full article: binary population synthesis is a useful tool for studying the statistical properties of stars , including the compact objects ( e.g. , pols & marinus 1994 ; bethe & brown 1998 ; portegies - zwart & yungelson 1998 ; bloom , sigurdsson , & pols 1999 ; belczynski & bulik 1999 )
. compact objects are stellar remnants of size much smaller than that of white dwarfs , so according to current views they could be either black holes or neutron stars or , possibly , quark stars .
we wish to address the following questions : what is the distribution of masses of the compact objects formed along different evolutionary paths ? given the distribution of compact object masses , what are the relative numbers of different types of objects ( neutron stars , quark stars , black holes ) both single and in binaries ?.
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what fraction of binaries give rise to single compact objects , and what fraction survives as binaries and of what type ? in section 2
we shortly describe the population synthesis code used here , in section 3 we summarize what is known about the masses of neutron stars , quark stars and of black holes . in section 4
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Suppose that you have an abstract for a scientific paper: the recent development of superconducting spintronics has revealed the spin - triplet superconducting proximity effect from a spin - singlet superconductor into a spin - polarized normal metal . in addition recently superconducting junctions using semiconductors are in demand for highly controlled experiments to engineer topological superconductivity .
here we report experimental observation of andreev reflection in junctions of spin - resolved quantum hall ( qh ) states in an inas quantum well and the spin - singlet superconductor nbti . the measured conductance indicates a sub - gap feature and two peaks on the outer side of the sub - gap feature in the qh plateau - transition regime increases .
the observed structures can be explained by considering transport with andreev reflection from two channels , one originating from equal - spin andreev reflection intermediated by spin - flip processes and second arising from normal andreev reflection .
this result indicates the possibility to induce the superconducting proximity gap in the the qh bulk state , and the possibility for the development of superconducting spintronics in semiconductor devices . a junction of superconductor and normal metal is a platform to observe superconducting proximity effect , in which the superconducting property penetrates to the normal metal . in a microscopic description of the proximity effect ,
an electron in the normal metal enters the spin - singlet superconductor , forming a cooper pair with another electron with opposite spin , reflecting a hole into the normal metal , in a process called andreev reflection ( ar ) @xcite . in this picture ,
no ar is expected in the case of a fully spin polarized normal metal , however recently , theoretical and experimental studies in junctions with spin - polarized normal metal , revealed existence of the spin - triplet superconducting proximity effect @xcite .
the spin - triplet proximity effect is only allowed when spin - flip processes intermediate `` equal - spin ''....
And you have already written the first three sentences of the full article: we greatly thank y. tanaka , p. burset , and r. s. deacon for fruitful discussions .
this work was partially supported by grant - in - aid for young scientific research ( a ) ( no .
jp15h05407 ) , grant - in - aid for scientific research ( a ) ( no ..
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jp16h02204 ) , grant - in - aid for scientific research ( s ) ( no .
jp26220710 ) , jsps research fellowship for young scientists ( no .
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Suppose that you have an abstract for a scientific paper: community detection of network flows conventionally assumes one - step dynamics on the links . for sparse networks and interest in large - scale structures , longer timescales
may be more appropriate .
oppositely , for large networks and interest in small - scale structures , shorter timescales may be better
. however , current methods for analyzing networks at different timescales require expensive and often infeasible network reconstructions . to overcome this problem ,
we introduce a method that takes advantage of the inner - workings of the map equation and evades the reconstruction step .
this makes it possible to efficiently analyze large networks at different markov times with no extra overhead cost .
the method also evades the costly unipartite projection for identifying flow modules in bipartite networks . .
And you have already written the first three sentences of the full article: researchers often represent interactions between components in social and biological systems with networks of nodes and links , and use community - detection algorithms to better understand their large - scale structure . depending on the system under study and the particular research question , the scale of interest varies . for an initial investigation , a birds - eye - view of the entire system may be most appropriate , while a more detailed study most likely will require a finer scale . methods for extracting hierarchically nested modules at different scales do exist @xcite , but there may still be a need for identifying large - scale structures at specific scales @xcite . when the links represent network flows , modeling the dynamics at different markov times is a natural way to capture the large - scale structures at different scales @xcite . in this approach ,
the original network is rebuilt such that one flow step along a link of the rebuilt network corresponds to the desired number of flow steps on the original network . however
, this approach is inefficient for large networks , because the rebuilt network can be dense to the degree that storage and further analysis is infeasible . to overcome this problem.
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, we introduce an efficient method that operates directly on the original network .
the method takes advantage of the mechanics of the information - theoretic community - detection method known as the map equation @xcite with no extra overhead cost . integrating the markov time scaling with the map equation
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Suppose that you have an abstract for a scientific paper: multi - colour ( jhk@xmath0 ) imaging and photometry of the field of the anomalous x - ray pulsar axp 1e 1841@xmath1045 is analysed in the light of new , accurate coordinates from _ chandra _ ( wachter et al , 2004 ) . from excellent quality images ,
we find multiple sources in and around the position error circle . of these
, none can be confidently identified as the infrared counterpart .
the limiting magnitudes reached were @xmath2 , @xmath3 and @xmath4 ( 95% confidence ) . .
And you have already written the first three sentences of the full article: the anomalous x - ray pulsars ( axps ) are a small group of young , energetic neutron stars , whose luminosity is thought to be powered by the decay of a super - strong magnetic field : _ magnetars _ ( thompson & duncan , 1996 ) . since the discovery of the first optical counterpart to an axp ( hulleman , van kerkwijk & kulkarni , 2000 )
, searches have been undertaken to identify further optical and infrared counterparts in different colours . due to the large extinction to most of these sources ,
the infrared has proved the more successful route ..
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see woods & thompson ( 2004 ) for a review of the axps and their counterparts to date .
1e 1841@xmath1045 is located within the supernova remnant kes 73 , and has a pulse period of 11.8s and a soft x - ray spectrum well - fitted by either a black - body plus power - law or the sum of two black - bodies with a fitted hydrogen absorption column of @xmath5@xmath6 ( morii et al . , 2003 ; gotthelf et al . , 2004 ) . as a recent surprise , this source was found by kuiper at al .
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Suppose that you have an abstract for a scientific paper: as part of a large - scale search for coherent pulsations from lmxbs in the _ rxte _ archive , we have completed a detailed series of searches for coherent pulsations of 4u 1820@xmath030 an ultracompact lmxb with a binary period of 11.4 min , located in the globular cluster ngc 6624 .
the short binary period implies any coherent signal would be highly accelerated , so we used phase modulation searches , orbital - parameter - fitting coherent searches , and standard acceleration searches to give significant sensitivity to millisecond pulsations .
we searched , in four energy bands and at a range of luminosities , a total of 34 archival _
rxte _ observations , 32 of which had on - source integration times longer than 10ks , and some of which were made consecutively which allowed us to combine them .
we found no pulsations . using our phase modulation search technique , which we ran on all 34 observations
, we have been able to place the first stringent ( 95% confidence ) pulsed fraction limits of @xmath1 0.8% for all realistic spin frequencies
( i.e. @xmath2 2khz ) and likely companion masses ( 0.02_@xmath3 @xmath4 0.3_@xmath3 ) . using our orbital - parameter - fitting coherent search , which we ran on only 11 selected observations ,
we have placed a pulsed fraction limit of @xmath1 0.3% for spin frequencies @xmath1 1.25khz and companion masses @xmath5 0.106_@xmath3 . by contrast , all five lmxbs known to emit coherent pulsations have intrinsic pulsed fractions in the range 3% to 7% when pulsations are observed .
hence , our searches rule out pulsations with significantly lower pulsed fractions than those already observed . .
And you have already written the first three sentences of the full article: one of the great scientific expectations when the rossi x - ray timing explorer ( _ rxte _ ) was launched in 1995 was the discovery of coherent pulsations from low - mass x - ray binaries ( lmxbs ) . at present , only five accreting millisecond pulsars in lmxbs are known .
all five are faint transient sources for which the pulsations at the spin period of the pulsar were discovered during outbursts ( @xcite ; @xcite ; @xcite ; @xcite ; @xcite ) .
surprisingly , no pulsations have ever been seen in the non - transient x - ray emission from any lmxb ..
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one possibility is that msp coherent pulsations are smeared out by rapidly changing orbital doppler shifts in short period binaries .
modern accelerated signal search techniques have not been applied systematically to many lmxbs so it is possible that there are millisecond pulsations in them that have gone unnoticed .
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Suppose that you have an abstract for a scientific paper: _ multi - label learning _ deals with the classification problems where
each instance can be assigned with multiple labels simultaneously . conventional multi - label learning approaches mainly focus on exploiting label correlations .
it is usually assumed , explicitly or implicitly , that the label sets for training instances are fully labeled without any missing labels .
however , in many real - world multi - label datasets , the label assignments for training instances can be incomplete .
some ground - truth labels can be missed by the labeler from the label set .
this problem is especially typical when the number instances is very large , and the labeling cost is very high , which makes it almost impossible to get a fully labeled training set . in this paper
, we study the problem of large - scale multi - label learning with incomplete label assignments .
we propose an approach , called mpu , based upon positive and unlabeled stochastic gradient descent and stacked models .
unlike prior works , our method can effectively and efficiently consider missing labels and label correlations simultaneously , and is very scalable , that has linear time complexities over the size of the data .
extensive experiments on two real - world multi - label datasets show that our mpu model consistently outperform other commonly - used baselines . .
And you have already written the first three sentences of the full article: _ multi - label learning _
has drawn much attention in recent years , where each data example can be assigned with multiple labels simultaneously .
multi - label learning has a wide range of real - world applications ..
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for example , in text categorization , one text document can belong to multiple categories , such as _ sports _ and _ entertainment _ ; researchers in text mining are interested in learning a model that can automatically predict a set of categories for each text document .
similarly , in image annotation tasks , one image can contain multiple objects or tags , and researchers in computer vision are interested in automatically predicting tags / objects for unlabeled image collections .
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Suppose that you have an abstract for a scientific paper: we present considerations about the transverse beam transfer function ( btf ) of beams under the influence of two effects : the strong strong beam beam effect and the influence of a gaussian electron lens .
the btf are investigated using two methods : btf excitation is simulated in a particle - in - cell ( pic ) code .
the btf model is verified using a known analytic expectation .
analytic expectations for btf of beams under a stationary electron lens are derived by extending btf from the formalism of berg and ruggiero .
finally we compare the analytic btf results for a stationary gaussian lens to both the pic simulation for split tune conditions and to pic simulations for a beam influenced by an electron lens .
we conclude that the formalism represents the electron lens well and can be applied to a limited extend to the beam beam effect under split tune conditions .
the analytic formalism allows us to recover the strength of an electron lens by means of fitting and can give clues regarding the strength of the beam beam effect under split tune conditions . .
And you have already written the first three sentences of the full article: for a long time there has been a desire at bnl to recover the beam beam parameter and with it the tune spreads from btf of beams undergoing the beam beam effect .
recently this desire has been intensified by the construction and installation of the electron lens @xcite .
normally the machine is run in conditions with the two rings tuned to identical or near - identical tunes ..
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we refer to these conditions as _
normal conditions_. under these circumstances , the coherent beam
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Suppose that you have an abstract for a scientific paper: we analyze the effects of finite - range corrections in halo effective field theory for s - wave proton halo nuclei .
we calculate the charge radius to next - to - leading order and the astrophysical s - factor for low - energy proton capture to fifth order in the low - energy expansion . as an application
, we confront our results with experimental data for the s - factor for proton capture on oxygen-16 into the excited @xmath0 state of fluorine-17 .
our low - energy theory is characterized by a systematic low - energy expansion , which can be used to quantify an energy - dependent model error to be utilized in data fitting .
finally , we show that the existence of proton halos is suppressed by the need for two fine tunings in the underlying theory .
halo nuclei , charge radius , radiative capture , effective field theory .
And you have already written the first three sentences of the full article: the quantitative description of both nuclear structure and reactions on the same footing is a major challenge of contemporary nuclear theory . with new experimental facilities such as frib and fair at the horizon , the task to find improved approaches for nuclear reactions has become very urgent . _
ab initio _ approaches to calculate nuclear scattering observables are limited by the computational complexity of the nuclear many - body problem .
scattering models perform well but use a number of uncontrolled approximations that make the errors of such calculations difficult to quantify . faced with these problems , it is important to note that there are a number of systems in the chart of nuclei for which the effective number of degrees - of - freedom is significantly smaller than the number of nucleons ..
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this phenomenon is known as clustering , with alpha clustering , e.g. in the hoyle state of @xmath1c , being the most prominent example .
clustering becomes even more extreme for so - called halo nuclei which consist of a tightly - bound core nucleus and a few weakly - bound valence nucleons @xcite .
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Suppose that you have an abstract for a scientific paper: a major area in neuroscience research is the study of how the brain processes spatial information .
neurons in the brain represent external stimuli via neural codes .
these codes often arise from stereotyped stimulus - response maps , associating to each neuron a convex receptive field .
an important problem consists in determining what stimulus space features can be extracted directly from a neural code .
the neural ideal is an algebraic object that encodes the full combinatorial data of a neural code .
this ideal can be expressed in a canonical form that directly translates to a minimal description of the receptive field structure intrinsic to the code . in here
, we describe a sagemath package that contains several algorithms related to the canonical form of a neural ideal . .
And you have already written the first three sentences of the full article: due to many recent technological advances in neuroscience , researchers ability to collect neural data has increased dramatically . with this
comes a need for new methods to process and understand this data .
one major question faced by researchers is to determine how the brain encodes spatial features of its environment through patterns of neural activity , as with place cell codes @xcite . in the recent paper @xcite , curto et al ..
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phrase this question as , `` what can be inferred about the underlying stimulus space from neural activity alone ? '' to answer this question , curto et al . introduced the _ neural ring _ and a related _ neural ideal _ , algebraic objects that encode the full combinatorial data of a neural code .
they further show that the neural ideal can be expressed in a _
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Suppose that you have an abstract for a scientific paper: we use images of high spatial and temporal resolution , obtained using both ground- and space - based instrumentation , to investigate the role magnetic field inclination angles play in the propagation characteristics of running penumbral waves in the solar chromosphere .
analysis of a near - circular sunspot , close to the center of the solar disk , reveals a smooth rise in oscillatory period as a function of distance from the umbral barycenter .
however , in one directional quadrant , corresponding to the north direction , a pronounced kink in the period distance diagram is found . utilizing a combination of the inversion of magnetic stokes vectors and force - free field extrapolations
, we attribute this behaviour to the cut - off frequency imposed by the magnetic field geometry in this location . a rapid , localised inclination of the magnetic field lines in the north direction results in a faster increase in the dominant periodicity due to an accelerated reduction in the cut - off frequency . for the first time
we reveal how the spatial distribution of dominant wave periods , obtained with one of the highest resolution solar instruments currently available , directly reflects the magnetic geometry of the underlying sunspot , thus opening up a wealth of possibilities in future magneto - hydrodynamic seismology studies .
in addition , the intrinsic relationships we find between the underlying magnetic field geometries connecting the photosphere to the chromosphere , and the characteristics of running penumbral waves observed in the upper chromosphere , directly supports the interpretation that running penumbral wave phenomena are the chromospheric signature of upwardly - propagating magneto - acoustic waves generated in the photosphere . .
And you have already written the first three sentences of the full article: waves and oscillations manifesting in the immediate vicinity of sunspots have been known for over @xmath0 years @xcite
. early work on oscillatory phenomena in sunspot structures helped validate the detection of long - period oscillations , which are generated by the response of the umbral photosphere to the 5-minute @xmath1-mode global oscillations @xcite .
while oscillations in solar active regions are dominated by periodicities intrinsically linked to the global @xmath1-mode spectrum , a wealth of alternative wave periods can also be identified in the sunspot locality , spanning three orders - of - magnitude from several seconds @xcite , through to in - excess of one hour @xcite ..
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the first observational evidence of running penumbral waves ( rpws ) came from @xcite and @xcite , who detected concentric intensity waves propagating outwards through the penumbra of a sunspot .
these waves , deemed as acoustic modes , were observed to propagate with a phase velocity of @xmath2 kms@xmath3 and intensity fluctuations in the range @xmath2% .
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Suppose that you have an abstract for a scientific paper: we present results towards the calculation of the pion electric form factor and structure function on a @xmath0 lattice using charge overlap . by
sacrificing fourier transform information in two directions , it is seen that the longitudinal four point function can be extracted with reasonable error bars at low momentum . .
And you have already written the first three sentences of the full article: the direct calculation of hadron structure functions by current overlap techniques is based on the simulation of the euclidean hadronic matrix elements @xmath1 | h({\bf 0 } ) \rangle $ ] , where @xmath2 is the full electromagnetic current and @xmath3 are the @xmath4 , @xmath5 quark flavor current densities .
such calculations are likely to be quite costly , so it seems worthwhile to check the validity of this approach by less ambitious calculations utilizing the basic current overlap technique . the longitudinal piece ( corresponding to @xmath6 above , where @xmath7 ) of structure functions for mesonic systems provides such a test@xcite .
we expect for the pion that vector dominance should hold , resulting in a known elastic limit for both the @xmath8 ( same flavor ) and @xmath9 ( different flavor ) sectors ..
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this calculation serves to test whether the lattice size is large enough in space and time , the size of statistical errors , and other important issues . since we use the conserved lattice current , there are also many useful numerical identities which serve as checks on the calculation . in constructing these four point functions ,
we make multiple use of the sequential source technique@xcite for quark propagators .
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Suppose that you have an abstract for a scientific paper: let @xmath0 . for @xmath1 and @xmath2 , we put @xmath3 . _ a projective flow _ is a solution to the projective translation equation @xmath4 , @xmath5 .
+ previously we have developed an arithmetic , topologic and analytic theory of @xmath6dimensional projective flows ( over @xmath7 and @xmath8 ) : rational , algebraic , unramified , abelian flows , commuting flows .
the current paper is devoted to highly symmetric flows - superflows . within flows with a given symmetry ,
superflows are unique and optimal .
+ our first result classifies all @xmath9-dimensional superflows . for any @xmath10
, there exists the superflow @xmath11 whose group of symmetries is the dihedral group @xmath12 . in the current paper
we explore the superflow @xmath13 , which leads to investigation of abelian functions over curve of genus @xmath14 .
+ we further investigate two different @xmath15dimensional superflows , both solenoidal , whose group of symmetries are , respectively , the full tetrahedral group @xmath16 ( all symmetries of a tetrahedron , the ring of invariants is polynomial ) , and the octahedral group @xmath17 ( orientation preserving symmetries of an octahedron , the ring of invariants is not polynomial ) , both isomorphic , though non - isomorphic as representations .
the generic orbits of the first flow are space curves of genus @xmath18 , and the flow itself can be analytically described in terms of jacobi elliptic functions .
the generic orbits of the second flow are curves of genus @xmath19 , and the flow itself can be described in terms of weierstrass elliptic functions ( via reduction of hyper - elliptic functions to elliptic ) . in the second part of this work we will classify all @xmath15dimensional superflows ( including the icosahedral superflow ) , and in the third we investigate superflows over @xmath8 . .
And you have already written the first three sentences of the full article: we always write @xmath20 instead of @xmath21 , and also @xmath22 .
the same convention applies to a @xmath15dimensional case , @xmath23 .
the current work is a continuation of @xcite , but it is completely independent from the cited papers ( including all classification theorems ) , apart from the fact that we use explicit methods to integrate vector fields developed there . yet , the final formulas can be double - verified , so the current work is self - contained ..
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+ _ the projective translation equation _ , or prte , is a special case of a general translation equation @xcite , and it was first introduced in @xcite .
it is the equation of the form @xmath24 this should be satisfied for @xmath25 small enough ( _ local flows _ ) .
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Suppose that you have an abstract for a scientific paper: we present rxte monitoring observations of the seyfert 2 galaxy mrk 348 spanning a 6 month period .
the time - averaged spectrum in the 320 kev band shows many features characteristic of a compton - thin seyfert 2 galaxy , namely a hard underlying power - law continuum ( @xmath0 ) with heavy soft x - ray absorption ( @xmath1 @xmath2 ) plus measureable iron k@xmath3 emission ( equivalent width @xmath4 ev ) and , at high energy , evidence for a reflection component ( @xmath5 ) . during the first half of the monitoring period the x - ray continuum flux from mrk 348 remained relatively steady .
however this was followed by a significant brightening of the source ( by roughly a factor of 4 ) with the fastest change corresponding to a doubling of its x - ray flux on a timescale of about 20 days .
the flux increase was accompanied by a marked softening of x - ray spectrum most likely attributable to a factor @xmath6 decline in the intrinsic line - of - sight column density .
in contrast the iron k@xmath3 line and the reflection components showed no evidence of variability .
these observations suggest a scenario in which the central x - ray source is surrounded by a patchy distribution of absorbing material located within about a light - week of the nucleus of mrk 348 .
the random movement of individual clouds within the absorbing screen , across our line of sight , produces substantial temporal variations in the measured column density on timescales of weeks to months and gives rise to the observed x - ray spectral variability .
however , as viewed from the nucleus the global coverage and typical thickness of the cloud layer remains relatively constant . .
And you have already written the first three sentences of the full article: the discovery of `` hidden '' broad - line regions ( blrs ) in several seyfert 2 galaxies @xcite has generated much interest in unified theories , in which the viewing orientation explains many of the observed differences between type 1 and 2 seyfert galaxies ( antonucci 1993 and references therein ) .
such theories posit that , in both types of seyfert galaxy , a luminous central source ( presumably an accreting supermassive blackhole ) is surrounded by a equatorial distribution of matter in the form of either a swollen accretion disk or a molecular torus @xcite .
a type 1 nucleus is then observed only if the viewing direction is sufficiently close to the axis of the system so as to fall within the opening angle of the putative torus ..
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more inclined lines of sight necessarily intercept the disk / torus material in which case we see an `` obscured '' type 2 system .
however , a caveat is that a small fraction of the nuclear flux can be scattered into our line of sight by highly ionized material filling the `` hole '' of the torus , thus explaining the detection of broad optical lines in polarized light and also weak uv and soft x - ray emission even in seyfert 2s where our direct view of the nucleus is completely blocked . x - ray measurements of intrinsic column densities of @xmath7 @xmath2 in many seyfert 2 galaxies @xcite lend support to the above unification picture . for column densities @xmath8 @xmath2
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Suppose that you have an abstract for a scientific paper: using a narrow intercombination line in alkaline earth atoms to mitigate large inelastic losses , we explore the optical feshbach resonance ( ofr ) effect in an ultracold gas of bosonic @xmath0sr .
a systematic measurement of three resonances allows precise determinations of the ofr strength and scaling law , in agreement with coupled - channels theory .
resonant enhancement of the complex scattering length leads to thermalization mediated by elastic and inelastic collisions in an otherwise ideal gas .
ofr could be used to control atomic interactions with high spatial and temporal resolution . the ability to control
the strength of atomic interactions has led to explosive progress in the field of quantum gases for studies of few- and many - body quantum systems .
this capability is brought about by magnetic field - induced feshbach scattering resonances ( mfr ) @xcite , where both the magnitude and sign of low - energy atomic interactions can be varied by coupling free particles to a molecular state .
mfr in ultracold alkali atoms have been used to realize novel few - body quantum states and study strongly correlated many - body systems and phase transitions @xcite .
however , magnetic tuning has limited current experiments to relatively slow time scales and low spatial resolution .
higher resolution could be achieved by controlling mfr optically @xcite .
scattering resonances can also arise under the influence of laser light tuned near a photoassociation ( pa ) resonance @xcite where free atom pairs are coupled to an excited molecular state @xcite .
this optical feshbach resonance ( ofr ) is expected to enable new and powerful control with high spatial and temporal resolution .
ofr has been studied in thermal @xcite and degenerate @xcite gases of rb , but it was not found useful due to large photoassociative losses .
much narrower optical intercombination lines are available in alkaline earth atoms and are predicted to overcome this loss problem @xcite . independently ,....
And you have already written the first three sentences of the full article: the collision of two identical bosons in the low energy near - threshold limit can be described in a scattering matrix treatment by a single @xmath2-wave scattering matrix element , @xmath116 , where @xmath19 is the relative momentum of the collision pair and @xmath117 is the scattering phase shift due to interactions . when there is loss of scattering flux from the entrance channel , as is the case of a decaying optical feshbach resonance , it is convenient to _ define _ a complex energy - dependent scattering length @xmath56 , related to the complex phase @xmath117 and @xmath118-matrix element by @xcite @xmath119 this reduces to the usual definition of complex scattering length as @xmath120 . the respective elastic and inelastic @xmath2-wave collision cross sections are @xcite @xmath121 where @xmath122^{-1 } \to 1 $ ] as @xmath120 and @xmath123 is the reduced mass of the pair . the second relations in eq .
[ om : eq:9 ] follow from the definition in eq .
[ complexa ] ..
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the corresponding collision rate coefficients are @xmath124 when the entrance channel is coupled by a single frequency laser to a single excited molecular bound state of the pair , the isolated resonance approximation for the the field - dressed @xmath2-wave scattering matrix element can be written as @xcite , @xmath125 here @xmath126 is the collision energy with @xmath25 .
the laser detuning @xmath27 from the pa resonance includes the light shift @xcite to simplify the presentation ( see eq .
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Suppose that you have an abstract for a scientific paper: in the theory and practice of inverse problems for partial differential equations ( pdes ) much attention is paid to the problem of the identification of coefficients from some additional information .
this work deals with the problem of determining in a multidimensional parabolic equation the lower coefficient that depends on time only . to solve numerically a nonlinear inverse problem , linearized approximations in time
are constructed using standard finite element procedures in space .
the computational algorithm is based on a special decomposition , where the transition to a new time level is implemented via solving two standard elliptic problems .
the numerical results presented here for a model 2d problem demonstrate capabilities of the proposed computational algorithms for approximate solving inverse problems .
inverse problem , control parameter , parabolic partial differential equation , finite element approximation , difference scheme 02.30.zz , 02.30.jr 65j22 , 65m32 .
And you have already written the first three sentences of the full article: mathematical modeling of many applied problems of science and engineering results in the numerical solution of inverse problems @xcite .
inverse problems often belong to the class of ill - posed ( conditionally correct ) problems , and therefore various regularization algorithms are employed to solve them numerically @xcite .
particular attention should be given to inverse problems for pdes @xcite ..
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in this case , a theoretical study includes the fundamental questions of uniqueness of the solution and its stability both from the viewpoint of the theory of differential equations @xcite and from the viewpoint of the theory of optimal control for distributed systems @xcite .
many inverse problems are formulated as non - classical problems for pdes .
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Suppose that you have an abstract for a scientific paper: new type of parametrization for parton distribution functions , based on an exact their @xmath0-evolution at large and small @xmath1 values , is constructed for valence quarks .
it preserves exactly the low @xmath1 and large @xmath1 asymptotics of the solution of the dglap equation and obeys the gross - llewellyn - smith sum rule . .
And you have already written the first three sentences of the full article: the parton distribution functions ( pdfs ) which contribute to the lhc processes , and the pdfs fitted at hera and fixed target experiments are defined at somewhat different @xmath2 ranges ( see , for example , fig .
[ lhckin ] taken from @xcite ) .
therefore , a direct application of the modern pdf sets @xcite to the lhc processes is not well justified ..
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this problem is really important , because the larger uncertainties for many processes at the lhc originate mainly from our restricted knowledge of the parton distributions ( see , for example , the recent paper @xcite and references therein ) . in the present paper
we propose an idea to overcome this problem .
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Suppose that you have an abstract for a scientific paper: [ [ background ] ] background : + + + + + + + + + + + phylogenetic tree comparison metrics are an important tool in the study of evolution , and hence the definition of such metrics is an interesting problem in phylogenetics . in a paper in taxon fifty years ago , sokal and rohlf proposed to measure quantitatively the difference between a pair of phylogenetic trees by first encoding them by means of their half - matrices of cophenetic values , and then comparing these matrices .
this idea has been used several times since then to define dissimilarity measures between phylogenetic trees but , to our knowledge , no proper metric on weighted phylogenetic trees with nested taxa based on this idea has been formally defined and studied yet . actually , the cophenetic values of pairs of different taxa alone are not enough to single out phylogenetic trees with weighted arcs or nested taxa . [ [ results ] ] results : + + + + + + + + for every ( rooted ) phylogenetic tree @xmath0 , let its _ cophenetic vector _
@xmath1 consist of all pairs of cophenetic values between pairs of taxa in @xmath0 and all depths of taxa in @xmath0 .
it turns out that these cophenetic vectors single out weighted phylogenetic trees with nested taxa .
we then define a family of cophenetic metrics @xmath2 by comparing these cophenetic vectors by means of @xmath3 norms , and we study , either analytically or numerically , some of their basic properties : neighbors , diameter , distribution , and their rank correlation with each other and with other metrics . [ [ conclusions ] ] conclusions : + + + + + + + + + + + + the cophenetic metrics can be safely used on weighted phylogenetic trees with nested taxa and no restriction on degrees , and they can be computed in @xmath4 time , where @xmath5 stands for the number of taxa .
the metrics @xmath6 and @xmath7 have positive skewed distributions , and they show a low rank correlation with the robinson - foulds metric and the nodal metrics , and a very high correlation with each....
And you have already written the first three sentences of the full article: many phylogenetic trees published in the literature or included in phylogenetic databases are actually alternative phylogenies for the same sets of organisms , obtained from different datasets or using different evolutionary models or different phylogenetic reconstruction algorithms @xcite .
this variety of phylogenetic trees makes it necessary to develop methods for measuring their differences ( * ? ? ?
* chapter 30 ) ..
Please generate the next two sentences of the article
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the comparison of phylogenetic trees is also used to compare phylogenetic trees obtained through numerical algorithms with other types of hierarchical classifications @xcite , to assess the stability of reconstruction methods @xcite , and in the comparative analysis of dendrograms and other hierarchical cluster structures @xcite . hence , and since the safest way to quantify the differences between a pair of trees is through a metric , `` tree comparison metrics are an important tool in the study of evolution '' @xcite .
many metrics for the comparison of phylogenetic trees have been proposed so far ( * ? ? ?
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10,499 |
Suppose that you have an abstract for a scientific paper: we analyze the bragg regime of the two - particle kapitza - dirac arrangement , completing the basic theory of this effect .
we provide a detailed evaluation of the detection probabilities for multi - mode states , showing that a complete description must include the interaction time in addition to the usual dimensionless parameter @xmath0 .
the arrangement can be used as a massive two - particle beam splitter . in this respect ,
we present a comparison with hong - ou - mandel - type experiments in quantum optics .
the analysis reveals the presence of dips for massive bosons and a differentiated behavior of distinguishable and identical particles in an unexplored scenario .
we suggest that the arrangement can provide the basis for symmetrization verification schemes .
pacs : 03.75.dg ; 42.50.xa ; 61.05.j- .
And you have already written the first three sentences of the full article: the kapitza - dirac proposal @xcite provides a beautiful demonstration of the diffraction of massive particles by standing light waves .
the proposal has been realized experimentally for atoms and electrons @xcite .
more recently , it has been suggested that additional effects could be present when we move from one- to two - particle massive systems interacting with the optical diffraction grating @xcite . in this type of arrangement two.
Please generate the next two sentences of the article
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different dynamics take place simultaneously . on the one hand ,
the particles interact with the optical wave generating diffraction patterns . on the other hand ,
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