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4,900 | Suppose that you have an abstract for a scientific paper: the subtracted kernel approach is shown to be a powerful method to be implemented recursively in scattering equations with regular plus point - like interactions .
the advantages of the method allows one to recursively renormalize the potentials , with higher derivatives of the dirac - delta , improving previous results .
the applicability of the method is verified in the calculation of the @xmath0 nucleon - nucleon phase - shifts , when considering a potential with one - pion - exchange plus a contact interaction and its derivatives .
the @xmath0 renormalization parameters are fitted to the data .
the method can in principle be extended to any derivative order of the contact interaction , to higher partial waves and to coupled channels .
pacs 03.65.ca , 11.10.hi , 05.10.cc , 03.65.nk renormalization , renormalization group , nonrelativistic scattering theory .
And you have already written the first three sentences of the full article: the pioneering work of weinberg @xcite launched the basis for the effective field theory ( eft ) of nuclear forces starting from the expansion of an effective chiral lagrangian .
it gives a nucleon - nucleon ( nn ) interaction which is , in leading order , the one - pion - exchange potential ( opep ) plus a dirac - delta .
the program of applying effective field methods to the nn system was pursued by many authors with significative results in few - nucleon systems ( see e.g. @xcite ) . in a more general context of few - body systems ,.
Please generate the next two sentences of the article | short range interactions have many applications which are discussed in detail in ref .
@xcite . |
4,901 | Suppose that you have an abstract for a scientific paper: resistivity , hall effect and magnetoresistance have been investigated systematically on single crystals of ba@xmath0k@xmath1fe@xmath2as@xmath2 ranging from undoped to optimally doped regions . a systematic evolution of the quasiparticle scattering has been observed .
it is found that the resistivity in the normal state of ba@xmath0k@xmath1fe@xmath2as@xmath2 is insensitive to the potassium doping concentration , which is very different from the electron doped counterpart ba(fe@xmath0co@xmath3)@xmath4as@xmath4 , where the resistivity at 300 k reduces to half value of the undoped one when the system is optimally doped . in stark contrast , the hall coefficient r@xmath5 changes suddenly from a negative value in the undoped sample to a positive one with slight k - doping , and it keeps lowering with further doping .
we interpret this dichotomy due to the asymmetric scattering rate in the hole and the electron pockets with much higher mobility of the latter .
the magnetoresistivity shows also a non - monotonic doping dependence indicating an anomalous feature at about 80 k to 100 k , even in the optimally doped sample , which is associated with a possible pseudogap feature . in the low temperature region
, it seems that the resistivity has the similar values when superconductivity sets in disregarding the different t@xmath6 values , which indicates a novel mechanism of the superconductivity .
a linear feature of resistivity @xmath7 vs. @xmath8 was observed just above @xmath9 for the optimally doped sample , suggesting a quantum criticality . .
And you have already written the first three sentences of the full article: the discovery of iron - based superconductors @xcite has triggered great interests in the field of condensed matter physics .
a lot of theoretical and experimental works suggest complicated fermi surfaces and unconventional pairing mechanism@xcite .
there is a common issue between the iron pnictides and the cuprates , that in both systems the superconductivity is in the vicinity of the antiferromagnetic ( af ) order , leading to a very similar phase diagram ..
Please generate the next two sentences of the article | however , the feature of the undoped parent phase is actually quite different .
the cuprate may be categorized as the so - called mott insulator , while the iron pnictide is a poor metal . |
4,902 | Suppose that you have an abstract for a scientific paper: a high - energy photon polarimeter for astrophysics studies in the energy range from 20 mev to 1000 mev is considered .
the proposed concept uses a stack of silicon micro - strip detectors where they play the roles of both a converter and a tracker .
the purpose of this paper is to outline the parameters of such a polarimeter and to estimate the productivity of measurements .
our study supported by a monte carlo simulation shows that with a one - year observation period the polarimeter will provide 6% accuracy of the polarization degree for a photon energy of 100 mev , which would be a significant advance relative to the currently explored energy range of a few mev .
the proposed polarimeter design could easily be adjusted to the specific photon energy range to maximize efficiency if needed . .
And you have already written the first three sentences of the full article: recent discoveries have underlined a key role of astrophysics in the study of nature . in this paper
we are presenting a potential instrument for measuring high energy photon polarization with a proven detector technique which should allow preparation of a reliable tool for the space - borne observatory .
polarization of the photon has played an important role ( sometimes even before it was recognized ) in physics discoveries such as the famous young s interference experiment @xcite , michelson - morley s test of the ether theory @xcite , determination of the neutral pion parity @xcite and many others , including more recently the spin structure of the nucleon @xcite ..
Please generate the next two sentences of the article | polarization of the cosmic microwave background ( cmb ) will likely be a crucial observable for the inflation theory ( see planck [ sci.esa.int/planck ] and bicep [ bicepkeck.org ] results ) . during the last decade ,
observations from the agile [ agile.rm.iasf.cnr.it ] and fermi - lat [ www-glast.stanford.edu ] pair production telescopes have enhanced our understanding of gamma ( @xmath0 ) ray astronomy . with the help of these telescopes numerous high energy @xmath0 ray sources have been observed . |
4,903 | Suppose that you have an abstract for a scientific paper: we present a new technique for calibrating the primary beam of a wide - field , drift - scanning antenna element .
drift - scan observing is not compatible with standard beam calibration routines , and the situation is further complicated by difficult - to - parametrize beam shapes and , at low frequencies , the sparsity of accurate source spectra to use as calibrators .
we overcome these challenges by building up an interrelated network of source crossing points " locations where the primary beam is sampled by multiple sources . using the single assumption
that a beam has 180@xmath0 rotational symmetry , we can achieve significant beam coverage with only a few tens of sources .
the resulting network of crossing points allows us to solve for both a beam model and source flux densities referenced to a single calibrator source , circumventing the need for a large sample of well - characterized calibrators .
we illustrate the method with actual and simulated observations from the precision array for probing the epoch of reionization ( paper ) . .
And you have already written the first three sentences of the full article: the past decade has seen a renewed interest in low frequency radio astronomy with a strong focus on cosmology with the highly redshifted 21 cm line of neutral hydrogen .
numerous facilities and experiments are already online or under construction , including the giant metre - wave radio telescope ( gmrt ; @xcite ) , the low frequency array ( lofar ; @xcite ) , the long wavelength array ( lwa ; @xcite ) and the associated large aperture - experiment to detect the dark ages ( leda ) experiment , the cylindrical radio telescope ( crt / baoradio , formerly hshs , @xcite ) , the experiment to detect the global eor step ( edges ; @xcite ) , the murchison widefield array ( mwa ; @xcite ) , and the donald c. backer precision array for probing the epoch of reionization ( paper ; @xcite )
. 21 cm cosmology experiments will need to separate bright galactic and extragalactic foregrounds from the neutral hydrogen signal , which can be fainter by as much as 5 orders of magnitude or more ( see , e.g. , @xcite and @xcite ) ..
Please generate the next two sentences of the article | as such , an unprecedented level of instrumental calibration will be necessary for the detection and characterization of the 21 cm signal . achieving this level of calibration accuracy is complicated by the design choice of many experiments to employ non - tracking antenna elements ( e.g. lwa , mwa , lofar and paper ) .
non - tracking elements can provide significant reductions in cost compared to traditional dishes , while also offering increased system stability and smooth beam responses . |
4,904 | Suppose that you have an abstract for a scientific paper: the sunyaev - zeldovich ( sz ) effect gives a measure of the thermal energy and electron pressure in groups and clusters of galaxies . in the near future sz surveys
will map hundreds of systems , shedding light on the pressure distribution in the systems .
the thermal energy is related to the total mass of a system of galaxies , but it is only a projection that is observed through the sz effect . a model for the 3d distribution of pressure is needed to link the sz signal to the total mass of the system . in this work
we construct an empirical model for the 2d and 3d sz profile , and compare it to a set of realistic high resolution sph simulations of galaxy clusters and groups , and to a stacked sz profile for massive clusters derived from wmap data .
furthermore , we combine observed temperature profiles with dark matter potentials to yield an additional constraint , under the assumption of hydrostatic equilibrium .
we find a very tight correlation between the characteristic scale in the model , the integrated sz signal , and the total mass in the systems with a scatter of only 4% .
the model only contains two free parameters , making it readily applicable even to low resolution sz observations of galaxy clusters .
a fitting routine for the model that can be applied to observed or simulated data can be found at http://www.phys.au.dk/~haugboel/software.shtml . .
And you have already written the first three sentences of the full article: when cosmic microwave background ( cmb ) photons pass through galaxy clusters , they compton up - scatter on hot electrons , making a small increment ( decrement ) above ( below ) the peak of the cmb primary spectrum .
the size of this distortion in the cmb spectrum , the sunyaev - zeldovich ( sz ) effect @xcite , is proportional to the electron pressure integrated along the line - of - sight . besides being an important probe of the physics of the intracluster medium
, the sz effect is a promising tool in cosmology : the signal produced by a cluster is practically redshift independent and can be observed to high redshifts ..
Please generate the next two sentences of the article | the planck surveyor satellite @xcite will produce a cluster catalogue with up to @xmath010.000 ( sufficiently massive ) clusters out to @xmath1 @xcite . by combining sz and x - ray observations of relaxed clusters
the hubble constant @xmath2 can be derived , limits can be put on @xmath3 , and the gas mass fraction in clusters can be measured @xcite . |
4,905 | Suppose that you have an abstract for a scientific paper: an overview of the main strategies followed in the search for non - baryonic particle dark matter in the form of wimps is given . to illustrate these searches the case for germanium ionization detectors
is selected .
= -4 mm .
And you have already written the first three sentences of the full article: experimental observations and robust theoretical arguments have established that our universe is essentially non - visible , the luminous matter scarcely accounting for one per cent of the critical density of a flat universe ( @xmath0 ) .
the current picture describes an universe consisting of unknown species of dark energy ( @xmath1 ) and dark matter ( @xmath2 ) of which less than @xmath3 is of baryonic origin .
most of the dark matter would then be made of non - baryonic particles filling the galactic halos , at least partially , according to a variety of models ..
Please generate the next two sentences of the article | weak interacting massive ( and neutral ) particles ( wimps ) are favourite candidates to such non - baryonic components . the lightest stable particles of supersymmetric theories , like the neutralino , describe a particular class of wimps . without entering into considerations about how about how large the baryonic dark component of the galactic halo could be ,
we take for granted that there is enough room for wimps in our halo , to try to detect them , either directly or through their by - products . |
4,906 | Suppose that you have an abstract for a scientific paper: we realize on an atom - chip a practical , experimentally undemanding , tomographic reconstruction algorithm relying on the time - resolved measurements of the atomic population distribution among atomic internal states . more specifically
, we estimate both the state density matrix as well as the dephasing noise present in our system by assuming complete knowledge of the hamiltonian evolution . the proposed scheme is based on routinely performed measurements and established experimental procedures , hence providing a simplified methodology for quantum technological applications . .
And you have already written the first three sentences of the full article: the estimation of quantum states by using measured data is crucial to verify the quality of any quantum device . to fully determine a quantum state , i.e. to perform a quantum state tomography
, one needs to accumulate enough data to compute the expectation values of an informationally complete set of observables @xcite .
the availability of a complete set of measurements to be implemented by the experimenter is not straightforward and in general quantum state reconstruction is carried out by complicated set - ups that have to be robust against noise and decoherence sources , in order not to limit the accuracy of the reconstruction @xcite ..
Please generate the next two sentences of the article | the standard technique used in quantum optics for the full reconstruction of quantum states is coherent homodyne detection @xcite , which has recently been extended to ultracold atoms in @xcite .
homodyne detection requires the use of a , not always available , local oscillator field that acts as a phase reference for the state under reconstruction @xcite . for atomic internal states simpler interferometric techniques |
4,907 | Suppose that you have an abstract for a scientific paper: we have employed the multiple image method to compute the interparticle force for a polydisperse electrorheological ( er ) fluid in which the suspended particles can have various sizes and different permittivites .
the point - dipole ( pd ) approximation being routinely adopted in computer simulation of er fluids is shown to err considerably when the particles approach and finally touch due to multipolar interactions .
the pd approximation becomes even worse when the dielectric contrast between the particles and the host medium is large . from the results ,
we show that the dipole - induced - dipole ( did ) model yields very good agreements with the multiple image results for a wide range of dielectric contrasts and polydispersity . as an illustration ,
we have employed the did model to simulate the athermal aggregation of particles in er fluids both in uniaxial and rotating fields .
we find that the aggregation time is significantly reduced . the did model accounts for multipolar interaction partially and is simple to use in computer simulation of er fluids . .
And you have already written the first three sentences of the full article: the prediction of the yield stress for electrorheological ( er ) fluids is the main concern in theoretical investigations of er fluids .
early studies failed to derive the experimental yield stress data @xcite because these studies were almost based on a point - dipole approximation @xcite .
the point - dipole approximation is routinely adopted in computer simulation because it is simple and easy to use . since many - body and multipolar interactions between particles have been neglected , the strength of er effects predicted by this model is of an order lower than the experimental results ..
Please generate the next two sentences of the article | hence , substantial effort has been made to sort out more accurate models .
klingenberg and coworkers developed empirical force expression from numerical solution of laplace s equation @xcite . |
4,908 | Suppose that you have an abstract for a scientific paper: we model a one - dimensional shock - tube using smoothed particle hydrodynamics and investigate the consequences of having finite shock - width in numerical simulations caused by finite resolution of the codes .
we investigate the cooling of gas during passage through the shock for three different cooling regimes . for a theoretical shock temperature of 10@xmath0k , the maximum temperature of the gas is much reduced .
when the ration of the cooling time to shock - crossing time was 8 , we found a reduction of 25 percent in the maximum temperature reached by the gas .
when the ratio was reduced to 1.2 maximum temperature reached dropped to 50 percent of the theoretical value . in both cases the cooling time was reduced by a factor of 2 . at lower temperatures , we are especially interested in the production of molecular hydrogen and so we follow the ionization level and abundance across the shock .
this regime is particularly relevent to simulations of primordial galaxy formation for halos in which the virial temperature of the galaxy is sufficiently high to partially re - ionize the gas .
the effect of in - shock cooling is substantial : the maximum temperature the gas reaches compared to the theoretical temperature was found to vary between 0.15 and 0.81 for the simulations performed , depending upon the strength of the shock and the mass resolution .
the downstream ionization level is reduced from the theoretical level by a factor of between @xmath1 and @xmath2 , and the resulting abundance was found to be reduced to a fraction of @xmath3 to @xmath4 of its theoretical value
. at temperatures above 10@xmath0k , radiative shocks are unstable and will oscillate .
we reproduce these oscillations and find good agreement with the previous work of chevalier and imamura ( 1982 ) , and imamura , wolff and durisen ( 1984 ) .
the effect of in - shock cooling in such shocks is difficult to quantify , but is undoubtedly present .
we conclude that extreme caution must be exercised when....
And you have already written the first three sentences of the full article: in order for hydrodynamics codes to be able to simulate shocks it is necessary that the width of the shock be spread over a few mesh cells , or represent a few inter - particle spacings , depending on whether a grid or particle based code is being used . in reality
, however , the true width of the shock is only a few mean free paths , giving a shock thickness @xmath5 , of @xmath6 where @xmath7 is the number density and @xmath8 is the collisional cross - section .
a few simple calculations show that the true shock thickness is orders of magnitude smaller than the shock thickness obtained in simulations ..
Please generate the next two sentences of the article | this allows the possibility that gas in simulations can cool artificially while passing through a shock , and that temperature - sensitive quantities , such as ionization levels and molecular abundances may also vary .
any such effects will be purely numerical because of the finite shock crossing time in simulations . in the present paper |
4,909 | Suppose that you have an abstract for a scientific paper: a new method is proposed for extracting limits on spin - dependent wimp - nucleon interaction cross sections from direct detection dark matter experiments .
the new method has the advantage that the limits on individual wimp - proton and wimp - neutron cross sections for a given wimp mass can be combined in a simple way to give a model - independent limit on the properties of wimps scattering from both protons _ and _ neutrons in the target nucleus .
extension of the technique to the case of a target material consisting of several different species of nuclei is discussed .
-1.cm shef - hep/00 - 2 , + mpi - pht/2000 - 16 , + may 2000 + + + + + + + + + : 95.35.+d ; 12.60.jv ; 14.80.ly _ keywords _ : dark matter ; wimp ; neutralino ; supersymmetry .
And you have already written the first three sentences of the full article: weakly interacting massive particles ( wimps ) are believed to be the most plausible candidate for dark matter ( dm ) in the universe .
wimps are predicted to exist in many extensions of the standard model of particle physics .
most of the well - motivated wimp candidates are majorana ( _ i.e. _ , @xmath0 ) fermions ..
Please generate the next two sentences of the article | this in particular is often the case in models based on supersymmetry ( susy ) .
perhaps the most popular wimp candidate is the lightest neutralino , a superposition of the susy partners of the electroweak gauge bosons ( gauginos ) and higgs particles ( higgsinos ) . |
4,910 | Suppose that you have an abstract for a scientific paper: the talk presents an update of the bottom quark mass determination from qcd moment sum rules for the @xmath0 system by the authors @xcite . employing the @xmath1 scheme
, we find @xmath2 .
the differences to our previous analysis will be discussed and we comment on the determination of the pole mass for the bottom quark . .
And you have already written the first three sentences of the full article: a precise determination of the bottom quark mass , being one of the fundamental parameters in the standard model ( sm ) , is of paramount interest in several areas of present day particle phenomenology . in the past
, qcd moment sum rule analyses have been successfully applied for extracting charm and bottom quark masses from experimental data on the charmonium and bottomium systems respectively @xcite .
the basic ingredient in these investigations is the vacuum polarisation @xmath3 , @xmath4 induced by the vector current @xmath5 for a heavy quark @xmath6 ..
Please generate the next two sentences of the article | inclusive quantities , like @xmath3 , where no reference to a particular hadronic state is needed , are especially well suited for a description in terms of quarks and gluons .
theoretically , @xmath3 can be calculated in the framework of the operator product expansion ( ope ) . |
4,911 | Suppose that you have an abstract for a scientific paper: analysis of high spatial resolution vla images shows that the free - free emission from ngc7538irs1 is dominated by a collimated ionized wind .
we have re - analyzed high angular resolution vla archive data from 6 cm to 7 mm , and measured separately the flux density from the compact bipolar core and the extended ( 15 - 3 ) lobes .
we find that the flux density of the core is @xmath0 , where @xmath1 is the frequency and @xmath2 is @xmath3 0.7 .
the frequency dependence of the total flux density is slightly steeper with @xmath2 = 0.8 .
a massive optically thick hypercompact core with a steep density gradient can explain this frequency dependence , but it can not explain the extremely broad recombination line velocities observed in this source .
neither can it explain why the core is bipolar rather than spherical , nor the observed decrease of 4% in the flux density in less than 10 years .
an ionized wind modulated by accretion is expected to vary , because the accretion flow from the surrounding cloud will vary over time .
bima and carma continuum observations at 3 mm show that the free - free emission still dominates at 3 mm .
hco@xmath4 j = @xmath5 observations combined with fcrao single dish data show a clear inverse p cygni profile towards irs1 .
these observations confirm that irs1 is heavily accreting with an accretion rate @xmath32 10@xmath6 /yr . .
And you have already written the first three sentences of the full article: ngc7538irs1 was first detected in the radio at 5 ghz by @xcite , who found three compact radio sources at the se edge of the large ( @xmath3 4 ) region ngc7538 , which is at a distance 2.65 kpc @xcite .
the brightest of the three , source b , has later become known as irs1 @xcite .
the far - infrared luminosity of the three sources is @xmath31.9 10@xmath7 , completely dominated by irs1@xcite ..
Please generate the next two sentences of the article | irs1 was first resolved with the vla at 14.9 ghz by @xcite , who showed that it has a compact ( @xmath302 ) bipolar n - s core with faint extended fan - shaped lobes , suggesting an ionized outflow .
this is an extremely well - studied source with numerous masers , a prominent molecular outflow and extremely broad hydrogen recombination lines indicating substantial mass motion of the ionized gas @xcite . |
4,912 | Suppose that you have an abstract for a scientific paper: models of hierarchical galaxy formation predict that large numbers of low - mass , dark matter halos remain around galaxies today .
these models predict an order of magnitude more halos than observed stellar satellites in the local group .
one possible solution to this discrepancy is that the high - velocity clouds ( hvcs ) around the milky way may be associated with the excess dark matter halos and be the gaseous remnants of the galaxy formation process .
if this is the case , then analogs to the hvcs should be visible in other groups . in this paper
, we review the observations of clouds lacking stars around other galaxies and in groups and present early results from our survey of loose groups analogous to the local group and its implications for the nature of hvcs and galaxy formation .
[ firstpage ] local group intergalactic medium galaxies :
dwarf galaxies : formation .
And you have already written the first three sentences of the full article: current models of hierarchical galaxy formation predict that galaxies form via the accretion of smaller lumps of gas , stars , and dark matter ( e.g. silk & norman 1981 ; kauffman , white , & guiderdoni 1993 ; cole et al .
recent simulations of this process assuming a lambda - dominated cold dark matter ( cdm ) universe uniformly reveal the presence of large numbers of low - mass dark matter halos persisting around larger galaxies into the present day ( e.g. klypin et al .
1999 , moore et al ..
Please generate the next two sentences of the article | it remains unclear if these dark matter halos are filled with gas and/or stars and can be associated with dwarf galaxies and/or clouds or if they lack the mass to retain any baryons .
this raises the question : do we see such gaseous remnants of galaxy formation in emission around galaxies today ? |
4,913 | Suppose that you have an abstract for a scientific paper: the construction of a catalogue of galaxy groups from the 2-degree field galaxy redshift survey ( 2dfgrs ) is described .
groups are identified by means of a friends - of - friends percolation algorithm which has been thoroughly tested on mock versions of the 2dfgrs generated from cosmological n - body simulations .
the tests suggest that the algorithm groups all galaxies that it should be grouping , with an additional 40 per cent of interlopers .
about @xmath0 per cent of the @xmath1 galaxies considered are placed into groups containing at least two members of which @xmath2 are found . of these , @xmath3 contain at least four galaxies , and these groups have a median redshift of @xmath4 and a median velocity dispersion of @xmath5 .
this 2dfgrs percolation - inferred galaxy group ( 2pigg ) catalogue represents the largest available homogeneous sample of galaxy groups .
it is publicly available on the www .
catalogues galaxies : clusters : general . .
And you have already written the first three sentences of the full article: groups of galaxies are useful tracers of large - scale structure .
they provide sites in which to study the environmental dependence of galaxy properties , the galactic content of dark matter haloes , the small - scale clustering of galaxies , and the interaction between galaxies and hot x - ray emitting intragroup gas .
thus , it is desirable to have an extensive , homogeneous catalogue of groups of galaxies representing the various bound systems in the local universe . many studies in the past relied upon the pioneering work of abell ( 1958 ) to provide a set of target galaxy clusters ( see also abell , corwin & olowin 1989 , lumsden 1992 and dalton 1997 for similar studies ) ..
Please generate the next two sentences of the article | however , because of the lack of redshift information available when abell was defining his cluster catalogue , concerns have been raised over the completeness of his sample and the impact that line - of - sight projections would have in contaminating it ( lucey 1983 ; sutherland 1988 ; frenk 1990 ; van haarlem , frenk & white 1997 ) . as a result of these worries , it became fashionable to select galaxy cluster samples based upon cluster x - ray emission ( gioia 1990 ; romer 1995 ; ebeling 1996 ; bhringer 2001 ) , this method being less prone to projection effects .
this strategy nevertheless brings its own complications , because x - ray emission depends sensitively on the details of intracluster gas physics . |
4,914 | Suppose that you have an abstract for a scientific paper: the h ii region w40 harbors a small group of young , hot stars behind roughly 9 magnitudes of visual extinction . we have detected gaseous carbon monoxide ( co ) and diatomic carbon ( c@xmath0 ) in absorption toward the star w 40 irs 1a .
the 2 - 0 r0 , r1 , and r2 lines of @xmath1co at 2.3 @xmath2 m were measured using the cshell on the nasa ir telescope facility ( with upper limits placed on r3 , r4 , and r5 ) yielding an @xmath3 of @xmath4 @xmath5 .
excitation analysis indicates @xmath6 k. the phillips system of c@xmath0 transitions near 8775 was measured using the kitt peak 4-m telescope and echelle spectrometer .
radiative pumping models indicate a total c@xmath0 column density of @xmath7 @xmath5 , two excitation temperatures ( 39 and 126 k ) , and a total gas density of @xmath8 @xmath9 .
the co ice band at 4.7 was not detected , placing an upper limit on the co depletion of @xmath10 .
we postulate that the sightline has multiple translucent components and is associated with the w40 molecular cloud . our data for w40 irs 1a coupled with other sightlines ,
shows that the ratio of co / c@xmath0 increases from diffuse through translucent environs .
finally , we show that the hydrogen to dust ratio seems to remain constant from diffuse to dense environments , while the co to dust ratio apparently does not . .
And you have already written the first three sentences of the full article: molecular species are useful diagnostics for understanding the physics and chemistry of the interstellar medium ( ism ) , and have been studied in various ways for many years .
most molecules are observed in dense molecular clouds via rotational emission lines in the radio band .
these emission studies are indispensable to our understanding of galactic ecology and the ism : they yield maps of dense regions , have very high spectral ( velocity ) resolution , and allow us to study complex molecules not otherwise observable ..
Please generate the next two sentences of the article | there are some drawbacks to molecular emission studies , however .
first , analysis of the line excitation is very model - dependent and can lead to significant systematic errors . |
4,915 | Suppose that you have an abstract for a scientific paper: we present a generic transfer matrix approach for the description of the interaction of atoms possessing multiple ground state and excited state sublevels with light fields .
this model allows us to treat multi - level atoms as classical scatterers in light fields modified by , in principle , arbitrarily complex optical components such as mirrors , resonators , dispersive or dichroic elements , or filters .
we verify our formalism for two prototypical sub - doppler cooling mechanisms and show that it agrees with the standard literature . .
And you have already written the first three sentences of the full article: the two - level model of atoms interacting with light fields @xcite has often been used to explore optical cooling mechanisms @xcite . its inherent simplicity
the atom has one ground state and one excited state makes the resulting models amenable to analysis , but also suppresses mechanisms @xcite that , in the appropriate parameter regimes , dominate the interaction .
a notable example of such an initially overlooked mechanism in atomic physics is three - dimensional optical molasses @xcite . by means of the two - level model.
Please generate the next two sentences of the article | , one can predict the equilibrium temperature , the so - called `` doppler '' temperature @xmath0 , of atoms in molasses to be @xmath1 , where @xmath2 is the ( half - width at half - maximum ) linewidth of the transition from the excited to the ground level @xcite .
data from early three - dimensional molasses experiments contradicted this @xcite , showing that the achievable equilibrium temperature was in fact much lower . |
4,916 | Suppose that you have an abstract for a scientific paper: we propose to test the dark matter ( dm ) interpretation of the positron excess observed by the pamela cosmic - ray ( cr ) detector through the identification of a galactic diffuse gamma - ray component associated to dm - induced prompt and radiative emission .
the goal is to present an analysis based on minimal sets of assumptions and extrapolations with respect to locally testable or measurable quantities .
we discuss the differences between the spatial and spectral features for the dm - induced components ( with an extended , possibly spherical , source function ) and those for the standard cr contribution ( with sources confined within the stellar disc ) , and propose to focus on intermediate and large latitudes .
we address the dependence of the signal to background ratio on the model adopted to describe the propagation of charged crs in the galaxy , and find that , in general , the dm - induced signal can be detected by the fermi gamma - ray space telescope at energies above 100 gev . an observational result in agreement with the prediction from standard
cr components only , would imply very strong constraints on the dm interpretation of the pamela excess . on the other hand ,
if an excess in the diffuse emission above 100 gev is identified , the angular profile for such emission would allow for a clean disentanglement between the dm interpretation and astrophysical explanations proposed for the pamela excess .
we also compare to the radiative diffuse emission at lower frequencies , sketching in particular the detection prospects at infrared frequencies with the planck satellite . .
And you have already written the first three sentences of the full article: recent measurements of the positron fraction in cosmic rays ( crs ) up to 100 gev by the pamela experiment @xcite ( and of the sum of the electron plus positron fluxes by atic @xcite and ppb - bets @xcite ) have triggered a lot of interest on the possibility that there may be a dominant contribution to these terms from the annihilation or decay of dark matter ( dm ) particles , assumed to compose the dark halo of the milky way .
indeed , the sharp raise in the positron fraction detected by pamela above 10 gev , confirming and super - exceeding previous hints of an anomaly @xcite is a feature which can not be accommodated within the `` standard picture '' , with primary electrons accelerated in supernova remnants ( snrs ) and secondary positrons produced mainly from the interaction of primary cosmic - rays with the interstellar medium ( ism ) during propagation .
it is instead suggestive of an extra primary source of positrons ..
Please generate the next two sentences of the article | pulsars are well - motivated candidates for this role , see , e.g. , @xcite .
another interesting possibility is the recent proposal that positrons ( and electrons ) are secondary products of hadronic interaction within the cosmic ray sources @xcite . |
4,917 | Suppose that you have an abstract for a scientific paper: for adiabatically and periodically manipulated dissipative quantum systems we derive , using floquet theory , a simple markovian master equation .
contrary to some previous works we explicitly take into account the time dependence of the hamiltonian and , therefore , obtain a master equation with a time - dependent dissipative part .
we illustrate our theory with two examples and compare our results with the previously proposed master equations . in particular , we consider the problem of cooper pair pumping and demonstrate the inadequacy of the secular ( rotating wave ) approximation when calculating the pumped charge .
the secular approximation producing a master equation of the lindblad type approximates well the quantum state ( density matrix ) of the system , while to determine the pumped charge a non - lindblad master equation beyond the rotating wave approximation is necessary . .
And you have already written the first three sentences of the full article: the hope to develop a quantum information processing machine has made a strong impact in several distinct branches of science , e.g. , in theoretical and experimental quantum physics , in computer science , and in electrical and chemical engineering .
to succeed , it is essential to achieve high - precision quantum transformations , which so far are hindered by two problems : decoherence ( see @xcite for notation ) and gate control .
while the former can be solved to some extend by proposing new types of less fragile qubits , or implementing decoherence free subspaces @xcite , the solution to the latter could be the use of adiabatic transformations @xcite ..
Please generate the next two sentences of the article | such transformations have the advantage that they can be surprisingly robust to various errors of experimental parameters .
this robustness of adiabatic gates , however , comes at the price of a significantly longer gate time , therefore giving the environment more time to destroy coherence . for this reason , |
4,918 | Suppose that you have an abstract for a scientific paper: in terms of transfer entropy , we investigate the strength and the direction of information transfer in the us stock market . through the directionality of the information transfer
, the more influential company between the correlated ones can be found and also the market leading companies are selected .
our entropy analysis shows that the companies related with energy industries such as oil , gas , and electricity influence the whole market .
, , , transfer entropy , information flow , econophysics , stock market + 05.20.gg , 89.65.gh , 89.70.+c .
And you have already written the first three sentences of the full article: recently , economy has become an active research area for physicists .
they have investigated stock markets using statistical tools , such as the correlation function , multifractal , spin - glass models , and complex networks @xcite . as a consequence , it is now found evident that the interaction therein is highly nonlinear , unstable , and long - ranged .
all those companies in the stock market are interconnected and correlated , and their interactions are regarded as the important internal force of the market ..
Please generate the next two sentences of the article | the correlation function is widely used to study the internal inference of the market @xcite . however , the correlation function has at least two limitations : first , it measures only linear relations , although a linear model is not a faithful representation of the real interactions in general .
second , all it says is only that two series move together , and not that which affects which : in other words , it lacks directional information . |
4,919 | Suppose that you have an abstract for a scientific paper: new independent constraints on the amount of water delivered to earth by comets are derived using the @xmath0n/@xmath1n isotopic ratio , measured to be roughly twice as high in cometary cn and hcn as in the present earth . under reasonable assumptions ,
we find that no more than a few percent of earth s water can be attributed to comets , in agreement with the constraints derived from d / h . our results also suggest that a significant part of earth s atmospheric nitrogen might come from comets .
since the @xmath0n/@xmath1n isotopic ratio is not different in oort - cloud and kuiper - belt comets , our estimates apply to the contribution of both types of objects . , , , and number of pages : + number of tables : 0 + number of figures : 1 + the delivery of cometary water and nitrogen to earth d. hutsemkers + institut dastrophysique et de gophysique + universit de lige + alle du 6 aot 17 + b-4000 lige , belgium + + email : [email protected] + phone : + 32 4 366 9760 + fax : + 32 4 366 9746 comets , earth , origin , solar system .
And you have already written the first three sentences of the full article: the origin of water on earth is still puzzling ( e.g. the reviews by * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * ; * ? ? ? * and references therein ) . at one end of the models ,
the high temperature in the inner accretion disk hampered hydrous phases to exist so that external sources were needed , the so - called late veneer of comets , asteroids and/or meteorites suggested by lunar cratering ( e.g. * ? ? ?
* ) . at the other end , earth accreted hydrous silicate phases , or grains having adsorbed water from the solar nebula ..
Please generate the next two sentences of the article | the d / h isotopic ratio plays a key role in constraining the models .
the comparable d / h ratio of earth s oceans and carbonaceous chondrites ( the only ones to contain enough water ) points towards a meteoritic veneer , while the cometary d / h ratio , twice as high as the terrestrial one , would require a mixture of cometary water with a roughly equal amount of primitive indigeneous d - poor terrestrial water . |
4,920 | Suppose that you have an abstract for a scientific paper: we present hst / wfpc2 photometry of the central regions of the phoenix dwarf .
accurate photometry allows us to : 1 ) confirm the existence of the horizontal branch previously detected by ground - based observations , and use it to determine a distance to phoenix , 2 ) clearly detect the existence of multiple ages in the stellar population of phoenix , 3 ) determine a mean metallicity of the old red giant branch stars in phoenix , and suggest that phoenix has evolved chemically over its lifetime , 4 ) extract a rough star formation history for the central regions which suggests that phoenix has been forming stars roughly continuously over its entire lifetime . .
And you have already written the first three sentences of the full article: the phoenix dwarf galaxy , discovered by schuster & west ( 1976 ) , has a morphological type of dirr / dsph ( mateo 1998 ) , meaning that although this galaxy has a low surface brightness and a mass and morphology like a dwarf spheroidal ( dsph ) galaxy , there is evidence of recent star formation ( canterna & flower 1977 ) .
color - magnitude diagrams obtained from ground - based images have been described by ortolani & gratton ( 1988 ) , van de rydt , demers , & kunkel ( 1991 ) , held , saviane , & momany ( 1999 ) , and martinez - delgado , gallart , & aparicio ( 1999 ) .
these studies find a broadly distributed metal - poor population of evolved giants , as well as a concentration of young stars in the central region of the galaxy ..
Please generate the next two sentences of the article | several studies have found h i in the direction of phoenix ( carignan , demers , & cote 1991 ; young & lo 1997 ) ; most recently , st - germain , carignan , cote , & oosterloo ( 1999 ) have found that a mass of @xmath0 @xmath1 of h i gas is likely associated with phoenix .
studying star formation in dwarf galaxies has the potential to provide clues about the mechanisms which govern star formation , and the relative formation epochs for different types of galaxies . |
4,921 | Suppose that you have an abstract for a scientific paper: the nature of current sheet formation in the vicinity of three - dimensional ( 3d ) magnetic null points is investigated .
the particular focus is upon the effect of the compressibility of the plasma on the qualitative and quantitative properties of the current sheet .
an initially potential 3d null is subjected to shearing perturbations , as in a previous paper [ pontin _ et al .
_ , phys .
plasmas , in press ( 2007 ) ] .
it is found that as the incompressible limit is approached , the collapse of the null point is suppressed , and an approximately planar current sheet aligned to the fan plane is present instead .
this is the case regardless of whether the spine or fan of the null is sheared .
both the peak current and peak reconnection rate are reduced .
the results have a bearing on previous analytical solutions for steady - state reconnection in incompressible plasmas , implying that fan current sheet solutions are dynamically accessible , while spine current sheet solutions are not . .
And you have already written the first three sentences of the full article: in astrophysical plasmas , such as the solar corona , the three - dimensional ( 3d ) magnetic field topology is often highly complex . in such complex 3d magnetic fields , where traditional two - dimensional ( 2d ) x - point magnetic reconnection models may no longer be applicable , determining the sites at which dynamic phenomena and energy release may occur is a crucial and non - trivial problem .
due to the typically very high lundquist number , such events occur only at locations where intense currents ( singular under an ideal mhd evolution ) may form .
one such site is a 3d magnetic null point ( e.g. refs ..
Please generate the next two sentences of the article | the nature of current sheet formation at such 3d nulls is investigated here .
3d null points are predicted to be present in abundance in the solar corona ( e.g. refs . [ ] ) . |
4,922 | Suppose that you have an abstract for a scientific paper: a deformable mirror ( dm ) is an important component of an adaptive optics system .
it is known that an on - axis spherical / parabolic optical component , placed at an angle to the incident beam introduces defocus as well as astigmatism in the image plane .
although the former can be compensated by changing the focal plane position , the latter can not be removed by mere optical re - alignment .
since the dm is to be used to compensate a turbulence - induced curvature term in addition to other aberrations , it is necessary to determine the aberrations induced by such ( curved dm surface ) an optical element when placed at an angle ( other than @xmath0 ) of incidence in the optical path . to this effect
, we estimate to a first order , the aberrations introduced by a dm as a function of the incidence angle and deformation of the dm surface .
we record images using a simple setup in which the incident beam is reflected by a 37 channel micro - machined membrane deformable mirror for various angles of incidence .
it is observed that astigmatism is a dominant aberration which was determined by measuring the difference between the tangential and sagital focal planes .
we justify our results on the basis of theoretical simulations and discuss the feasibility of using such a system for adaptive optics considering a trade - off between wavefront correction and astigmatism due to deformation . .
And you have already written the first three sentences of the full article: it is known that the most important component of an adaptive optics ( ao ) system is the corrector , which is the deformable mirror ( dm ) .
it can be a continuous face sheet or a surface formed by mirror segments @xcite . in the former the mirror boundary
is fixed and voltage applied to any one actuator influences the neighbouring surface as well . in the case of the micro - machined membrane deformable mirror(mmdm ) [ 2 ] this influence can be as large as 60@xmath1 [ 3 ] ..
Please generate the next two sentences of the article | however , they are still preferred in many ao systems [ 4 - 8 ] because of their low cost and capability of achieving large stroke . a 37 channel mmdm from okotech , netherlands ,
is being used by us at the udaipur solar observatory ( uso ) for its solar adaptive optics [ 9 - 11 ] ( sao ) system . |
4,923 | Suppose that you have an abstract for a scientific paper: we do several simple calculations and measurements in an effort to gain understanding of global warming and the carbon cycle .
some conclusions are interesting : ( i ) there has been global warming since the end of the " around 1700 .
there is no statistically significant evidence of acceleration of global warming since 1940 .
( ii ) the increase of @xmath0 in the atmosphere , beginning around 1940 , accurately tracks the burning of fossil fuels . burning all of the remaining economically viable reserves of oil , gas and coal over the next 150 years or so
will approximately double the pre - industrial atmospheric concentration of @xmath0 .
the corresponding increase in the average temperature , due to the greenhouse effect , is quite uncertain : between 1.3 and 4.8k .
this increase of temperature is ( partially ? ) offset by the increase of aerosols and deforestation .
( iii ) ice core samples indicate that the pre - historic @xmath0 concentration and temperature are well correlated .
we conclude that changes in the temperatures of the oceans are probably the cause of the changes of pre - historic atmospheric @xmath0 concentration .
( iv ) data suggests that large volcanic explosions can trigger transitions from glacial to interglacial climates .
( v ) most of the carbon fixed by photosynthesis in the amazon basin returns to the atmosphere due to aerobic decay . .
And you have already written the first three sentences of the full article: we , two non - experts , present several " calculations and some simple measurements related to global warming and the carbon cycle .
our purpose is to understand which phenomena are important in determining the temperature of the earth .
in this article we will use the following measured data.@xcite the power of the radiation of the sun per square perpendicular meter above the atmosphere is measured to be @xmath1w / m@xmath2 ..
Please generate the next two sentences of the article | is @xmath3 , with @xmath4wm@xmath5k@xmath6 .
the power radiated by the sun is @xmath7 . |
4,924 | Suppose that you have an abstract for a scientific paper: in the majorana representation of a spin 1/2 we find an identity which relates spin - spin correlators to one - particle fermionic correlators .
this should be contrasted with the straightforward approach in which two - particle ( four - fermion ) correlators need to be calculated .
we discuss applications to the analysis of the dynamics of a spin coupled to a dissipative environment and of a quantum detector performing a continuous measurement of a qubit s state . .
And you have already written the first three sentences of the full article: an analysis of spin dynamics involves calculations of spin correlators .
spin operators do not satisfy the wick theorem , and various methods have been used to still enable the use of perturbative ( diagrammatic ) methods .
one of the approaches is based on the majorana - fermion representation of spin operators ..
Please generate the next two sentences of the article | this approach has a long history and was applied recently to condensed - matter problems .
@xcite in this approach one introduces three majorana fermions @xmath0 ( per spin ) and expresses the spin ( or pauli ) operators via these fermions : @xmath1 obviously , an analysis of spin - spin correlations based on eq . |
4,925 | Suppose that you have an abstract for a scientific paper: a new channel of direct photon production from a quark gluon plasma ( qgp ) is explored .
this process appears at next - to - leading - order in the presence of a charge asymmetry in the heated matter and may be effectively described as the bremsstrahlung of a real photon from a thermal gluon .
the photon production from this new mechanism is calculated in the effective theory of qcd at high temperature .
the results show that the photon production rate may not as big as the annihilation and compton scattering at low baryon density , but could become important in baryon - rich matter . .
And you have already written the first three sentences of the full article: it is the object of relativistic heavy - ion collisions to create and study strongly interacting matter excited beyond its hadronic phase @xcite .
the existence of such a phase [ the quark gluon plasma ( qgp ) ] has been predicted by lattice qcd calculations @xcite which exhibit a sudden rise in the scaled pressure and entropy density as the temperature is raised just beyond @xmath0 mev .
detailed models of nuclear reactions had predicted that the energy deposition in the center - of - mass frame should be sufficient to cause temperatures at mid - rapidity in central collisions of gold nuclei to reach upwards of @xmath1 mev @xcite ..
Please generate the next two sentences of the article | these predictions have been confirmed by the experimental results of the four relativistic heavy - ion collider ( rhic ) detector collaborations , which have set a lower bound of about @xmath2 gev/@xmath3 on the energy density at a time @xmath4 fm / c in central au+au collisions @xcite . according to lattice calculations
, such energy densities should place the excited matter firmly in the deconfined region . |
4,926 | Suppose that you have an abstract for a scientific paper: @xmath0-symmetric models with a wick rotation of time ( @xmath1 ) show spectral phase transitions that are similar to those of dissipative systems driven out of equilibrium .
optics can provide an accessible test bed to explore spectral phase transitions of wick - rotated @xmath0-symmetric models .
this is shown by considering the transverse dynamics of laser light in optical cavities with variable reflectivity and tilted mirrors .
two specific examples are discussed : the optical analogue of the hydrodynamic squire model of vorticity , and the wick - rotated @xmath0-symmetric nonlinear dimer model . in the latter case the spectral phase transition
is associated with the universal phase locking - unlocking transition in adler s theory of coupled oscillators .
pt symmetry breaking ; dynamic laser instabilities ; coupled oscillators .
And you have already written the first three sentences of the full article: in 1998 , bender and boettcher showed that a wide class of non - hermitian hamiltonians @xmath2 can possess entirely real spectra as long as they respect parity - time ( @xmath0 ) symmetry @xcite .
while the implications of @xmath0 symmetry in theoretical physics are still a matter of debate @xcite , classical systems such as optical @xcite and electronic @xcite systems provide an accessible test bed where the @xmath0 symmetry notion can be explored .
@xmath0-symmetric hamiltonians show a sharp spectral transition when a control parameter is varied , with the appearance of pairs of complex conjugate energies in the broken @xmath0 phase ..
Please generate the next two sentences of the article | the phase transition is associated with the appearance of exceptional points @xcite or spectral singularities @xcite .
similar transitions are found in pseudo - hermitian hamiltonians @xcite , pseudo-@xmath0-symmetric driven hamiltonians @xcite , wick - rotated @xmath0 symmetric hamiltonians @xcite , and in liouvillean operators in the lindblad form @xcite . in particular , in ref.@xcite it was shown that a combination of unitary and antiunitary symmetry of quantum liouvilleans associated to certain open quantum systems implies a dihedral symmetry of the complex liouvillean spectrum . |
4,927 | Suppose that you have an abstract for a scientific paper: we report on the development of the medium
resolution spectrophotometer to accompany ( in real time ) spectral observations performed with the high resolution spectrographs on the 6-m telescope bta . .
And you have already written the first three sentences of the full article: we report on the development of the medium
resolution spectrophotometer to accompany ( in real time ) spectral observations performed with the high resolution spectrographs @xcite on the 6meter telescope bta of the special astrophysical observatory .
the spectrophotometer uses a 0.7meter optics of the bta guide telescope and have a separate system for object positioning ..
Please generate the next two sentences of the article | the spectrophotometer is managed via the internet . in high resolution ( r )
spectral observations on the bta the size of the spectral region simultaneously recorded depends mainly on the format of ccd used . for example , the spectral region simultaneously recorded with the nasmyth echelle spectrograph ( nes ) is equal approximately to 1000 , 1500 , 3000 at the ccd format 1k@xmath01k , 2k@xmath02k , 2k@xmath04k . |
4,928 | Suppose that you have an abstract for a scientific paper: this paper highlights security issues that can arise when incorrect assumptions are made on the capabilities of an eavesdropper . in particular , we analyze a channel model based on a split binary symmetric channel ( bsc ) .
corresponding security parameters are chosen based on this channel model , and assumptions on the eavesdroppers capabilities
. a gradual relaxation of the restrictions on the eavesdropper s capabilities will be made , and the resulting loss of security will be quantified .
an alternative will then be presented that is based on stochastic encoding and creating artificially noisy channels through the usage of private keys .
the artificial channel will be constructed through a deterministic process that will be computationally intractable to reverse . .
And you have already written the first three sentences of the full article: to securing communications through the use of information theoretic notions was started by shannon in the 1940 s . in his papers he related fundamental notions , such as entropy , to the secrecy of cryptographic systems @xcite .
inspired by the work of shannon , wyner published a paper proving that it was theoretically possible to secure communications solely through the choice of an encoding scheme for a specific channel model @xcite .
wyner s security model capitalizes on the eavesdropper receiving a noisier copy of what the intended user receives . in general , for communications security.
Please generate the next two sentences of the article | , assumptions on the capabilities of eavesdroppers are required to design systems . in wyner
s paper , the presumption is on the channel noise of the eavesdropper . |
4,929 | Suppose that you have an abstract for a scientific paper: we discuss the appearance at the qcd phase transition , and the subsequent decay , of axion walls bounded by strings in @xmath0 axion models .
we argue on intuitive grounds that the main decay mechanism is into barely relativistic axions .
we present numerical simulations of the decay process . in these simulations
, the decay happens immediately , in a time scale of order the light travel time , and the average energy of the radiated axions is @xmath1 for @xmath2 .
@xmath3 is found to increase approximately linearly with @xmath4 .
extrapolation of this behaviour yields @xmath5 in axion models of interest .
we find that the contribution to the cosmological energy density of axions from wall decay is of the same order of magnitude as that from vacuum realignment , with however large uncertainties .
the velocity dispersion of axions from wall decay is found to be larger , by a factor @xmath6 or so , than that of axions from vacuum realignment and string decay .
we discuss the implications of this for the formation and evolution of axion miniclusters and for the direct detection of axion dark matter on earth .
finally we discuss the cosmology of axion models with @xmath7 in which the domain wall problem is solved by introducing a small u@xmath8(1 ) breaking interaction .
we find that in this case the walls decay into gravitational waves . .
And you have already written the first three sentences of the full article: the axion @xcite was postulated approximately twenty years ago to explain why the strong interactions conserve the discrete symmetries p and cp in spite of the fact that the standard model of particle interactions as a whole violates those symmetries .
it is the quasi - nambu - goldstone boson associated with the spontaneous breaking of a @xmath9 symmetry which peccei and quinn postulated . at zero temperature the axion mass is given by : @xmath10 where @xmath11 is the magnitude of the vacuum expectation value that breaks @xmath9 and @xmath12 is a strictly positive integer that describes the color anomaly of @xmath9 .
axion models have @xmath12 degenerate vacua @xcite ..
Please generate the next two sentences of the article | searches for the axion in high energy and nuclear physics experiments have only produced negative results . by combining the constraints from these experiments with those from astrophysics @xcite ,
one obtains the following bound : @xmath13 ev . |
4,930 | Suppose that you have an abstract for a scientific paper: we study the excitonic coupling and homogeneous spectral line width of brick layer j - aggregate films .
we begin by analysing the structural information revealed by the two - exciton states probed in two - dimensional spectra .
our first main result is that the relation between the excitonic couplings and the spectral shift in a two - dimensional structure is different ( larger shift for the same nearest neighbour coupling ) from that in a one - dimensional structure , which leads to an estimation of dipolar coupling in two - dimensional lattices .
we next investigate the mechanisms of homogeneous broadening - population relaxation and pure dephasing - and evaluate their relative importance in linear and two - dimensional aggregates .
our second main result is that pure dephasing dominates the line width in two - dimensional systems up to a crossover temperature , which explains the linear temperature dependence of the homogeneous line width .
this is directly related to the decreased density of states at the band edge when compared with linear aggregates , thus reducing the contribution of population relaxation to dephasing .
pump - probe experiments are suggested to directly measure the lifetime of the bright state and can therefore support the proposed model . .
And you have already written the first three sentences of the full article: organic molecules are promising candidates for the next generation of electronic devices and for solar energy conversion.@xcite among these , assemblies of dye molecules in the form of j - aggregates have attracted attention for their special optical properties.@xcite these are understood from delocalization of the exciton formed upon the absorption of light over tens to hundreds of monomers.@xcite because the dominant resonant transfer interactions between molecules are negative in a j - aggregate , the optically bright state is found at the bottom of the band , leading to a redshift of the absorption peak compared to a single chromophore .
other properties resulting from this exciton delocalization are superradiance and a hidden level structure at the band edge.@xcite the exciton delocalization in linear aggregates is reflected in the pump - probe spectrum@xcite and in the two - dimensional optical spectrum.@xcite most early studies focused on j - aggregates for which the optical properties can be explained with a model of a linear aggregate , which self - assemble in solution and are often studied at low temperature in a glass environment.@xcite over the past years there has been an intense interest in tubular j - aggregates.@xcite it is also possible to manufacture two - dimensional thin film j - aggregates of chromophore molecules , which were found to exhibit a redshift in the absorption.@xcite nonlinear optical experiments produced a two - dimensional spectrum similar to the spectrum of a linear aggregate , consisting of a single pair of positive and negative peaks.@xcite in order to analyse these findings , a model of a truly two - dimensional aggregate must be used,@xcite which goes beyond weakly coupled linear aggregates.@xcite in general , the transfer interactions between molecules depend strongly on their relative orientation .
this means that the absorption spectrum is sensitive to the details of the molecular arrangement ..
Please generate the next two sentences of the article | therefore , modeling of the spectrum can help in determining the structure .
this is particularly helpful in cases where the structure is not known from other measurements.@xcite it is clear from experiment , as well as from consideration of the molecular structure , that the excitons in j - aggregates must couple to their environment . |
4,931 | Suppose that you have an abstract for a scientific paper: algebraic quantum field theory is an approach to relativistic quantum physics , notably the theory of elementary particles , which complements other modern developments in this field .
it is particularly powerful for structural analysis but has also proven to be useful in the rigorous treatment of models . in this contribution a non technical survey is given with emphasis on interesting recent developments and future perspectives .
topics covered are the relation between the algebraic approach and conventional quantum field theory , its significance for the resolution of conceptual problems ( such as the revision of the particle concept ) and its role in the characterization and possibly also construction of quantum field theories with the help of modular theory .
the algebraic approach has also shed new light on the treatment of quantum field theories on curved spacetime and made contact with recent developments in string theory ( algebraic holography ) . .
And you have already written the first three sentences of the full article: in the present year 2000 we are celebrating the 100th birthday of quantum theory and the 75th birthday of quantum mechanics .
thus it took only 25 years from the first inception of the new theory until its final consolidation .
quantum field theory is almost as old as quantum mechanics ..
Please generate the next two sentences of the article | but the formulation of a fully consistent synthesis of the principles of quantum theory and classical relativisitic field theory has been a long and agonizing process and , as a matter of fact , has not yet come to a satisfactory end , in spite of many successes . the best approximation to nature in the microscopic and relativistic regime of elementary particle physics which we presently have , the so called _ standard model _
, does not yet have the status of a mathematically consistent theory . |
4,932 | Suppose that you have an abstract for a scientific paper: the goal of _ photoacoustic tomography _ ( pat ) is to estimate an _ initial pressure function _ @xmath0 from pressure data measured at a boundary surrounding the object of interest .
this paper is concerned with a time reversal method for pat that is based on the dissipative wave equation of nachman , smith and waag @xcite .
this equation has the advantage that it is more accurate than the _ thermo - viscous _ wave equation . for simplicity , we focus on the case of one _ relaxation process_. we derive an exact formula for the _ time reversal image _ @xmath1 , which depends on the _ relaxation time _ @xmath2 and the _ compressibility _ @xmath3 of the dissipative medium , and show @xmath4 for @xmath5 .
this implies that @xmath6 holds in the dissipation - free case and that @xmath1 is similar to @xmath0 for sufficiently small compressibility @xmath3 .
moreover , we show for tissue similar to water that the _ small wave number approximation
_ @xmath7 of the time reversal image satisfies @xmath8 with @xmath9 for @xmath10 . for such tissue ,
our theoretical analysis and numerical simulations show that the time reversal image @xmath1 is very similar to the initial pressure function @xmath0 and that a resolution of @xmath11 is feasible ( in the noise - free case ) . .
And you have already written the first three sentences of the full article: the enhancement of _ photoacoustic tomography _ ( pat ) by taking dissipation into account is currently a very active subfield of pat with various contributions from engineers , mathematicians and physicists . for basic facts on pat in the absence and presence of dissipation ,
we refer for example to @xcite and @xcite , respectively .
there are several strategies for solving this class of problem ..
Please generate the next two sentences of the article | firstly , _ regularization methods _ focus on a rigorous mathematical analysis and numerical solution of the inverse problem bearing its degree of ill - posedness in mind .
due to its mathematical character , this aspect of pat is usually carried out by mathematicians . |
4,933 | Suppose that you have an abstract for a scientific paper: we prove that the seasonally - forced sir model with a @xmath0-periodic forcing has a periodic solution with period @xmath0 whenever the basic reproductive number @xmath1 .
the proof uses the leray - schauder degree theory .
we also describe some numerical results in which we compute the @xmath0-periodic solution , where in order to obtain the @xmath0-periodic solution when the behavior of the system is subharmonic or chaotic , we use a galerkin scheme .
* msc * : 34v25 , 37j45 , 92d30 . .
And you have already written the first three sentences of the full article: the periodically forced sir model @xmath2 @xmath3 @xmath4 and variants of it , are extensively used to model seasonally recurrent diseases @xcite . here
@xmath5 are the fractions of the population which are susceptible , infective , and recovered , @xmath6 denotes the birth and death rate , @xmath7 the recovery rate , and @xmath8 , which we assume is a positive continuous @xmath0-periodic function , is the seasonally - dependent transmission rate ( so that @xmath0 is the yearly period ) . when simulating this model numerically ( see section [ numerical ] ) , it is observed that : \(i ) if @xmath9 , where @xmath10 @xmath11 then all solutions tend to the disease free equilibrium @xmath12
this fact can be rigorously proved , see @xcite ..
Please generate the next two sentences of the article | \(ii ) if @xmath13 , then depending on the values of the parameters , one observes convergence to @xmath0-periodic orbits , or to @xmath14-periodic orbits with @xmath15 ( subharmonics ) , or chaotic behavior .
a fundamental question , that is addressed here , is the _ existence _ of a @xmath0-periodic solution of the system . |
4,934 | Suppose that you have an abstract for a scientific paper: brownian dynamics simulations of bidisperse hard discs moving in two dimensions in a given steady and homogeneous shear flow are presented close to and above the glass transition density .
the stationary structure functions and stresses of shear melted glass are compared quantitatively to parameter free numerical calculations for monodisperse hard discs using mode coupling theory ( mct ) within the integration through transients ( itt ) framework .
theory qualitatively explains the properties of the yielding glass but quantitatively overestimates the shear driven stresses and structural anisotropies .
[ firstpage ] .
And you have already written the first three sentences of the full article: shear flow can drive dense colloidal dispersions into states far from equilibrium .
especially of interest is the possibility to shear melt colloidal solids , in particular metastable colloidal glasses and gels , and to investigate shear - melted ( yielding ) colloidal glasses .
does a yield stress and/or yield strain exist ( petekidis _ et al ..
Please generate the next two sentences of the article | are shear - melted states necessarily heterogeneous ( e.g. shear banded ) ?
does ageing prevent stationary states under steady shearing ? |
4,935 | Suppose that you have an abstract for a scientific paper: pulsars are magnetized rotating compact objects .
they spin down due to magnetic dipole radiation and wind emission .
if photon has a nonzero mass , the spin down rate would be smaller than the zero mass case .
we show that an upper limit of the photon mass , i.e. @xmath0 , could be placed if a pulsar with period @xmath1 is observed to spin down . recently
, a white dwarf ( wd ) m dwarf binary , ar scorpii was found to emit pulsed broadband emission with pulses @xcite .
the spin - down luminosity of the wd can comfortably power the non - thermal radiation from the system . applying our results to the wd pulsar with @xmath2
, we obtain a stringent upper limit of the photon mass of @xmath3 assuming vacuum dipole spindown , or @xmath4 for @xmath5 assuming wind spindown , where @xmath6 is the ratio of wind spindown luminosities between the cases with and without photon mass . .
And you have already written the first three sentences of the full article: according to the theory of relativity or quantum electrodynamics ( qed ) , the rest mass of photon should be exactly zero .
however , even if the photon rest mass is not zero , qed and classical electromagnetism remain intact @xcite .
this is because a non - zero photon mass would not damage gauge invariance of the first kind ( which would lead to non - conservation of charge ) , but would only damage the gauge invariance of the second kind ..
Please generate the next two sentences of the article | thus , the question of the photon mass is experimental , since it is impossible to fully prove that the photon rest mass is exactly zero via experiments .
the only experimental strategy is to place ever tighter upper limits on photon rest mass . due to the uncertainty principle |
4,936 | Suppose that you have an abstract for a scientific paper: we present a preliminary report on the first deep infrared photometry of and ( gc01 and gc02 hereafter ) - new galactic globular cluster ( gc ) candidates , discovered by the 2mass .
they both appear to be genuine disk gcs though highly obscured .
the location of the two gcs suggests that they are metal rich - [ fe / h]@xmath00.5 .
we estimated their distance and reddening using the @xmath1 brightness of the red giant branch ( rgb ) bump , and @xmath2 color of the rgb at @xmath3 mag : @xmath4 , @xmath5 kpc , and @xmath6 , @xmath7 mag , for and respectively .
variation in the metal abundance can change our results within @xmath8% . .
And you have already written the first three sentences of the full article: the known galactic globular clusters ( gc ) - less than 150 ( harris @xcite ) - were discovered mostly through optical searches , that are obviously biased against highly obscured gcs .
since the galaxy is estimated to have @xmath9 gcs ( harris @xcite ) , a certain number of them may still be hidden behind the galactic disk .
the two micron all sky survey ( 2mass ) offers an opportunity to carry a search for the missing gcs , and recently hurt et al ..
Please generate the next two sentences of the article | ( @xcite , @xcite ) reported a serendipitous discovery of two new gcs : 2mass gc01 and 2mass gc02 ( gc01 and gc02 hereafter ) .
their estimates suggest @xmath10 mag , rendering these clusters unobservable in the optical wavebands . a summary of the available data for the new clusters is given in table [ tbl-1 ] ( hurt et al . |
4,937 | Suppose that you have an abstract for a scientific paper: we have theoretically investigated the spin and charge fluctuations in the quasi - one dimensional organic superconductor @xmath0 . using the extended multi - site hubbard model , which contains four sites in a unit cell and the transfer energies obtained by the extended hckel method
, we calculate the linearized gap equation with the random phase approximation , to find novel order parameters of superconductivity due to several kinds of charge fluctuations induced by the anisotropic intersite repulsive interactions . for the singlet state ,
the order parameter with line nodes appears in the case of the strong charge fluctuation , while the order parameter with anisotropic gap suggested by shimahara is reproduced in the spin fluctuation .
the triplet state is also obtained for the wide parameter range of repulsive interactions due to a cooperation between charge and spin fluctuations .
organic conductor , tmtsf , superconductivity , electron correlation , spin fluctuation , charge fluctuation .
And you have already written the first three sentences of the full article: in quasi - one dimensional organic conductors tmtsf ( tetrametyltetraselenafulvalence ) salts , there are several experimental evidences of superconductivity , @xcite which exhibit the large critical field being much larger than the pauli limit.@xcite for @xmath1 , the triplet superconducting(sc ) state has been maintained from the measurement of the knight shift and the nmr relaxation rate .
@xcite for @xmath0 , @xcite in the weak magnetic field , the singlet state with line nodes has been suggested by the the knight shift and relaxation rate of the nmr experiment in the sc phase.@xcite further , it has been suggested that the triplet or fflo state emerges under strong magnetic field.@xcite the specific property of @xmath0 emerges due to the anion ordering below 24k .
the folded fermi surfaces with a unit cell containing four tmtsf molecules is obtained from the transfer integrals , which are estimated from the extended hckel method based on the x - ray diffraction measurement.@xcite several theoretical works have been performed to understand the superconductivity in the quasi - one dimensional organic conductors ..
Please generate the next two sentences of the article | the single band models for @xmath1 has been investigated by perturbation theories .
@xcite the magnetic field favors the triplet or fflo superconductivity , @xcite while the on - site repulsion induces the singlet superconductivity in the absence of magnetic field . |
4,938 | Suppose that you have an abstract for a scientific paper: a comprehensive hot line list is calculated for @xmath0ph@xmath1 in its ground electronic state .
this line list , called salty , contains almost 16.8 billion transitions between 7.5 million energy levels and it is suitable for simulating spectra up to temperatures of 1500 k. it covers wavelengths longer than 1 @xmath2 m and includes all transitions to upper states with energies below @xmath3 @xmath4 and rotational excitation up to @xmath5 .
the line list is computed by variational solution of the schrdinger equation for the rotation - vibration motion employing the nuclear - motion program trove .
a previously reported _ ab initio _
dipole moment surface is used as well as an updated ` spectroscopic ' potential energy surface ( pes ) , obtained by refining an existing _ ab initio _ surface through least - squares fitting to the experimentally derived energies .
detailed comparisons with other available sources of phosphine transitions confirms salty s accuracy and illustrates the incompleteness of previous experimental and theoretical compilations for temperatures above 300 k. atmospheric models are expected to severely underestimate the abundance of phosphine in disequilibrium environments , and it is predicted that phosphine will be detectable in the upper troposphere of many substellar objects .
this list is suitable for modelling atmospheres of many astrophysical environments , namely carbon stars , y dwarfs , t dwarfs , hot jupiters and solar system gas giant planets .
it is available in full as supplementary data to the article and at www.exomol.com .
molecular data ; opacity ; astronomical data bases : miscellaneous ; planets and satellites : atmospheres ; stars : low - mass ; stars : brown dwarfs .
[ firstpage ] .
And you have already written the first three sentences of the full article: over the past twenty years , discoveries of planets , stars and substellar objects have demonstrated the enormous diversity of astrophysical bodies in the universe .
thanks to modern techniques and technology , it is now possible to study the atmospheres of these objects and retrieve some knowledge of their composition , structure and dynamics .
however , these are extremely complex systems to model and accurate observations are still difficult to perform . in particular , it is crucial for the correct characterisation of these atmospheres that complete and accurate descriptions of the molecules that comprise them are available . here.
Please generate the next two sentences of the article | phosphine , or ph@xmath6 , is considered .
phosphorus is the one of the most abundant chemically reactive volatile elements in a solar type system ( with s , after h , c , n and o ) . |
4,939 | Suppose that you have an abstract for a scientific paper: equilibrium dynamical models are essential tools for extracting science from surveys of our galaxy .
we show how models can be tested with data from a survey before the survey s selection function has been determined .
we illustrate the application of this method by presenting some results for the rave survey .
we extend our published analytic distribution functions to include chemistry and fit the chosen functional form to a combination of the geneva copenhagen survey ( gcs ) and a sample of g - dwarfs observed at @xmath0 by the segue survey . by including solid dynamics we are able to predict the contribution that the thick disc / halo stars surveyed by segue should make to the gcs survey .
we show that the measured [ fe / h ] distribution from the gcs includes many fewer stars at @xmath1 than are predicted .
the problem is more likely to lie in discordant abundance scales than with incorrect dynamics . #
1to 0pt#1 = cmmib10 = cmmib7 = = # 1 ii aa # 1#2 # 1#1 = # 1fig . [ # 1 ] .
And you have already written the first three sentences of the full article: very significant resources are being invested in large surveys of the stellar content of our galaxy .
we clearly are under an obligation to make every effort to extract as much science from these expensive data as we can .
a survey catalogue is always dominated by selection effects : it contains stars that are nearby and luminous ..
Please generate the next two sentences of the article | moreover several of the quantities measured for stars , for example parallax @xmath2 , proper motion @xmath3 , @xmath4 enhancement @xmath5 $ ] , contain non - negligible errors , and the quantities of physical interest that we derive from them , such as distance @xmath6 , luminosity @xmath7 and velocity @xmath8 , have correlated errors with highly non - gaussian error distributions .
models play a vital role in extracting science from surveys by taking into account ( i ) selection effects ( ii ) measurement errors and ( iii ) combining constraints on the properties of the galaxy from different surveys . here |
4,940 | Suppose that you have an abstract for a scientific paper: alkali - filled hollow - core fibres are a promising medium for investigating light - matter interactions , especially at the single - photon level , due to the tight confinement of light and high optical depths achievable by light - induced atomic desorption . however , until now these large optical depths could only be generated for seconds at most once per day , severely limiting the practicality of the technology .
here we report the generation of highest observed transient ( @xmath0 for up to a minute ) and highest observed persistent ( @xmath1 for hours ) optical depths of alkali vapours in a light - guiding geometry to date , using a caesium - filled kagom - type hollow - core photonic crystal fibre .
our results pave the way to light - matter interaction experiments in confined geometries requiring long operation times and large atomic number densities , such as generation of single - photon - level nonlinearities and development of single photon quantum memories .
optical quantum memories are a crucial component of photonic quantum technologies , enabling the storage and manipulation of optically encoded quantum information @xcite or temporal multiplexing of probabilistic operations @xcite .
such memories require strong light - matter coupling that facilitates the transformation of a photon into a matter excitation .
the coupling strength can be increased from the material side , by increasing the number of atoms interacting with light , i.e. the optical depth ( od ) , or from the photonic side , by confining the photons in a waveguide geometry , which overcomes the focused light interaction length limit imposed by free - space diffraction .
warm vapours contained in hollow - core photonic crystal fibres ( hc - pcf ) are therefore a promising candidate for such applications @xcite .
another exciting approach are cold atomic gases coupled to tapered optical fibres @xcite .
hc - pcfs filled with alkali vapours have been used to demonstrate the basic building blocks required for....
And you have already written the first three sentences of the full article: this work was supported by air force office of scientific research ( afosr ) ( fa8655 - 09 - 1 - 3020 ) ; engineering and physical sciences research council ( epsrc ) ( ep / k034480/1 ( bloqs ) ; ep/ j000051/1 , nqit ) ; european commission ( ec ) ( piefga-2013 - 62737 , ief - ga-2012 - 331859 , ip siqs ( 600645 ) , piif - ga-2013 - 629229 ) ; european research council ( erc ) ( moquacino ) ; royal society .
we thank a. abdolvand and p. st .
j. russell from the max planck institute for the science of light ( germany ) for providing us with the hollow - core fibres and their characterization ..
Please generate the next two sentences of the article | we would also like to thank i. g. hughes for his insighftul comments on the early version of the manuscript .
j. nunn , n. k. langford , w. s. kolthammer , t. f. m. champion , m. r. sprague , p. s. michelberger , x .- |
4,941 | Suppose that you have an abstract for a scientific paper: we discuss system with non - isotropic non - heisenberg hamiltonian with nearest neighbor exchange within a mean field approximation process .
we drive equations describing non - heisenberg non - isotropic model using coherent states in real parameters and then obtain dispersion equations of spin wave of dipole and quadrupole branches for a small linear excitation from the ground state . in final , soliton solution for quadrupole branches for these linear equations obtained . .
And you have already written the first three sentences of the full article: during the past decade study of nonlinear behavior of magnetic crystals has been attracted large attention , specially it accompany with the progress in some other fields such as development of theory of nonlinear differential equation , achieving new laboratory results and also potential applications in other branches of science and technology [ 1 , 2 ] .
particles with spin @xmath0 are more interesting among the other nano particles [ 3 , 4 ] .
this is because of existing of complexity in their behavior due to their multipole dynamic spin excitations . in such systems ,.
Please generate the next two sentences of the article | the number of necessary parameters for complete description of macroscopic properties increases up to 4s , that s stands for magnitude of system spin .
also it worthwhile , the process of achieving classical spin equations and dynamic multipoles is based on coherent states that are obtained in @xmath1 group[5 ] . |
4,942 | Suppose that you have an abstract for a scientific paper: a ramsey - type interferometer is suggested , employing a cold trapped ion and two time - delayed off - resonant femtosecond laser pulses .
the laser light couples to the molecular polarization anisotropy , inducing rotational wavepacket dynamics .
an interferogram is obtained from the delay dependent populations of the final field - free rotational states .
current experimental capabilities for cooling and preparation of the initial state are found to yield an interferogram visibility of more than 80% .
the interferograms can be used to determine the polarizability anisotropy with an accuracy of about @xmath0 , respectively @xmath1 , provided the uncertainty in the initial populations and measurement errors are confined to within the same limits . .
And you have already written the first three sentences of the full article: interference of waves both in the form of light and massive particles , such as electrons , neutrals , and atoms , has proven to be a very sensitive method of measuring physical quantities ( see e.g. ref .
@xcite and references therein ) .
this includes precise measurements of electromagnetic fields , gyromagnetic constants , gravitational acceleration and rotation relative to an inertial system ..
Please generate the next two sentences of the article | when it comes to interference of quantum objects with internal energy structure , the method of ramsey interferometry , involving two - level objects , has been in particular successful @xcite .
the accuracy in determining the internal state energies by ramsey interferometry scales inversely proportional to the square root of the interrogation time . |
4,943 | Suppose that you have an abstract for a scientific paper: let @xmath0 be a hypersurface which allow only generic corank one singularities , and admits globally defined unit normal vector field @xmath1 .
then we show the existence of an index formula .
for example , when @xmath2 or @xmath3 , it holds that @xmath4 respectively , where @xmath5 ( resp .
@xmath6 ) is the subset of @xmath7 at which the co - orientation of @xmath7 induced by @xmath1 coincides ( resp
. does not coincide ) with the orientation of @xmath7 for @xmath2 , @xmath8 , and @xmath9 ( resp .
@xmath10 ) for @xmath11 is the euler number of the set of positive ( resp .
negative ) @xmath12-singular points of @xmath13 .
the formula for @xmath2 is known . to prove the results ,
we prepare an index formula for corank one singularities of vector bundle homomorphisms on @xmath7 . as its application , an index formula for blaschke normal map of strictly convex hypersurfaces in @xmath14
is also given . .
And you have already written the first three sentences of the full article: let @xmath15 be an oriented closed @xmath16-manifold , and @xmath17 a homomorphism between the tangent bundle @xmath18 and an oriented vector bundle @xmath19 of rank @xmath16 on @xmath20 .
suppose that @xmath21 allows only generic corank one singularities , namely it has only @xmath22-singularities .
when @xmath23 is an even number , the euler characteristic @xmath24 of the vector bundle @xmath19 satisfies the following formula @xmath25 where @xmath26 ( resp ..
Please generate the next two sentences of the article | @xmath27 ) is the euler characteristic of the subset @xmath28 ( resp .
@xmath29 ) of @xmath20 at which the co - orientation induced by @xmath21 is ( resp . is not ) |
4,944 | Suppose that you have an abstract for a scientific paper: the characterization of the atmospheres of habitable - zone earth - mass exoplanets that transit across main - sequence stars , let alone the detection of bio - markers in their atmospheres , will be challenging even with future facilities .
it has been noted that white dwarfs ( wds ) have long - lived habitable zones and that a large fraction of wds may host planets .
we point out that during a transit of an earth - mass planet across a wd , the planet s atmospheric transmission spectrum obtains a much higher contrast over the stellar background compared to a main - sequence host , because of the small surface area of the wd .
the most prominent bio - marker in the present - day terrestrial atmosphere , molecular oxygen , is readily detectable in a wd transit via its a - band absorption at @xmath0 m .
a potentially life - sustaining earth - like planet transiting a wd can be found by assembling a suitable sample of @xmath1 wds and then surveying them for transits using small telescopes . if and when a transiting case is found , the o@xmath2 absorption in the planetary atmospheric transmission spectrum would be detectable with the james webb space telescope ( jwst ) in about 5 hours of total exposure time , integrated over 160 2-minute transits .
characterization of the planet atmosphere using other tracers such as water vapour and co@xmath2 will be considerably easier .
we demonstrate this future discovery space by simulating a possible transmission spectrum that would be obtained with jwst .
[ firstpage ] planets : extrasolar white dwarfs : .
And you have already written the first three sentences of the full article: the discovery of the first transiting exoplanet , hd209458 ( charbonneau et al . 2000 ) was quickly followed by a measurement and characterization of the planet s atmospheric transmission spectrum ( charbonneau et al . 2002 ) .
spectroscopic observations of this type provide invaluable probes of planetary physics , formation , and evolution .
the measurement , however , is difficult because of the tiny contrast , @xmath3 , between the signal ( the absorption lines in the light transmitted through the planet atmosphere ) and the background ( the unobstructed light from the host star ) . in hd209458.
Please generate the next two sentences of the article | the observation was possible owing to the closeness ( and hence brightness , @xmath4 mag ) of the star , combined with the stability provided by the _ hubble space telescope_. only a few measurements of this kind have been successful to date ( e.g tinetti et al . 2007 ; redfield et al .
2008 ; zhou & bayliss 2012 ; see also berta et al . |
4,945 | Suppose that you have an abstract for a scientific paper: we outline a method for characterizing deviations from the properties of a standard model ( sm ) higgs boson .
we apply it to current data in order to characterize up to which degree the sm higgs boson interpretation is consistent with experiment .
we find that the sm higgs boson is consistent with the current data set at the @xmath0 confidence level , based on data of excess events reported by cms and atlas , which are interpreted to be related to the mass scale @xmath1 , and on published @xmath2 exclusion regions .
we perform a global fit in terms of two parameters characterizing the deviation from the sm value in the gauge and fermion couplings of a higgs boson .
we find two minima in the global fit and identify observables that can remove this degeneracy .
an update for moriond 2012 data is included in the appendix , which finds that the sm higgs boson is now consistent with the current data set at only the @xmath3 confidence level ( which corresponds to @xmath4 tension compared to the best fit point ) . .
And you have already written the first three sentences of the full article: the main goal of the lhc physics program is to unravel the origin of electroweak symmetry breaking , with the leading explanation being the standard model higgs boson . in considering the sm higgs hypothesis , or more generally the correct description of electroweak symmetry breaking ( ewsb ) as realized in nature , it is important to synthesize the experimental results which are determined to date , in terms of symmetries that must be ( at least approximately ) respected in a successful effective description of physics at the weak scale .
probes of the mechanism of electroweak symmetry breaking can be summarized in terms of tests of the properties of the @xmath5 , @xmath6 bosons through electroweak precision data observables ( ewpd ) , probes of the low energy flavour changing signatures of weak scale physics , and direct searches .
the results of the first two of these probes indicate that a viable theory of ewsb can reduce parameter tuning by adopting an approximate @xmath7 custodial symmetry to comply with ewpd @xcite , and imposing approximate minimal flavour violation ( mfv ) @xcite , in order to be robustly consistent with the results of the flavour physics program ..
Please generate the next two sentences of the article | the sm higgs sector with renormalizable couplings to the fermions is exactly consistent with mfv by definition , but it is only approximately @xmath7 symmetric
. recently , atlas and cms have reported significant exclusion limits for a standard model higgs boson over a broad range of masses . |
4,946 | Suppose that you have an abstract for a scientific paper: in real flocks , it was revealed that the angular density of nearest neighbors shows a strong _ anisotropic structure _ of individuals by very recent extensive field studies by ballerini et al [ _ proceedings of the national academy of sciences usa _ * 105 * , pp.1232 - 1237 ( 2008 ) ] . in this paper , we show that this empirical evidence in real flocks , namely , the structure of anisotropy also emerges in an artificial flock simulation based on the _ boids _ by reynolds [ _ computer graphics _ * 21 * , pp.25 - 34 ( 1987 ) ] .
we numerically find that appropriate combinations of the weights for just only three essential factors of the boids , namely , ` cohesion ' , ` alignment ' and ` separation ' lead to a strong anisotropy in the flock .
this result seems to be highly counter - intuitive and also provides a justification of the hypothesis that the anisotropy emerges as a result of self - organization of interacting intelligent agents ( birds for instance ) . to quantify the anisotropy
, we evaluate a useful statistics ( a kind of _ order parameters _ in statistical physics ) , that is to say , the so - called @xmath0-value defined as an inner product between the vector in the direction of the lowest angular density of flocks and the vector in the direction of the moving of the flock .
our results concerning the emergence of the anisotropy through the @xmath0-value might enable us to judge whether an arbitrary flock simulation seems to be _
realistic _ or not .
+ * keywords * : self - organization , anisotropy , boids , swarm intelligence simulation , collective behaviour + .
And you have already written the first three sentences of the full article: collective behaviour of interacting _ intelligent _ agents such as birds , insects or fishes shows highly non - trivial properties and sometimes it seems to be quite counter - intuitive @xcite . as well - known , many - body systems having a lot of _ non - intelligent _ elements , for instance , spins ( tiny magnets in atomic scale length ) , particles , random - walkers etc .
also show a collective behaviour like a critical phenomenon of order - disorder phase transitions with ` spontaneous symmetry breaking ' in spatial structures of the system .
up to now , a huge number of numerical studies in order to figure it out have been done by theoretical physicists and mathematicians @xcite ..
Please generate the next two sentences of the article | they attempted to describe these phenomena by using some probabilistic models and revealed the ` universality class ' of the critical phenomena by solving the problem with the assistance of computer simulations .
of course , the validity of the studies should be checked by comparing the numerical results with the experimental findings . if their results disagree with the empirical data , |
4,947 | Suppose that you have an abstract for a scientific paper: we present here a new conjecture for the nature of the mersenne prime numbers by connecting it with the collatz - kakutani problem . by introducing a natural _ path length _ on the basis of the collatz - kakutani tree ,
we conjecture that this path length of a mersenne prime from the root of the collatz - kakutani tree is approximately proportional to the index of the mersenne prime .
we also discuss difference of behaviors between mersenne numbers and mersenne primes . .
And you have already written the first three sentences of the full article: prime numbers have attracted mathematically oriented minds .
they are fountains of the interesting problems which are left unresolved to the present . as well as prime numbers , natural numbers themselves sometimes show unexpected behaviors in spite of their simple appeal . in this note
, we would like to present a simple property arising from the combination of two unsolved problems in number theory ; the mersenne prime numbers and the collatz - kakutani conjecture ..
Please generate the next two sentences of the article | namely , we show that there exists an approximate linear relation between an index of the mersenne prime and its collatz - kakutani path length , both of which are defined in the next section .
let us start with a brief descriptions of the mersenne primes and the collatz - kakutani conjecture@xcite . |
4,948 | Suppose that you have an abstract for a scientific paper: the bose - hubbard model in an external magnetic field is investigated with strong - coupling perturbation theory .
the lowest - order secular equation leads to the problem of a charged particle moving on a lattice in the presence of a magnetic field , which was first treated by hofstadter .
we present phase diagrams for the two - dimensional square and triangular lattices , showing a change in shape of the phase lobes away from the well - known power - law behavior in zero magnetic field .
some qualitative agreement with experimental work on josephson - junction arrays is found for the insulating phase behavior at small fields . .
And you have already written the first three sentences of the full article: the simplest model of strongly interacting bosons is the bose - hubbard model ( bhm ) , which has been used to describe superfluid helium@xcite , cooper pairs in thin granular superconducting films@xcite and josephson junction arrays@xcite .
much theoretical work has concentrated on the phase diagram of the bhm in zero magnetic field@xcite because of the technical problems associated with introducing an external magnetic field ( such as the sign problem in quantum monte carlo simulations ) .
experimentalists on the other hand have concentrated on studying systems in an external magnetic field because the phase transition can be tuned by adjusting the magnetic field rather than changing the samples measured@xcite ..
Please generate the next two sentences of the article | we study the bhm on two - dimensional lattices in a perpendicular magnetic field by extending the strong - coupling perturbation theory for the field - free case@xcite .
this theoretical technique can incorporate magnetic - field dependence in a straightforward manner and is useful in studying field - tuned transitions . |
4,949 | Suppose that you have an abstract for a scientific paper: the spin liquid ground state of tb@xmath0ti@xmath0o@xmath1 has remained a long standing problem . by synchrotron
based terahertz measurements , we provide evidence of strong coupling between the magnetic and lattice degrees of freedom that begins to develop at high temperatures .
this is revealed by hybrid crystal electric field - phonon excitations which appear at 0.67thz below 200k , and around 0.42thz below 50k .
this double vibronic process only occurs for tb@xmath2 in the titinate family due to adequate energy matching and strong quadrupolar moments .
lattice motion is then the driving force behind spin flips , promoting quantum terms in the effective hamiltonian that describes tb@xmath0ti@xmath0o@xmath1 . .
over the last decade , spin - ice physics has aroused significant attention @xcite .
it emerges in pyrochlore magnets , like ho@xmath0ti@xmath0o@xmath1 or dy@xmath0ti@xmath0o@xmath1 , as a result of effective ferromagnetic interactions coupling the ising - like rare earth magnetic moments constrained along the local @xmath3 directions by the crystal field @xcite(fig .
[ fig : absspec ] ( a , b ) ) .
this combination impedes long range order , favoring a disordered and macroscopically degenerate magnetic state governed by an organizing principle , the so - called ice rule " , where two spins point into and two out of each elementary tetrahedron in the structure @xcite . the possibility that quantum fluctuations can melt
the spin ice state is a topical issue .
it is expected to lead to a wealth of exotic phenomena such as a quantum superposition of `` two - in two - out '' configurations and emergent electrodynamics with new deconfined particles @xcite . in this context , the puzzling behavior of the spin liquid tb@xmath0ti@xmath0o@xmath1 has attracted much attention . despite effective antiferromagnetic interactions ,
tb@xmath0ti@xmath0o@xmath1 features no long range order @xcite .
remarkably , the ground state supports elastic power law spin correlations @xcite....
And you have already written the first three sentences of the full article: this work was supported by the french anr project no . anr-13-bs04 - 0013 - 01 .
we thank j. debray for sample preparation and f. lvy - bertrand for infrared measurements .
m. j. harris , s. t. bramwell , d. f. mcmorrow , t. zeiske and k. w. godfrey , phys ..
Please generate the next two sentences of the article | lett . * 79 * , 2554 ( 1997 ) .
a. p. ramirez , a. hayashi , r. j. cava , r. siddharthan and b. s. shastry , nature * 399 * , 333 ( 1999 ) . |
4,950 | Suppose that you have an abstract for a scientific paper: the goal of this paper is to give an explicit description of the triangulated categories of tate and artin tate motives with finite coefficients @xmath0 over a field @xmath1 containing a primitive @xmath2-root of unity as the derived categories of exact categories of filtered modules over the absolute galois group of @xmath1 with certain restrictions on the successive quotients .
this description is conditional upon ( and its validity is equivalent to ) certain koszulity hypotheses about the milnor k - theory / galois cohomology of @xmath1 .
this paper also purports to explain what it means for an arbitrary nonnegatively graded ring to be koszul .
tate motives with integral coefficients are discussed in the `` conclusions '' section . .
And you have already written the first three sentences of the full article: [ [ section ] ] in the paper @xcite published in 1987 , a. beilinson formulated his famous conjectures on the properties of hypothetical categories of mixed motivic sheaves over a scheme .
in addition to the classical case of motives with rational coefficients , some conjectures about the category of motives with a finite coefficient ring @xmath0 were proposed there .
equivalent conjectures describing motivic complexes with finite coefficients were earlier formulated by s. lichtenbaum in @xcite . in the subsequent works of v..
Please generate the next two sentences of the article | voevodsky @xcite and others , triangulated categories @xmath3 of motives over @xmath1 were constructed ( assuming only the resolution of singularities ) for any field @xmath1 and any coefficient ring @xmath4 , @xmath5 , or @xmath0 .
beilinson predicted existence of abelian categories of mixed motives ; the triangulated categories now known would then be equivalent to the derived categories of those abelian categories . |
4,951 | Suppose that you have an abstract for a scientific paper: background : : two new @xmath0 states are recently observed around a few mev above the hoyle state ( the second @xmath1 state in @xmath2 ) . the characters of them are only poorly discussed in theory and are still mysterious .
purpose : : i give for the first time a comprehensive understanding of the structures of the @xmath1 states by analyzing their wave functions , and discuss relationship with the hoyle state , similarities , and differences between the states .
method : : i extend a microscopic @xmath3-cluster model called tohsaki - horiuchi - schuck - rpke ( thsr ) wave function so as to incorporate @xmath4 asymmetric configuration explicitly . the so - called @xmath5-constraint method to effectively eliminate spurious continuum components is also used .
results : : the @xmath6 state is shown to have a very large squared overlap with a single configuration of the extended thsr wave function in an orthogonal space to the hoyle state as well as to the ground state .
the @xmath7 state has a maximal squared overlap with a single extended thsr wave function with an extremely prolately - deformed shape .
conclusions : : the @xmath6 state appears as a family of the hoyle state to have a higher nodal structure in the internal motions of the @xmath8 clusters , due to the orthogonalization to the hoyle state .
the @xmath7 state dominantly has a linear - chain structure , where the @xmath8 clusters move freely in a non - localized way , like a one - dimensional gas of the @xmath8 clusters . .
And you have already written the first three sentences of the full article: nuclear cluster structure in the hoyle state , the second @xmath0 state at @xmath9 mev in @xmath2 , has been discussed for a long time by many authors @xcite .
cluster model approaches play an important role in understanding the structure and clarified that it has well developed @xmath8 cluster structure with more dilute density than that of saturation in the ground state , where @xmath3 clusters weakly interact with each other in a relative @xmath10-wave @xcite . in the recent fifteen years , however , the understanding of the hoyle state structure has been much deepened , by an advent of a new type of microscopic cluster model wave function , which is referred to as the tohsaki - horiuchi - schuck - rpke ( thsr ) wave function @xcite .
this wave function retains a structure that constituent @xmath3 clusters are loosely bound like a gas and occupy an identical orbit , and this structured phenomenon is now called the @xmath3 condensation ..
Please generate the next two sentences of the article | one of the most important properties for the thsr wave function is to give a single and optimal configuration that is equivalent to a solution of full microscopic three - body problem @xcite . since it is well known that the solutions of the full microscopic three - body problem via @xmath8 resonating group method ( rgm ) @xcite and via generator
coordinate method ( gcm ) @xcite nicely reproduce many experimental data for the hoyle state , like the energy , width , electro - magnetic properties , etc , the equivalence leads to the conclusion that the hoyle state exists as the @xmath3 condensate composed of a weakly interacting and gaslike @xmath8 clusters . not only the hoyle state but also some other excited states in @xmath2 trigger a special interest in recent years . |
4,952 | Suppose that you have an abstract for a scientific paper: experiment shows that the top quark is far heavier than the other elementary fermions .
this finding has stimulated research on theories of electroweak and flavor symmetry breaking that include physics beyond the standard model .
efforts to accommodate a heavy top quark within existing frameworks have revealed constraints on model - building .
other investigations have started from the premise that a large top quark mass could signal a qualitative difference between the top quark and other fermions , perhaps in the form of new interactions peculiar to the top quark .
such new dynamics may also help answer existing questions about electroweak and flavor physics .
this talk explores the implications of the heavy top quark in the context of weakly - coupled ( e.g. susy ) and strongly - coupled ( e.g. technicolor ) theories of electroweak symmetry breaking . .
And you have already written the first three sentences of the full article: two outstanding mysteries in particle theory are the cause of electroweak symmetry breaking and the origin of flavor symmetry breaking by which the quarks and leptons obtain their diverse masses .
the standard model of particle physics , based on the gauge group @xmath0 accommodates both symmetry breakings by including a fundamental weak doublet of scalar ( `` higgs '' ) bosons @xmath1 with potential function @xmath2 .
however the standard model provides no explanation of the dynamics responsible for the generation of mass ..
Please generate the next two sentences of the article | furthermore , the scalar sector suffers from two serious problems .
the scalar mass is unnaturally sensitive to the presence of physics at any higher scale @xmath3 ( e.g. the planck scale or a grand - unification scale ) : this is known as the gauge hierarchy problem . |
4,953 | Suppose that you have an abstract for a scientific paper: compact relativistic jets in active galactic nuclei offer an effective tool for investigating the physics of nuclear regions in galaxies .
the emission properties , dynamics , and evolution of jets in agn are closely connected to the characteristics of the central supermassive black hole , accretion disk and broad - line region in active galaxies .
recent results from studies of the nuclear regions in several active galaxies with prominent outflows are reviewed in this contribution . .
And you have already written the first three sentences of the full article: substantial progress achieved during the past decade in studies of active galactic nuclei has brought an increasingly wider recognition of the ubiquity of relativistic outflows ( jets ) in galactic nuclei , turning them into an effective probe of nuclear regions in galaxies @xcite .
emission properties , dynamics , and evolution of an extragalactic jet are intimately connected to the characteristics of the supermassive black hole , accretion disk and broad - line region in the nucleus of the host galaxy .
high - resolution radio observations access directly the regions where the jets are formed @xcite , and trace their evolution and interaction with the nuclear environment ( mundell et al ..
Please generate the next two sentences of the article | these studies , combined with optical and x - ray studies , yield arguably the most detailed picture of the galactic nuclei @xcite . presented below is a brief summary of recent results in this field , outlining the relation between jets , supermassive black holes and nuclear regions in prominent active galactic nuclei ( agn ) . in this respect , this review is complementary to other recent reviews @xcite focused on formation and propagation of extragalactic relativistic jets .
jets in active galaxies are formed in the immediate vicinity of the central black hole @xcite , and they interact with every major constituent of agn ( see table [ lobanov : tb1 ] . |
4,954 | Suppose that you have an abstract for a scientific paper: a method to efficiently compute , in a automatic way , helicity amplitudes for arbitrary scattering processes at leading order in the standard model is presented .
the scattering amplitude is evaluated recursively through a set of dyson - schwinger equations .
the computational cost of this algorithm grows asymptotically as @xmath0 , where @xmath1 is the number of particles involved in the process , compared to @xmath2 in the traditional feynman graphs approach .
unitary gauge is used and mass effects are available as well .
additionally , the color and helicity structures are appropriately transformed so the usual summation is replaced by monte carlo techniques .
some results related to the production of vector bosons and the higgs boson in association with jets are also presented . .
And you have already written the first three sentences of the full article: multi - particle and multi - jet final states are of great importance at the tevatron and at the future lhc or @xmath3 linear collider .
they serve both as signals and as important backgrounds to many new and already discovered physics channels . as an example
the production and decay of top quarks , higgs boson(s ) or susy particles can be mentioned ..
Please generate the next two sentences of the article | a typical background is the production of weak vector bosons in association with jets . among others
the proper evaluation of the eight jet qcd background will be needed . to describe the production process of a number of particles the corresponding amplitudes have to be constructed . |
4,955 | Suppose that you have an abstract for a scientific paper: using a self - consistent delta - hole model the pion propagation in isospin asymmetric nuclear matter is studied . in neutron - rich matter , corresponding to heavy nuclei , a significant difference in positive and negative pion light - cone distributions is obtained leading to a nuclear enhancement of up antiquark distribution compared to the down antiquark one .
this means that the sea - quark asymmetry in the free nucleon can not be extracted model independently from an experiment on a neutron - rich nucleus . _
pacs : _ 21.65.+f ; 24.85.+p ; 13.40.-f isospin - asymmetric medium ; drell - yan scattering ; antiquark flavour asymmetry . .
And you have already written the first three sentences of the full article: the meson - cloud model plays an important role in dealing with non - perturbative quantum chromodynamics effects in the nucleon .
it has been used by several groups to interpret momentum distributions of sea quarks in the nucleon @xcite , measured in deep inelastic scattering .
the standard approach is based upon the sullivan process @xcite , in which the only essential parameter is the cut - off in the pion - nucleon - nucleon vertex ..
Please generate the next two sentences of the article | originally the emphasis was mainly on the description of the isoscalar @xmath0 distributions .
more recently , since the observed violation of the gottfried sum rule , showing an excess of @xmath1 over @xmath2 in proton , the interest focussed on the properties of @xmath3 in the nucleon , whose @xmath4 dependence was measured recently @xcite . |
4,956 | Suppose that you have an abstract for a scientific paper: we present the hybrid opacity code sco - rcg which combines statistical approaches with fine - structure calculations .
radial integrals needed for the computation of detailed transition arrays are calculated by the code sco ( super - configuration code for opacity ) , which calculates atomic structure at finite temperature and density , taking into account plasma effects on the wave - functions .
levels and spectral lines are then computed by an adapted rcg routine of r. d. cowan .
sco - rcg now includes the partially resolved transition array model , which allows one to replace a complex transition array by a small - scale detailed calculation preserving energy and variance of the genuine transition array and yielding improved high - order moments .
an approximate method for studying the impact of strong magnetic field on opacity and emissivity was also recently implemented .
the hybrib detailed / statistical opacity code sco - rcg : new developments and applications jean - christophe pain@xmath0 , franck gilleron@xmath1 , quentin porcherot@xmath2 and thomas blenski@xmath3 @xmath1cea , dam , dif , f-91297 arpajon , france @xmath2dga , 94110 arcueil , france @xmath3cea , dsm , iramis , f-91191 gif - sur - yvette , france .
And you have already written the first three sentences of the full article: when lines coalesce into broad unresolved patterns due to physical broadening mechanisms ( stark effect , auto - ionization , etc . ) , they can be handled by global methods @xcite .
on the other hand , some transition arrays exhibit a small number of lines that must be taken into account individually .
those lines are important for plasma diagnostics , interpretation of spectroscopy experiments and for calculating the rosseland mean , which is very sensitive to the gaps between lines in the spectrum ..
Please generate the next two sentences of the article | the hybrid opacity code sco - rcg @xcite combines statistical methods and fine - structure calculations , assuming local thermodynamic equilibrium . in order to decide whether a detailed treatment of lines is necessary or not and to determine the validity of statistical methods
, the code uses criteria to quantify the porosity ( localized absence of lines ) of transition arrays . |
4,957 | Suppose that you have an abstract for a scientific paper: we investigate , analytically and numerically , the emergence of spatio - temporal order in nonequilibrium scalar field theories . the onset of order is triggered by destabilizing interactions ( dis ) , which instantaneously change the interacting potential from a single to a double - well , tunable to be either degenerate ( sdw ) or nondegenerate ( adw ) . for the sdw case , we observe the emergence of spatio - temporal coherent structures known as oscillons .
we show that this emergence is initially synchronized , the result of parametric amplification of the relevant oscillon modes .
we also discuss how these ordered structures act as bottlenecks for equipartition . for adw potentials ,
we show how the same parametric amplification mechanism may trigger the rapid decay of a metastable state . for a range of temperatures ,
the decay rates associated with this resonant nucleation can be orders of magnitude larger than those computed by homogeneous nucleation , with time - scales given by a simple power law , @xmath0^b$ ] , where @xmath1 depends weakly on the temperature and @xmath2 is the free - energy barrier of a critical fluctuation . .
And you have already written the first three sentences of the full article: the emergence of spatio - temporal ordered structures in nonlinear systems is an ideal laboratory for investigating the trend toward complexification observed in nature at the physical , chemical , and biological level @xcite .
it is known that localized , or spatially - bound , order emerges in systems which are out of thermodynamic equilibrium , at the expense of growing overall disorder @xcite .
examples can be found in hydrodynamics , in networks of chemical reactions @xcite , in phase transitions and critical phenomena @xcite , and in living organisms @xcite ..
Please generate the next two sentences of the article | for these localized ordered structures to survive , they must interact with an external environment , which maintains nonequilibrium conditions : in general , an isolated nonlinear system will eventually reach equilibrium , maximizing its entropy to the detriment of localized ordered structures . in other words , if localized ordered structures emerge during the approach to equilibrium of a closed system , they will eventually disappear as energy becomes increasingly equipartitioned amongst the system s many degrees of freedom .
the emergence of localized ordered structures is thus a nonequilibrium phenomenon , usually corresponding to an unequal partitioning of energy : if they are long - lived , they will serve as bottlenecks to equipartition . |
4,958 | Suppose that you have an abstract for a scientific paper: we in the paper study the metric perturbations generated in a bouncing universe driven by the quintom matter .
firstly , we review the background evolution of quintom bounce and the power spectrum of scalar perturbations .
secondly , we study the non - gaussianity of curvature perturbations and then calculate the tensor perturbations of the model . .
And you have already written the first three sentences of the full article: inflation was invented to resolve problems existing in hot big bang cosmology , such as flatness , horizon , primordial monopole problem@xcite ( for some early attempts see refs .
@xcite ) . after more than twenty years development
, one has obtained a deep sight at this theory ..
Please generate the next two sentences of the article | however , it is still puzzled by an initial singularity which exists in usual inflationary models@xcite .
it has been suggested that , bouncing cosmology , which requires our universe initially experience a contracting phase before the hot big bang expansion , could provide a solution to the problem of the initial singularity . for years |
4,959 | Suppose that you have an abstract for a scientific paper: we explore the relation between the hopf algebra associated to the renormalization of qft and the hopf algebra associated to the ncg computations of tranverse index theory for foliations .
= msbm10 = msbm7 = msbm5 = = = .
And you have already written the first three sentences of the full article: in @xcite it was shown that the combinatorics of the subtraction procedure inherent to perturbative renormalization gives rise to a hopf algebra @xmath0 which provides a conceptual framework to understand the intricacies of the forest formula of zimmermann . in @xcite
, it was shown that the delicate computational problem which arises from the transverse hypoelliptic theory of foliations , as formulated in noncommutative geometry , can only be settled thanks to a hopf algebra @xmath1 associated to each integer codimension .
this hopf algebra reduces transverse geometry , to a universal geometry of affine nature ..
Please generate the next two sentences of the article | the aim of this paper is to establish a close relation between the above hopf algebras @xmath0 and @xmath1 .
we shall first recall the first results of @xcite which describe in the simplest case of codimension @xmath2 the presentation of the hopf algebra @xmath1 . |
4,960 | Suppose that you have an abstract for a scientific paper: we present ground - based optical and near infrared photometric observations and hubble space telescope cos spectroscopic observations of the old nova v842 cen ( nova cen 1986 ) .
analysis of the optical light curves reveals a peak at [email protected] with an amplitude of [email protected] mma , which is consistent with the rotation of a magnetic white dwarf primary in v842 cen that was detected earlier by woudt et al . , and led to its classification as an intermediate polar.however , our uv lightcurve created from the cos time - tag spectra does not show this periodicity .
our synthetic spectral analysis of an hst cos spectrum rules out a hot white dwarf photosphere as the source of the fuv flux .
the best - fitting model to the cos spectrum is a full optically thick accretion disk with no magnetic truncation , a low disk inclination angle , low accretion rate and a distance less than half the published distance that was determined on the basis of interstellar sodium d line strengths.truncated accretion disks with truncation radii of 3@xmath1 and 5@xmath1 yielded unsatisfactory agreement with the cos data .
the accretion rate is unexpectedly low for a classical nova only 24 years after the explosion when the accretion rate is expected to be high and the white dwarf should still be very hot , especially if irradiation of the donor star took place .
our low accretion rate is consistent with low accretion rates derived from x - ray and ground - based optical data . .
And you have already written the first three sentences of the full article: the old nova v842 cen ( nova cen 1986 ) was discovered on 1986 november 22 by mcnaught ( 1986 ) and reached a maximum magnitude of 5.6 from its pre - outburst brightness of about 18.5 .
whitelock ( 1987 ) and sekiguchi et al .
( 1989 ) estimated the @xmath2 decay time to be 48 d , thus classifying it as a moderately fast nova ..
Please generate the next two sentences of the article | since 1987 , this object has been followed with photometric and spectroscopic observations from the ground and in space .
a summary of observations through 2005 is given by schmidtobreick et al . |
4,961 | Suppose that you have an abstract for a scientific paper: the next generation of e+/e- colliders will require a very intense flux of gamma rays to allow high current polarized positrons to be produced .
this can be achieved by converting polarized high energy photons in polarized pairs into a target . in that context
, an optical system consisting of a laser and a four - mirror passive fabry - perot cavity has recently been installed at the accelerator test facility ( atf ) at kek to produce a high flux of polarized gamma rays by inverse compton scattering . in this contribution , we describe the experimental system and present preliminary results . an ultra - stable four - mirror non planar geometry has been implemented to ensure the polarization of the gamma rays produced . a fiber amplifier is used to inject about 10w in the high finesse cavity with a gain of 1000 . a digital feedback system is used to keep the cavity at the length required for the optimal power enhancement .
preliminary measurements show that a flux of about @xmath0 @xmath1/s with an average energy of about 24 mev was generated .
several upgrades currently in progress are also described . .
And you have already written the first three sentences of the full article: future electron - positrons colliders will require a flux of positrons much higher than what can be produced with current methods .
one of the scheme that has been proposed to achieve such flux is to use an intense flux of polarized high energy gamma rays @xcite which can be converted into polarized electron - positron pairs .
although promising this method requires the demonstration that such high intensity flux of gamma rays can be produced ..
Please generate the next two sentences of the article | polarized positrons can be produced by compton interaction between an electron beam and a laser .
however given the low cross - section of this process , it is desirable to recycle both the photons and the electrons by , for instance , using an electron ring and a fabry - perot cavity ( fpc ) . |
4,962 | Suppose that you have an abstract for a scientific paper: the single - photon transport in a single - mode waveguide , coupled to a cavity embedded with a two - leval atom is analyzed .
the single - photon transmission and reflection amplitudes , as well as the cavity and the atom excitation amplitudes , are solved exactly via a real - space approach .
it is shown that the dissipation of the cavity and of the atom respectively affects distinctively on the transport properties of the photons , and on the relative phase between the excitation amplitudes of the cavity mode and the atom . .
And you have already written the first three sentences of the full article: controllable single - photon transport is of central importance in quantum information processing .
there have been many recent experimental @xcite and theoretical @xcite works probing the photon transport properties of a wavelength - scale cavity that incorporates a two- or multi - level system .
these works encompass both the weak and the strong coupling regime ..
Please generate the next two sentences of the article | traditionally , such a system is typically studied with quantum trajectory method @xcite which , as a monte carlo approach , is inherently stochastic @xcite .
other approaches include employing a master equation @xcite or input - output formalism @xcite that assume a weak input coherent state , and usually involves uncontrolled approximations @xcite . however , the recent experiments allow us to determine the response to the input of a single injected photon . |
4,963 | Suppose that you have an abstract for a scientific paper: we report the discovery by b. g. harris and s. dvorak on jd 2455224.9385 ( 2010 jan 28.4385 ut ) of the predicted eruption of the recurrent nova u scorpii ( u sco ) .
we also report on 815 magnitudes ( and 16 useful limits ) on the pre - eruption light curve in the ubvri and sloan r and i bands from 2000.4 up to 9 hours before the peak of the january 2010 eruption .
we found no significant long - term variations , though we did find frequent fast variations ( flickering ) with amplitudes up to 0.4 mag .
we show that u sco did not have any rises or dips with amplitude greater than 0.2 mag on timescales from one day to one year before the eruption .
we find that the peak of this eruption occurred at jd [email protected] and the start of the rise was at jd [email protected] . from our analysis of the average b - band flux between eruptions , we find that the total mass accreted between eruptions is consistent with being a constant , in agreement with a strong prediction of nova trigger theory .
the date of the next eruption can be anticipated with an accuracy of @xmath05 months by following the average b - band magnitudes for the next @xmath110 years , although at this time we can only predict that the next eruption will be in the year 2020@xmath02 . .
And you have already written the first three sentences of the full article: recurrent novae ( rne ) are ordinary novae ( binary systems with mass accreting onto a white dwarf until thermonuclear runaway is triggered ) for which the recurrence time scale is between a decade and a century , such that more than one eruption has been observed ( payne - gaposchkin 1964 ; bode & evans 2008 ; evans et al . 2008 ) . to have the fast recurrence time scale
, the novae must have the white dwarf near the chandrasekhar mass and have a high accretion rate .
these properties , at face value , imply that the white dwarf will soon exceed the chandrasekhar mass and become a type ia supernova , and thus rne are one of the premier candidates for the progenitor class of these supernovae ..
Please generate the next two sentences of the article | rne typically have relatively fast eruptions , high ejection velocities , and small eruption amplitudes when compared to ordinary novae .
only ten rne are known with certainty in our milky way ( schaefer 2010 ) . |
4,964 | Suppose that you have an abstract for a scientific paper: in this work , we report the pressure dependence of the effective coulomb interaction parameters ( hubbard @xmath0 ) in paramagnetic nio within the constrained random phase approximation ( crpa ) .
we consider five different low energy models starting from the most expensive one that treats both ni-@xmath1 and o-@xmath2 states as correlated orbitals ( @xmath3-@xmath3 model ) to the smallest possible two - orbital model comprising the @xmath4 states only ( @xmath4-@xmath4 model ) .
we find that in all the considered models , the bare interactions are not very sensitive to the compression .
however the partially screened interaction parameters show an almost linear increment as a function of compression , resulting from the substantial weakening of screening effects upon compression .
this counterintuitive trend is explained from the specific characteristic changes of the basic electronic structure of this system .
we further calculate the nearest neighbor inter - site @xmath1-@xmath1 interaction terms which also show substantial enhancement due to compression .
our results for both the experimental and highly compressed structures reveal that the frequency dependence of the partially screened interactions can not be ignored in a realistic modeling of nio .
we also find that the computed interaction parameters for the antiferromagnetic nio are almost identical to their paramagnetic counter parts . .
And you have already written the first three sentences of the full article: the study of the role of electronic correlations in transition metal compounds is one of the most actively developing fields of modern condensed matter physics .
this class of materials exhibits rich and highly nontrivial physical phenomena such as unconventional transport properties including metal - insulator transitions , bad metal behavior or superconductivity , or ordering phenomena involving charge , orbital or spin degrees of freedom .
it is by now clear that most of these properties arise due to electronic correlations , in particular strong coulomb interactions among the partially occupied 3@xmath1 electrons of the metal ion . among these oxides ,.
Please generate the next two sentences of the article | nio is a prototype system for strong electronic correlations with a high spin antiferromagnetic structure at low temperatures @xcite . the exact origin , nature and size of the fundamental gap and , more broadly ,
the electronic structure of nio , has been studied intensely for many years , and is also a major topic of text books on condensed matter physics @xcite . |
4,965 | Suppose that you have an abstract for a scientific paper: we study convolutions that arise from noncommutative probability theory . in the case of free convolutions , we prove that the absolutely continuous part , with respect to the lebesgue measure , of the free convolution of two probability measures is always nonzero , and has a locally analytic density . under slightly less general hypotheses , we show that the singular continuous part of the free additive convolution of two probability measures is zero .
we also show that any probability measure belongs to a partially defined one - parameter free convolution semigroup . in this context
, we find a connection between free and boolean infinite divisibility . for monotonic convolutions , we prove that any infinitely divisible probability measure with respect to monotonic additive or multiplicative convolution belongs to a one - parameter semigroup with respect to the corresponding convolution .
our main tools are several subordination and inversion theorems for analytic functions defined in the upper half - plane .
we prove these theorems using the theory of denjoy - wolff fixed points .
lv first of all , my deepest thanks go to professor hari bercovici . without his teaching and
constant , careful , and patient guidance , nothing of my phd , including this thesis , could have been accomplished .
i am deeply grateful also to professor zhenghan wang .
i have learned a lot from him , and his help and support ( including financial , through an raship ) have been determinant for the completion of my work towards a phd .
i regret very much i was nt able to do more !
i thank professors ayelet lindenstrauss and scott w. brown for their active participation in my phd committee .
i have learned very much from many faculty members of the iu department of mathematics , either during courses , or in private discussions . among them
, i would like to mention professors steen andersson , eric bedford , hari bercovici , michael larsen , ayelet lindenstrauss , charles livingston , russel....
And you have already written the first three sentences of the full article: the idea of noncommutative analogues of classical mathematical notions like topology , geometry , measure theory , or probability , derives from operator algebras . in the classical ( commutative ) context
, one can usually associate to a given space an appropriate set of complex - valued functions defined on that space .
this set becomes a commutative algebra under the operations of pointwise addition and multiplication of functions ..
Please generate the next two sentences of the article | properties of the original space can be then expressed in terms of the algebra associated to that space . in the noncommutative context ,
one replaces the commutative algebra of functions with a noncommutative algebra ( usually , but not necessarily , of operators ) . |
4,966 | Suppose that you have an abstract for a scientific paper: optical whispering gallery mode ( wgm ) resonators have been very attracting platforms for versatile kerr frequency comb generations .
we report a systematic study on the material dispersion of various optical materials that are capable of supporting quality factors above @xmath0 . using an analytical approximation of
wgm resonant frequencies in disk resonators , we investigate the effect of the geometry and transverse mode order on the total group - velocity dispersion ( @xmath1 ) .
we demonstrate that the major radii and the radial mode indices play an important role in tailoring the @xmath1 of wgm resonators .
in particular , our study shows that in wgm disk - resonators , the polar families of modes have very similar @xmath1 , while the radial families of modes feature dispersion values that can differ by up to several orders of magnitude .
the effect of these giant dispersion shifts are experimentally evidenced in kerr comb generation with magnesium fluoride . from a more general perspective
, this critical feature enables to push the zero - dispersion wavelength of fluorite crystals towards the mid - infrared ( mid - ir ) range , thereby allowing for efficient kerr comb generation in that spectral range .
we show that barium fluoride is the most interesting crystal in this regard , due to its zero dispersion wavelength ( @xmath2 ) at @xmath3 and an optimal dispersion profile in the mid - ir regime .
we expect our results to facilitate the design of different platforms for kerr frequency comb generations in both telecommunication and mid - ir spectral ranges . 10 p. delhaye , a. schliesser , o. arcizet , t. wilken , r. holzwarth , and t. kippenberg , `` optical frequency comb generation from a monolithic microresonator , '' nature * 450 * , 12141217 ( 2007 ) .
y. k. chembo , d. v. strekalov , and n. yu , `` spectrum and dynamics of optical frequency combs generated with monolithic whispering gallery mode resonators , '' phys .
rev .
lett . * 104 * , 103902 ( 2010....
And you have already written the first three sentences of the full article: optical frequency combs have been very useful scientific and technological tools in a wide range of applications such as optical clocks , precision spectroscopy , low phase noise microwave generation and optical communications . the general approach for producing frequency combs
is based on mode - locking in lasers .
an alternative approach has been recently demonstrated in a silica monolithic toroidal microresonator @xcite , where cavity enhanced four - wave mixing ( fwm ) occurs . as a result , this type of comb using the third - order susceptibility in resonators is usually referred to as kerr optical frequency comb . the emergence of such combs provides a compact and energy efficient solution ..
Please generate the next two sentences of the article | therefore , extensive amount of works in both theories and experiments have been devoted to this field .
for example , the understanding of the comb formation is now very elaborate , and involves both coupled - mode and spatiotemporal models @xcite ; various applications have also been experimentally explored ranging from low phase noise microwave oscillations @xcite , ultra - short pulse generation @xcite , and optical communications @xcite . compared with kerr comb generation platforms based on chip - scale waveguide racetrack resonators @xcite , |
4,967 | Suppose that you have an abstract for a scientific paper: we present a simple , natural @xmath0-complete problem .
let @xmath1 be a directed graph , and let @xmath2 be a positive integer .
we define @xmath3 as follows . at each vertex @xmath4
, we place a @xmath2-dimensional complex vector @xmath5 . we take the product , over all edges @xmath6 , of the inner product @xmath7 .
finally , @xmath3 is the expectation of this product , where the @xmath5 are chosen uniformly and independently from all vectors of norm @xmath8 ( or , alternately , from the gaussian distribution ) .
we show that @xmath3 is proportional to @xmath1 s cycle partition polynomial , and therefore that it is @xmath0-complete for any @xmath9 . .
And you have already written the first three sentences of the full article: let @xmath10 be @xmath2-dimensional complex - valued vectors .
we denote their inner product as @xmath11 now suppose we have a directed graph @xmath12 .
let us associate a vector @xmath13 with each vertex @xmath4 , and consider the product over all edges @xmath6 of the inner products of the corresponding vectors : @xmath14 for instance , for the graph in figure [ fig : example ] this product is @xmath15 the expectation of this product , where each @xmath5 is chosen independently and uniformly from the set of vectors in @xmath16 of norm @xmath8 , is a type of moment , where each @xmath5 appears with order @xmath17 ..
Please generate the next two sentences of the article | it is a function of the graph @xmath1 and the dimension @xmath2 , which we denote as follows : @xmath18 .,width=172 ] a simple observation is that @xmath3 is zero unless @xmath1 is eulerian that is , unless @xmath19 for each vertex @xmath4 .
since @xmath5 appears in the product @xmath20 times unconjugated and @xmath21 times conjugated , multiplying @xmath5 by @xmath22 multiplies @xmath3 by @xmath23 . but |
4,968 | Suppose that you have an abstract for a scientific paper: the fourth harmonic of the azimuthal distribution of particles @xmath0 has been measured for au - au collisions at the relativistic heavy ion collider ( rhic ) .
the centrality dependence of @xmath0 does not agree with the prediction from hydrodynamics .
in particular , the ratio @xmath1 , where @xmath2 denotes the second harmonic of the azimuthal distribution of particles , is significantly larger than predicted by hydrodynamics .
we argue that this discrepancy is mostly due to elliptic flow ( @xmath2 ) fluctuations .
we evaluate these fluctuations on the basis of a monte carlo glauber calculation .
the effect of deviations from local thermal equilibrium is also studied , but appears to be only a small correction .
combining these two effects allows us to reproduce experimental data for peripheral and midcentral collisions .
however , we are unable to explain the large magnitude of @xmath1 observed for the most central collisions . introduction the azimuthal distribution of emitted particles is a good tool for understanding the bulk properties of the matter created in non central nucleus - nucleus collisions . in the center of mass rapidity region , it can be expanded in fourier series : @xmath3 where @xmath4 is the azimuthal angle with respect to the direction of the impact parameter , and odd harmonics are zero by symmetry .
the large magnitude of elliptic flow @xmath2 observed at rhic suggests that the matter created in au - au collisions behaves like an almost perfect fluid .
however , recent experiments @xcite observe that , at midrapidity and fixed @xmath5 , @xmath6 , while ideal hydrodynamics predicts that @xmath7 @xcite . in this talk ,
i investigate this discrepancy .
fluctuations in initial conditions axis defines the reaction plane while the @xmath8 axis is the minor axis of the ellipse drawn by the participating nucleons ( grey dots ) .
, width=230 ] figure [ fig : fig1 ] presents a schematic picture of a non central heavy - ion collision ( hic ) .
....
And you have already written the first three sentences of the full article: this work is funded by ` agence nationale de la recherche ' under grant anr-08-blan-0093 - 01 .
+ 00 b. i. abelev _ et al . _ [ the star collaboration ] , phys .
c * 75 * ( 2007 ) 054906 ..
Please generate the next two sentences of the article | s. huang [ phenix collaboration ] , j. phys .
g * 35 * ( 2008 ) 104105 . |
4,969 | Suppose that you have an abstract for a scientific paper: the sensitivity of two - proton emitting decays to the nuclear pairing correlation is discussed within a time - dependent three - body model .
we focus on the @xmath0be nucleus assuming @xmath1 configuration , and its decay process is described as a time - evolution of the three - body resonance state .
a noticeable model - dependence of two - proton decay width is found by utilizing schematic density - dependent contact ( sddc ) and the finite - range minnesota pairing models .
the model - dependence with the sddc pairing interaction can be understood by monitoring the time - dependent density distribution , which reflects ( i ) density dependence of pairing correlation inside the core , and ( ii ) @xmath2 scattering properties in vacuum .
our result suggests that two - proton decay width can be a suitable reference quantity to sophisticate the nuclear pairing model beyond the nucleon driplines . .
And you have already written the first three sentences of the full article: description of nuclear pairing correlation has been a major subject in recent nuclear physics . for instance , in self - consistent meanfield ( scmf ) description of atomic nuclei , there have been various approaches in order to take the nuclear pairing correlation into account @xcite . these approaches based on the scmf or the nuclear density functional theory ( dft )
have provided considerable agreements with the measured binding energy as well as its odd - even staggering for bound nuclei . even with these efforts , however , the complete character of the nuclear pairing correlation has not been revealed .
for example , whether the phenomenological pairing interaction should have the volume or surface type of density dependence is still an open question @xcite . at present.
Please generate the next two sentences of the article | , one can find several candidates for the sophisticated nuclear pairing model @xcite . in order to validate these models
, one may need reference observables to fit not only for bound nuclei . |
4,970 | Suppose that you have an abstract for a scientific paper: we present a quantum - theoretical treatment of biphoton generation in single - resonant type - ii parametric down - conversion . the nonlinear medium is continuously pumped and is placed inside a cavity which is resonant for the signal field , but nonresonant for the idler deflected by an intra - cavity polarizing beam splitter .
the intensity of the classical pump is assumed to be sufficiently low in order to yield a biphoton production rate that is small compared to the cavity loss rate .
explicit expressions are derived for the rate of biphoton generation and for the biphoton wave function .
the output spectra of the signal and idler field are determined , as well as the second - order signal - idler cross - correlation function which is shown to be asymmetric with respect to the time delay . due to frequency entanglement in the signal - idler photon pair
, the idler spectrum is found to reveal the longitudinal mode structure of the cavity , even though the idler field is not resonant . .
And you have already written the first three sentences of the full article: in parametric down - conversion , a pump photon of frequency @xmath0 incident on a medium with a second - order nonlinear susceptibility @xmath1 is split into two photons with lower frequency @xcite .
spontaneous parametric down conversion produces photon pairs that can be entangled in many degrees of freedom @xcite .
the resulting two - photon state , consisting of a signal photon at frequency @xmath2 and an idler photon at frequeny @xmath3 , is often called a biphoton . upon post - selection on the idler photons ,.
Please generate the next two sentences of the article | the process provides a source of heralded single photons which represent the principal resource in many quantum information processing protocols like quantum cryptography @xcite or linear optics quantum computation @xcite .
quantum networks have been proposed @xcite that rely on stationary atoms or ions as information processing nodes and on single photons to transmit information via optical fibers . |
4,971 | Suppose that you have an abstract for a scientific paper: high - resolution astronomical imaging at sub - ghz radio frequencies has been available for more than 15 years , with the vla at 74 and 330 mhz , and the gmrt at 150 , 240 , 330 and 610 mhz .
recent developments include wide - bandwidth upgrades for vla and gmrt , and commissioning of the aperture - array - based , multi - beam telescope lofar .
a common feature of these telescopes is the necessity to deconvolve the very many detectable sources within their wide fields - of - view and beyond .
this is complicated by gain variations in the radio signal path that depend on viewing direction .
one such example is phase errors due to the ionosphere . here
i discuss the inner workings of spam , a set of aips - based data reduction scripts in python that includes direction - dependent calibration and imaging .
since its first version in 2008 , spam has been applied to many gmrt data sets at various frequencies .
many valuable lessons were learned , and translated into various spam software modifications .
nowadays , semi - automated spam data reduction recipes can be applied to almost any gmrt data set , yielding good quality continuum images comparable with ( or often better than ) hand - reduced results . spam is currently being migrated from aips to casa with an extension to handle wide bandwidths .
this is aimed at providing users of the vla low - band system and the upcoming wide - bandwidth gmrt with the necessary data reduction tools .
[ firstpage ] atmospheric effects methods : data analysis instrumentation : interferometers .
And you have already written the first three sentences of the full article: low - frequency radio telescopes have relatively large fields - of - view , because the telescope primary beam size scales with wavelength . current high - resolution ( sub - arcminute ) radio interferometers that operate at sub - ghz frequencies , like the giant metrewave radio telescope ( gmrt ) , the low - frequency array ( lofar ) , or the very large array ( vla ) , have field diameters measured in ( sometimes tens of ) degrees . typical challenges of handling high - resolution , low - frequency continuum observations are ( i ) imaging and deconvolving many sources inside ( and outside ! ) the large primary beam area , ( ii ) direction - dependent ( dd ) visibility amplitude and phase variations across the field - of - view due to antenna beam patterns , pointing errors , ionosphere , etc . , and the abundance of radio frequency interference ( rfi ) . processing data coming from these telescopes can be daunting , since all the challenges mentioned above ( and more ) needs to be dealt with at the same time . in data reduction ,
the _ art _ is to determine at any given time which effect is dominant in limiting the image quality .
generally , a few _ big effects _ stand out and are generally easy to identify and fix ..
Please generate the next two sentences of the article | but subsequenty , many _ smaller effect _ will present themelves , which may be more difficult to recognize , and harder to identify and disentangle .
a effective way to mitigate the smaller effects is to perform iterations of ( dd ) calibration , imaging and flagging , in each step refining the quality of both the visibility data and the reconstructed sky model . |
4,972 | Suppose that you have an abstract for a scientific paper: we constrain the properties of the progenitor system of the highly reddened type ia supernova ( sn ) 2014j in messier 82 ( m82 ; @xmath0 mpc ) .
we determine the sn location using keck - ii _ k_-band adaptive optics images , and we find no evidence for flux from a progenitor system in pre - explosion near - ultraviolet through near - infrared _ hubble space telescope ( hst ) _ images .
our upper limits exclude systems having a bright red giant companion , including symbiotic novae with luminosities comparable to that of rs ophiuchi . while the flux constraints are also inconsistent with predictions for comparatively cool he - donor systems ( @xmath1 35,000 k ) , we can not preclude a system similar to v445 puppis .
the progenitor constraints are robust across a wide range of @xmath2 and @xmath3 values , but significantly greater values than those inferred from the sn light curve and spectrum would yield proportionally brighter luminosity limits . the comparatively faint flux expected from a binary progenitor system consisting of white dwarf stars
would not have been detected in the pre - explosion _ hst _ imaging .
infrared _ hst _
exposures yield more stringent constraints on the luminosities of very cool ( @xmath4 k ) companion stars than was possible in the case of sn ia 2011fe . .
And you have already written the first three sentences of the full article: the exceptional luminosity of type ia supernovae ( sn ia ) , and the tight empirical relationships among the decline rate , color , and peak luminosity of their light curves @xcite , make sn ia useful probes of the cosmic expansion history @xcite .
sn ia spectra and
inferred @xmath5ni masses ( e.g. , @xcite ) show reasonable agreement with models of the thermonuclear explosions of carbon - oxygen white dwarfs ( @xcite ; @xcite ; @xcite ; @xcite ) ..
Please generate the next two sentences of the article | additional evidence for a comparatively old progenitor population comes from the presence of sn ia in passive galaxies , and the observation that they show no preference for the brightest regions of their hosts , in contrast to core - collapse explosions that also exhibit h- and he - deficient spectra ( @xcite ; see also @xcite ) .
for sufficiently nearby sn ia ( @xmath6 mpc ) , pre - explosion _ hst _ imaging has the sensitivity to detect several classes of candidate progenitor systems . |
4,973 | Suppose that you have an abstract for a scientific paper: heat conduction in three - dimenisional nonlinear lattice models is studied using nonequilibrium molecular dynamics simulations .
we employ the fermi - pasta - ulam-@xmath0 model , in which nonlinearity exists in the interaction of the biquadratic form .
it is confirmed that the thermal conductivity , the ratio of the energy flux to the temperature gradient , diverges with increasing system size up to @xmath1 lattice sites .
this size corresponds to nanoscopic to mesoscopic scales of approximately 100 nm . from these results
, we conjecture that the energy transport in insulators with perfect crystalline order exhibits anomalous behavior .
the effects of the lattice structure , random impurities , and the natural length in interactions are also examined .
we find that fcc lattices display stronger divergence than simple cubic lattices . when impurity sites of infinitely large mass , which are thus fixed , are randomly distributed , such divergence vanishes . .
And you have already written the first three sentences of the full article: it is a long - standing problem to reproduce irreversible heat conduction phenomena , which are described by the fourier law , @xmath2 , where @xmath3 denotes the heat conductivity , on the basis of time - reversible microscopic dynamics .
recent studies have succeeded in reproducing the fourier law@xcite , and other linear nonequilibrium transport phenomena@xcite .
however , there remains an unsolved problem ..
Please generate the next two sentences of the article | the studies cited above mainly used particle systems , such as hard spheres and lennard - jones particles , for example , but historically , nonlinear lattice systems have also been studied@xcite .
_ showed that the fourier law is reproduced in a three - dimensional ( 3d ) polymer - like lattice with an fermi - pasta - ulam-@xmath0 ( fpu-@xmath0 ) type interaction@xcite , but shiba _ et al . |
4,974 | Suppose that you have an abstract for a scientific paper: diffusive shock acceleration ( dsa ) at relativistic shocks is expected to be an important acceleration mechanism in a variety of astrophysical objects including extragalactic jets in active galactic nuclei and gamma ray bursts .
these sources remain strong and interesting candidate sites for the generation of ultra - high energy cosmic rays . in this paper , key predictions of dsa at relativistic shocks that are salient to the issue of cosmic ray ion and electron production
are outlined .
results from a monte carlo simulation of such diffusive acceleration in test - particle , relativistic , oblique , mhd shocks are presented .
simulation output is described for both large angle and small angle scattering scenarios , and a variety of shock obliquities including superluminal regimes when the de hoffman - teller frame does not exist .
the distribution function power - law indices compare favorably with results from other techniques .
they are found to depend sensitively on the mean magnetic field orientation in the shock , and the nature of mhd turbulence that propagates along fields in shock environs .
an interesting regime of flat spectrum generation is addressed , providing evidence for its origin being due to shock drift acceleration .
the impact of these theoretical results on gamma - ray burst and blazar science is outlined .
specifically , _ fermi _ gamma - ray observations of these cosmic sources are already providing significant constraints on important environmental quantities for relativistic shocks , namely the frequency of scattering and the level of field turbulence . to appear in proc .
of the _ 8th international astrophysics conference _
+ `` shock waves in space and astrophysical environments , '' ( 2010 ) , + eds .
x. ao , r. burrows & g. p. zank ( aip conf . proc . 1183 , new york ) .
address=@xmath0 department of physics and astronomy , ms-108 , rice university , p. o. box 1892 , + houston , tx 77251 - 1892 , usa email : [email protected] + @xmath1....
And you have already written the first three sentences of the full article: there is bountiful evidence for efficient particle acceleration at collisionless shocks in the universe .
the heliosphere , with its planetary bow shocks and traveling interplanetary shocks , has provided interesting and useful test cases for shock acceleration theories . in the remote regions of the universe , supersonic jets from active galactic nuclei ( agns ) and gamma - ray bursts ( grbs )
have offered fascinating windows into an energetic part of the cosmos , where non - thermal radio waves , x - rays and gamma - rays abound . fully understanding these sources mandates knowledge of how the particles that generate their light emission are energized ..
Please generate the next two sentences of the article | the foremost paradigms invoke acceleration at relativistic shocks .
radio imaging reveals very structured and time - variable jets in agns , rapid x - ray and gamma - ray variability in both blazar agns and grbs suggest compact emission regions with relativistic bulk motions . |
4,975 | Suppose that you have an abstract for a scientific paper: in this work we address the problem of blindly reconstructing compressively sensed signals by exploiting the co - sparse analysis model . in the analysis model
it is assumed that a signal multiplied by an analysis operator results in a sparse vector .
we propose an algorithm that learns the operator adaptively during the reconstruction process .
the arising optimization problem is tackled via a geometric conjugate gradient approach .
different types of sampling noise are handled by simply exchanging the data fidelity term .
numerical experiments are performed for measurements corrupted with gaussian as well as impulsive noise to show the effectiveness of our method . .
And you have already written the first three sentences of the full article: in recent years , compressive sensing ( cs ) has influenced many fields in signal processing .
basically , the theory states that if an unknown signal @xmath0 can be sparsely represented , only a few @xmath1 linear and non - adaptive measurements @xmath2 of the signal suffice to accurately reconstruct it . denoting the measurement vectors by @xmath3
, the measurement process can be compactly written as @xmath4^{\top } \bf{s } + \bf{z } = \bf{\phi } \bf{s } + \bf{z},\ ] ] where @xmath5 is the measurement matrix , and @xmath6 constitutes possible sampling errors . due to the reduced dimensionality ,.
Please generate the next two sentences of the article | reconstructing @xmath7 from the measurements is ill - posed in general , and can not be done by simply inverting @xmath8 . however
, additional model assumptions on @xmath7 may help to find a solution . in this context , |
4,976 | Suppose that you have an abstract for a scientific paper: a strong - coupling expansion for the phase boundary of the ( incompressible ) mott insulator is presented for the bose hubbard model .
both the pure case and the disordered case are examined .
extrapolations of the series expansions provide results that are as accurate as the monte carlo simulations and agree with the exact solutions .
the shape difference between kosterlitz - thouless critical behavior in one - dimension and power - law singularities in higher dimensions arises naturally in this strong - coupling expansion .
bounded disorder distributions produce a `` first - order '' kink to the mott phase boundary in the thermodynamic limit because of the presence of lifshitz s rare regions . .
And you have already written the first three sentences of the full article: strongly interacting bosonic systems have attracted a lot of recent interest@xcite .
physical realizations include short correlation - length superconductors , granular superconductors , josephson arrays , the dynamics of flux lattices in type ii superconductors , and critical behavior of @xmath0 in porous media .
the bosonic systems are either tightly bound composites of fermions that act like effective bosonic particles with soft cores , or correspond to bosonic excitations that have repulsive interactions ..
Please generate the next two sentences of the article | for this reason , these systems are modeled by soft - core bosons which are described most simply by the bose hubbard model .
various aspects of this model were investigated analytically by mean - field theory @xcite , by renormalization group techniques @xcite and by projection methods @xcite . |
4,977 | Suppose that you have an abstract for a scientific paper: we analyze the violations of linear fluctuation - dissipation theorem ( fdt ) in the coarsening dynamics of the antiferromagnetic ising model on percolation clusters in two dimensions .
the equilibrium magnetic response is shown to be non linear for magnetic fields of the order of the inverse square root of the number of sites .
two extreme regimes can be identified in the thermoremanent magnetization : ( i ) linear response and out - of - equilibrium relaxation for small waiting times ( ii ) non linear response and equilibrium relaxation for large waiting times .
the function @xmath0 characterizing the deviations from linear fdt cross - overs from unity at short times to a finite positive value for longer times , with the same qualitative behavior whatever the waiting time .
we show that the coarsening dynamics on percolation clusters exhibits stronger long - term memory than usual euclidian coarsening .
16.8cm-.4cm-1 cm plus 0.2pt minus 0.1pt .
And you have already written the first three sentences of the full article: aging experiments in spin glasses @xcite first carried out by lundgren
_ et al . _ , have generated a large amount of experimental as well as theoretical work .
two types of experiments have been investigated : the zero - field - cooled experiment and the thermoremanent magnetization experiment , both leading to similar results . in the present article.
Please generate the next two sentences of the article | , we will restrict ourselves to the thermoremanent magnetization experiment , consisting in first quenching the system below its glass transition temperature at time @xmath1 , applying a small constant magnetic field up to the waiting time @xmath2 , switching off the magnetic field at time @xmath2 , and measuring the magnetization relaxation at time @xmath3 .
it is an experimental observation that the magnetization relaxation depends on the `` age '' of the system , namely , on the waiting time . |
4,978 | Suppose that you have an abstract for a scientific paper: motivated by the recent lhc hints of a higgs boson around 125 gev , we assume a sm - like higgs with the mass 123 - 127 gev and study its implication in low energy susy by comparing the mssm and nmssm .
we consider various experimental constraints at @xmath0 level ( including the muon @xmath1 and the dark matter relic density ) and perform a comprehensive scan over the parameter space of each model .
then in the parameter space which is allowed by current experimental constraints and also predicts a sm - like higgs in 123 - 127 gev , we examine the properties of the sensitive parameters ( like the top squark mass and the trilinear coupling @xmath2 ) and calculate the rates of the di - photon signal and the @xmath3 ( @xmath4 ) signals at the lhc .
our typical findings are : ( i ) in the mssm the top squark and @xmath2 must be large and thus incur some fine - tuning , which can be much ameliorated in the nmssm ; ( ii ) in the mssm a light stau is needed to enhance the di - photon rate of the sm - like higgs to exceed its sm prediction , while in the nmssm the di - photon rate can be readily enhanced in several ways ; ( iii ) in the mssm the signal rates of @xmath5 at the lhc are never enhanced compared with their sm predictions , while in the nmssm they may get enhanced significantly ; ( iv ) a large part of the parameter space so far survived will be soon covered by the expected xenon100(2012 ) sensitivity ( especially for the nmssm ) . .
And you have already written the first three sentences of the full article: as the only missing particle in the standard model ( sm ) , the higgs boson is being intensively hunted at the lhc . recently ,
both the atlas and cms experiments have revealed hints of a higgs particle around @xmath6 @xcite .
while such a higgs mass can be well accommodated in the sm and the reported signal rates in several channels are also in agreement with the sm expectations after taking into account the large experimental uncertainty @xcite ( albeit the central value of the observed di - photon rate is somewhat above the sm prediction ) , the low energy supersymmetry ( susy ) seems to be a better framework to account for such a higgs . in low energy susy.
Please generate the next two sentences of the article | the sm - like higgs mass is theoretically restricted in a narrow range and its di - photon rate at the lhc may exceed the sm prediction @xcite , both of which are welcomed by the lhc results . however , as the most popular low energy susy model , the minimal supersymmetric standard model ( mssm ) @xcite may have some tension to accommodate such a 125 gev higgs . as is well known , in the mssm the sm - like higgs mass is upper bounded by @xmath7 at tree - level and to get a higgs around @xmath6 we need sizable top / stop loop contributions , which depend quartically on the top quark mass and logarithmically on the stop masses @xcite .
this will , on the one hand , impose rather tight constraint on the mssm , and on the other hand , incur some fine - tuning @xcite . |
4,979 | Suppose that you have an abstract for a scientific paper: we study the dynamics of confinement - deconfinement ( c - d ) phase transition in the context of relativistic heavy - ion collisions within the framework of effective models for the polyakov loop order parameter .
we study the formation of @xmath0 walls and associated strings in the initial transition from the confining ( hadronic ) phase to the deconfining ( qgp ) phase via the so called kibble mechanism .
essential physics of the kibble mechanism is contained in a sort of domain structure arising after any phase transition which represents random variation of the order parameter at distances beyond the typical correlation length .
we implement this domain structure by using the polyakov loop effective model with a first order phase transition and confine ourselves with temperature / time ranges so that the first order c - d transition proceeds via bubble nucleation , leading to a well defined domain structure . the formation of @xmath0 walls and associated strings results from the coalescence of qgp bubbles expanding in the confining background .
we investigate the evolution of the @xmath0 wall and string network .
we also calculate the energy density fluctuations associated with @xmath0 wall network and strings which decay away after the temperature drops below the quark - hadron transition temperature during the expansion of qgp . we discuss evolution of these quantities with changing temperature via bjorken s hydrodynamical model and discuss possible experimental signatures resulting from the presence of @xmath0 wall network and associate strings .
key words : quark - hadron transition , relativistic heavy - ion collisions , z(3 ) domain walls .
And you have already written the first three sentences of the full article: search for the quark - gluon plasma ( qgp ) at relativistic heavy - ion collision experiments ( rhice ) has reached a very exciting stage with the ongoing experiments at rhic and with the upcoming heavy - ion experiments at the large hadron collider .
no one doubts that the qgp phase has already been created at rhic but conclusive evidence for the same is still lacking .
many signatures have been proposed for the detection of the qgp phase @xcite and these have been thoroughly investigated both theoretically and experimentally . along with continued investigation of these important signatures of qgp , there is a need for investigating novel signals exploring qualitatively non - trivial features of the qgp phase and/or the quark - hadron phase transition . with this view we focus on the non - trivial vacuum structure of the qgp phase which arises when one uses the expectation value of the polyakov loop @xmath1 as the order parameter for the confinement - deconfinement phase transition @xcite ..
Please generate the next two sentences of the article | this order parameter transforms non - trivially under the center @xmath0 of the color su(3 ) group and is non - zero above the critical temperature @xmath2 .
this breaks the global @xmath0 symmetry spontaneously above @xmath2 , while the symmetry is restored below @xmath2 in the confining phase where this order parameter vanishes . in the qgp phase , due to spontaneous breaking of the discrete @xmath0 symmetry , |
4,980 | Suppose that you have an abstract for a scientific paper: attempts to interpret the observed oscillation spectrum of the spb star hd50230 are reported .
we argue that a nearly equidistant period spacing found in the oscillation spectrum of the star is most likely accidental .
the observed period distribution requires excitation of modes with the degree @xmath0 .
much more may be learned from the rich oscillation spectrum of the star but most of the work is still ahead of us . .
And you have already written the first three sentences of the full article: hd50230 is a star of the b3v spectral type and a visual brightness of 8.95 mag .
the star had been regarded as constant until its first satellite observations were conducted .
* degroote et al ..
Please generate the next two sentences of the article | ( 2010 , 2012 ) ) detected more than 500 significant peaks in the _ corot _ data . with their spectroscopic observations they discovered that hd50230 is a double - lined spectroscopic binary with projected equatorial velocity of 7 and 117 kms@xmath1 for the primary and secondary , respectively .
for the primary component , they determined effective temperature of @xmath2 k and surface gravity of @xmath3 dex . for the secondary component they found only an upper limit @xmath4 k and assumed @xmath5 dex . |
4,981 | Suppose that you have an abstract for a scientific paper: the torsional oscillation is a well established observational fact and there are theoretical attempts for its description but no final solution has yet been accepted .
one of the possible candidates for its cause is the presence of sunspots modifying the streaming conditions .
the present work focuses on the temporally varying latitudinal distribution of several sunspot features , such as the spot sizes and spot numbers .
these features are different faces of the butterfly diagram .
in fact some weak spatial correlations can be recognized . .
And you have already written the first three sentences of the full article: the torsional oscillation was discovered by howard and labonte 1980 as a travelling wave pattern superposed on the differential rotation .
the waves propagate from the poles toward the equator and they consist of prograde and retrograde zones with respect to the mean differential rotation profile , the amplitude of the deviations is about 7 m / sec .
two waves ( two prograde and retrograde belts ) coexist in both hemispheres . the feature was absolutely unexpected at the time of discovery and several attempts.
Please generate the next two sentences of the article | have been made to check and interpret it .
the empirical studies basically confirmed the existence of the phenomenon by using either surface measurements ( ulrich , 2001 ) or subsurface detection by gong and mdi data ( howe et al . |
4,982 | Suppose that you have an abstract for a scientific paper: magneto - structural properties of films of diluted ferromagnetic alloys ni@xmath0cu@xmath1 in the concentration range @xmath2 are studied experimentally .
films deposited by magnetron sputtering show partial phase separation , as evidenced by structural analysis and ferromagnetic resonance measurements .
the phase diagram of the ni@xmath0cu@xmath1 bulk system is obtained using numerical theoretical analysis of the electronic structure , taking into account the inter - atomic exchange interactions .
the results confirm the experimentally found partial phase separation , explain it as magnetic in origin , and indicate an additional metastable region connected with the ferromagnetic transition in the system .
dilute ferromagnets , thin films , phase diagram , ferromagnetic resonance , curie temperature .
And you have already written the first three sentences of the full article: magnetic multilayered films have been receiving much attention from the research community in the field of spintronics .
recently , a device has been proposed @xcite and demonstrated @xcite , in which the magnetic and spin - transport properties are controlled thermo - electrically . at the core of
the new design is a tri - layer ( _ f / f / f _ ) of two strong ferromagnets ( _ f _ ) exchange - coupled by a weakly ferromagnetic spacer ( _ f _ ) having the curie point at / or near room temperature ( @xmath3 k ) ..
Please generate the next two sentences of the article | the spacer _ f _ , controlling the exchange coupling between the outer layers , can be made of a diluted ferromagnetic alloy , such as ni@xmath0cu@xmath1 @xcite .
it is desirable that the spacer is compositionally uniform and does not contain multiple phases , which can form as a result of atomic segregation during film deposition or subsequent heat treatment . |
4,983 | Suppose that you have an abstract for a scientific paper: we investigate the kondo lattice model on 2d clusters using the finite temperature lanczos method .
the temperature dependence of thermodynamic and correlations functions are systematically studied for various kondo couplings @xmath0 .
the ground state value of the total local moment is presented as well .
finally , the phase diagrams of the finite clusters are constructed for periodic and open boundary conditions .
for the two boundary conditions , two different regimes are found for small @xmath1 , depending on the distribution of non - interacting conduction electron states .
if there are states within @xmath2 around the fermi level , two energy scales , linear and quadratic in @xmath0 , exist .
the former is associated with the onsite screening and the latter with the rkky interaction .
if there are no states within @xmath0 around the fermi level , the only energy scale is that of the rkky interaction .
our results imply that the form of the electron density of states ( dos ) plays an important role in the competition between the kondo screening and the rkky interaction .
the former is stronger if the dos is larger around the fermi level , while the latter is less sensitive to the form of the dos . .
And you have already written the first three sentences of the full article: the kondo lattice model ( klm ) is used to describe compounds containing localized magnetic moments , such as heavy fermion systems and kondo insulators .
@xcite the klm hamiltonian is given by : @xmath3here , @xmath4 and @xmath5 are itinerant and local ( @xmath6- ) spins on site @xmath7 , respectively .
the klm takes into account hopping of conduction electrons , @xmath8 , and their kondo interaction , @xmath0 , with local @xmath6-spins ..
Please generate the next two sentences of the article | the kondo term causes a screening of local spins , but also induces indirect rkky interactions between the local spins on the lattice .
these two interactions compete , leading to either magnetically ordered or non - magnetic ground states , separated by the quantum critical point ( qcp ) . |
4,984 | Suppose that you have an abstract for a scientific paper: single - particle resonant states in spherical nuclei are studied by an analytic continuation in the coupling constant ( accc ) method within the framework of the self - consistent relativistic mean field ( rmf ) theory .
taking the neutron resonant state @xmath0 in @xmath1ca as an example , we examine the analyticity of the eigenvalue and eigenfunction for the dirac equation with respect to the coupling constant by means of a @xmath2 approximant of the second kind .
the rmf - accc approach is then applied to @xmath3zr and , for the first time , this approach is employed to investigate both the energies , widths and wave functions for @xmath4 resonant states close to the continuum threshold .
predictions are also compared with corresponding results obtained from the scattering phase shift method . .
And you have already written the first three sentences of the full article: the physics of exotic nuclei with unusual @xmath5 ratios ( isospin ) has attracted world - wide attention . these nuclei are usually loosely bound and often exhibit resonances with a pronounced single - particle character since the fermi surface approaches the continuum . in some nuclei , the valence nucleons can be easily scattered into single - particle resonant states ( or gamow states ) in the continuum which is essential for the existence of exotic phenomena .
for example , the halo in @xmath6li @xcite can be successfully reproduced @xcite and giant halo nuclei @xcite are predicted by the relativistic continuum hartree - bogoliubov ( rchb ) theory @xcite in which the contribution from the continuum has been proven to be crucial to understand these halo phenomena .
there are also other attempts to include the contribution from the continuum in the non - relativistic @xcite and relativistic approaches @xcite . by taking into account a few resonant states close to the continuum threshold with the bcs method @xcite , the relativistic mean field ( rmf ) theory seems to be able to reproduce the rchb results and describe the main effects of the continuum ..
Please generate the next two sentences of the article | it has also been shown that the contribution of the continuum to the giant resonances mainly comes from gamow states @xcite .
therefore , a proper treatment of resonant states is important for a deeper understanding of the properties in exotic nuclei . |
4,985 | Suppose that you have an abstract for a scientific paper: we investigate the electronic dispersion of high-@xmath0 superconductor on the basis of the two - dimensional three - band hubbard model with the electron - phonon interaction together with the strong electron - electron interaction . in our model
, it is shown across the hole - doped region of high-@xmath0 superconductor that the electron - phonon interaction makes a dispersion kink , observed along the nodal direction , and that the small isotope effect appears on the electronic dispersion . .
And you have already written the first three sentences of the full article: for the past two decades , extensive studies of high-@xmath0 cuprates have spotlighted many curious phenomena .
it has been argued that most phenomena are attributable to the strong correlations among electrons , which play significant roles in these materials .
however , since the discovery of sudden changes in the electron dispersion or `` kinks '' shown by the angle - resolved photoemission spectroscopy ( arpes ) , @xcite effects of electron - boson interactions on electronic self - energies have been recognized ..
Please generate the next two sentences of the article | while the kinks are now indisputable in cuprates , @xcite their origin as arising from electronic coupling to phonons @xcite or magnetic excitations @xcite remains unclear .
recent scanning tunneling microscope study showed that the statistical distribution of energy of bosonic modes ( @xmath1 ) has meaningful difference between @xmath2 and @xmath3 materials . |
4,986 | Suppose that you have an abstract for a scientific paper: it is still on open question to what degree the cluster environment influences the sizes of protoplanetary discs surrounding young stars .
particularly so for the short - lived clusters typical for the solar neighbourhood in which the stellar density and therefore the influence of the cluster environment changes considerably over the first 10myr . in previous studies often
the effect of the gas on the cluster dynamics has been neglected , this is remedied here . using the code nbody6++ we study the stellar dynamics in different developmental phases - embedded , expulsion , expansion - including the gas and quantify the effect of fly - bys on the disc size .
we concentrate on massive clusters @xmath0 , which are representative for clusters like the onc or ngc6611 .
we find that not only the stellar density but also the duration of the embedded phase matters .
the densest clusters react fastest to the gas expulsion and drop quickly in density , here @xmath1 of relevant encounters happen before gas expulsion .
by contrast , discs in sparser clusters are initially less affected but as they expand slower @xmath2 of discs are truncated after gas expulsion . for onc - like clusters we find that usually discs larger than 500au are affected by the environment , which corresponds to the observation that 200au - sized discs are common . for ngc6611-like clusters disc sizes are cut - down on average to roughly 100au .
a testable hypothesis would be that the discs in the centre of ngc6611 should be on average @xmath320au and therefore considerably smaller than in the onc . .
And you have already written the first three sentences of the full article: most stars are born in stellar clusters , which in turn form from dense cores in giant molecular clouds ( gmcs ) . at least for massive clusters ( @xmath4 ) , it is known that they are highly dynamical structures and follow well - defined evolutionary tracks , depending on their initial mass and size @xcite . at very young ages
they are still embedded in their natal gas ; the duration of this embedded phase is thought to last between @xmath5 for clusters in the solar neighbourhood @xcite .
comparing the gas and stellar content in nearby star forming regions , observations find that the fraction of gas in a gmc which is turned into stars ( referred to as star formation efficiency - sfe ) lies in the range of @xcite ..
Please generate the next two sentences of the article | similarly , simulations that model the expansion history of massive clusters in the solar neighbourhood find that the sfe of these clusters must have been of the order @xmath6 @xcite . in comparison , the sfe for an entire molecular clouds is much lower , only of the order of just a few per cent at most ( see e.g. * ? ? ?
* ; * ? ? ? |
4,987 | Suppose that you have an abstract for a scientific paper: we consider the classical motion of a probe d - brane moving in the background geometry of a ring of ns5 branes , assuming that the latter are non - dynamical .
we analyse the solutions to the dirac - born - infield ( dbi ) action governing the approximate dynamics of the system . in the near horizon ( throat )
approximation we find several exact solutions for the probe brane motion .
these are compared to numerical solutions obtained in more general cases .
one solution of particular interest is when the probe undergoes oscillatory motion through the centre of the ring ( and perpendicular to it ) . by taking the ring radius sufficiently large ,
this solution should remain stable to any stringy corrections coming from open - strings stretching between the probe and the ns5-branes along the ring .
qmul - ph-04 - 11 + * d - brane dynamics and ns5 rings * * steven thomas and john ward * _ department of physics , + queen mary , university of london , + mile end road , + london e1 4ns , u.k . + _ .
And you have already written the first three sentences of the full article: there has been a flourish of recent work concerned with time dependence in string theory ( see , for example @xcite,@xcite , @xcite , @xcite and references therein ) , where we have a @xmath0-brane probing the backgrounds of various supergravity solutions . whilst some of this work has focused on @xmath1-brane backgrounds ( @xcite , @xcite ) ,
much of it has dealt with @xmath25-branes .
this has been particularly fruitful since it is known that the instability of the probe brane can be explained using tachyon rolling @xcite , and has also emphasised the relationship betweeen bps and non - bps branes @xcite , @xcite . in a recent paper @xcite.
Please generate the next two sentences of the article | , the dynamics of a @xmath1-brane in the background of @xmath3 coincident @xmath4-branes was considered using the dbi action .
the @xmath1-brane is effectively a probe , since it can explore the background without disturbing it . |
4,988 | Suppose that you have an abstract for a scientific paper: we consider the problem of non degenerate in energy metastable states forming a series in the framework of reversible finite state space markov chains .
we assume that starting from the state at higher energy the system necessarily visits the second one before reaching the stable state . in this framework
we give a sharp estimate of the exit time from the metastable state at higher energy and , on the proper exponential time scale , we prove an addition rule . as an application of the theory , we study the blume capel model in the zero chemical potential case . .
And you have already written the first three sentences of the full article: metastable states in finite volume statistical mechanics lattice systems , in which stochastic transition between states are controlled by an energy function , is a well understood phenomenon .
different mathematical theories have been developed in the last decades .
the pioneering _ pathwise approach _.
Please generate the next two sentences of the article | @xcite , further developed for non
reversible dynamics in @xcite , and the more recent _ potential theoretic approach _ |
4,989 | Suppose that you have an abstract for a scientific paper: we explicitly construct genus-@xmath0 lefschetz fibrations whose total spaces are minimal symplectic @xmath1-manifolds homeomorphic to complex rational surfaces @xmath2 for @xmath3 , and to @xmath4 for @xmath5 .
complementarily , we prove that there are no minimal genus-@xmath0 lefschetz fibrations whose total spaces are homeomorphic to any other simply - connected @xmath1-manifold with @xmath6 , with one possible exception when @xmath7
. meanwhile , we produce positive dehn twist factorizations for several new genus-@xmath0 lefschetz fibrations with small number of critical points , including the smallest possible example , which follow from a reverse engineering procedure we introduce for this setting .
we also derive exotic minimal symplectic @xmath1-manifolds in the homeomorphism classes of @xmath8 and @xmath9 from small lefschetz fibrations over surfaces of higher genera . .
And you have already written the first three sentences of the full article: existence of minimal symplectic structures on @xmath1-manifolds is a fundamental question in smooth @xmath1-manifold topology .
there has been much interest especially in producing minimal symplectic @xmath1-manifolds in the homeomorphism classes of standard simply - connected @xmath1-manifolds with small second homology , such as blow - ups of @xmath10 or @xmath11 . over the last two decades
, many ingenious construction techniques , such as rational blowdowns , generalized fiber sum , knot surgery and luttinger surgery , have been introduced to effectively address this problem by fintushel and stern , gompf , jongil park , and several others ..
Please generate the next two sentences of the article | ( e.g. @xcite . ) resting on spectacular results of taubes on seiberg - witten invariants of symplectic @xmath1-manifolds , these constructions have demonstrated that minimal symplectic @xmath1-manifolds not only constitute _ small exotic @xmath1-manifolds _ ( which are homeomorphic but not diffeomorphic to standard ones ) , but also resource them in almost all the known instances . on the other hand ,
since the pioneering works of donaldson and gompf in late @xmath12s , it is known that symplectic @xmath1-manifolds , up to blow - ups , correspond to lefschetz fibrations , which can be studied combinatorially as _ positive factorizations _ , |
4,990 | Suppose that you have an abstract for a scientific paper: we present the discovery of seven new t dwarfs identified in the two micron all sky survey .
low - resolution ( r@xmath0150 ) 0.82.5 @xmath1 spectroscopy obtained with the irtf spex instrument reveal the characteristic h@xmath2o and ch@xmath3 bands in the spectra of these brown dwarfs .
comparison to spectral standards observed with the same instrument enable us to derive classifications of t3 to t7 for the objects in this sample .
moderate - resolution ( r@xmath01200 ) near - infrared spectroscopy for a subset of these discoveries reveal line strengths consistent with previously observed trends with spectral type .
follow - up imaging observations provide proper motion measurements for these sources , ranging from @xmath4 0@xmath51 to 1@xmath555 yr@xmath6 .
one object , 2mass 0034 + 0523 , has a spectrophotometric distance placing it within 10 pc of the sun .
this source also exhibits a depressed k - band peak reminiscent of the peculiar t dwarf 2mass 0937 + 2931 , and may be a metal - poor or old , high - mass brown dwarf .
we also present low resolution spex data for a set of m and l - type dwarf , subdwarf , and giant comparison stars used to classify 59 additional candidates identified as background stars .
these are primarily m5-m8.5 dwarfs , many exhibiting paschen @xmath7 , but include three candidate ultracool m subdwarfs and one possible early - type l subdwarf . .
And you have already written the first three sentences of the full article: t dwarfs are a spectral class of brown dwarfs distinguished by the presence of ch@xmath3 , h@xmath2o , and h@xmath2 collision - induced absorption ( cia ) in the near - infrared @xcite , and heavily pressure - broadened and absorption at optical wavelengths @xcite .
these objects have effective temperatures ( t@xmath8s ) ranging from @xmath01300 k at the transition between l and t dwarfs @xcite to @xmath0750 k for the latest - type t dwarf 2mass 0415@xmath90935 @xcite .
t dwarfs therefore comprise the coldest and intrinsically faintest brown dwarfs currently known , and as such are key objects for testing brown dwarf and extrasolar giant planet atmosphere models @xcite , probing the extreme low - mass end of the initial mass function @xcite , and expanding the census of the sun s nearest neighbors . for the past two years.
Please generate the next two sentences of the article | , we have been conducting a wide - field ( 74% of the sky ) search for t dwarfs in the two micron all sky survey ( * ? ? ?
* ; * ? ? ? |
4,991 | Suppose that you have an abstract for a scientific paper: when investigating the dynamical properties of complex multiple - component physical and physiological systems , it is often the case that the measurable system s output does not directly represent the quantity we want to probe in order to understand the underlying mechanisms . instead , the output signal is often a linear or nonlinear function of the quantity of interest . here ,
we investigate how various linear and nonlinear transformations affect the correlation and scaling properties of a signal , using the detrended fluctuation analysis ( dfa ) which has been shown to accurately quantify power - law correlations in nonstationary signals .
specifically , we study the effect of three types of transforms : ( i ) linear ( @xmath0 ) ; ( ii ) nonlinear polynomial ( @xmath1 ) ; and ( iii ) nonlinear logarithmic [ @xmath2 filters .
we compare the correlation and scaling properties of signals before and after the transform .
we find that linear filters do not change the correlation properties , while the effect of nonlinear polynomial and logarithmic filters strongly depends on ( a ) the strength of correlations in the original signal , ( b ) the power @xmath3 of the polynomial filter , and ( c ) the offset @xmath4 in the logarithmic filter .
we further apply the dfa method to investigate the `` apparent '' scaling of three analytic functions : ( i ) exponential [ @xmath5 , ( ii ) logarithmic [ @xmath6 , and ( iii ) power law [ @xmath7 , which are often encountered as trends in physical and biological processes .
while these three functions have different characteristics , we find that there is a broad range of values for parameter @xmath8 common for all three functions , where the slope of the dfa curves is identical .
we further note that the dfa results obtained for a class of other analytic functions can be reduced to these three typical cases .
we systematically test the performance of the dfa method when estimating long - range power - law correlations in the output signals for different....
And you have already written the first three sentences of the full article: many physical and biological systems under multi - component control mechanisms exhibit scale - invariant features characterized by long - range power - law correlations in their output .
these scaling features are often difficult to quantify due to the presence of erratic fluctuations , heterogeneity , and nonstationarity embedded in the output signals .
this problem becomes even more difficult in certain cases : ( i ) when we can not probe directly the quantity of interest in experimental settings , i.e. , the measurable output signal is a linear or nonlinear function of the quantity of interest ; ( ii ) when measuring devices impose a linear or nonlinear filter on the system s output ; ( iii ) when we are interested not in the output signal but in a specific component of it , which is obtained through a nonlinear transform ( e.g. , the magnitude or the sign of the fluctuations in the signal ) ; ( iv ) when comparing the dynamics of different systems by applying nonlinear transforms to their output signals ; or ( v ) when pre - processing the output signal by means of linear or nonlinear filters before the actual analysis ..
Please generate the next two sentences of the article | thus , to understand the intrinsic dynamics of a system , in such cases it is important to correctly analyze and interpret the dynamical patterns in the system s output .
conventional two - point correlation , power spectrum , and hurst analysis methods are not suited for nonstationary signals , the statistical properties of which change with time @xcite . to address this problem , detrended fluctuation analysis ( dfa ) method was developed to accurately quantify long - range correlations embedded in a nonstationary time series @xcite . |
4,992 | Suppose that you have an abstract for a scientific paper: time - domain balanced homodyne detection is performed on two well - separated temporal modes sharing a single photon .
the reconstructed density matrix of the two - mode system is used to prove and quantify its entangled nature , while the wigner function is employed for an innovative tomographic test of bell s inequality based on the theoretical proposal by banaszek and wodkiewicz ( phys .
rev .
lett .
82 , 2009 ( 1999 ) ) .
provided some auxiliary assumptions are made , a clear violation of banaszek - bell s inequality is found . .
And you have already written the first three sentences of the full article: the concept of entanglement , as first introduced by schrdinger @xcite and discussed by einstein , podolsky , and rosen @xcite in 1935 , has historically been associated with systems of two or more quanta .
its counterintuitive consequences found a mathematical formulation in the work of bell @xcite of 1965 : pairs of quanta entangled in discrete variables ( i.e. , bohm - like entangled systems @xcite ) may give rise to purely quantum nonlocal correlations .
unfortunately , no loophole - free test of bell s inequality has been realized so far @xcite . besides their relevance in fundamental physics ,.
Please generate the next two sentences of the article | these phenomena have attracted much attention due to their usefulness in quantum information technology .
extravagant but promising protocols such as quantum teleportation , quantum cryptography , and quantum computation have been proposed and experimentally verified ( see , e.g. , @xcite and references therein ) . in the early nineties , |
4,993 | Suppose that you have an abstract for a scientific paper: extragalactic radio sources are a unique cosmological probe in that they trace large - scale structure on scales inaccessible to other wavelengths .
however as radio survey data is inherently 2@xmath0 , the redshift distribution , @xmath1 , is necessary to derive spatial information . to obtain this distribution either we measure thousands of radio source redshifts to directly determine @xmath1 _ or _ we derive @xmath1 from statistical analyses of radio source count and identification data . in this paper
we show how the dual - population unification scheme can be incorporated into a rigorous statistical analysis of radio source count data , with the result that our simple parametric evolution and beaming model revises previous estimations of @xmath1 , specifically at low flux densites .
this revision is particularly pertinent given that the new generation of radio surveys extend to milli - jansky flux density levels : sampling source densities high enough to reveal spatial structure . in turn
, these new radio surveys will provide potent tests which will refine our model . .
And you have already written the first three sentences of the full article: the development of large - scale structure had to take place at epochs coresponding to redshifts greater than 0.2 ; moreover structure is now known to extend beyond scales of @xmath2 mpc .
both factors place the extent and evolution of large - scale structure beyond the reach of current optical and ir surveys and we must look outside these bands to address such key cosmological issues .
it has now been established that _.
Please generate the next two sentences of the article | extragalactic radio sources _ can trace structure both to very early epochs and on very large scales @xcite,@xcite,@xcite .
this is a direct result of their uniform selection function : away from the galactic plane extragalactic radio sources are visible to very high redshifts ( @xmath3 ) with detection unaffected by obscuration . |
4,994 | Suppose that you have an abstract for a scientific paper: we have assembled a homogeneous database of 417 ultraviolet ( uv ) extinction curves for reddened sightlines having international ultraviolet explorer ( iue ) spectra .
we have combined these with optical and 2mass photometry allowing estimates of the ratio of total - to - selective extinction , r@xmath0 , for the entire sample .
fitzpatrick - massa ( fm ) parameters have also been found for the entire sample .
this is the largest study of parameterized uv extinction curves yet published and it covers a wide range of environments , from dense molecular clouds to the diffuse interstellar medium ( ism ) , with extinctions a@xmath1 ranging from 0.50 to 4.80 .
it is the first to extend far beyond the solar neighborhood and into the galaxy at large , with 30 sightlines having distances @xmath2 5 kpc .
previously , the longest sightlines with fm parameters and r@xmath1 extended @xmath3 1 kpc .
we find that ( 1 . )
the ccm extinction law applies for 93% of the sightlines , implying that dust processing in the galaxy is efficient and systematic ; ( 2 . )
the central wavelength of the 2175 bump is constant ; ( 3 . ) the 2175 bump width is dependent on environment .
only four sightlines show systematic deviations from ccm , hd 29647 , 62542 , 204827 , and 210121 .
these sightlines all sample dense , molecule - rich clouds . the new extinction curves and values of r@xmath1
allow us to revise the ccm law . .
And you have already written the first three sentences of the full article: astronomical ultraviolet studies were not possible before the advent of rocket - borne instruments and satellites due to atmospheric absorption and rayleigh scattering . the first satellite capable of uv observations , oao-2 , was launched in 1968 , and was followed by a host of other satellites ( cox 2000 ) , including thor delta-1 ( td-1 ) , astronomy netherlands satellite ( ans ) , and iue , among others .
the data obtained by these instruments are responsible for the vast majority of contributions to studies of interstellar dust , as dust grains preferentially extinguish short - wavelength light . by comparing heavily extinguished stars against their intrinsic fluxes ( the pair method ) ,
we can better understand grain properties and composition ..
Please generate the next two sentences of the article | this is important for two reasons .
first , solid knowledge of grain properties will allow us to build more realistic grain models and correct for the effects of dust in stellar and galactic photometry and spectra more accurately . |
4,995 | Suppose that you have an abstract for a scientific paper: we performed magnetohydrodynamic simulation of coronal mass ejections ( cmes ) and associated giant arcade formations , and the results suggested new interpretations of observations of cmes .
we performed two cases of the simulation : with and without heat conduction . comparing between the results of the two cases
, we found that reconnection rate in the conductive case is a little higher than that in the adiabatic case and the temperature of the loop top is consistent with the theoretical value predicted by the yokoyama - shibata scaling law .
the dynamical properties such as velocity and magnetic fields are similar in the two cases , whereas thermal properties such as temperature and density are very different . in both cases ,
slow shocks associated with magnetic reconnection propagate from the reconnection region along the magnetic field lines around the flux rope , and the shock fronts form spiral patterns . just outside the slow shocks ,
the plasma density decreased a great deal .
the soft x - ray images synthesized from the numerical results are compared with the soft x - ray images of a giant arcade observed with the soft x - ray telescope aboard _ yohkoh _ , it is confirmed that the effect of heat conduction is significant for the detailed comparison between simulation and observation .
the comparison between synthesized and observed soft x - ray images provides new interpretations of various features associated with cmes and giant arcades .
1 ) it is likely that y - shaped ejecting structure , observed in giant arcade 1992 january 24 , corresponds to slow and fast shocks associated with magnetic reconnection .
2 ) soft x - ray twin dimming corresponds to the rarefaction induced by reconnection .
3 ) the inner boundary of the dimming region corresponds to the slow shocks .
4 ) `` three - part structure '' of a cme can be explained by our numerical results .
5 ) the numerical results also suggest a backbone feature of a flare / giant arcade may correspond to the fast shock....
And you have already written the first three sentences of the full article: coronal mass ejections ( cmes ) are one of the most spectacular phenomena in the solar corona .
cmes show some kind of association with various forms of solar activities ; 40% of cmes were associated with flares , but more than 70% were associated with eruptive prominence or disappearing filaments ( munro et al . 1979 ; webb & hundhausen 1987 ; see kahler 1992 for review ) .
on the other hand , observations with soft x - ray telescope ( sxt ) aboard _ yohkoh _ revealed that formations of giant arcades are associated with filament eruptions that are not associated with flares ( tsuneta et al ..
Please generate the next two sentences of the article | 1992 ; hiei et al .
1993 , hanaoka et al . 1994 ; mcallister et al . |
4,996 | Suppose that you have an abstract for a scientific paper: the superkamiokande experiment suggests the large flavor mixing between @xmath0 and @xmath1 .
we show that the mixing angle receives significant corrections from the renormalization group equation ( rge ) when both the second and the third generation neutrino masses are larger than @xmath2 .
this means that the mixing angle must be small at the decoupling scale of right - handed neutrinos in the model containing a sterile neutrino @xmath3 with the mass spectrum of @xmath4 . [
cols="^,^ " , ] the renormalization group analysis of the large lepton flavor mixing and the neutrino mass + n. haba@xmath5 , @xmath6 , @xmath7 + @xmath5_department of physics , the ohio state university , columbus , ohio 43210 , usa _
+ @xmath6_theory group , kek , oho 1 - 1 , tsukuba 305 - 0801 , japan
_ + @xmath7_department of physics , nagoya university , nagoya , 464 - 8602 , japan _ + .
And you have already written the first three sentences of the full article: the recent superkamiokande data suggests the large neutrino flavor mixing between @xmath0 and @xmath1@xcite . according to this experimental result
, there have been a lot of theoretical attempts to explain why the large flavor mixing is realized in the lepton sector@xcite .
one of the interesting approaches is concentrating on the effects of the the renormalization group equation ( rge ) ..
Please generate the next two sentences of the article | the rge effects cause the enhancement of the neutrino flavor mixing in some situations@xcite@xcite@xcite . in this paper
we analyze the rge of the neutrino flavor mixing between @xmath0 and @xmath1 in the minimal supersymmetric standard model ( mssm ) with right - handed neutrinos . here |
4,997 | Suppose that you have an abstract for a scientific paper: we study the interplay between evolutionary game and network structure and show how the dynamics of the game affect the growth pattern of the network and how the evolution of the network influence the cooperative behavior in the game .
simulation results show that the payoff - based preferential attachment mechanism leads to the emergence of a scale - free structural property , @xmath0 .
moreover , we investigate the average path length and the assortative mixing features .
the obtained results indicate that the network has small - world and positive assortative behaviors , which are consistent with the observations of some real social networks . in parallel
, we found that the evolution of the underlying network structure effectively promotes the cooperation level of the game .
we also investigate the wealth distribution obtained by our model , which is consistent with the pareto law in the real observation .
in addition , the analysis of the generated scale - free network structure is provided for better understanding the evolutionary dynamics of our model . .
And you have already written the first three sentences of the full article: game theory provides a useful framework for describing the evolution of systems consisting of selfish individuals @xcite .
the prisoner s dilemma game ( pdg ) as a metaphor for investigating the evolution of cooperation has drawn considerable attention @xcite . in the pdg
, two players simultaneously choose whether to cooperate or defect ..
Please generate the next two sentences of the article | mutual cooperation results in payoff @xmath1 for both players , whereas mutual defection leads to payoff @xmath2 gained both . if one cooperates while the other defects , the defector gains the highest payoff @xmath3 , while the cooperator bears a cost @xmath4 .
this thus gives a simply rank of four payoff values : @xmath5 . |
4,998 | Suppose that you have an abstract for a scientific paper: we present results for two - body observables that are sensitive to the parity - violating component of nucleon - nucleon interactions .
these interactions are studied using an effective field theory in which the only dynamic degrees of freedom are nucleon fields .
the observables we study are cross - section asymmetries in nucleon - nucleon scattering and asymmetries and induced polarizations in the process @xmath0 . .
And you have already written the first three sentences of the full article: the low - energy interaction between hadrons contains a parity - violating ( pv ) component due to the weak interactions of quarks contained in the hadrons .
hadronic parity violation has received renewed interest with a number of ongoing and planned experiments @xcite as well as theoretical developments . traditionally , there are two different theoretical approaches to hadronic parity violation .
the most commonly used framework is the one - meson exchange model of desplanques , donoghue and holstein ( ddh ) @xcite . in a different approach by danilov @xcite the pv hadronic interactions.
Please generate the next two sentences of the article | are described in terms of 5 low - energy amplitudes .
more recently , effective field theories ( efts ) have been applied to the problem of hadronic parity violation @xcite . |
4,999 | Suppose that you have an abstract for a scientific paper: flaps can be detached from a thin film glued on a solid substrate by tearing and peeling . for flat substrates
, it has been shown that these flaps spontaneously narrow and collapse in pointy triangular shapes . here
we show that various shapes , triangular , elliptic , acuminate or spatulate , can be observed for the tears by adjusting the curvature of the substrate . from combined experiments and theoretical models ,
we show that the flap morphology is governed by simple geometric rules .
cracks and fractures are commonly observed around us in various contexts @xcite ranging from drying mud @xcite to broken windows or ice floes @xcite .
the classical fracture theories , initially formulated by griffith and irwin @xcite , can reliably predict the onset of cracks motion .
in contrast , no general theory is able to predict the path of a crack as it propagates . in some specific cases however , interesting insight has been gained about cracks trajectories .
for example , thin films offer a particularly efficient set - up to study fracture propagation by limiting the crack motion to a two - dimensional manifold . in this context
, the crucial role of geometry was identified in some oscillatory fracture patterns obtained when a brittle elastic thin sheet is cut by a moving object @xcite .
the propagation of two interacting cracks in torn thin films is another example where fracture path can be understood @xcite . .
( a ) flat substrate , triangular shape . when the peeling front propagates by a infinitesimal @xmath0 along @xmath1-axis , it produces two cracks of length @xmath2 together with a variation of the width @xmath3 and a variation of the peeling area @xmath4 .
( b ) substrate with negative curvature , acuminate .
( c , d ) substrate with positive curvature with @xmath5 , spatulate ( c ) and @xmath6 , elliptic ( d ) , where @xmath7 is the initial width of the flap .
negative ( positive ) curvature , @xmath8 , @xmath9 and @xmath10 are defined in the text .
scale bars....
And you have already written the first three sentences of the full article: in fig . [ fig01]a below ( see also fig . 3 of the main text ) , a sheet of paper is wrapped around a cylinder to model the shape adopted by the thin adhesive film during our peeling / tearing experiments .
the blue solid line indicates the peeling front whose shape is identified to a curve @xmath21 obtained by the intersection between a cylinder and a plane forming an angle @xmath57 with the @xmath1-axis ( see fig .
[ fig01]b , c ) ..
Please generate the next two sentences of the article | when the sheet is unrolled and flattened , the creasing of the paper sheet reveals the curvature of the peeling front relevant for our study ( see fig . [ fig01]d , e ) .
this procedure allows to distinguish the part of the curvature of the curve @xmath21 that is due to the cylinder and the one that comes from the peeling front itself . in mathematical terms |
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