Using a kinetic simulation of magnetic reconnection it was recently shown that magnetic - field -...

it is widely believed that magnetic reconnection energizes electrons and is the source of superthermal electrons observed during solar flare events and through _ in situ _ measurements in the earth s magnetosphere . several previous studies of reconnection conclude that the dissipation sites ( where electrons are energized ) are limited to electron scale regions and are insufficient in size to account for the large scale electron energization . to circumvent this conundrum recent models have invoked the possibility of multiple reconnection locations and flux - rope formation , which can facilitate energy release in a larger spatial volume and thereby help energize the large number of electrons required by observations . while there exists clear evidence of magnetic flux - ropes forming in the earth s magnetosphere , these flux - ropes do not appear to be volume filling such that energization at multiple x - lines becomes effective . this suggests that energization within the exhaust from a single x - line needs to be efficient to account for the extensive energization levels recorded experimentally . we therefore revisit electron energization in single x - line reconnection and find that superthermal electrons are produced over large spatial scales in the single x - line reconnection exhaust when the total pressure of the plasma upstream of the reconnection region is dominated by the magnetic field ( ) . in our kinetic simulation , a key to the strong electron energization is the break - down of adiabatic electron dynamics along the magnetic field lines , which , we find , is likely to occur when . the documented heating mechanism and non - adiabatic parallel electron dynamics lead to the formation of strong magnetic field , aligned ( parallel ) electric fields , . these structures are consistent with double layers , where local charge separation generates strong parallel electric fields . the double layers provide an initial energization of electrons streaming into

We present a kinetic simulation of the electron energization in single x - line reconnection and find that superthermal electrons are produced over large spatial scales in the single X - line. This is consistent with double layers where local charge separation generates strong parallel electric fields.

using a kinetic simulation of magnetic reconnection it was recently shown that magnetic - field - aligned electric fields ( ) can be present over large spatial scales in reconnection exhausts . the largest values of are observed within double layers . the existence of double layers in the earth s magnetoshere is well documented . in our simulation their formation is triggered by large parallel streaming of electrons into the reconnection region . these parallel electron fluxes are required for m


Models without an explicit time dependence , called singular models , are widely used for fitting...

we are interested in the problem of what happens when a set of nominally identical liquid water droplets are cooled at some rate , until they freeze . it is observed that the droplets do not all freeze at the same temperature ; they freeze over a broad range of temperatures . we want to understand this , and make predictions about this phenomenon , using a simple model . to do this , we define the probability that a randomly selected droplet has _ not _ frozen , at the time when we have cooled it down to a temperature . note that is a cumulative probability , the probability that a sample freezes between and , is . in an experiment , can be approximated by the fraction of a large number of identically prepared droplets that are still liquid at a temperature . levine s model for the freezing of liquid water droplets is simple . he made the following assumptions : 1 . each droplet contains impurities that have a total of nucleation sites . 2 . each nucleation site induces nucleation of ice rapidly at a well defined temperature . this temperature varies from one nucleation site to another . the sites are independent , and the values of are drawn from a probability distribution function . 4 . only one nucleation event is required to induce crystallisation of the droplet , and so the droplet crystallises at the highest of its nucleation sites . we denote this maximum value of a set of s , by . assumption 4 allows us to use extreme - value statistics , see for an introduction to these statistics . here we define a singular model as being a model in which assumptions 1 to 4 are made . in particular , assumption 2 eliminates any time dependence , giving us a model with only a temperature dependence . this definition of a singular model agrees with that of pruppacher and klett . levine then made a fifth assumption : 1 . the distribution of nucleation temperatures at the sites , , is exponential , i.e. , this distribution has two parameters : ( dimensionless ) and ( dimension

We study the freezing of liquid water droplets, using a simple model. We define the probability that a random sample has not frozen at the same temperature, and then make predictions about this phenomenon. In particular, we denote the maximum value of a set of s, by.

models without an explicit time dependence , called singular models , are widely used for fitting the distribution of temperatures at which water droplets freeze . in 1950 levine developed the original singular model . his key assumption was that each droplet contained many nucleation sites , and that freezing occurred due to the nucleation site with the highest freezing temperature . the fact that freezing occurs due to the maximum value out of large number of nucleation temperatures , means th


A successful effective field theory program requires besides the most general effective lagrangian...

effective field theory ( eft ) has become a powerful tool in the description of the strong interactions at low energies . the central idea is due to weinberg: `` ... if one writes down the most general possible lagrangian , including all terms consistent with assumed symmetry principles , and then calculates matrix elements with this lagrangian to any given order of perturbation theory , the result will simply be the most general possible s matrix consistent with analyticity , perturbative unitarity , cluster decomposition and the assumed symmetry principles . '' the application of these ideas to the interactions among the goldstone bosons of spontaneous chiral symmetry breaking in qcd is referred to as ( mesonic ) chiral perturbation theory ( chpt ) and has been highly successful ( see , e.g. , ref . for a pedagogical introduction ) . besides the most general lagrangian a successful eft program requires a consistent power counting scheme to assess the importance of a given ( renormalized ) diagram . in the following we will outline some recent developments in devising a renormalization scheme leading to a simple and consistent power counting for the renormalized diagrams of a manifestly lorentz - invariant approach to baryon chpt . the standard effective lagrangian relevant to the single - nucleon sector consists of the sum of the purely mesonic and lagrangians , respectively, which are organized in a derivative and quark - mass expansion . the aim is to devise a renormalization procedure generating , after renormalization , the following power counting : a loop integration in dimensions counts as , pion and fermion propagators count as and , respectively , vertices derived from and count as and , respectively . here , generically denotes a small expansion parameter such as , e.g. , the pion mass . in order to illustrate the issue of power counting , we consider as an example the one - loop contribution of fig . [ fig : nucleonselfenergypionloop ] to the nucleon se

We consider the one - loop contribution of fig in the single - nucleon sector. We show that the one loop contribution is consistent with the standard effective lagrangian and that it can be used to calculate the power counting for the renormalized diagrams of a manifestly lorentz - invariant approach to baryon chiral perturbation theory.

a successful effective field theory program requires besides the most general effective lagrangian a perturbative expansion scheme for observables in terms of a consistent power counting method . we discuss a renormalization scheme for manifestly lorentz - invariant baryon chiral perturbation theory generating a simple and consistent power counting for renormalized diagrams . the approach may be used in an iterative procedure to renormalize higher - order loop diagrams and also allows for implem


We show that the star counts in the spheroid of the milky way are not symmetric about the , plane

while the milky way galaxy gives us a much better view of the individual component stars than any other galaxy , it is difficult to view our galaxy as an assembled whole . new surveys such as 2mass and sdss , are allowing us to start assembling the global picture one star at a time . other surveys that are in progress such as rave , gaia , pan - starrs , ukidss / vista , and sdss ii / segue will extend our view of the stars not only in positional information but also in kinematic information for a large number of galactic stars . sdss color - magnitude hess diagrams such as figure 11 of show two populations with distinct turnoffs ( see fig . 1 ) . the brighter population has a turnoff at and is associated with the thick disk . the fainter population has a turnoff at , and is associated with the spheroid . 1 shows the color - magnitude selection boxes for thick disk , spheroid , and faint spheroid data samples selected from sdss - dr3 . 2 shows the number counts of spheroid stars as a function of position in the galaxy from sdss dr3 . where there are no counts , we have no data . note that the number counts do not appear to be symmetric about the galactic center . 3 shows this numerically , by plotting star counts along several lines of constant galactic latitude . there are more spheroid stars in quadrant iv than in quadrant i , and the minimum is at rather than , as we would have expected . 4 shows that the spheroid number counts are not significantly asymmetric about the galactic equator . 5 shows the star counts for the thick disk selection for all of dr3 , while fig . 6 shows quantitatively that the thick disk is symmetric about . fig . 7 is a cartoon , looking down on the galactic plane , depicting the star counts that would be observed at a constant height above or below the galactic plane for a sample triaxial spheroid . this type of model can explain a minimum in quadrant ii , and a maximum in quadrant iv for samples of stars close to the sun . it predicts t

We present a new sdss color - magnitude selection box for the thick disk and spheroid data from s - dr3. The number counts of sppheroid stars are calculated by using the sms / scs, ss st, and mss models. We find that the star count is not significantly asymmetric about the galactic center.

we show that the star counts in the spheroid of the milky way are not symmetric about the , plane . the minimum counts are found towards . the galactic longitude of maximum star counts depends on the magnitude and color selection of the halo stars . we interpret this as evidence that the spheroid population is triaxial with a major axis oriented from the line of sight from the sun to the galactic center , and approximately perpendicular to the galactic bar . large local star concentrations from


A system with two correlated gaussian white noises is analysed

stochastic models with multiplicative , or parametrical , noise find numerous applications in a variety of branches of science and technology . unfortunately , models for which analytical results are known are very scarce and any such a model deserves a thorough discussion . recently , denisov and horsthemke have discussed a model given by the equation where , is a gaussian noise , possibly coloured , and have found that it can describe anomalous diffusion and stochastic localization . denisov and horsthemke have also discussed several physical systems in which models of the type can be useful ; see references provided in their paper . later vitrenko has generalized to include two noise terms : where are certain coloured and correlated gaussian noises . this system has a very nice feature : for , it interpolates between a linear transmitter with multiplicative and additive noises ( ) and a linear system with a purely multiplicative noise ( ) . the two limiting cases , and , are very well known in the literature ( see e.g. ref. and references quoted therein ) . vitrenko has formally linearized the system by means of a substitution that has been already used in : and solved the resulting equation for the trajectories . converting back to the original variable proves to be rather tricky and that author has managed to do so only if the noises are correlated in a very specific ( not to say peculiar ) manner . it is now widely recognized that correlations between various noises can lead to many interesting effects . it is , however , possible that phenomena reported by vitrenko result principally from the very specific form of correlations assumed by this author and are not generic to the system . we find it interesting to see how the system behaves for the intermediate values of when the correlation requirements are less restrictive than those discussed by vitrenko . coloured noises introduce more complexity . however , if a dynamical effect is present in the white noise

We study the correlated gaussian noise of a linear system with multiplicative and additive noises. We find that it is possible to describe anomalous diffusion and stochastic localization in a model given by the equation where is a gausian noise, possibly coloured.

a system with two correlated gaussian white noises is analysed . this system can describe both stochastic localization and long tails in the stationary distribution . correlations between the noises can lead to a nonmonotonic behaviour of the variance as function of the intensity of one of the noises and to a stochastic resonance . a method for improving the transmission of external periodic signal by tuning parameters of the system discussed in this paper is proposed . correlated gaussian noise


Density functional theory ( dft ) calculations of the energy of magnetic anisotropy for diluted...

microscopic understanding of anisotropic properties of any ferromagnet constitutes a very challenging theoretical task and is very important from the point of view of possible applications . particularly , in the case of ferromagnetic semiconductors , a deep understanding of the mechanisms responsible for the behavior of magnetization becomes crucial because a number of semiconductor properties may be changed by external factors . it was established that direction of the easy axis of magnetization can be changed by changing the density of free carriers or by applying a strain . the carrier concentration can be varied by applying gate voltage to the layer , and strain in a film can be imposed by cementing it to a piezoelectric actuator . these and other related phenomena are described in a recent review . previous theoretical descriptions of magnetic anisotropy in semiconductors were based either on the mean - field zener model , or on the concept of single ion anisotropy . the zener model was applied to iii - v and ii - vi diluted ferromagnetic semiconductors . in this approach , it is assumed that the nonzero macroscopic magnetization of magnetic ions leads , via exchange interaction , to the spin splitting of band states . because of the presence of spin - orbit ( s - o ) interaction , the band structure , and thus the energy of carriers populating band states , depend on the direction of magnetization . in this model the magnetic anisotropy is due to the simultaneous presence of two factors , i.e. the finite concentration of free carriers , and the non - vanishing s - o coupling in the host crystal . for insulating crystals , or for the vanishing band s - o interaction , a vanishing magnetic anisotropy is predicted . ( note that the limit of isolated impurities is beyond the scope of the model . ) the zener model explained , at least semiquantitavely , a number of experiments . + the second approach is based on the concept of single ion anisotropy . the anisotrop

We present a theoretical study of the magnetic anisotropy in ferromagnetic semiconductors. The model is applied to iii - v and iv diluted ferROMagnetic silicon. It is assumed that the nonzero macroscopic magnetization of magnetic ions leads to the spin splitting of band states. For insulating crystals, the magnetic - anisotropies are predicted by the mean - field zener model.

density functional theory ( dft ) calculations of the energy of magnetic anisotropy for diluted ferromagnetic semiconductor were performed using openmx package with fully relativistic pseudopotentials . the influence of hole concentration and magnetic ion neighbourhood on magnetic anisotropy energy is presented . analysis of microscopic mechanism of magnetic anisotropy is provided , in particular the role of spin - orbit coupling , spin polarization and spatial changes of electron density are di


Secure transmission of data packets in wireless sensor networks is an important area of research

wireless sensor networks ( wsns ) consists of a large number of ultra - small , low - cost , battery - powered devices that have limited energy resources , computation , memory and communication capabilities . wsns are often deployed in a vast terrain to detect events of interest and deliver data reports over wireless path to the sink . wsns are used in environment monitoring , military applications , home appliance management , commercial applications , etc .. + + the major services of security are : confidentiality , access control , authentication , non - repudiation and integrity . : it means the data to be transmitted should be protected from passive attacks . _ access control _ : it is the capability to control the access to host systems through the communication links . : it assures that the communication is established between the authentic user . it provides confidence in the identity of the entities connected and assures that the received data is from the claimed source . : it provides the proof that the message was sent or received from the specified device . : it assures that the received data is exactly the same as it was sent by the authorized entity . + + even in the presence of security protocols , the adversaries are able to break the cipher text and find the plain text . data security is essential for critical applications to work in hostile environments . it is easy for the attackers to inject malicious data messages or alter the content of legitimate messages during hop forwarding of data , due to the wireless environment in sensor networks . thus , in sensor network communication , it is essential for authentication mechanisms to ensure that data from a valid source is not altered during transit . in this paper , we have focused on node compromise attack . + + _ motivation _ : data packets are usually forwarded from one node to another using single or multiple hops in wsns . the adversary observes the traffic during routing and tries to compromi

We present a node compromise attack on wireless sensor networks ( wsns ). The attackers are motivated by a malicious intent to forwarded data from one node to another using single or multiple hops in wSns and try to compromi the traffic during routing. We show that the attacker can not only forwarded the data from a valid source but also modify the content of legitimate messages.

secure transmission of data packets in wireless sensor networks is an important area of research . there is a possibility of an attacker creating security holes in the network . hence , network security and reliability can be achieved by discovering random multiple paths using multiple domains , and forwarding data packets from the source node to the destination node . we have designed , multiple domain routing with overlap of nodes ( mdron ) and multiple domain routing without overlap of nodes


Recently , using an atomic force microscope and a single cantilever excited at different...

capillary condensation occurs as soon as a confined geometry is in a presence of a vapor phase . capillary forces are among the most intense at nanoscale , playing an important role in the interaction between almost all surfaces . the importance of dynamical properties of water bridges becomes evident if one considers interacting surfaces with roughness scales down to few nanometers , since in that case , even at moderate speeds of m / s sliding will generate frequencies above 1 mhz . between an atomic force microscope ( afm ) tip and a surface , this interaction , in a long time range , is attractive and remains at the thermodynamical equilibrium . it is described by the young - laplace equation , the nanomeniscus has to adapt its radii of curvature to keep the chemical potentials equal . we have highlighted that a nanomeniscus can appear as a stiff material ( 0.1gpa ) at the nanoscale when excited at high frequency . this was observed using an afm mode called force feedback microscopy ( ffm ) . we have argued that molecular exchange progressively loses efficiency , when the frequency of the tip oscillation is increased and thus the nanomeniscus is no longer at the thermodynamical equilibrium . the capillary bridge is then led to acquire a constant volume during oscillations at high frequencies . in addition to the constant volume picture , the ability of the bridge to adapt to a new shape looses efficiency resulting in a progressive locking of the contact line resulting in changes of the mean curvature radius of the capillary bridge this appears as a transition between a negative stiffness ( n / m ) in the long time regime to positive stiffness at high frequency . the estimated characteristic time is s . our work published in ref was a first approach to this question based on a non - conventional use of afm . it is important to stress that even though the methodology used before is sound it is not well established among the afm community . here we want to show tha

We present a new method for the study of nanomeniscuss at high frequency in an atomic force microscope ( afm ) mode. This technique is based on a non - conventional use of a ffm and it is a first approach to the question of how the bridge can be adapted to a different shape. We show that the mechanism of the bridge is not well established among the aem community, but it is well established by a simple method.

recently , using an atomic force microscope and a single cantilever excited at different frequencies it was shown that water nanomeniscus can exhibit a transition in mechanical responses when submitted to stimuli above few tens of khz . the use of a single cantilever to explore phenomena at frequencies far from the cantilever resonance frequency is not a common and well - established strategy , and because water meniscus are ubiquitous in nature , we have also studied the water meniscus mechanic


Recent _ suzaku _ x - ray observations revealed that the observed entropy profile of the...

in recent years , galaxy clusters have emerged as one of the unique and powerful laboratories for cosmology and astrophysics . being the largest and most magnificent structures in the universe , clusters of galaxies serve as excellent tracers of the growth of cosmic structures . current generation of x - ray cluster surveys have provided independent confirmation of cosmic acceleration and significantly tighten constraints on the nature of dark energy and alternative theories of gravity ( e.g. , * ? ? ? * ) . new x - ray survey missions ( e.g. , _ erosita _ ) are underway to improve current cosmological constraints . outskirts of galaxy clusters have special importance in cluster cosmology , because they are believed to be much less susceptible to complicated cluster astrophysics , such as radiative gas cooling , star formation , and energy injection from active galactic nuclei . dominant physical processes in the outskirts are limited to the gravity - driven collisionless dynamics of dark matter and hydrodynamics of the intracluster medium ( icm ) . however , until very recently , observational studies of the icm have been limited to radii considerably smaller than the virial radius of clusters . recently , x - ray observations with _ suzaku _ have extended measurements of the icm profile out to and beyond the virial radius for a number of clusters . while measurement uncertainties are still large , the initial results indicate that the observed icm profiles deviate significantly from the predictions of hydrodynamical cluster simulations ( e.g. , * ? ? ? in addition to testing model of structure formation , these new measurements are important for controlling systematic uncertainties for cluster - based cosmological measurements . in the hierarchical structure formation model , clusters grow by accreting materials from the surrounding large - scale structure in their outer envelope . numerical simulations predict that accretion and mergers are ubiquitous and importa

We present a new study of the intracluster medium ( icm ) for a number of clusters. The icM is a large - scale structure that grows by accretion and mergers from the surrounding large _ scale _ structure. Our results are consistent with previous observations of the cdm, which have been limited to radii considerably smaller than the virial radius of cluster. We also show that the observed ic - ray profiles deviate significantly from the predictions of hydrodynamical cluster simulations, indicating that.

recent _ suzaku _ x - ray observations revealed that the observed entropy profile of the intracluster medium ( icm ) deviates significantly from the prediction of hydrodynamical simulations of galaxy clusters . in this work , we show that gas clumping introduces significant biases in x - ray measurements of the icm profiles in the outskirts of galaxy clusters . using hydrodynamical simulations of galaxy cluster formation in a concordance cdm model , we demonstrate that gas clumping leads to an o


The presence of two distant fri radio galaxies in the hubble deep field plus flanking fields...

early statistics of radio sources indicated that the space density of radio sources was much higher at early cosmological epochs than in the present universe ( ryle & clarke 1961 ) . subsequent deeper radio surveys showed a turnover in the number counts , implying that this strong cosmological evolution must have been confined to only the most powerful radio sources ( longair 1966 ) , and a simple model was developed with two distinct population of radio sources ; one low - luminosity non - evolving population , and one high - luminosity strongly - evolving population ( doroshkevich , longair & zeldovich 1970 ) . wall ( 1980 ) suggested that these two populations of non - evolving and strongly evolving radio sources correspond to the fanaroff & riley ( 1974 ) class i and ii galaxies respectively . this idea of a ` dual population scheme ' has formed the basis of a comprehensive study by jackson & wall ( 1999 ) , who in addition linked through orientation the non - evolving and strongly evolving populations of fri and frii radio galaxies to bl lacs and flat spectrum quasars respectively . a similar scheme has recently been developed by willott et al . ( 2001 ) , but here a weakly evolving and a strongly evolving population correspond to radio galaxies with low and high optical line luminosity , not to fr class . in the mean time , substantial differences were found between the host galaxies of fri and ii radio sources . owen & laing ( 1989 ) found that fris are hosted by larger galaxies than friis . in addition , zirbel & baum ( 1995 ) showed that at the same radio power , friis have 5 times more optical line luminosity than fris . it was therefore proposed that the fr dichotomy may be due to fundamental differences in the structural properties of the central engines in these two types of sources , such as the accretion rate and/or the spin of the central black hole . however , more recently it has been shown by ledlow and owen ( 1996 ) that the owen & laing result w

We present a new model for the evolution of radio sources in the cosmological context, which is based on two distinct populations of radio galaxies: one with low luminosity and one with high luminosities. The two populations correspond to the fanaroff & riley ( 1974 ) class i and ii galaxis respectively. We find that the non - evolving population corresponds to the bl lacs and flat spectrum quasars respectively and that the strong cosmology of these two populations is due to the spin of the.

the presence of two distant fri radio galaxies in the hubble deep field plus flanking fields indicates that the number density of these objects is about 10 times higher at z than in the local universe . this is in strong contrast with the idea that fris undergo no cosmological evolution . we advocate that the cosmological evolution of radio sources may be independent of fr class , and instead solely a function of radio power . in this scenario the evolutionary properties of extragalactic radio s


It is important to understand the mechanism of high - temperature superconductivity

a basic question in the study of superconductivity is on an upper limit of the critical temperature . it has been suggested that the maximum of is in the range from 30k to 40k when the superconducting transition is based on the electron - phonon interaction [ 1 , 2 ] . the prime reason of low for the electron - phonon mechanism is that the debye frequency is of the order of 100k and is reduced by more than one digit than . in general , the electron - phonon coupling constant is small . thus there is an upper limit for within the electron - phonon mechanism . the interaction of large energy scale will be responsible for high temperature superconductivity . the electronic origin mechanisms of superconductivity are worth studying in the search of high temperature superconductors . the electronic interaction comes from the coulomb interaction between electrons . from this point of view , it is important to consider the intra - atomic coulomb interactions that are of the order of ev . then a question arises as to whether the superconductivity is indeed induced by the coulomb interaction . this subject has been studied intensively by using electronic models with the on - site coulomb interaction including the two - dimensional ( 2d ) hubbard model [ 3 - 26 ] , the d - p model [ 27 - 33 ] and also the ladder hubbard model [ 34 - 38 ] . it remains matter of controversial as to whether the 2d hubbard model accounts for high - temperature superconductivity . most of the results of quantum monte carlo methods have failed to show the existence of superconductivity [ 13,14,18 ] , and some results , however , still keep open the possibility of superconductivity [ 15 , 24 ] . we must note that quantum monte carlo methods are methods being applicable only in the weakly correlated region where is not large and is at most from 4 to 5 . the existence of superconductivity in strongly correlated regions should be considered further . this may account for properties of high - temperature

We study the superconductivity of a two - dimensional hubbard model with the on - site coulomb interaction. The supercoherence is found to be in the range from 30k to 40k when the electron -phonon coupling constant is low. This is due to the fact that the debye frequency is of the order of 100k and is reduced by more than one digit than. We also consider the effect of the coulibration of the electrons in the two dimensional Hubbard models.

it is important to understand the mechanism of high - temperature superconductivity . it is obvious that the interaction with large energy scale is responsible for high critical temperature . the coulomb interaction is one of candidates that bring about high - temperature superconductivity because its characteristic energy is of the order of ev . there have been many works for the hubbard model including three - band d - p model with the on - site coulomb repulsion to investigate a possibility o


A generalized vertex join of a graph is obtained by joining an arbitrary multiset of its vertices...

graph polynomials contain various information about graphs and are used to analyze the properties of graphs and networks . two of the most important single - variable graph polynomials are the chromatic polynomial and the flow polynomial . studying these polynomials is an active area of research with many theoretical consequences and practical applications . the chromatic polynomial is related to the potts model , which models the behavior of certain elements of solid state physics , like crystals and ferromagnets . the coefficients of the chromatic polynomial have another application in statistical mechanics they are used to model state changes , as described in the work of sokal . the chromatic polynomial is also related to stirling numbers , and thus finds applications in a variety of analytic and combinatorics problems ; see . there are important theoretical questions surrounding the flow polynomial as well , such as the 5-flow conjecture and other flow existence theorems and conjectures . the flow polynomial also has an application in crystallography and statistical mechanics as it is related to models of the physical properties of ice and crystal lattices . for more applications of chromatic and flow polynomials , see the comprehensive survey of ellis - monaghan and merino and the bibliography therein . unfortunately , computing the chromatic and flow polynomials of a graph are very challenging tasks . these problems are np - hard for general graphs , and even for bipartite planar graphs as shown in , and sparse graphs with . in fact , most of the terms of the chromatic and flow polynomials of general graphs can not even be approximated ( see ) . thus , a large volume of work in this area is focused on exploiting the structure of specific types of graphs in order to derive closed formulas , algorithms , or heuristics for computing their chromatic and flow polynomials . in particular , classes of graphs which are generalizations of trees , cliques , and cycles

We study the chromatic and flow polynomials of general graphs. We use the heuristics of the eigenvalues of these polynomies to derive closed formulas for the, and the corresponding, terms of the flow polynomies of. In particular, we find that the np - hard terms of, are not even approximated by the hysteresis, which is a function of the number of h - h functions.

a generalized vertex join of a graph is obtained by joining an arbitrary multiset of its vertices to a new vertex . we present a low - order polynomial time algorithm for finding the chromatic polynomials of generalized vertex joins of trees , and by duality we find the flow polynomials of arbitrary outerplanar graphs . we also present closed formulas for the chromatic and flow polynomials of vertex joins of cliques and cycles , otherwise known as generalized wheel " graphs . * keywords : * chro


For an exact quantitative description of spectral properties in the theory of synchrotron radiation...

as one of the major quantitative characteristics of spectral distributions for electromagnetic radiation , one commonly uses the concept of spectral half - width . for spectral distributions having a sharp maximum , spectral half - width is the most informative physical characteristic . however , once a spectral distribution has no pronounced maximum , spectral half - width ceases to be an adequate quantitative characteristic . in particular , this is exactly the case of spectral distributions for synchrotron radiation ( sr ) , and therefore sr spectral half - width has neither been calculated theoretically , nor measured experimentally . instead of spectral half - width , the present study proposes to introduce a new precise quantitative characteristic of sr spectral distributions : effective spectral width . it is shown how this quantity can be calculated theoretically , and which physically relevant information can be obtained using this quantity . at present , the theory of synchrotron radiation is a fairly well - developed area of theoretical physics . its main elements are described in monographs ( e.g. ) and numerous articles . among the most important sr physical features , one should take into account a high polarization degree of radiation and a unique structure of spectral distributions . all theoretically predictable sr properties have been confirmed by experiment . the development of sr theory allows one not only to predict radiation characteristics qualitatively , but also to offer exact quantitative characteristics of physically important properties . for example , the high degree of sr polarization was qualitatively predicted by theory more than half a century ago ( see , e.g., ) ; precise quantitative characteristics for linear polarization were also obtained , whereas such quantitative characteristics for circular polarization were obtained much later . in order to set up the problem , we now present some well - known expressions of the classical s

We present a new quantitative characteristic of synchrotron radiation ( sr ) spectral distributions, effective spectral width. This quantity can be calculated theoretically and measured experimentally. It is shown how this quantity is calculated theoreticalally, and which physically relevant information can be obtained using this quantity.

for an exact quantitative description of spectral properties in the theory of synchrotron radiation , the concept of effective spectral width is introduced . in the classical theory , numeric calculations of effective spectral width ( using an effective width not exceeding 100 harmonics ) for polarization components of synchrotron radiation are carried out . the dependence of the effective spectral width and initial harmonic on the energy of a radiating particle is established .


The possibility of flavor transitions into sterile neutrinos ( accompanying the dominant lma...

the sno and kamland experiments have played a crucial role in resolving the longstanding solar neutrino problem in terms of large mixing angle ( lma ) msw oscillations and are expected to play an important role in the refinement of the lma solution which is undergoing a deeper scrutiny . does the lma solution explain all the solar neutrino data satisfactorily ? there are , at least , two generic predictions of lma indicating new physics beyond lma . one of these is the prediction of the high argon production rate for homestake experiment which is about 2 above the observed rate . another generic prediction of the lma scenario is the ` spectral upturn ' at low energies . within the lma parameter space , the survival probability should increase with decrease in energy and for the best fit parameters , the upturn could be as large as 10 - 15% between 8 mev and 5 mev . in fact , the spectral upturn at low energies is expected to increase further with the kamland 766.3 ty spectral data favoring a larger value of . however , neither superkamiokande nor sno has reported any statistically significant ` rise - up ' in the observed neutrino survival probability . both these predictions of the lma solution can , only , be tested in the forthcoming phase of high precision measurements in the solar neutrino experiments and are crucial for the final confirmation of the lma solution . another unresolved issue is whether the solar neutrinos oscillate into the sterile component . the main motivation for postulating the existence of the sterile neutrino species comes from the lsnd experiment which reported a significant oscillation probability which requires a new mass scale . since , the z - decay width constrains the number of weakly interacting light neutrino species to be very close to three , one is forced to postulate a sterile neutrino . while the purely sterile oscillation solution is excluded at 7.6 , the solar electron neutrinos could still oscillate into both active and st

We present a new analysis of the spectral upturn at low energies in the solar neutrino experiment. The spectra are obtained from the sno and kamland experiments and show that the z - decay width is significantly lower than the sterile component. We also find that the upturn is larger than the standard spectroscopic upturn, which is expected to be as large as 10 - 15% between 8 mev and 5 mev.

the possibility of flavor transitions into sterile neutrinos ( accompanying the dominant lma transitions ) in the solar boron neutrino flux has been examined in a scenario proposed by hollanda and smirnov to overcome some generic problems of the pure lma scenario . it is found that the most recent sno salt phase solar neutrino data and the kamland 766.3 ty spectral data , allow for a significant sterile presence in the solar boron neutrino flux reaching the earth .


Using the etfsi ( extended thomas - fermi plus strutinsky integral ) method , we have calculated...

the r - process of stellar nucleosynthesis depends crucially on the masses and fission barriers ( among other quantities ) of nuclei that are so neutron - rich that there is no hope of being able to measure them in the laboratory ( see refs . for reviews discussing the nuclear data required for an understanding of the r - process ) . it is thus of the greatest importance to be able to make reliable extrapolations of these quantities away from the known region , relatively close to the stability line , out towards the neutron - drip line . until recently the masses and barriers used in all studies of the r - process were calculated on the basis of one form or another of the liquid - drop(let ) model ( ldm ) . however , in an attempt to put the extrapolations on as rigorous a footing as possible we have developed a mass formula that is based entirely on microscopic forces , the etfsi-1 mass formula . calculations of the r - process using the etfsi-1 masses have already been performed , but they are incomplete in that fission had to be neglected , barriers not yet having been calculated in the etfsi model . of course , recourse could have been made to the extensive barrier calculations based on the ldm that had been used in earlier r - process studies , but it would have been inconsistent to use one model for the masses ( required for the neutron - separation energies and the beta - decay energies ) , and another for the barriers . here we remedy this deficiency by presenting the results of etfsi - method calculations of the fission barriers of all of the nearly 2000 nuclei lying in the region of the ( , ) plane shown in fig . 1 . this region covers the range , and extends from moderately neutron - deficient to extremely neutron - rich nuclei , including thereby not only a large fraction of the nuclei whose barriers are known experimentally , but also all nuclei with whose barriers can reasonably be expected to be relevant to the r - process . towards the upper limit o

We present the results of etfsi - method calculations of the fission barriers of all of the nearly 2000 nuclei lying in the region of the plane. These nucleions are known experimentally and have been studied using the liquid drop(let ) model ( ldm ), but they are not yet relevant to the r - process. We show that the mass formula for the fi.

using the etfsi ( extended thomas - fermi plus strutinsky integral ) method , we have calculated the fission barriers of nearly 2000 exotic nuclei , including all the neutron - rich nuclei up to that are expected to be relevant to the r - process , and all superheavy nuclei in the vicinity of , with . our calculations were performed with the skyrme force sksc4 , which was determined in the etfsi-1 mass fit . for proton - deficient nuclei in the region of = 184 we find the barriers to be much hig


In this paper we explore maximal deviations of large random structures from their typical behavior

one of the principal problems in probability and statistics is the understanding of maximal deviations of averages from their means . the revolutionary work of vapnik and chervonenkis introduced a completely new combinatorial approach that opened many paths and helped us understand this fundamental phenomena . today , the vapnik - chervonenkis theory has become the theoretical basis of statistical machine learning , empirical process theory , and has applications in a diverse array of fields . the purpose of this paper is to initiate the exploration of maximal deviations of complex random structures from their typical behavior . we introduce a model for a high - dimensional random graph process and ask analogous questions to those of vapnik and chervonenkis for deviations of averages : how `` rich '' does the process have to be so that one sees atypical behavior . in particular , we study a process of erds - rnyi random graphs . in the model introduced by erds - rnyi , a graph on vertices is obtained by connecting each pair of vertices with probability , independently , at random . the model has been thoroughly studied and many of its properties are well understood see , e.g. , the monographs of bollobs and janson , uczak , and ruciski . in this paper we introduce a random graph process indexed by unit vectors in , defined as follows . for positive integer , write =\{1, , n\}$ ] . for , let be independent standard normal vectors in . denote by the collection of these random points . for each ( where denotes the unit sphere in ) and we define the random graph with vertex set $ ] and edge set , where denotes the usual inner product in . for any fixed and , is distributed as an erds - rnyi random graph , with where is the distribution function of a standard normal random variable . in particular , is a random graph . with a slight abuse of notation , we write for . we study the _ random graph process _ is a stationary process of random graphs , indexed by -dimensional

We study a process of erds - rnyi random graphs. The process is a stationary random graph with a normal distribution function in. For any fixed and, it is distributed as an erdas - random graph.

in this paper we explore maximal deviations of large random structures from their typical behavior . we introduce a model for a high - dimensional random graph process and ask analogous questions to those of vapnik and chervonenkis for deviations of averages : how `` rich '' does the process have to be so that one sees atypical behavior . in particular , we study a natural process of erds - rnyi random graphs indexed by unit vectors in . we investigate the deviations of the process with respect


We have studied the interference of degenerate quantum gases in a vertical optical lattice

atom interferometry lies at the heart of quantum mechanics because it directly reveals the wave nature of massive particles . it is also important with respect to technical applications because it can be used for precision measurements of forces and rotations . to observe the interference , an atomic beam or a trapped atomic sample is subjected to a periodic scatterer often realized with an optical lattice . the lattice probes the coherence of the atoms between neighboring lattice sites , thus leading to constructive or destructive interference , depending on the relative phase between the different paths . on a distant screen , an interference pattern is observed if the width of the initial momentum spread of the atoms in the direction of the lattice is smaller than the recoil momentum of the lattice , where is the lattice spacing . for a thermal beam this condition can be achieved by using apertures which filter out a coherent part of the beam . for a trapped sample however , the temperature of the atoms must be reduced below the recoil temperature . an optical lattice created by two counter propagating laser beams has a lattice spacing of , where is the wavelength of the laser . the recoil temperature which is associated with the recoil momentum is in general below 1 k . consequently , the experimental conditions for observing interference with trapped atoms are similar to the requirements for achieving bose - einstein condensation . it is for this reason , that the first experimental observation of the interference of trapped atoms was made with a bose - einstein condensate . being a completely coherent sample a condensate shows high contrast and good visibility . however the required momentum condition can also be achieved with other atomic samples such as thermal clouds or degenerate fermi gases . indeed our experimental results presented in this work prove that the observation of atomic interference within a trapped sample is not restricted to bose - einstein

We present a new method for observing the interference of trapped atoms in an optical lattice. This technique is used to observe the interference with a bose - einstein condensate. The experiment is performed using a spectral analysis of the atomic sample and a numerical simulation of the observed interference pattern.

we have studied the interference of degenerate quantum gases in a vertical optical lattice . the coherence of the atoms leads to an interference pattern when the atoms are released from the lattice . this has been shown for a bose - einstein condensate in early experiments . here we demonstrate that also for fermions an interference pattern can be observed provided that the momentum distribution smaller then the recoil momentum of the lattice . special attention is given to the role of interacti


On - demand creation of entanglement between distant qubits is desirable for quantum communication...

an arm of the mzi is considered to be a one - dimensional superconducting transmission line guiding microwave photons from beamsplitter i to beamsplitter ii . accordingly , each arm ( ) of the mzi hosts a one - dimensional continuum of modes the mode operators and , obeying the commutation relations =2 _{jl } (k - k')$ ] , create and annihilate photon states from the vacuum in arm of the mzi . the wave number of a photon is related to its frequency by the linear dispersion relation . in our setup each transmission line ( arm of the mzi ) is intercepted by a microwave resonator enclosing a transmon qubit . for simplicity both cavities are characterized by a single mode described by operators and . the transmon qubit inside a cavity is dispersively coupled to the cavity mode . therefore we can describe each cavity - transmon subsystem by eq . ( [ eq : qubit - cavity - hamiltonian ] ) of the main text . photons inside the cavity can leak into the transmission line and vice versa . this process is described by the coupling hamiltonian \ ] ] where characterizes the degree of hybridization between the cavity and its environment . then , photons from the transmission line , which enter the cavity , interact with the qubit inside the cavity and are re - emitted into the transmission line . this scattering process is captured by the total hamiltonian far apart from the cavities for , photons in the transmission lines are considered to be freely propagating with respect to . this suggests the definition of the time - dependent input and output fields where the operators and generate asymptotically free scattering states for . for simplicity we will omit the space coordinate in the following and consider only the point where the transmission line is connected to the cavity . as follows from standard input - output theory for cavities , the input and output fields in eqs . ( [ eq : in - state ] ) and ( [ eq : out - state ] ) obey the boundary equation here is the time - depende

We present a new method for the analysis of cavity - transmon subsystems in the microwave resonator arm of the mzi. The method is based on the hamiltonian theory and the eqs of the main text. We show that the resonsons of each cavity, which are characterized by a single mode, can be dispersed into the transmission line and vice versa.

on - demand creation of entanglement between distant qubits is desirable for quantum communication devices but so far not available for superconducting qubits . we propose an entanglement scheme that allows for single - shot deterministic entanglement creation by detecting a single photon passing through a mach - zehnder interferometer with one transmon qubit in each arm . the entanglement production essentially relies on the fact that superconducting microwave structures allow to achieve strong


Achieving and controlling strong light - matter interactions in many - body systems is of paramount...

the field of nanoplasmonics is rapidly expanding to various research fields including materials science and chemistry due to tremendous capabilities offered by modern nanofabrication techniques. outstanding control is achieved in patterning metal surfaces. such a control provides a wider accessibility to evanescent electromagnetic modes to manipulate individual atoms and molecules. being able to couple molecules to cavity modes in the strong coupling regime , i.e. when the coupling strength surpasses all damping rates , is appealing due to various applications in molecular and material science by changing and allowing one to control the optical properties of the emitters or absorbers . recently , the strong optical coupling of plasmonic and excitonic systems has been achieved for different plasmonic structures , involving both localized and propagating surface plasmon - polaritons . hybrid exciton - plasmon modes formed due to strong coupling between molecules and plasmons have been observed as upper and lower polariton branches. the separation between the branches at zero - detuning referred to as a rabi splitting determines how strong two subsystems are coupled and how quickly the energy is transferred between them . the research in exciton - plasmon systems has its origins in the physics of semiconductor microcavities , where a typical rabi splitting can easily achieve tens of mev. plasmon - sustaining nanomaterials offer significantly smaller volume of a resonant mode ( in this case surface plasmon - polaritons ) and thus higher local fields and in turn greater rabi splittings well surpassing mev mark. in this paper , we examine the light - matter interaction in the strong coupling limit by combining the bragg - plasmon ( bp ) mode of a hybrid organo - metallic colloidal array with excitonic j - aggregates dispersed on top of the grating . in order to control and maximize the rabi splitting energy , the spatial and spectral confinements of the electric field in

We study the light - matter interaction in the strong coupling limit by combining the bragg - plasmon ( bp ) mode of a hybrid organo - metallic colloidal array with excitonic j - aggregates dispersed on top of the grating. The resulting rabi splitting energy is obtained by using the spectral confinement of the electric field in the weak coupling regime.

achieving and controlling strong light - matter interactions in many - body systems is of paramount importance both for fundamental understanding and potential applications . in this paper we demonstrate both experimentally and theoretically how to manipulate strong coupling between the bragg - plasmon mode supported by a organo - metallic array and molecular excitons in the form of j - aggregates dispersed on the hybrid structure . we observe experimentally the transition from a conventional st


We study the preparation of entangled pure gaussian states via reservoir engineering

gaussian states play an essential role in continuous - variable quantum information processing . therefore , the preparation of pure gaussian states is an important task . mathematically , any pure gaussian state can be prepared beginning with the vacuum state , and then applying a gaussian unitary action whose heisenberg action is a symplectic linear transformation on the vector of quadrature operators . this method of pure gaussian state preparation is a closed - system approach . here we consider the preparation of pure gaussian states via an open - system approach . the main idea is that by engineering coherent and dissipative processes , a quantum system can be made strictly stable and will evolve into a given pure gaussian state . this approach is known as _ reservoir engineering _ it is an efficient and robust approach to driving a quantum system into a desired target quantum state . in the finite - dimensional case , the problem of pure quantum state stabilization by reservoir engineering has been studied theoretically in . in the infinite - dimensional case , the problem of preparing a pure gaussian state via reservoir engineering has recently been explored in . in this paper , we focus on the preparation of pure gaussian states via reservoir engineering . we consider an open quantum system , the time evolution of which is governed by a markovian lindblad master equation : + _{j=1}^{k} ( _{j} _{j}^ * -{2}_{j}^*_{j} -{2} _{j}^*_{j}),\ ] ] where is the density operator , is the hamiltonian operator , is a set of lindblad operators that represent the coupling of the system with its environment , and is the number of dissipative channels . for convenience , we collect all of the lindblad operators into a vector ^{}$ ] , and we call the _ coupling vector_. the lindblad master equation can typically be derived if the system is coupled weakly to a very large environment . under some circumstances , the evolution described by the lindblad master equation will be st

We consider a closed - system approach to the preparation of pure gaussian states via reservoir engineering. We consider an open quantum system, where the time evolution is governed by a markovian lindblad master equation. The coupling vector is derived from the lind Blad master, and the corresponding hamiltonian operator is a set of lind Blair operators that represent the couping of the system with its environment.

we study the preparation of entangled pure gaussian states via reservoir engineering . in particular , we consider a chain consisting of quantum harmonic oscillators where the central oscillator of the chain is coupled to a single reservoir . we then completely parametrize the class of -mode pure gaussian states that can be prepared by this type of quantum harmonic oscillator chain . this parametrization allows us to determine the steady - state entanglement properties of such quantum harmonic o


Model independent reconstructions of dark energy have received some attention

it is very timely to continue to explore the acceleration of the universe , as its discovery has very recently finally gathered the top recognition of the community . the question of whether such evolution is produced by a dark energy component or rather a manifestation of bold unknown physics remains one of the most puzzling topics in cosmology . assuming the dark energy scenario , and beyond theoretical questioning about its physical nature , it is most vital to learn to extract the best and most relevant information from current astronomical data . many methods are strongly tied to the assumption of a background cosmological model or , equivalently , of an analytical dark energy equation of state ( eos ) . such is precisely the case of the reconstruction of the hubble diagram of type ia supernovae ( sneia ) , which provided the first evidence for the acceleration of the universe . the diagram presents the corresponding distance modulus at different redhsifts and is computed from the eos itself after a convenient integration in redshift . variations of this procedure apply as well when considering other observational tests such as gamma ray bursts ( grbs ) , baryon acoustic oscillations ( bao ) or the cosmic microwave background ( cmb ) . but even though biases on final results may depend on the previously described assumptions , that route , and in particular giving a specific prescription of the eos is still the most popular data analysis method , as opposed to model independent methods ( eos free prescriptions ) for the reconstruction of dark energy . fortunately , literature sources about this alternative way to explore the accelerated universe have mounted considerably , and thus the state of the art has turned promising . in the authors present a different approach to this model independent reconstruction : the dimensionless coordinate distance and its first and second order derivatives with respect to redshift are reconstructed using a polynomial fit inside

We present a new approach to the reconstruction of the hubble diagram of type ia supernovae ( sneia ) using a polynomial fit inside the redshift. The first and second order derivatives of the dimensionless coordinate distance and its first and Second order derivative are reconstructed using a symmetric fit inside. This method is based on the assumption of an analytical dark energy equation of state ( eos ), which is still the most popular data analysis method. In particular, it is strongly tied to the assumption that.

model independent reconstructions of dark energy have received some attention . the approach that addresses the reconstruction of the dimensionless coordinate distance and its two first derivatives using a polynomial fit in different redshift windows is well developed . in this work we offer new insights into the problem by focusing on two types of observational probes : sneia and grbs . our results allow to highlight some of the intrinsic weaknesses of the method . one of the directions we foll


We prove the asymptotic formulas for the transition densities of isotropic unimodal convolution...

let be an isotropic unimodal lvy process on with the lvy khintchine exponent . in the recent paper , the estimates of the transition densities were studied under the assumption that has lower and upper matuszewska indices strictly between and . in fact , more detailed information can be obtained whenever stronger assumption about the behaviour of is imposed . namely , in , it is proved that if varies regularly at infinity with index then and where moreover , the asymptotics implies that varies regularly at infinity with index . a similar result was proved also for regularly varying at the origin . the natural question arises : what are the asymptotic behaviour and estimates of the semigroup for the endpoints . regarding estimates , the case was investigated for subordinate brownian motions in the recent paper . however , the case seems to be hardly studied . in ( * theorem 5.52 ) there are estimates of for small values of time variable for a geometric stable process , that is when for some . to the authors best knowledge the asymptotics were never studied before . this article is an attempt to fill that gap in the theory . we provide a solution for a large class of slowly varying symbols including geometric stable and iterated geometric stable cases . namely , we study processes with symbols belonging to de haan class associated with a function slowly varying at infinity , for definition see . for an isotropic unimodal lvy process on with the lvy khintchine exponent , which is equivalent to regular variation with index at the origin of the density of lvy s measure of the process ( see theorem [ thm:5 ] ) , we derive several asymptotic results describing the behaviour of the transition density and the green function . to be more precise , in section [ sec:3 ] , we prove that we also study the density of the lvy measure of the process . in particular , implies that for the green function of , if the process is transient ( what always holds if ) , we show that in parti

We study the asymptotic behaviour of a large class of slowly varying symbols including geometric stable and iterated geometric stable cases. In particular, we derive several asymtotic results describing the behaviour of the transition density and the green function.

we prove the asymptotic formulas for the transition densities of isotropic unimodal convolution semigroups of probability measures on under the assumption that its lvy khintchine exponent varies slowly . we also derive some new estimates of the transition densities and green functions .


A search for neutrino oscillations of the type has been conducted at the los alamos meson physics...

standard electroweak theory has three lepton families , each with a charged and neutral partner . it is widely accepted that lepton family number is conserved and so these families are not expected to transform into one another . the minimal theory also assumes that neutrino masses are zero , providing a natural explanation for the left - handed character of the weak interaction . in the last few years it has gradually become accepted that the standard model may well need to be extended to accept finite neutrino mass . the deficit of solar neutrinos and indications from anomalies in atmospheric neutrino events have raised expectations that neutrino oscillations may occur , implying lepton family number mixing and finite neutrino masses . a search for neutrino oscillations has been conducted with the apparatus described in this paper , both from neutrinos generated by muon decay at rest as well as those from pion decay in flight . the source is unique in that the backgrounds expected from conventional processes are very small . the liquid scintillator neutrino detector ( lsnd ) was designed to detect neutrinos originating in a proton target and beam stop at the los alamos meson physics facility ( lampf ) . the primary goal was to search for transitions from muon - type to electron - type neutrinos in two complementary ways . the lsnd experiment was proposed for this purpose in 1989 and first operated in 1993 . first results have been published on the search for the appearance of from the large flux of from muon decay at rest ( dar ) . a search is also being conducted for electron neutrinos in a dominantly beam from pions that decay in flight ( dif ) . this paper focuses on the apparatus that was used in both searches . details of the experiment are included that could not appear in a more compressed format . for the``at rest '' experimental strategy to be successful , the target had to be a copious source of in a particular energy range of interest with relatively fe

The liquid scintillator neutrino detector ( lsnd ) is designed to detect neutrinos generated by muon decay at rest and those from pion decay in flight. The experiment was designed to search for transitions from muon - type to electron -type neutrinox in two complementary ways. Both searches are performed with the same apparatus, which can be used to detect the appearance of from the large flux of from muonal decay at Rest and electron neutrintz in a dominantly beam from a proton that decay in Flight.

a search for neutrino oscillations of the type has been conducted at the los alamos meson physics facility using from muon decay at rest . evidence for this transition has been reported previously . this paper discusses in detail the experimental setup , detector operation and neutrino source , including aspects relevant to oscillation searches in the muon decay - at - rest and pion decay in flight channels .


Broad iron emission lines are observed in many accreting systems from black holes in agn and x -...

x - ray emission from compact objects can often be characterized as a mixture of two direct emission components : thermal emission from an accretion disk ( and stellar surface , in the case of neutron stars ) , and non - thermal emission that often takes a power - law form . the non - thermal or hard " emission is attributed to a a short and incomplete list of viable models for the corona includes : thermal comptonization in the innermost accretion flow ( e.g. * ? ? ? * ) , magnetic flares above the inner disk ( e.g. * ? ? ? * ) , and a mixture of processes in the base of a relativistic jet ( e.g. * ? ? ? regardless of the specific form of the corona , however , hard x - ray irradiation of the inner accretion disk is inevitable , and the reaction or reflection " spectrum has been calculated in detail ( e.g. * ? ? ? * ) . the most prominent feature of reflection is a broad iron emission line . theoretical treatments of disk reflection have advanced continually , largely driven by observational results . spectroscopic features consistent with the x - ray irradiation of the inner accretion disk have now been observed in stellar - mass black holes , massive black holes in active galactic nuclei , and x - ray binaries harboring neutron stars ( for reviews and summary papers , see , e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? disk reflection spectra are calculated in the fluid frame of the disk , and must be convolved with a relativistic blurring function to fit the spectra that are observed ( for recent examples , see * ? ? ? * ; * ? ? ? the full power of disk reflection is then harnessed : the extent to which the spectra are blurred by doppler shifts in the inner disk , and gravitational redshifts near to the compact object , can be used to measure the inner radius of the disk and black hole spin ( e.g. * ? ? ? * ; * ? ? ? * ; * ? ? ? * and references therein ) . in neutron star x - ray binaries , the inner extent of the disk can be used to set a limit on the stellar radius

We present a new method for the analysis of disk reflection spectra in the inner accretion disk. We use a simple, non - linear approach to the calculation of the x - ray emission spectrum from the disk, and compare it with the results obtained by a previous study. The spectroscopic properties of the disk reflection spectrum are discussed, including the presence of a broad iron emission line, the extent to which the spectral features are blurred by doppler shifts in the disk and gravitational redshifts near to the.

broad iron emission lines are observed in many accreting systems from black holes in agn and x - ray binaries to neutron star low - mass x - ray binaries . the origin of the line broadening is often interpreted as due to dynamical broadening and relativistic effects . however , alternative interpretations have been proposed , included broadening due to compton scattering in a wind or accretion disk atmosphere . here we explore the observational signatures expected from broadening in a wind , in


We have investigated the optical properties of a single inasp quantum dot embedded in a standing...

semiconductor quantum dots ( ods ) are called artificial atoms because of their atom - like discrete electronic structure due to quantum confinement . exciton spin confined in their structure can relax via a wide variety of interaction and/or scattering : valence band mixing , coulomb interaction with environmental charge fluctuation , nuclear spin fluctuation , and so on . in narrow bandgap semiconductor nanostructures , heavy hole - light hole mixing is enhanced by strong spin - orbit interaction . recently , research on semiconductor nanowires ( nws ) has been revived because of their great potentials for nano - scale electrical and optical devices such as quantum logic circuits , photon detectors , and photon sources for quantum information processing due to the controllability of doping , shape , position , composition , and the possibility of electrical nano - contacts with the improvements in growth and nano - fabrication technology . fast dephasing of carriers in nw structures fabricated by top - down techniques such as photolithography and electron - beam lithography is improved by the reduction of surface traps induced by defects and/or disorders with epitaxially grown bottom - up single or multi core(-shelled ) nw structures . qds embedded nws ( hereafter called nw - qd ) , i.e. combined 0-d . structures , are among of the most promising candidates for realizing single - photon detector and on - demand single - photon sources with high ( long ) coherence ( dephasing ) . emitter dephasing and polarization instability set up bit errors and debase communication distance limit when implementing phase and polarization coding quantum key distribution protocol . in this paper we investigate the transverse and longitudinal exciton spin relaxation times . the transverse exciton spin relaxation time of our nw - qd caused by fluctuation in surrounding excess charges in the nw is suppressed with decreasing excitation power , which was observed by first - order photon

We study the transverse and longitudinal exciton spin relaxation times of embedded semiconductor quantum dots ( qds ). The transversal excitonic spin relaxation time is suppressed with decreasing excitation power, which was observed by first - order photons.

we have investigated the optical properties of a single inasp quantum dot embedded in a standing inp nanowire . a regular array of nanowires was fabricated by epitaxial growth and electron - beam patterning . the elongation of transverse exciton spin relaxation time of the exciton state with decreasing excitation power was observed by first - order photon correlation measurements . this behavior is well explained by the motional narrowing mechanism induced by gaussian fluctuations of environment


Emission from active galactic nuclei is known to vary strongly over time over a wide energy band ,...

optical continuum variability is a universal property of radio - quiet agn which has been studied for several decades , but its origin is still unclear . the optical continuum emission almost certainly originates from the accretion disc , so it is natural to assume that disc variability ( e.g. through accretion rate fluctuations ) drives the optical variability . models where the variability is _ intrinsic _ to the disc , however , suffer from several problems . firstly , optical variability is seen on time - scales as short as a day , whereas accretion variability time - scales in standard accretion discs should be long in the optically - emitting regions , comparable to the viscous time - scale which can be of the order of a year or more . secondly , variations are well - correlated in different optical bands , with only short ( days ) delays between bands , in the sense that longer - wavelength variations lag shorter - wavelength variations . since local disc temperature should decrease with radius as , shorter wavelengths originate from smaller radii . therefore , in the case of inward - propagating fluctuations the long - wavelength variations lead , rather than lag , the short - wavelength variations . also , the resulting delays would be large , comparable to the radial drift time - scale , contrary to the observed day - scale delays . to account for the observed optical properties , suggested that the variability is driven by changes of the x - ray continuum which illuminates and thereby heats the disc , causing optical continuum variations . since the x - ray emission is likely to be centrally concentrated , blue bands should respond to the x - ray variations first , followed by red , with short delays corresponding to the light - travel time delay between the blue and red - emitting parts of the disc . the predicted optical time - delay scales with wavelength as , and the observed dependencies of optical continuum lags on wavelength are consistent with thi

We present a model of optical continuum variability in the accretion disc. The model is based on the x - ray emission from the disc and its dependence on the time - scales of the corresponding bands is investigated. We find that the optical variability is driven by changes of the disc x and ray continuum which illuminates and thereby heats the disc in the presence of a large number of x wavelength variations.

emission from active galactic nuclei is known to vary strongly over time over a wide energy band , but the origin of the variability and especially of the inter - band correlations is still not well established . here we present the results of our x - ray and optical monitoring campaign of the quasar , covering a period of 2.5 years . the x - ray 210 kev flux is remarkably well correlated with the optical b , v and r bands , their fluctuations are almost simultaneous with a delay consistent with


54

fig . 1 . numerically obtained order parameter along a polyacetylene chain of 80 pairs of carbon atoms for one particular ( but typical ) realization of off - diagonal disorder . the thin line does not account for lattice relaxation , the thick line does . fig . 2 . illustration of the energies of several multi - kink configurations as a function of the magnitude of the disorder fluctuation . from bottom to top ( at zero disorder ) , the curves correspond to chains with 0 to 4 soliton - antisoliton pairs .

We present a numerical analysis of the order parameter along a polyacetylene chain of 80 pairs of carbon atoms for one particular ( but typical ) realization of off - diagonal disorder. The thin line does not account for lattice relaxation, the thick line does.

54.8pt 54.8pt we show that weak off - diagonal disorder in degenerate ground state conjugated polymers results in a finite density of randomly positioned kinks ( solitons and antisolitons ) in the lattice dimerization . for realistic values of the disorder , these kinks should clearly show up in the optical and magnetic properties . for over thirty years , conjugated polymers have provided a rich field of fundamental and technological research . they belong to a large class of quasi - one - dime


We introduce a method for identifying `` twin '' type ia supernovae , and using them to improve...

type ia supernovae ( sne ia ) have a well - established history as standardized candles for cosmological distance measurements . in the late 1990s , studies of high - redshift type ia supernovae led to the discovery of the accelerated expansion of the universe a remarkable and paradigm - shifting discovery . before standardization is applied , among `` normal '' sne ia there exists a dispersion of approximately 40% . the physical source of this variation is not fully understood , but a number of methods have been developed to reduce this natural dispersion . the most established approach uses the light curve width and color as standardization parameters . sne ia with broader light curves tend to be brighter . to some degree , the color correction seems able to account for extrinsic reddening due to dust and intrinsic color differences ( presumably arising from differences in the physics of the supernova explosion ) . with these corrections , the variation in brightness drops to % , allowing precision cosmology measurements using large samples of sne ia . since the discovery of the accelerating expansion , many large type ia supernova programs have been undertaken , resulting in sufficiently large data sets that statistical errors have become subdominant to systematic errors . much of the effort in reducing systematic errors has focused on the flux calibration of sne ia at low - redshift relative to those at high redshift since this error is relatively large and there are clear , though technically challenging , means of addressing it . if the remaining dispersion of 15% were due to a statistically homogeneous process , then correction of flux calibration issues would clear the way for more large sn surveys using conventional light curve width and color standardization . however , there is ample evidence that the remaining dispersion is not statistically homogeneous . only relatively recently have significant biases correlated with host galaxy environment been uncove

We present a new method for standardizing the light curve width and color of type ia supernovae ( sne ii ) using the light curvature width and Color standardization technique. This method is based on the light - curve width, color, and light curve length parameters. The method is applied to a large sample of ssn, which has been previously used as a standard candle for cosmological distance measurements. We find that the dispersion of 15% is due to a statistically homogeneous process.

we introduce a method for identifying `` twin '' type ia supernovae , and using them to improve distance measurements . this novel approach to type ia supernova standardization is made possible by spectrophotometric time series observations from the nearby supernova factory ( snfactory ) . we begin with a well - measured set of supernovae , find pairs whose spectra match well across the entire optical window , and then test whether this leads to a smaller dispersion in their absolute brightnesse


We present a systematic observational study of the relationship between bars and boxy / peanut -...

many spiral galaxies display boxy or peanut - shaped bulges when viewed edge - on . unfortunately , statistical studies of the incidence of these objects have not used objective criteria to quantify the boxiness of the bulges , and they are therefore hard to compare and yield moderately different results . nevertheless , it seems clear that at least 20 - 30% of edge - on spirals possess a boxy / peanut - shaped ( hereafter b / ps ) bulge ( see jarvis 1986 ; shaw 1987 ; de souza & dos anjos 1987 ) . spiral galaxies with a b / ps bulge are therefore a significant class of objects . the fact that the boxy / peanut shape is seen only in edge - on spirals indicates that the shape is related to the vertical distribution of light . compared to the usual light distribution of spheroids , b / ps bulges have excess light above the plane at large galactocentric radii ( see shaw 1993 ) . furthermore , the three - dimensional ( hereafter 3d ) light distribution of b / ps bulges must be even more extreme than their projected surface brightness ( see , e.g. , binney & petrou 1985 for axisymmetric models ) . b / ps bulges also appear to rotate cylindrically , i.e. their rotation is independent of the height above the plane ( e.g. kormendy & illingworth 1982 ; rowley 1986 ) . several models have been proposed to explain the structure of b / ps bulges ( e.g. combes & sanders 1981 ; may , van albada , & norman 1985 ; binney & petrou 1985 ) . however , despite their prevalence and interesting structural and dynamical properties , b / ps bulges remain poorly studied observationally , probably because the edge - on projection makes the interpretation of observational data difficult . in this paper , we present new kinematical data for a large sample of spiral galaxies with a b / ps bulge . our main goals are to determine their 3d structure and to identify their likely formation mechanism . we use our data to show that b / ps bulges are simply thick bars viewed edge - on . in [ sec : form

We present a new kinematical model for the boxy / peanut - shaped bulge of spiral galaxies with edge - on projections. We show that the bulge is related to the vertical distribution of light, and that the shape is related with the horizontal distribution of the light. The two -dimensional ( hereafter 3d ) light distribution is also found to be even more extreme than the projected surface brightness.

we present a systematic observational study of the relationship between bars and boxy / peanut - shaped ( b / ps ) bulges . we first review and discuss proposed mechanisms for their formation , focussing on accretion and bar - buckling scenarios . using new methods relying on the kinematics of edge - on disks , we then look for bars in a large sample of edge - on spiral galaxies with a b / ps bulge and in a smaller control sample of edge - on spirals with more spheroidal bulges . we present posi


The rates for diffractive quarkonium plus prompt - photon associated production at the lhc are...

in recent years , a wide variety of small- and hard diffractive processes which are under intense study experimentally has been used to improve our knowledge about quantum chromodynamics ( qcd ) . an outstanding process is the diffractive heavy quarkonium production , where their large masses provide a natural hard scale that allows the application of perturbative qcd . there are several mechanisms proposed for the quarkonium production in hadron colliders , as the color singlet model , the color octet model and the color evaporation model . an important feature of these perturbative qcd models is that the cross section for quarkonium production is expressed in terms of the product of two gluon densities at large energies . in a similar way , the diffractive quarkonium production is also sensitive to the gluon content of the pomeron at small- and may be particularly useful in studying the different mechanisms for quarkonium production . from the experimental point of view , the heavy quarkonium production is of special significance because they have an extremely clean signature through their leptonic decay modes . as long diffractive processes are concerned , in hadron collisions they are well described , with respect to the overall cross - sections , by regge theory in terms of the exchange of a pomeron with vacuum quantum numbers . however , the nature of the pomeron and its reaction mechanisms are not completely known . a good channel is the use of hard scattering to resolve the quark and gluon content in the pomeron . such a parton structure is natural in a modern qcd approach to the strongly interacting pomeron . the systematic observations of diffractive deep inelastic scattering ( ddis ) at hera have increased the knowledge about the qcd pomeron , providing us with the diffractive distributions of singlet quarks and gluons in pomeron as well as the diffractive structure function . in hadronic collisions , we shall characterize an event as single diffractive i

We study the gluon and quark production in hadronic collisions by using the qcd deep inelastic scattering ( ddis ) method. We find that the dcd process is sensitive to the Gluon content of the pomeron at small energies, which is a good channel for studying the diffractive structure function of the interacting pomerone.

the rates for diffractive quarkonium plus prompt - photon associated production at the lhc are estimated . the theoretical framework considered in the ( or ) production associated with a direct photon at the hadron collider is the non - relativistic qcd ( nrqcd ) factorization formalism . the corresponding single diffractive cross section is computed based on the hard diffractive scattering factorization supplemented by absorptive corrections . such processes are sensitive to the gluon content o


The measured data on the nuclear modification factor for pions and reconstructed jets as well as on...

one of the formidable tasks in heavy - ion physics is to identify a precise understanding of the jet - medium dynamics , the jet - medium interactions , and the jet - energy loss formalism . below , we study the influence of the details of the jet - medium coupling and the medium background on the simultaneous description of the nuclear modification factor ( ) and the high- elliptic flow ( ) measured at rhic and lhc for a radiative pqcd energy - loss ansatz . we contrast media determined via the viscous hydrodynamic approach vish2 + 1 with the parton - cascade bamps as well as a jet - medium coupling depending on the collision energy with a jet - medium coupling influenced by the energy of the jet , the temperature of the medium and non - equilibrium effects around the phase transition . besides this , we compare the jet - energy loss based on radiative pqcd with the hybrid ads energy - loss ansatz of ref . we contrast the pion nuclear modification factor obtained via the radiative pqcd - energy loss and the hybrid ads energy - loss ansatz with a parton - jet nuclear modification factor that can be considered as an idealized lo jet at rhic and lhc energies . the pqcd - based energy loss model studied is parametrized as with the jet - energy dependence , the path - length dependence , and the energy dependence . in the following , the jet - medium coupling will depend either on the collision energy or the energy of the jet and the temperature of the background medium considered . the jet - energy loss fluctuations are distributed via , allowing for an easy interpolation between non - fluctuating ( ) , uniform dirac distributions and distributions increasingly skewed towards small . the jets are spread according to a transverse initial profile specified by the bulk flow fields given by the vish2 + 1 and bamps backgrounds considered . on the other hand , the jet - energy loss of the hybrid ads energy - loss ansatz is based on falling strings where the initial jet energ

We study the influence of the jet - medium coupling and the medium background on the simultaneous description of the nuclear modification factor ( ) and the high elliptic flow ( ), measured at rhic and lhc for a radiative pqcd energy - loss ansatz. We compare the jets with the hybrid ads energy - Loss ansatz of ref, which is based on falling strings where the initial jet energ.

the measured data on the nuclear modification factor for pions and reconstructed jets as well as on the high- elliptic flow at rhic and lhc energies are compared to results from a linear pqcd and a highly non - linear hybrid ads holographic model of jet - energy loss . we find that the high- ellitic flow requires to include realistic medium transverse flow fields and a jet - medium coupling including the effects of the energy of the jet , the temperature of the bulk medium , and non - equilibriu


The molecular outflow from iras 04166 + 2706 was mapped with the submillimeter array ( sma ) at 350...

the outflow driven by the low - luminosity ( 0.4 ) class 0 source iras 04166 + 2706 ( hereafter i04166 ) is one of the few outflows with an extremely - high - velocity component . it is also the first such source reported in the nearby taurus molecular cloud at 140 pc by . in their study , distinct velocity regimes were identified with respect to the systemic velocity of 6.7 kms ( relative to the lsr ) derived from nh(1,1 ) : the standard - high - velocity ( shv ) component corresponds to velocity displacements of 2 to 10 kms , the intermediate - high - velocity ( ihv ) component of 10 to 30 kms , and the extremely - high - velocity ( ehv ) component of 30 to 50 kms . the division is clearly demonstrated in their co = 21 spectra , where emission in the ehv regime appears to be a prominent and distinct feature from the slower shv component ( spectra of other molecular lines such as so also show distinct velocity components ; see * ? ? ? these different velocity components in the spectra were also found to have remarkably different spatial distributions . observed a series of well - collimated knots in the ehv regime lying along the outflow axis ( position angle ) , and a pair of limb - brightened conical cavity walls close to the systemic velocity . the measured opening angle of the shell is much wider than that of the collimated ehv gas , and there is no sign of momentum transfer from the jet to the ambient because the ehv knots keep an almost constant mean velocity . the velocity structure suggests that the shell can be understood as a shear flow of accelerated ambient gas moving along the cavity walls . argued that the shv shell component is unlikely accelerated by the ehv jet . an unseen wide - angle wind component may be required to explain the simultaneous presence of both components in the case of i04166 outflow . the authors pointed out that a unified wind model that naturally produces high - velocity well - collimated jet and low - velocity shell - like swep

We present a new study of the outflow driven by the low - luminosity ( 0.4 ) class 0 source iras 04166 + 2706 ( hereafter i04166 ). The outpour is driven by a high - velocity component that is characterized by limb - brightened conical cavity walls close to the systemic velocity. We find that the shell component is unlikely accelerated by the ehv jet, and that the limbs are well - collimated in the spectra.

the molecular outflow from iras 04166 + 2706 was mapped with the submillimeter array ( sma ) at 350 ghz continuum and co = 32 at an angular resolution of . the field of view covers the central arc - minute , which contains the inner four pairs of knots of the molecular jet . on the channel map , conical structures are clearly present in the low velocity range ( vv km s ) , and the highly collimated knots appear in the extremely high velocity range ( ehv , 50vv km s ) . the higher angular resolut


The cosmological model of the modified chaplygin gas interacting with cold dark matter is studied

there is increasing evidence that our universe is presently in a state of cosmic accelerating expansion . this result has been confirmed with observations via supernovae ia , cosmic microwave background anisotropies , large scale structure formation , baryon oscillations and weak lensing , etc . these observations strongly suggest that the universe is spatially flat and is dominated by an extra component with negative pressure , dubbed as dark energy . in the recent years , various candidates of dark energy have been proposed . the simplest candidate is the cosmological constant . but this scenario is plagued by the severe fine - tuning problem and the coincidence problem . other possible forms of dark energy include quintessence , k - essence , phantom , born - infeld scalars , quintom , tachyon field , holographic dark energy , and so on . additionally , the conjecture that dark energy and dark matter can be unified by using the so - called chaplygin gas ( cg ) obeying an exotic equation of state ( eos ) has been investigated in several literatures . recently , the cg model was generalized to some possible forms . as an alternative model , the eos of the generalized chaplygin gas ( gcg ) reads where . it is clear that the case corresponds to the cg . within the framework of friedmann - robertson - walker ( frw ) cosmology , this eos leads , after inserted into the relativistic energy conservation equation , to an energy density evolving as where is an integration constant . hence , we see that at early time the energy density behaves as a dust - like matter , while at late time it behaves like a cosmological constant . so the gcg model can also be interpreted as an entangled mixture of dark matter and dark energy . this dual role is at the heart of the surprising properties of the gcg model . however , these so - called unified dark matter models have been ruled out because they produce oscillations or exponential blowup of the matter power spectrum inconsistent w

We study the unified chaplygin gas ( gcg ) model in the context of friedmann - robertson - Walker ( frw ) cosmology. We find that the gg model is a generalized version of the cg model, which obeys an exotic equation of state ( eos ) and a holographic dark energy density. This eonization leads to a new unified dark matter model.

the cosmological model of the modified chaplygin gas interacting with cold dark matter is studied . our attention is focused on the final state of universe in the model . it turns out that there exists a stable scaling solution , which provides the possibility to alleviate the coincidence problem . in addition , we investigate the effect of the coupling constants and on the dynamical evolution of this model from the statefinder viewpoint . it is found that the coupling constants play a significa


[ sec : abstract ] the late - stage evolution of very massive stars such as carinae may be...

the last stages of the evolution of the most massive ( mm ) stars may be dominated by episodic large mass - ejections ( e.g. , * ? ? ? * ; * ? ? ? this leads to dust condensing out of the ejecta , obscuring the star in the optical but revealing it in the mid - infrared ( mid - ir ) as the absorbed uv and optical photons are re - emitted at longer wavelengths ( e.g. , * ? ? ? the best known example is carinae ( car ) which contains one of the most massive ( 100 - 150 ) and most luminous ( ) stars in our galaxy ( e.g. , * ? ? ? its great eruption in the mid-1800s led to the ejection of of material now seen as a dusty nebula around the star . while ongoing studies are helping us further analyze the great eruption ( see , e.g. , * ? ? ? * ; * ? ? ? * ) , deciphering the rate of such events and their consequences is challenging because no analog of this extraordinary laboratory for stellar astrophysics ( in terms of stellar mass , luminosity , ejecta mass , time since mass ejection etc . ) has previously been found . a related puzzle is the existence of the typeii superluminous supernovae ( slsn - ii ) that are plausibly explained by the sn ejecta colliding with a massive shell of previously ejected material ( e.g. , sn2006gy ; * ? ? ? a number of sne , such as the typeib sn2006jc and the typeiin sn2009ip ( e.g. , * ? ? ? * ; * ? ? ? * ; * ? ? ? * ) , have also shown transients that could be associated with mass ejections shortly prior to the final explosion . but the relationship between these transients and car or other lbvs surrounded by still older , massive dusty shells ( e.g. , * ? ? ? * ) is unclear . there are presently no clear prescriptions for how to include events like the great eruption into theoretical models . even basic assumptions such as whether the mass loss is triggered by the final post - carbon ignition phase as suggested statistically by or by an opacity phase - transition in the photosphere ( e.g. , * ? ? ? * ) or by interactions with a binary com

We present a new study of the evolution of the typeii superluminous supernovae ( slsn - ii ) in the last stages of the formation of the most massive ( mm ) stars in our galaxy. We find that the sn2006jc and the typein ssn2009ip are both found to be associated with mass ejections shortly prior to the ejecta collapse. The resulting smsn is characterized by a large, dusty nebula around the star,.

[ sec : abstract ] the late - stage evolution of very massive stars such as carinae may be dominated by episodic mass ejections which may later lead to typeii superluminous supernova ( slsn - ii ; e.g. , sn2006gy ) . however , as long as car is one of a kind , it is nearly impossible to quantitatively evaluate these possibilities . here we announce the discovery of five objects in the nearby ( mpc ) massive star - forming galaxies m51 , m83 , m101 and ngc6946 that have optical through mid - ir p