Pressure and temperature dependence of the negative thermal expansion in zn(cn) is fully...

negative thermal expansion ( nte ) is a rare and counter - intuitive phenomenon found primarily in low density materials with crystal structures that are networks of linked coordination polyhedra . the study of these materials is not only of fundamental scientific importance , but also has many technological applications such as aerospace technologies , optics , and electronics . while much effort has been put into finding new materials and investigating the origin of nte in them , much less attention has been paid to the change in nte behaviour subject to heating and stress , which holds great importance for the possible applications of the material . for example , due to stresses and heating , problems such as phase transitions of the nte filler and thermal expansion misfit between the nte filler and matrix are always encountered in designed composites with tailored thermal expansion . in this paper , we conduct a simulation study of zn(cn) focusing on the pressure and temperature effects on its negative thermal expansion . we chose this material for several reasons . firstly , zn(cn) is a well - known representative nte material . it has a framework structure consisting of tetrahedral groups of atoms linked by diatomic rods of c n and has exceptionally large isotropic nte of mk ( twice as large as that of zrwo ) . secondly , the material shows a variety of exotic properties in experiments , including reduction of its nte on heating , pressure - enhanced thermal contraction , and pressure - induced softening , none of which are fully understood . thirdly , with previous dft calculations of zn(cn) explaining the origin of nte of the material in terms of grneisen theory , it would be useful to draw a clear link between the values of the grneisen parameters in energy space and the structural vibrations in real space with full anharmonicity ( which should be important in such an nte system ) based on theoretically reproducing the aforementioned exotic properties . her

We study the effect of pressure and temperature on negative thermal expansion in zn(cn ). We find that the material exhibits an unusually large isotropic nte of mk ( twice as large as that of zrwo ) and has a very large is - shape nthe of the same size as that found in a well - known representative ne material. The result is consistent with previous calculations of nn(bn, cn and cmn ), which are based on the gr.

pressure and temperature dependence of the negative thermal expansion in zn(cn) is fully investigated using molecular dynamics simulations with a built potential model . the advantage of this study allows us to reproduce the exotic behaviours of the material , including the negative thermal expansion ( nte ) , the reduction of nte with elevated temperature , the pressure enhancement of nte and the pressure - induced softening . results of the study provide us detailed data to link the properties


Training time on large datasets for deep neural networks is the principal workflow bottleneck in a...

estimates of the data gathered by a self - driving car start from at least 750 mb / s . with proper annotation or through an unsupervised learning scheme , all of this data can become useful for training the object detection system or grid - occupancy system of a self - driving car . the resulting training set can lead to weeks or more of training time on a single cpu / gpu system . therefore , for such applications training time defines the most time consuming element of the workflow , and reduced training time is highly desirable . to achieve significant reductions in training time , the training must be distributed across multiple cpus / gpus with the goal of strong scaling : as more nodes are thrown at the problem , the training time should ideally decrease proportionally . there are two primary approaches to distributed stochastic gradient descent ( sgd ) for training deep neural networks : ( i ) synchronous all - reduce sgd based on a fast all - reduce collective communication operation , and ( ii ) asynchronous sgd using a parameter server . both approaches ( i ) and ( ii ) have weaknesses at scale . synchronous sgd is penalized by straggling processors , underutilizes compute resources , and is not robust in the face of failing processors or nodes . on the other hand , asynchronous approaches using parameter servers create a communication bottleneck and underutilize the available network resources , slowing convergence . individual researchers also have different numbers of nodes at their disposal , including compute and network resources . so determining the best approach for a given number of nodes , as well as the approach that scales to the most number of nodes , is of interest to practitioners with finite resources . we are concerned with the following questions : 1 . how fast do asynchronous and synchronous sgd algorithms converge at both the beginning of training ( large step sizes ) and at the end of training ( large step sizes ) ? 2 . how does the c

We study the convergence of distributed stochastic gradient descent ( sgd ) algorithms on a self - driving car using a parameter server. We show that sggd is a robust and efficient method for training deep neural networks, and that it can be used to train objects. In particular, we find that asynchronous all - reduce sGd is more robust than s - based ssg, which is based on symmetries.

training time on large datasets for deep neural networks is the principal workflow bottleneck in a number of important applications of deep learning , such as object classification and detection in automatic driver assistance systems ( adas ) . to minimize training time , the training of a deep neural network must be scaled beyond a single machine to as many machines as possible by distributing the optimization method used for training . while a number of approaches have been proposed for distri


The star lhs 3250 is found to be a white dwarf at a distance of 30 pc

the star lhs 3250 ( lp70 - 238 ; wd1653 + 630 ) is a faint star discovered by luyten ( 1970 ; 1976 ) to have a proper motion of 0.512 arcsec yr in a position angle of 275.2 and a color - class `` f '' . these properties indicate that it is likely to be a white dwarf , and it was observed spectroscopically by hintzen ( 1986 ) who verified it as being a white dwarf with a classification of dc9 . usno parallax observations began in 1992 , and they have now confirmed that the star has the very low luminosity of a cool white dwarf ( discussed in section 2 ) . however , in the process of measuring its colors accurately , we have found it to have a unique spectral energy distribution . optical spectra and polarization data have been obtained , and lead us to conclude that most likely it has an extremely low temperature . this conclusion is of particular interest because low - temperature , low - luminosity white dwarfs in the galactic disk can constrain the early star - formation history of the disk , and because such stars in the galactic halo potentially can contribute significant mass to the halo . in this paper , we discuss the unusual properties of this star , and attempt to arrive at a plausible description of its nature . lhs 3250 was observed with the 1.5 m strand telescope and a tektronix 2048x2048 ccd camera as part of the usno parallax program during 19921998 . this configuration gives typical errors of .5 mas in the relative parallax with 50 observations or more . lhs 3250 was observed with 84 images taken on 81 nights . the general observing and reduction procedures for the tek2048 astrometry are described by monet et al . the astrometric results are shown in table 1 . future observers should note that the coordinates given in the lhs catalogue are incorrect by 1.6 arcmin the lhs atlas has the correct star marked , and the correct coordinates are given in table 1 . also , the proper motion given in the lhs catalogue differs from that given in table 1 by much m

We present a new spectral analysis of the star lhs 3250 ( lp70 - 238; wd1653 + 630 ), which is a faint white dwarf with a proper motion of 0.512 arcsec yr in a position angle of 275.2. The spectra and polarization data are obtained from the tek2048 ccd camera, and show that it has an extremely low temperature.

the star lhs 3250 is found to be a white dwarf at a distance of 30 pc . its absolute magnitudes ( ; ) put it among the least - luminous white dwarfs known . its optical spectrum shows no features , indicating it has a dc classification , and it shows no detectable polarization , indicating it does not have a very strong magnetic field . however , its broadband colors show it to have a unique spectral energy distribution , and it stands out from all other stars in and other broadband photometric


We study the stress developed during the drying of a colloidal drop of silica nanoparticles

[ [ floating - films ] ] floating films + + + + + + + + + + + + + + polydimethylsiloxane ( pdms , sylgard 184 , dow corning ) is mixed and degassed at c to slow down the reaction and to ensure a reproducible viscosity . a silicon wafer is first coated with a 10% wt . aqueous solution of polyvinyl alcohol ( pva , sigma - aldrich , kda ) . the coating is dried until a uniform color is obtained . then , the pdms is spin coated on this wafer and placed in an oven at c for 10 hours . the edge of the coated pdms is removed to obtain a circular film of diameter mm . a petri dish , painted in black to enhance the contrast on the picture , is partially filled with deionized water . the wafer is dipped in this bath to dissolve the sacrificial layer of pva and to detach the pdms film . once the pdms film is fully detached and floats at the surface , the wafer is removed . we used a white light spectrometer ( oceanoptics usb2000 + used with a ls-1-ll tungsten halogen light source ) to measure the film thicknesses , which range between $ ] m . the presence of pva lowers the surface tension of the bath , which is mn / m . [ [ visualisation ] ] visualisation + + + + + + + + + + + + + our experiments of controlled drying of drops are performed in a transparent glove box , which has humidity controller presented in fig . [ fig : si_setup ] . the relative humidity is set to % in all of our experiments . a grid is placed in the glove box on the top of the sample and a light source is placed behind a light diffuser to obtain an even illumination . the deformation of the membrane is visualised by the distortion of the pattern made by the grid . the time evolution of the system is recorded by a nikon camera ( d7100 ) mounted with a 18 - 55 mm nikon objective ( fig . [ fig : si_setup ] ) . [ [ dialysis ] ] dialysis + + + + + + + + each suspension was dialysed to ensure that they have the same properties ( ionic strength and ph ) . dialysis bags ( 12 - 14 kda , fisherbrand ) are partially

We present a new method for the control of the drying of polydimethylsiloxane ( pdms ) films in a transparent glove box. The solution is heated to a temperature of mn / m and the film thicknesses are measured by a white light spectrometer. We show that the pvw - pva coating is a good candidate for controlling the drying process.

we study the stress developed during the drying of a colloidal drop of silica nanoparticles . in particular , we use the wrinkling instability of a thin floating sheet to measure the net stress applied by the deposit on the substrate and we focus on the effect of the particle polydispersity . in the case of a bidisperse suspension , we show that a small number of large particles substantially decreases the expected stress , which we interpret as the formation of lower hydrodynamic resistance pat


We perform a detailed investigation of total lifetimes for the doubly heavy baryons , in the...

at present a number of powerful techniques based on operator product expansion ( ope ) and effective field theories have been developed . these tools allow one consistently to include into consideration various nonperturbative contributions , written in terms of a few number of universal quantities . the coefficients ( wilson coefficients ) in front of these operators are generally expanded in series over the qcd coupling constant , inverse heavy quark mass and/or relative velocity of heavy quarks inside the hadron . the accuracy , obtained in such calculations , can be systematically improved , and it is limited only by the convergence properties of the mentioned series . the described approach have been already widely used for making the precise predictions in the heavy quark sector of standard model ( sm ) , such as decays , distributions and partial width asymmetries involving the cp violation for the heavy hadrons . the sensitivity of wilson coefficients to virtual corrections caused by some higher - scale interactions makes this approach to be invaluable in searching for a `` new '' physics at forthcoming experiments . the approach under discussion has been successfully used in the description of weak decays of the hadrons containing a single heavy quark , as carried out in the framework of heavy quark effective theory ( hqet ) , in the annihilation and radiative decays of heavy quarkonia , where one used the framework of non - relativistic qcd ( nrqcd ) , and in the weak decays of long - lived heavy quarkonium with mixed flavours .- meson was recently reported by the cdf collaboration ; see ref. for a theoretical review of -meson physics before the observation . ] the experimental data on the weak decays of heavy hadrons can be used for the determination of basic properties of weak interactions at a fundamental level , in particular , for the extraction of ckm matrix elements . the same approach is also valid for the baryons containing two heavy quarks . in a

We present a new approach to the description of weak decays of heavy hadrons in the framework of operator product expansion ( ope ) and effective field theories. The method is based on the wilson coefficients, which are generally expanded in series over the qcd coupling constant, inverse heavy quark mass and/or relative velocity of heavy qurons inside the hadron. This approach is applicable for the determination of basic properties of weak interactions at a fundamental level, in particular, for the extraction of ckm matrix elements.

we perform a detailed investigation of total lifetimes for the doubly heavy baryons , in the framework of operator product expansion over the inverse heavy quark mass , whereas , to estimate matrix elements of operators obtained in ope , approximations of nonrelativistic qcd are used . = -18 mm = -22 mm # 10= 0=0 1= 1=1 0>1 # 1 / * lifetimes of doubly heavy baryons * + a.k . likhoded , a.i . onishchenko + + _ protvino , moscow region , 142284 russia _ + b ) institute for theoretical and experime


We studied in detail the binary cluster candidates sl538 and ngc2006 in the large magellanic cloud...

the existence of gravitationally bound pairs of star clusters is important for the understanding of formation and evolution of star clusters . since the probability of tidal capture of one cluster by another one is very small ( bhatia et al . 1991 ) , we can assume that the components of a true binary star cluster have a common origin . star clusters form in giant molecular clouds ( gmcs ) ( e.g. elmegreen & elmegreen 1983 ) , but the details of cluster formation are not yet well understood . if the components of a cluster pair or multiple cluster formed simultaneously or sequentially in the same fragmenting gmc they should have similar properties like age , metallicity and stellar content . in the milky way only a few binary clusters are known , though lyng & wramdemark ( 1984 ) suggest the common origin of a group of six galactic open clusters . later pavloskaya & filippova ( 1989 ) , and more recently subramaniam et al . ( 1995 ) , propose the existence of more possible galactic binary clusters and cluster complexes . the apparent lack of binary clusters in our own galaxy may be explained in different ways . subramaniam et al . ( 1995 ) argue that since we are looking at the galaxy from inside , double clusters may be harder to detect than in the distant magellanic clouds , where binary clusters can easily be detected due to the closeness of their projected positions on the sky . the distance to the galactic clusters must also be taken into account , but only approximately 400 of 1400 open clusters have known distances ( lyng 1987 ) . subramaniam et al . ( 1995 ) found 16 galactic binary cluster candidates on the base of the lyng catalogue , which corresponds to 8 % of the investigated number of clusters . from this they conclude that binary clusters in the milky way may not be uncommon . the evolution of a gravitationally bound pair of star clusters depends on the interaction between the components as well as on the tidal forces of the parent galaxy . if the tid

We present a new method for the identification of gravitationally bound pairs of star clusters in the milky way. We use the lyng catalogue to find 16 galactic binary cluster candidates on the basis of the lng catalogue, which corresponds to 8 % of the investigated number of clusters. The results are consistent with the hypothesis that the existence of gravitationsally bound pair of star Clusters is not uncommon.

we studied in detail the binary cluster candidates sl538 and ngc2006 in the large magellanic cloud ( lmc ) . this cluster pair is located in the northwestern part of the large ob association lh77 in supergiant shell lmc4 . a third star cluster , kmhk1019 , is located within from the cluster pair . our study is the first age determination of sl538 and ngc2006 that is based on cmds . we derived an age of myr for sl538 , myr for ngc2006 , and myr for kmhk1019 . thus the three clusters are ( nearly


We derive an explicit expression for the coupling constants of individual eigenstates of a closed...

during the last years quantum chaotic scattering was a field of intense research . a great deal of the results obtained was based on the projection operator formalism due to feshbach , weidenmller and others . in this approach the scattering system is decomposed into a closed subsystem described by the internal hamiltonian with discrete bound states and a continuum of external scattering states labeled by the energy and an index corresponding to different open scattering channels . the coupling between the internal and external subsystems is then incorporated by an operator with matrix elements . the s - matrix of the complete system can be expressed in terms of these matrix elements and the hamiltonian . this relation can be cast into the form here , and are energy - dependent square matrices of dimension , and has dimension . while this setting is very general , the tools developed for the subsequent analysis of the properties of the s - matrix require additional assumptions . in particular , the energy thresholds for the opening of new scattering channels are usually neglected . as a consequence the energy dependence of the coupling matrix can be considered weak and then the s - matrix ( [ sk ] ) can be rewritten in terms of an effective non hermitian hamiltonian this canonical formalism for expressing the s - matrix is sometimes denoted as the heidelberg description of scattering , and we use this name to distinguish it from an s - matrix obtained directly , i. e.without reference to any auxiliary closed system . when the internal hamiltonian in ( [ seffh2 ] ) describes a chaotic system , it is justified to replace it by a random matrix , and by performing an average over the appropriate ensemble a statistical theory for the s - matrix is obtained which allows to calculate quantities of interest such as correlation functions or the distribution of wigner delay times and resonance poles . it was found that the results of such an approach are to a large extent ind

We present a new method for the analysis of quantum chaotic scattering in terms of an effective non hermitian hamiltonian. This method is based on the projection operator formalism due to feshbach and weidenmller. The results obtained are compared with those obtained by the projection operators, which are based upon the heidelberg description of scattering.

we derive an explicit expression for the coupling constants of individual eigenstates of a closed billiard which is opened by attaching a waveguide . the wigner time delay and the resonance positions resulting from the coupling constants are compared to an exact numerical calculation . deviations can be attributed to evanescent modes in the waveguide and to the finite number of eigenstates taken into account . the influence of the shape of the billiard and of the boundary conditions at the mouth


We demonstrate the onset of strong on - site localization in a one - dimensional many - particle...

disorder - induced localization has been one of the central problems of condensed matter physics , starting with the anderson paper . it has also attracted much attention in other physical contexts , quantum chaos being an example . recent interest in quantum computing has further emphasized its importance and allowed looking at it from a somewhat different perspective . in many proposed physical implementations of a quantum computer ( qc ) the qubit - qubit interaction is not turned off . the interaction may lead to excitation hopping from one qubit to another . however , control and measurement should be presumably performed on individual qubits . therefore it is essential to prevent excitation transfer between operations . this makes localization a prerequisite for quantum computing with perpetually coupled qubits . several approaches to quantum computing with perpetually coupled qubits have been proposed recently in a multi - excitation system like a system of interacting electrons or a qc , inter - site ( or inter - qubit ) transitions are a many - body effect , they involve several excitations . in spite of the broad interest in the problem of many - particle localization , only a limited number of analytical results has been obtained . numerical results are also limited : classical computers do not allow studying a large number of particles , because the hilbert space is exponentially large . on the other hand , qc s with perpetually coupled qubits provide a unique means for investigating localization in a controllable setting . in this paper we study strong on - site many - particle localization . it implies that each particle ( or excitation ) is nearly completely confined to one site . this is a stronger condition than just exponential decay of the wave function , and it is this condition that must be met in a qc . a well - known argument suggests that it is hard to strongly localize a disordered many - particle system where the on - site energies are rand

We study strong on - site many - particle localization in a quantum computer ( qc ) with perpetually coupled qubits. The on _ site _ energy is nearly completely confined to one site, and the on_site energies are rand. This condition is a stronger condition than just exponential decay of the wave function.

we demonstrate the onset of strong on - site localization in a one - dimensional many - particle system . the localization is obtained by constructing , in an explicit form , a bounded sequence of on - site energies that eliminates resonant hopping between both nearest and remote sites . this sequence leads to quasi - exponential decay of the single - particle transition amplitude . it also leads to strong localization of stationary many - particle states in a finite - length chain . for an _ in


We investigate the rare - earth polychalcogenide te ( =nd , sm and gd ) charge - density - wave (...

the rare - earth polychalcogenides x ( where is the rare earth element , x denotes s , se and te , and n=2 , 2.5 , 3 ) have recently attracted great interest due to their low dimensionality . among the x families are members that variously host large commensurate distortions , ordered and disordered vacancy structures , and ( small - amplitude ) fermi surface driven charge - density - wave ( cdw ) . furthermore , the discovery of a pressure - induced superconductivity state in cete competing with a cdw phase and an antiferromagnetic order makes the rare - earth tellurides an ideal system to investigate the consequences that the interplay or competition between those phases has on fermionic excitations at the fermi energy . in a broader perspective , they may help providing a deeper understanding of how superconductivity might result from such an interplay , an issue of great interest in the solid state community . the cdw state has its origin in the well - known peierls transition . peierls first pointed out that a one - dimensional metal is unstable , when turning on the electron - phonon interaction , and undergoes a metal - insulator phase transition accompanied by a lattice distortion . the new modulation of the lattice induces a periodic potential , which will be screened by the itinerant charge carriers through the formation of the charge - density - wave condensate . consequently , the opening of a ( cdw ) gap at the fermi surface ( fs ) as well as the formation of a collective density wave state are the two most relevant fingerprints , characterizing a cdw broken symmetry ground state . the cdw gap acts as an order parameter of the phase transition and its determination is of relevance in order to get more insight about the impact of the transition on the electronic properties and fermi surface , as well . optical spectroscopic methods proved to be a powerful experimental tool and were widely used over the past few decades , in order to address the electrody

We present a new method for the determination of the charge - density - wave ( cdw ) gap at the fermi surface. This technique is based on the spectral analysis of the x family and its interactions with the fermions. The results are presented in terms of the coupling between the two phases, which can be used to study the effects of the transition on the electronic properties and fermi surfaces.

we investigate the rare - earth polychalcogenide te ( =nd , sm and gd ) charge - density - wave ( cdw ) compounds by optical methods . from the absorption spectrum we extract the excitation energy of the cdw gap and estimate the fraction of the fermi surface which is gapped by the formation of the cdw condensate . in analogy to previous findings on the related te ( n=2 and 3 ) families , we establish the progressive closing of the cdw gap and the moderate enhancement of the metallic component up


How to macroscopically control the flow of heat at will is up to now a challenge , which , however...

the flow of heat is a common phenomenon in nature . however , how to macroscopically manipulate the heat flow at will remains poorly explored in the literature , which , however , is very important for human life or military uses , say , efficient refrigerators , solar cells , energy - saving buildings , or infrared camouflage . it is known that our world has been changing by _ intelligent _ electronic components or _ intelligent _ materials . here intelligent _ means that the component or material has properties that can be tuned in a controllable manner by external stimuli . for example , electronic diodes belong to intelligent electronic components , which have much lower resistance to electric current along one direction than the other ; shape memory alloys are a kind of intelligent materials , which can recover their original shapes by stimuli ( say , heating or adding an external magnetic field ) after big deformations . manipulating thermal conduction equations to achieve desired temperature distributions or heat flux patterns in thermal metamaterials is promising for thermal extensions of _ intelligent _ electronic components or _ intelligent _ materials . as a result , this manipulation might produce a unique class of intelligent thermal metamaterials , thus yielding a novel ( intelligent ) way for macroscopically controlling the flow of heat at will . for this purpose , let s trace back to the birth of transformation optics theory . in 2006 , leonhardt and pendry _ et al . _ independently established the transformation optics theory , which leads to a new concept of invisibility cloaking . such a significant progress soon enlightened a lot of scientists in different fields since it offers a powerful method for designing metamaterials with new properties like optical illusions . in essence , this theory demands the form invariance of domain equations under linear coordinate transformations . this characteristic serves as the foundation of transformation opt

We study the thermal properties of a thermal metamaterial with an invariance of domain equations under linear coordinate transformations. We find that the thermal flux patterns are determined by the form invariant of the domain equation, which is a new concept for invisibility cloaking. This theory is based on the principle of invariability of domain - equations, and it is applied to the design of thermal meta materials with new properties like optical illusions; the results show that the flow of heat can be controlled by the shape memory alloys whose shapes can be tuned.

how to macroscopically control the flow of heat at will is up to now a challenge , which , however , is very important for human life since heat flow is a ubiquitous phenomenon in nature . inspired by intelligent electronic components or intelligent materials , here we demonstrate , analytically and numerically , a unique class of intelligent bifunctional thermal metamaterials called _ thermal cloak - concentrators _ , which can automatically change from a cloak ( concentrator ) to a concentrato


The casimir and van der waals interaction between two dissimilar thick dielectric plates is...

both the casimir and van der waals interactions are the quantum phenomena caused by fluctuating electromagnetic fields . in the framework of quantum field theory , these interactions can be described through the alteration by the material boundaries of the zero - point electromagnetic energy that pervades all of space . thus , the casimir and van der waals forces are found to be closely connected with the fundamental properties of quantum vacuum ( see the original ref . and monographs ) . in the last few years the casimir interaction has been actively investigated in connection with topical applications in extra - dimensional physics ( where it provides an effective mechanism for spontaneous compactification of extra spatial dimensions ) and in the bag model of hadrons . several measurements of the casimir and van der waals forces between metal macrobodies were performed with increased precision using modern laboratory techniques . the experimental results were used to obtain stronger constraints on the yukawa - type long - range interaction , predicted by many extensions to the standard model , in the micrometer interaction range . concurrent with the fundamental applications in elementary particle physics , the use of the casimir and van der waals forces in nanotechnology , in quantum reflection and bose - einstein condensation and in noncontact atomic friction was begun . the numerous applications of the casimir and van der waals forces and the extensive experimental work impose severe demands on the accuracy of theoretical predictions . the basic theory of these forces acting between real materials was developed by e. m. lifshitz and his collaborators . it expresses the free energy and force acting between two macrobodies in terms of their frequency - dependent dielectric permittivities . the original derivation of the lifshitz formulas for the free energy and pressure between two thick dielectric plates is based on the concept of a fluctuating electromagnetic f

We present a new theory of the casimir and van der waals forces between metal macrobodies. The theory is based on the concept of a fluctuating electromagnetic field, which is a quantum phenomena caused by fluctuations in the electromagnetic field that pervades all of space. It is shown that the force acting between two metal macrobody is dependent on the dielectric permittivities of the dipoles.

the casimir and van der waals interaction between two dissimilar thick dielectric plates is reconsidered on the basis of thermal quantum field theory in matsubara formulation . we briefly review two main derivations of the lifshitz formula in the framework of thermal quantum field theory without use of the fluctuation - dissipation theorem . a set of special conditions is formulated under which these derivations remain valid in the presence of dissipation . the low - temperature behavior of the


In 2001 astumian published a very simple game which can be described by a markov chain with...

the present note was initiated by the revisited astumian s paradox . in august 2004 piotrowski and sladowski asserted that astumian s analysis was flawed . however , as shown by astumian , this statement was wrong . since the analysis of the problem in a slightly more general frame than it was done earlier could be a good exercise for graduate students , we came to the conclusion that it might be useful to publish our elementary considerations about the properties of markov chains corresponding to astumian type games . for entirely didactic reasons , in sections ii and iii we present a brief summary of definitions and statements which are needed for the analysis of the astumian type markov chains . in section iv we analyze the properties of such chains and determine the probabilities of losing and winning . conclusions are made in section v. let be a finite set of positive integers , and be a set of non - negative integers . denote by the random variable which assumes the elements of . we say that the sequence forms a markov chain if for all and for all possible values of random variables the equation is fulfilled . if then the process is said to be in _ state _ at the th ( discrete time instant ) step . the states define _ the space of states _ of the process . the probability distribution of the random variable is called the _ initial distribution _ and the conditional probabilities are called _ transition probabilities_. if and , then we say that the process made a transition at the th step . the markov chain is _ homogeneous _ if the transition probabilities are independent of . in this case we may write and it obviously holds that in what follows we shall consider only homogeneous markov chains . we would like to emphasize that the transition probability matrix which is a _ stochastic matrix _ , and the initial distribution determine the random process uniquely . for the sake of simplicity , we assume that the process is a random walk of an abstract object , ca

We consider the astumian type markov chains corresponding to astUMian types of games. In this paper we discuss the properties of such chains and determine the probabilities of losing and winning.

in 2001 astumian published a very simple game which can be described by a markov chain with absorbing initial and final states . in august 2004 piotrowski and sladowski asserted that astumian s analysis was flawed . however , as was shown by astumian , this statement was wrong . in this comment the properties of markov chains corresponding to games that are more general than that studied by astumian , are investigated .


We show that under certain symmetry , the images of complete harmonic embeddings from the complex...

let and be oriented surfaces with metrics and , where and are local complex coordinates of and , respectively . a map from to is harmonic if and only if satisfies the hopf differential of a map between these surfaces is defined by . if is harmonic , then it is well - known that is a holomorphic quadratic differential on . the -_energy density _ and -_energy density _ of are defined by in terms of the -_energy density _ and -_energy density _ , the energy density and jacobian of can be written as in this paper , we are interested in the case that , , and that is an orientation preserving open harmonic embedding . in this case , the jacobian is strictly positive , i.e. , , and hence . therefore , one can consider the -energy metric on the complex plane . as mentioned in the introduction , is called _ complete _ if its -energy metric is a complete metric on . as the completeness is only defined for orientation preserving , the term _ complete harmonic open embedding _ implies implicitly that the harmonic embedding is orientation preserving . it was shown in that for each holomorphic quadratic differential which is not identically zero , there is a complete harmonic open embedding , unique up to conformal transformations , such that the hopf differential of is exactly . let be a holomorphic quadratic differential on , which is given in local coordinate as , where is in general a holomorphic function . for any with , there is a choice of a continuous branch of in a neighborhood of . then for a given base point sufficiently close to , the mapping is univalent in possibly a smaller neighborhood of in . this defines local charts on and determines two measured foliations on with singularities at the zeros of . in particular , the leaves of them are curves given locally by the sets , each and is called a _ horizontal trajectory _ and _ vertical trajectory , _ respectively . the foliations formed by these curves are called _ horizontal foliation _ and _ vertical foliation _ co

We study the holomorphic quadratic differential on which is given in local coordinate as, where is in general a holographic function. For each holotic quadrastic differential which is not identically zero, there is a complete harmonic open embedding, unique up to conformal transformations. This allows us to determine two measured foliations on with singularities at the zeros of.

we show that under certain symmetry , the images of complete harmonic embeddings from the complex plane into the hyperbolic plane is completely determined by the geometric information of the vertical measured foliation and is independent of the horizontal measured foliation of the corresponding hopf differentials . in this paper , we find a new explicit relation between the image of harmonic embeddings , with certain symmetry , from the complex plane into the hyperbolic plane and the metric of t


We present ccd photometry for stars in the nuclei of the young double cluster and persei

the precise determination of galactic open clusters main physical parameters plays a central role in the study of the stellar structure and evolution . with accurate photometric data , and once the external variables such as reddening are corrected for , the cluster distances , ages and chemical abundances can be inferred from the study of the photometric colour - magnitude and colour - colour diagrams . the usual way to obtain the cluster age is by means of isochrone fitting to the main sequence in a colour - magnitude diagram . in the case of young clusters -younger than 50 myr- isochrone fitting is made difficult by the usual presence of differential reddening across the cluster face , which widens the observed main sequence . moreover , the presence of emission line stars , like be o pms stars , which occupy anomalous positions in the photometric diagrams , additionally contributes to a further main sequence widening . hence , the fit of a particular isochrone can be a very uncertain process , and it is not difficult to find recent age determinations with very diverging values for a given young cluster . in a recent paper , fabregat & torrejn ( ) propose the use of isochrone fitting in the plane of the photometric system as an adequate tool to obtain accurate cluster ages . the range of variation of the index along the b - type sequence amounts more than 1 mag . , being significantly larger than most common used photometric colours . moreover , the index is less affected by reddening , and allows an efficient segregation of emission - line stars . in order to produce accurate and homogeneous dating for a sample of young galactic clusters , we have undertaken an observational programme to obtain ccd photometry . in this paper we present the first results , related to the clusters and persei . the double cluster and is one of the richest young open clusters in the galaxy , and also one of the brightest and closest to us . on a clear night , far from the light poll

We present the first results of a new observational programme to obtain ccd photometry for a sample of young galactic clusters. The two - type cluster is one of the richest young open clusters in the galaxy, and also one of brightest and closest to us. On a clear night, far from the light poll, near the light - poll.

we present ccd photometry for stars in the nuclei of the young double cluster and persei . we find that the reddening is highly variable through the per nucleus , increasing from west to east , with values ranging from in the western part to in the south - east . towards per the reddening is fairly constant , with . both clusters share a common distance modulus of 11.7.1 mag . , and an age of years .


Parton cascade models ( pcm ) , which describe the full time - evolution of a system of quarks and...

recent data from the relativistic heavy - ion collider ( rhic ) at brookhaven have provided strong evidence for the existence of a transient quark - gluon - plasma ( qgp ) with the properties of a near ideal fluid and high opacity . the discovery of the qgp has been anchored by the measurement of elliptic flow and the suppression of particles with high transverse momentum , jet quenching . the suppression of high hadrons as measured at rhic is a key signature of the formation of a qgp and of the modification of jets , collections of collimated high momentum particles , by this matter . the modification of hard probes provides an opportunity to learn about the physical properties of the qgp . it has been shown that elastic energy loss is insufficient to entirely account for the fivefold suppression of high momentum partons as seen in the rhic data . medium induced radiation must therefore play an important part in this process , furthermore at high probe energies quantum effects can not be neglected . the lpm effect is a quantum modification to the radiation of highly energetic particles passing through amorphous matter . at high energies forward scattering momentum transfers will be small and so the wavefunction of the particle will probe long distances in the material . interactions with the medium can no longer be treated as single scatterings . instead interactions with collections of scattering centers must be treated coherently . this gives rise to interference effects which suppress the radiation spectrum . in the non - abelian lpm effect it is the rescattering of bremsstrahlung gluons with medium particles which leads to the dominant interference process . during emission collinear soft gluons are indistinguishable from their parent partons for some period , which can be characterized by a formation time . if this time becomes longer than the mean free path , i.e small emission angles and soft radiation , the gluon will interact coherently with additional sca

We present a new study of the formation of a transient quark - gluon - plasma ( qgp ) at brookhaven. The lpm effect is a quantum modification to the radiation of highly energetic particles passing through amorphous matter. It is shown that the rescattering of bremsstrahlung gluones with medium particles leads to the dominant interference process.

parton cascade models ( pcm ) , which describe the full time - evolution of a system of quarks and gluons using pqcd interactions are ideally suited for the description of jet production , including the emission , evolution and energy - loss of the full parton shower in a hot and dense qcd medium . the landau - pomeranchuk - migdal ( lpm ) effect , the quantum interference of parton wave functions due to repeated scatterings against the background medium , is likely the dominant in - medium effe


We have identified four circumstellar disks with a deficit of dust emission from their inner 15 -...

the evolutionary processes transforming massive , gas - rich circumstellar disks into tenuous , gas - poor debris disks are still not well understood . during this crucial interval , planets form and the remaining disk material is accreted or dispersed . the path by which this transition proceeds remains uncertain . do disks clear uniformly throughout via grain growth and settling or is the process accelerated in the inner regions forming gaps ( e.g. ) ? evidence of dust clearing should be visible in the infrared ( ir ) spectral energy distribution ( sed ) . the _ spitzer space telescope _ , with its wide wavelength coverage and increased sensitivity , is starting to reveal a new population of disks with unusual seds . lack of mid - ir excess emission from disks has been interpreted as a sign of dust clearing since the first disk seds were observed with iras . further examples and some spectra ( e.g. hd 100546 , ) were obtained of a few herbig ae / be stars with the iso satellite . in this paper , we designate disks with this characteristic missing mid - ir emission as ` cold disks ' due to the lack of emission from warm dust . these seds morphologically fall between the seds of classical optically thick disks , which show excess emission throughout the ir , and debris disks characterized by very weak far - ir excesses , leading them to be considered as transitional objects between the two classes . spitzer spectra are particularly important to characterize the sharp rise , since they cover the critical 8 - 30 range . the earliest example discovered with spitzer was coku tau 4 modelled to have an inner hole within 10 au ( , ) . three additional t tauri stars , tw hya , gm aur and dm tau , have been identified as also containing cleared inner regions . one of the most exciting proposed explanations for these cold disks is that a planet has cleared a gap in the disk and thus that these inner holes may trace the presence of planetary systems . in this paper we present

We present a new class of disks with unusual mid - ir emission, characterized by a lack of mid / irared emission from warm dust. The disks are characterized in the presence of a gap in the disk and a planet has cleared a hole within 10 au. We find that these disks have a very low - energy spectra, which are consistent with the hypothesis that a star has cleared an inner hole within the disk.

we have identified four circumstellar disks with a deficit of dust emission from their inner 15 - 50 au . all four stars have f - g spectral type , and were uncovered as part of the spitzer space telescope `` cores to disks '' legacy program infrared spectrograph ( irs ) first look survey of pre - main sequence stars . modeling of the spectral energy distributions indicates a reduction in dust density by factors of 100 - 1000 from disk radii between .4 and 15 - 50 au , but with massive gas - ric


Planetary nebulae ( pn ) represent the evolutionary fate of the asymptotic giant branch ( agb )...

planetary nebulae ( pn ) represent the fate of ejected envelopes of asymptotic giant branch ( agb ) stars , while their central stars ( cs ) are the remnants of the agb cores . single ( or detached binary ) stars with 1 m is the mass on the main sequence ] evolve through the agb , and eventually eject their envelope . the central star temperature increases after the envelope ejection , until it is high enough for hydrogen to be ionized , giving birth to a pn . planetary nebulae are characterized by their emission spectra , with the brightest lines corresponding to the balmer series and the forbidden [ o iii ] lines , thus they are easy to detect and to identify even in outer galaxies . the duration of the pn phase is extremely short if compared with any stellar evolutionary phase , since pn evolve on a dynamical rather than nuclear time scale . these circumstances contribute to make pn excellent probes of the recent past of the agb stars they evolved from . the spectra of pn may be analyzed relatively easily to determine their chemical abundances . the impact of pn chemistry is twofold : first , nebular abundances of elements that are expected to vary with the evolution of low- and intermediate - mass stars allow to use pn as probes of agb stars as actors , and to determine the impact of agb evolution within the hosting galaxy ; second , the study of elements that are invariant with respect to the evolution of low- and intermediate - mass stars enable pn to be used as probes of the environment at the time of progenitor formation . with the current technology , applications concerning the use of pn to determine the chemical impact of agb stars are feasible in the galaxy and the magellanic clouds . beyond that , a few studies of extragalactic pn spectroscopy are setting the stage for future endeavors . in this paper i review the most recent and homogeneous data sets of pn abundances , including galactic disk , bulge , and magellanic cloud pn . a study of these abundan

We present the latest data on planetary nebulae ( pn ) in the symmetries of the agb core. The p - spectra of png are analyzed to determine their chemical abundances. We find that the n - line emission spectrometer is sensitive to the presence of a large number of elements, and that the emission spectrometer can be used as a tool for determining the chemical abundance of planetary stars.

planetary nebulae ( pn ) represent the evolutionary fate of the asymptotic giant branch ( agb ) stellar envelopes , thus are ideally suited to study the chemical impact of agb stars . stellar evolution predict elemental enrichment through the agb evolution , and convective dredge - up episodes allow the products of stellar evolution to reach the stellar outer layers . planetary nebulae are probes of these processes , and are also probes of the environment at the time of formation of their progen


In physics there are two masses , the gravitational and inertial , and an open question : what is...

inertial forces appear in a non - inertial reference system . but what determines an inertial reference system ? according to newton , an inertial reference system is a system that moves at a constant velocity with respect to the absolute space . according to mach s principle , inertial reference system is a system that moves with constant velocity with respect to the distant stars . if the rest of the universe determines the inertial frame , it follows that inertia is not an intrinsic property of the matter , but arises as a result of the interaction of matter with the rest of the matter in the universe . alfred einstein was inspired by mach s principle . the general theory of relativity attempted to interpret inertia , considering that it is the gravitational effect of the whole universe , but as pointed out by einstein , it failed to do so [ 1 ] . einstein showed that the field equation of general relativity implies that an object in an empty universe has inertial properties . following mach s principle , dennis sciama in a paper in 1952 attempted to interpret inertia using a model where gravitational forces are described by equations similar to maxwell equations [ 2 ] . in this paper , the inertia of an accelerating object is an inductive effect of all other objects of the universe and the principle of equivalence is a result of the theory and need not be introduced axiomatically . but no answer was given to the question of how inertial forces appear exactly at the time when a body is accelerating . in electrodynamics inertia has the name radiation reaction . in an attempt to explain the radiation reaction in 1945 wheeler and feynman created a new theory , the absorber theory of radiation [ 3][4 ] . according to this theory , the radiation reaction in an accelerated charge comes from all other charges in the universe and travels with advanced waves , waves that propagate from the future to the past , to reach the charge exactly the moment when it starts accelera

We study the inertia of a charged object in an accelerated charge and show that it is an inductive effect of all other objects of the universe. We also discuss the implications of this theory for the theory of electromagnetic radiation.

in physics there are two masses , the gravitational and inertial , and an open question : what is the relation between these two masses ? the answer to that must pass through the explanation of inertia . in the experiments that have been made , it has been shown that the ratio of inertial mass to gravitational mass of an object is constant and equal for each material . this has led through the general theory of relativity in responses which led to dramatic predictions confirmed experimentally .


= 0

in recent years , the anti - de sitter / conformal field theories ( ads / cft ) correspondence , which can connect a strongly correlated system in a -dimensional flat spacetime with a ( )-dimensional asymptotic ads spacetime , has been used to provide some meaningful theoretical insights in order to understand the mechanism of the high temperature superconductors from the gravitational dual ; for reviews , see refs . and references therein . it was found that the so - called holographic superconductor model , which admits black holes with scalar hair at low temperatures ( superconducting phase ) but without scalar hair at high temperatures ( normal phase ) , turns out to be quite successful in giving the qualitative features of the s - wave superconductivity . introducing an yang - mills field into the bulk , where a gauge boson generated by one generator is dual to the vector order parameter , the authors of ref . presented a holographic realization of p - wave superconductivity . interestingly , ref . constructed a new holographic p - wave superconductor model by introducing a charged vector field into an einstein - maxwell theory with a negative cosmological constant , which is a generalization of the model with a general mass and gyromagnetic ratio . in refs . , the holographic d - wave superconductivity was realized by introducing a charged massive spin two field propagating in the bulk . the aforementioned works on the gravitational dual models of the superconductorlike transition focus on the vanishing spatial components of the gauge field on the ads boundary . since the supercurrent in superconducting materials is very important in condensed matter systems , it is worthwhile to construct the corresponding holographic superfluid models by turning on the spatial components of the gauge field according to the ads / cft correspondence . performing a deformation of the superconducting black hole , i.e. , turning on a spatial component of the gauge field that only

We present a new holographic superfluid model for the gravitational dual of black holes with scalar hair at low temperatures ( superconducting phase ) but without scaar hair in high temperatures ( normal phase ). The hologram is constructed by introducing a charged vector field into an einstein - maxwell theory with a negative cosmological constant, which is a generalization of the model with a General mass and gyromagnetic ratio.

= 0.6 cm * abstract * we construct the holographic p - wave superfluid in gauss - bonnet gravity via a maxwell complex vector field model and investigate the effect of the curvature correction on the superfluid phase transition in the probe limit . we obtain the rich phase structure and find that the higher curvature correction hinders the condensate of the vector field but makes it easier for the appearance of translating point from the second - order transition to the first - order one or for


Recent experiments find the signal of giant nonlocal resistance in h - shaped graphene samples due...

nonlocal measurement refers to the detection of a voltage signal outside the path , along which charge current is expected to flow . one way to generate the nonlocal voltage is to modify the charge current path away from the classic ohmic mode . for instance , in the quantum hall regime , the current transports along edges while the bulk is insulating . another important way for the generation of the nonlocal voltage is to induce current with other degrees of freedom ( i.e. spin / valley ) , so that the current direction will deviate from the exciting field . since the nonlocal voltage always originates from nontrivial physics that is not easy to detect directly , the nonlocal measurement has now become a powerful tool to discover such kinds of electromagnetic phenomena in many novel materials . spin hall effect ( she ) is a phenomenon arising from the spin - orbit coupling in which charge current passing through a sample leads to spin transport in the transverse direction . since only the electron spin , rather than the electron charge , accumulates during the spin transport process , it is always difficult to observe the she with local measurements . fortunately , with the method of nonlocal measuring , a large nonlocal resistance was reported near the dirac point in h - shaped graphene sample , which confirms the existence of the she . moreover , the nonlocal measurement was also used to detect valley hall effect ( vhe ) , whose transport mechanism is similar to the she , and a giant nonlocal resistance can be observed as well . abanin et al . developed a theory to discuss the origin of the above - mentioned nonlocal resistance . in their paper , they demonstrated that the relationship between the nonlocal resistance and the local resistance can be described by a simple function of , where is the spin hall conductance . however , this equation remains difficult to explain some experimental results . specifically , besides the giant peak of , people also find anot

We present a theory for the nonlocal resistance of graphene in which the spin hall conductance is determined by the local resistance and the spin - orbit coupling. The non local resistance is derived from the equation of where is the spin Hall conductance, and the local resistivity is calculated by the function of, where is anot.

recent experiments find the signal of giant nonlocal resistance in h - shaped graphene samples due to the spin / valley hall effect . interestingly , when the fermi energy deviates from the dirac point , decreases to zero much more rapidly compared with the local resistance , and the well - known relation of is not satisfied . in this work , based on the non - equilibrium green s function method , we explain such transport phenomena in the h - shaped graphene with rashba spin - orbit coupling .


Photonic events with large missing energy have been observed in collisions at centre - of - mass...

we describe measurements and searches using a data sample of photonic events with large missing energy collected in 1997 with the opal detector at lep . the events result from collisions at centre - of - mass energies of 130.0 , 136.0 and 182.7 gev with integrated luminosities of 2.35 , 3.37 and 54.5 pb , respectively . the present paper complements our recent publication of results from earlier data samples consisting of a total of 25 pb at centre - of - mass energies of 130 , 136 , 161 and 172 gev . results on photonic events without missing energy at 183 gev are presented in a separate paper . recent measurements of photonic event production have also been made by the other lep collaborations at centre - of - mass energies above the w pair threshold , including new results at 183 gev . related searches in collisions have been reported in . the interest in the 1997 data is twofold . the main motivation is that the large data set at a higher centre - of - mass energy ( 183 gev ) gives discovery potential in a new kinematic regime . additionally , the lower energy data sets allow the experiment at 130 and 136 gev to be repeated leading to a check of our previous results which indicated an excess of events with acoplanar photons . the single - photon and acoplanar - photons search topologies presented here are designed to select events with one or more photons and significant missing transverse energy , indicating the presence of at least one neutrino - like invisible particle which interacts only weakly with matter . the event selections for these search topologies are similar to those used in our recent publication . the main changes are improvements in the rejection of backgrounds from cosmic ray interactions which allow for an increased kinematic acceptance of the single - photon topology . the single - photon search topology is sensitive to neutral events in which there are one or two photons and missing energy which , within the standard model , are expected fr

We describe measurements and searches using a data sample of photonic events with large missing energy collected in 1997 with the opal detector at lep. The events result from collisions at centre - of - mass energies of 130.0, 136.0 and 182.7 gev with integrated luminosities of 2.35, 3.37 and 54.5 pb. Results on photonic événements without missing energy at 183 gev are presented in a separate paper.

photonic events with large missing energy have been observed in collisions at centre - of - mass energies of 130 , 136 and 183 gev collected in 1997 using the opal detector at lep . results are presented for event topologies with a single photon and missing transverse energy or with an acoplanar photon pair . cross - section measurements are performed within the kinematic acceptance of each selection . these results are compared with the expectations from the standard model process + photon(s )


We introduce and investigate a class of complex semi - infinite banded toeplitz matrices satisfying...

with a laurent series with complex coefficients , one can associate a semi - infinite toeplitz matrix whose elements are given by in the theory of toeplitz matrices , is referred to as the symbol of . according to what properties of are of interest , the class of symbols is usually further restricted . for the spectral analysis of , the special role is played by the wiener algebra which consists of symbols defined on the unit circle whose laurent series is absolutely convergent for . in this case , is a bounded operator on the banach space , for any , and its spectral properties are well - known , see . rather than actual spectrum of , this paper focuses on an asymptotic spectrum of , meaning the set of all limit points of eigenvalues of matrices , as , where denotes the principal submatrix of . an intimately related subject concerns the asymptotic eigenvalue distribution of toeplitz matrices for which the most complete results were obtained if the symbol of the matrix is a laurent polynomial . more precisely , one considers symbols of the form for which the toeplitz matrix is banded and is not lower or upper triangular . this subject has an impressive history going a century back to the famous work of szeg on the asymptotic behavior of the determinant of for . the most essential progress was achieved by schmidt and spitzer who proved that the eigenvalue - counting measures where are the eigenvalues of ( repeated according to their algebraic multiplicity ) and the dirac measure supported at , converge weakly to a _ limiting measure _ , as . recall that converges weakly to , as , if and only if for every bounded and continuous function on . the measure is supported on the _ limiting set _ the limit which appears above exists , see or ( * ? ? ? moreover , schmidt and spitzer derived another very useful description of which reads where are ( not necessarily distinct ) roots of the polynomial arranged in the order of increase of their absolute values , i.e. , ( if there

We study the asymptotic spectrum of, where are the eigenvalues of ( repeated according to their algebraic multiplicity ) and the dirac measure supported at. We find that the limiting set is supported on the limit which appears above exists.

we introduce and investigate a class of complex semi - infinite banded toeplitz matrices satisfying the condition that the spectra of their principal submatrices accumulate onto a real interval when the size of the submatrix grows to . we prove that a banded toeplitz matrix belongs to this class if and only if its symbol has real values on a jordan curve located in . surprisingly , it turns out that , if such a jordan curve is present , the spectra of all the submatrices have to be real . the la


We present _ xmm - newton _ observations of the _ chandra _ -detected nuclear x - ray source in ngc...

the past decade has seen extraordinary growth in our understanding of supermassive black holes ( smbhs ) , with secure detections , mass measurements and new demographic information ( see and references therein ) . knowledge of the mass function of smbhs directly affects our understanding of smbh formation and growth , nuclear activity , and the relation of smbhs to the formation and evolution of galaxies in hierarchical cold dark matter models ( e.g. , ) . the cumulative mass function needed to explain the energetics of high redshift quasars implies that all galaxies in the local universe should host a smbh ( e.g. , , ) . observationally , however , we do not know whether every galaxy hosts a smbh . traditional methods of finding smbhs , viz . stellar dynamics and gas dynamics are powerful only at the high - mass end of the smbh mass function : the bh sphere of influence can not be resolved for bh masses less than m beyond a distance of a couple of mpc , even with _ hst _ ( ) . one way , and perhaps the most efficient way to find smbhs in galaxies is to look for active smbhs . in fact , looking for agn activity is perhaps the only viable way to probe the low - mass end of the local smbh mass function . x - ray observations provide the best opportunity for this purpose because x - ray emission is an ubiquitous property of agns and x - rays can penetrate obscuring material that might hide an agn at other wavelengths . indeed , x - ray observations have detected agn activity in what were thought to be `` normal '' galaxies in clusters ( e.g. , ) and in the field ( e.g. , ) . in an effort to study the demographics of local smbhs , we had undertaken a _ chandra _ program to look for nuclear x - ray sources in nearby optically `` normal '' spiral galaxies ( within 20mpc ) . this program was highly successful ; we discovered agns in the nuclei of what were thought to be `` normal '' galaxies ( , , ; see also ; ) . the nuclear x - ray sources , however , could be stars , b

We present a new method for finding supermassive black holes ( smbhs ) in clusters and clusters. The method is based on x - ray observations of galaxies with agn activity at the low - mass end of the local s - function. We find that the sst - ( ) - emission is a very effective way to detect a s.

we present _ xmm - newton _ observations of the _ chandra _ -detected nuclear x - ray source in ngc 4561 . the hard x - ray spectrum can be described by a model composed of an absorbed power - law with = 2.5 , and column density atoms . the absorption corrected luminosity of the source is l(0.2 - 10.0 kev ) ergs s , with bolometric luminosity over ergs s . based on the spectrum and the luminosity , we identify the nuclear x - ray source in ngc 4561 to be an agn , with a black hole of mass m m .


Exploiting a relationship between closed geodesics on a generic closed hyperbolic surface and a...

one motivation for this work came from two well - known conjectures : ( the hyperbolic ehrenpreis conjecture)(, ) let and let be two closed hyperbolic surfaces . then there exists finite - sheeted locally isometric covers of ( for ) such that there is a bi - lipschitz homeomorphism between and . attempting to understand these conjectures led to the study of immersions of three - holed spheres into -manifolds and cross products ; we would like to glue such immersions together to obtain an immersion of a closed surface or with tight control on its geometric structure . [ cnj : singlesurface ] given , for sufficiently large , does there exist a finite sheeted cover such that admits a pair of pants decomposition , every geodesic of which has length in ? another motivation for the present work comes from a desire to `` bridge the gap '' between two research areas : group growth and subgroup growth . the former concerns itself with the asymptotic number of elements in a given group of word length less than , the latter with the asymptotic number of subgroups with finite index less than . is there something in between ? among other things , here we study the asymptotic number of conjugacy classes of 2-generator subgroups of a surface group satisfying certain geometric conditions with the aim ( not yet realized ) of amalgamating these subgroups together to obtain finite index subgroups with geometric constraints . let be a fixed closed hyperbolic surface . regard as the quotient space where is a fixed lattice in the group of all orientation - preserving isometries of the hyperbolic plane . let be an arbitrary unit vector in the unit tangle bundle . consider the geodesic segment of length tangent to with based at its midpoint . if the tangent vectors at the endpoints are close then a short segment can be adjoined to it to obtain a closed path in . the closed geodesic in the homotopy class of this path is very close to the original segment . a calculation we will use often qu

We study the asymptotic number of conjugacy classes of 2-generator subgroups of a closed hyperbolic surface with finite index less than. We consider the as -manifolds and cross products in the homotopy class of the closed geodesic segment of length tangent to with based at its midpoint. The tangential vectors at the endpoints are close to the original segment, which is very close to.

exploiting a relationship between closed geodesics on a generic closed hyperbolic surface and a certain unipotent flow on the product space , we obtain a local asymptotic equidistribution result for long closed geodesics on . applications include asymptotic estimates for the number of pants immersions into satisfying various geometric constraints . also we show that two closed geodesics of length close to chosen uniformly at random have a high probability of partially bounding an immersed -holed


Higher orders in perturbation theory require the calculation of feynman integrals at multiple loops

symbolic summation amounts to finding a closed - form expression for a given sum or series . systematic studies have been pioneered by euler , and for specific sums , exact formulae have been known for a long time . today , general classes of sums , for example harmonic sums , have been investigated ( see e.g. refs . ) and symbolic summation has further advanced through the development of algorithms suitable for computer algebra systems . here , the possibility to obtain exact solutions by means of recursive methods has lead to significant progress , for instance in the summation of rational or hypergeometric series , see e.g. ref . . in quantum field theory , higher - order corrections in perturbation theory require the evaluation of feynman diagrams , which describe real and virtual particles in a given scattering process . in mathematical terms , feynman diagrams are given as integrals over the loop momenta of the associated particle propagators . these integrals may depend on multiple scales and are usually divergent , thus requiring some regularization . the standard choice is dimensional regularization , i.e. an analytical continuation of the dimensions of space - time from 4 to , which keeps underlying gauge symmetries manifest . analytical expressions for feynman integrals in dimensions may lead to transcendental or generalized hypergeometric functions , which have a series representation through nested sums with symbolic arguments . the main computational task is then to obtain the laurent series upon expansion of the relevant functions in the small parameter . the basic recursive definition of nested sums is given by where generally all . the sum of all is called the weight of the sum , while the index denotes the depth . this definition actually includes as special cases the classical polylogarithms , nielsen functions , multiple and harmonic polylogarithms in their series representations . for all , the above definition reduces to harmonic sums and , if

We present a new method for the analysis of symbolic summation in quantum field theory. It is based on the recursive approach to the feynman diagrams, which are given as integrals over the loop momenta of the associated particle propagators. The method is characterized by an analytical continuation of the dimensions of space - time from 4 to, where the weight of the sum is called the weight and the index denotes the depth. We show that the nested sums can be obtained by using the dimensional regularization algorithm.

higher orders in perturbation theory require the calculation of feynman integrals at multiple loops . we report on an approach to systematically solve feynman integrals by means of symbolic summation and discuss the underlying algorithms . examples such as the non - planar vertex at two loops , or integrals from the recent calculation of the three - loop qcd corrections to structure functions in deep - inelastic scattering are given .


Extended numerical simulations of threshold models have been performed on a human brain network...

theoretical and experimental research provides many signals for the brain to operate in a critical state between sustained activity and an inactive phase . critical systems exhibit optimal computational properties , suggesting why the nervous system would benefit from such mode . for criticality , certain control parameters need to be tuned , leading to the obvious question why and how this is achieved . this question is well known in statistical physics , the theory of self - organized criticality ( soc ) of homogeneous systems has a long history since the pioneering work of . in case of competing fast and slow processes soc systems can self - tune themselves in the neighborhood of a phase transition point . many simple homogeneous models have been suggested to describe power - laws ( pl ) and various other critical phenomena , very often without identifying soc responsible processes . alternatively , it has recently been proposed that living systems might also self - tune to criticality as the consequence of evolution and adaptation . real systems , however , are highly inhomogeneous and one must consider if heterogeneity is weak enough to use homogeneous models to heterogeneity is also called disorder in statistical physics and can lead to such rare - region ( rr ) effects that smear the phase transitions . rr - s can have various effects depending on their relevancy . they can change a discontinuous transition to a continuous one , or can generate so - called griffiths phases ( gp ) , or can completely smear a singular phase transition . in case of gp - s critical - like power - law dynamics appears over an extended region around the critical point , causing slowly decaying auto - correlations and burstyness . this behavior was proposed to be the reason for the working memory in the brain . furthermore , in gp the susceptibility is infinite for an entire range of control parameters near the critical point , providing a high sensitivity to stimuli , beneficial fo

We study the effect of griffiths phases ( gp ) on the working memory in the brain. We show that the susceptibility is infinite for an entire range of control parameters near the critical point, providing a high sensitivity to stimuli and a good sensitivity for the working memories.

extended numerical simulations of threshold models have been performed on a human brain network with connected nodes available from the open connectome project . while in case of simple threshold models a sharp discontinuous phase transition without any critical dynamics arises , variable thresholds models exhibit extended power - law scaling regions . this is attributed to fact that griffiths effects , stemming from the topological / interaction heterogeneity of the network , can become relevan


We apply both analytical and ab - initio methods to explore heterostructures composed of a three -...

it is generally recognized that there is one - to - one correspondence between the presence of nontrivial topological invariants characterizing the bulk electron states of a crystal and the appearance of specific electron modes localized at the crystal boundary . this statement , which is known as the bulk - boundary correspondence theorem , reflects profound interrelation between the interior and exterior electron states of the truncated crystal . while the formulated assertion is based on general arguments of the topological concept for solids , in real materials and/or heterostructures , the effect of the peculiar bulk properties on the surface may be quite intricate . this problem has been widely discussed in the context of an existence of topological bound states on the surface of a three - dimensional topological insulator ( 3d ti ) or at the interface between 3d ti and topologically trivial material in various hybrid structures . angle - resolved photoemission spectra have given evidence for the dirac - like dispersion and the momentum - dependent spin texture of the 3d ti surface states in a family of bi- and sb - based narrow - gap semiconductors with strong spin - orbit coupling ( soc ) , which leads to the inverted band structure characterized by nontrivial topological invariants . although the topologically protected surface states are often considered as the most important and even decisive property of 3d tis , in practice , the specific manifestations of the boundary - related electron properties in semiconductor materials with an inverted energy gap go far beyond the bulk - boundary correspondence paradigm . in other words , being formally correct , the topological arguments tell us too little about characteristics of the topologically protected surface / interface states ( e.g. , the details of the dispersion , actual length scale , spin texture ) or what other in - gap electron states might form at the real boundary of a 3d ti material . while a rap

We present a new method for the analysis of the bulk - boundary correspondence of three - dimensional topological insulators ( 3d ti ) with an inverted energy gap. The method is based on the spherical - wave equations and the eigenvalues of the truncated crystal, which are derived from the spectral data. We show that the spectra of the surface states of the 3dti material are consistent with the generalization of the topological theory of solids.

we apply both analytical and ab - initio methods to explore heterostructures composed of a three - dimensional topological insulator ( 3d ti ) and an ultrathin normal insulator ( ni ) overlayer as a proof ground for the principles of the topological phase engineering . using the continual model of a semi - infinite 3d ti we study the surface potential ( sp ) effect caused by an attached ultrathin layer of 3d ni on the formation of topological bound states at the interface . the results reveal th


We apply perturbative renormalization group theory to the symmetric phase of a dilute interacting...

dilute , repulsively interacting bose gases in a three - dimensional harmonic trap have been at the focus of attention of the theoretical physics community since the experimental realization of bose - einstein condensation ( bec ) in 1995 . a vast amount of literature has been published recently on this topic based on the mean - field approach . it is however known that mean - field theory is not appropriate near the critical temperature because the fluctuations dominate the mean field in this region . this follows from applying the so - called ginzburg criterion and has triggered several attempts to go beyond mean - field theory near the critical region by means of various renormalization group ( rg ) techniques in the homogeneous interacting bose gas . this recent work was added to a significant amount of existing literature on the application of rg methods to interacting bose gases , that was written when such systems were only an interesting theoretical problem . all these studies so far concern the homogeneous case ; the real challenge however is to apply renormalization techniques to the experimentally relevant system , the trapped bose gas . this challenge is met here for the first time , at least when we approach the transition region from above the critical temperature ( symmetric phase ) . in this case the theoretical treatment is simpler than in the symmetry - broken phase and allows us to see how to apply renormalization techniques . in particular , we shall use a method similar to what in the homogeneous case is known as momentum - shell renormalization . in the trapped case it is energy shells instead of momentum shells that we will be integrating out . of course , since we are dealing here with a finite system , there is , strictly speaking , no phase transition . however , as we approach the thermodynamic limit , a quasi - phase transition develops , and renormalization methods are expected to enable us to study non - universal properties such as the

We present a new method for the renormalization of bose gases in a three - dimensional harmonic trap. This technique is similar to momentum - shell re normalization, which is used to study non - universal properties such as the energy shells and the phase transition. We show that the resulting re Normalization method can be applied to any interacting bosenic gas at the critical temperature.

we apply perturbative renormalization group theory to the symmetric phase of a dilute interacting bose gas which is trapped in a three - dimensional harmonic potential . using wilsonian energy - shell renormalization and the -expansion , we derive the flow equations for the system . we relate these equations to the flow for the homogeneous bose gas . in the thermodynamic limit , we apply our results to study the transition temperature as a function of the scattering length . our results compare


This paper presents distributed adaptive algorithms based on the conjugate gradient ( cg ) method...

in recent years , distributed processing has become popular in wireless communication networks . this kind of processing can collect data at each node in a given area and convey the information to the whole network in a distributed way . for instance , each node can get the information from its neighbors , and then combine it with the use of distributed adaptive algorithms ; each node has the ability to estimate the nearby environment itself . when compared with the centralized solution , the distributed solution has significant advantages . the centralized solution needs a central processor , where each node sends its information to the central processor and gets the information back after the processor completes the task . this type of communication needs the central processor to be powerful and reliable . with distributed solutions , each node only requires the local information and its neighbors to process the information . this kind of processing can significantly reduce the amount of processing and the communications bandwidth requirements . there are three main cooperation modes : the incremental , the diffusion , and the probabilistic diffusion modes . for the incremental mode , we can interpret it as a cycle in which the information goes through the nodes in one direction , which means each node passes the information to its adjacent node in a pre - determined direction . because of its simple method , the need for communication and power is the least . for the diffusion mode , each node transfers information to its whole neighbors . this kind of processing costs a huge amount of communication resources , but each node will get more information . to avoid the high communication cost , another kind of diffusion termed probabilistic diffusion is used . instead of transferring information to all its neighbors , each node transfers data to a selected group of its neighbors , which can be chosen randomly . several algorithms have already been developed and repor

We present a distributed adaptive algorithm for the transmission of information in wireless networks. It is based on a stochastic distribution of the local information and its neighbors, which can be used to estimate the nearby environment itself. The algorithm is a combination of the sequential diffusion and probabilistic diffusion modes.

this paper presents distributed adaptive algorithms based on the conjugate gradient ( cg ) method for distributed networks . both incremental and diffusion adaptive solutions are all considered . the distributed conventional ( cg ) and modified cg ( mcg ) algorithms have an improved performance in terms of mean square error as compared with least - mean square ( lms)-based algorithms and a performance that is close to recursive least - squares ( rls ) algorithms . the resulting algorithms are di


We present the results from a survey , designed to investigate the accretion process of massive...

the scenario of formation of low mass stars ( m 8 m ) , through disk accretion controlled by magnetic field is already well understood . for high masses ( m 8 m ) , however , there are theoretical problems for applying the same scenario . from the observational point of view , there are too few bona fide candidates to test the models . this is due to the fact that massive young stellar objects ( mysos ) are short lived and occur inside large molecular clouds , subject to huge reddening . the relevant phases of massive stars formation are not seen directly at wavelengths shorter than the mid - infrared ( mir ) and also to wavelengths longer than radio - mm . shocked molecular outflows are `` smoking guns '' of the accretion process and can be traced outside the central heavily obscured zone . the aim of this work is to use the h =1 - 0 s(1 ) emission to constrain the possible models . even after decades of progress both theoretical and observational fronts , formation of massive stars remains an open question . the short timescale for myso formation indicates that high rates of mass accretion are required . two scenarios currently dominate the discussions , in the first , high mass stars are formed by accretion through a disk ; in the second , high mass stars are formed via coalescence of low mass stars . in the last decade , a number of observations have been presented favoring the first scenario , among them and . low and intermediate mass stars are formed by the gravitational collapse of the parental giant molecular cloud ( gmc ) , followed by the accretion process . during the accretion phase , material is ejected as well via collimated bipolar jets . however , when a yso reaches 8 m , the radiative flux becomes so intense ( using , the ratio between the radiative fluxes of an o5 and a b3 star masses of and m , respectively is ) that it may interrupt the accretion flow . a process that constrains the outcoming radiation field to narrower angles may leave some roo

We present a new method for constraining the possible models of formation of massive young stellar objects ( mysos ) by using the h =1 - 0 emission. The model is based on the accretion process through a disk and the outflow from the parent giant molecular cloud. We use the s(1 ) emission to constrain the models, which are based upon the m = 1 - 0.

we present the results from a survey , designed to investigate the accretion process of massive young stellar objects ( mysos ) through near infrared narrow band imaging using the h =1 - 0 s(1 ) transition filter . a sample of 353 massive young stellar object ( myso ) candidates was selected from the red msx source survey using photometric criteria at longer wavelengths ( infrared and submillimeter ) and chosen with positions throughout the galactic plane . our survey was carried out at the soar


The usual kondo - lattice , including an antiferromagnetic exchange interaction between nearest -...

the denomination _ kondo lattice_ applies to systems which are characterized by a lattice of localized magnetic moments coexisting with a conduction band . examples are found among cerium compounds , such as ceal , cecu , cecusi , etc., as well as some uranium or other rare - earth compounds. at high temperatures , the localized moments behave essentially as independent impurities , similarly to what happens in dilute alloys . at low temperatures , a coherent _ heavy - fermion _ behavior is observed where the system resembles a fermi - liquid with enhanced values of parameters such as the specific - heat constant and the magnetic susceptibility . this is a scenario found in the cerium compounds mentioned above . however , deviations from this behavior are observed : some systems can show a magnetically ordered ground state , as happens , for example , in ceal , ceb , and cepdal , or become superconducting at low temperatures , as is the case of cecusi, cecuge at high pressures, and some uranium compounds like upt, ube, and urusi, among others . besides that , neutron - scattering experiments point to the presence of strong short - range magnetic correlations in cecu , ceincu , and cerusi , for which a fermi - liquid ground state is stable , but that are probably close to the conditions for a magnetic instability . this coexistence of magnetic correlations and kondo effect was recently discussed by iglesias , lacroix , and coqblin within a mean - field approach that has points in common with a slave - boson treatment by coleman and andrei. their analysis was restricted to the case of a half - filled conduction band , which is of relevance for kondo insulators. the role played by the conduction - band filling is obviously very important for metallic compounds that show heavy - fermion behavior , and to the discussion of _ underscreened _ systems. in this paper we study the effect of band filling in the stability of the kondo state and short - range magnetic correlatio

We study the effect of band filling on a magnetically ordered ground state in cerium compounds. We find that the system is strongly dependent on the conduction - band fillING, and that it can be observed at low temperatures. The results are consistent with previous studies of the kondo lattice.

the usual kondo - lattice , including an antiferromagnetic exchange interaction between nearest - neighboring localized spins , is treated here in a mean - field scheme that introduces two mean - field parameters : one associated with the local kondo effect , and the other related to the magnetic correlations between localized spins . phases with short - range magnetic correlations or coexistence between those and the kondo effect are obtained . by varying the number of electrons in the conducti


All the observations performed with the ibis telescope aboard the integral observatory during the...

many x - ray bursts detected by orbital observatories are associated with thermonuclear explosions on weakly magnetized accreting neutron stars ( type - i bursts ) . they provide us with direct information on processes near the surface of neutron stars under conditions of strong gravity , extreme pressure and high temperatures . the detection of type - i bursts , along with the detection of coherent pulsations , serves the most important criterion for identifying the nature of the compact object in x - ray binaries . type - i bursts are generally observed from weak x - ray sources ( or transients in their quiescent state ) . during the burst the luminosity of such a source ( a burster ) can increase by two or three orders of magnitude relative to its persistent level , reaching a critical eddington value . the typical burst at the galactic center distance ( kpc ) provides a peak flux of about 23 crab and can be easily detected . this opens up a possibility for using the bursts in searching for previously unknown bursters with persistent x - ray fluxes below the level of reliable detection by currently available wide - field instruments . the integral observatory is best suited for performing such a search . it is equipped with unique wide - field telescopes that allow sky fields with an area of 1000 square degrees to be simultaneously studied with a flux sensitivity up to 1 mcrab ( over several hours of observations ) and an angular resolution reaching several arcminutes . in addition , integral devotes up to 85% of the whole time to observations of the galactic center region and the galactic plane , where the bulk of the galactic stellar mass is concentrated . in this paper , to find x - ray bursts , we analyze time records of the total 15 - 25 kev count rate of the ibis / isgri detector aboard integral obtained from february 10 , 2003 , through august 31 , 2005 . the main objective of this study was an attempt to discover new bursters or fast x - ray transients .

We present the results of a survey of the total 15 - 25 kev count rate of the integral observatory from february 10, 2003 to august 31, 2005. The data are obtained from the ibis / isgri detector aboard integral. We find that the time records of the x - ray burst count rate for the entire period of the survey are consistent with the observed x.

all the observations performed with the ibis telescope aboard the integral observatory during the first 2.5 years of its in - orbit operation have been analyzed to find x - ray bursts . there were 1788 statistically confident events with a duration from 5 to 500 s revealed in time records of the 1525 kev count rate of the ibis / isgri detector , 319 of them were localized and , with one exception , identified with persistent x - ray sources . the known bursters were responsible for 215 of the lo


We present submillimeter observations of the local group , metal - poor , irregular dwarf galaxy ic...

ic 10 , an irregular , low metallicity dwarf galaxy ( ibm or `` magellanic cloud '' type ) , is one of the most active star - forming galaxies in the local group . its galaxy - wide massive star surface density is comparable to that of the starburst regions of m 33 ( massey , armandroff , & conti 1992 ) . because ic 10 is a nearby system that in many ways resembles primeval galaxies ( morphologically irregular , metal - poor , and very actively forming stars ) we have targeted it for a study of the interstellar medium ( ism ) at submillimeter wavelengths that has direct relevance to star formation at high redshifts . this galaxy , at a distance of 0.82 mpc ( wilson et al . 1996 ) , is comparable in mass and size to the small magellanic cloud . its metallicity ( , lequeux et al . 1979 ) falls between that of the large and the small magellanic clouds . ic 10 is an ideal laboratory to study the interaction between a metal - poor ism and strong radiation fields . metallicity greatly influences the composition and structure of the ism , especially when intense uv fields are present . photodissociation regions ( pdrs ) are those portions of the interstellar medium where uv radiation dominates the physical and chemical processes . because low metallicity pdrs have fewer heavy elements their gas phase chemistry is altered , changing the equilibrium abundances of the molecular species ( e.g. , van dishoeck & black 1988 ; lequeux et al . 1994 ) . the deficiency of heavy elements also lowers the dust - to - gas ratio . this in turn allows the uv radiation to penetrate more deeply into the molecular material , thereby causing widespread photodissociation and photoionization . the interaction between the starburst and the ism in a low metallicity system is thus maximized , as the uv photons permeate the ism relatively unimpeded . molecular hydrogen is largely unaffected by this enhanced uv radiation because of the strong h self - shielding and the mutual shielding between coinci

We present a new study of the interstellar medium ( ism ) in ic 10, an irregular low metallicity dwarf galaxy. It is a low metallicität system that has been observed for several years. The ism is composed of two regions: the ionized region and the nebula region. Both regions are located at a distance of 0.82 mpc. We find that the is dominated by uv radiation, which is correlated with the stellar mass. This results in a large number of photodis.

we present submillimeter observations of the local group , metal - poor , irregular dwarf galaxy ic 10 , directly relevant to the interaction between interstellar medium and star formation activity in primeval galaxies . using the jcmt , we have observed the fine structure neutral carbon transition pp at 492 ghz and the rotational transition of co and co in the most massive giant molecular cloud complex in this galaxy , ic 10-se . we find that , although the }/i_{co}$ ] ratio for this object is