July 1998 arXiv papers — page 11

A. Airapetian

A measurement of the proton spin structure function g1p(x,Q^2) in deep-inelastic scattering is presented. The data were taken with the 27.6 GeV longitudinally polarised positron beam at HERA incident on a longitudinally polarised pure hydrogen gas target internal to the storage ring. The kinematic range is 0.021<x<0.85 and 0.8 GeV^2<Q^2<20 GeV^2. The integra

P. Hajicek

Recently, a variational principle has been derived from Einstein-Hilbert and a matter Lagrangian for the spherically symmetric system of a dust shell and a black hole. The so-called physical region of the phase space, which contains all physically meaningful states of the system defined by the variational principle, is specified; it has a complicated boundar

Arlen Anderson, James W. York,

Hamiltonian time evolution in terms of an explicit parameter time is derived for general relativity, even when the constraints are not satisfied, from the Arnowitt-Deser-Misner-Teitelboim-Ashtekar action in which the slicing density $α(x,t)$ is freely specified while the lapse $N=αg^{1/2}$ is not. The constraint ``algebra&#39;&#39; becomes a well-posed evolu

John D. Barrow, Kerstin E. Kunze

An overview is given of the formulation of low-energy string cosmologies together with examples of particular solutions, successes and problems of the theory.

Kenji Tomita

New exact vacuum solutions with various singularities in the plane-symmetric spacetime are shown, and they are applied to the analysis of inhomogeneous cosmological models and colliding gravitational waves. One of the singularities can be true null singularities, whose existence was locally clarified by Ori. These solutions may be interesting from the viewpo

Rajiv R. P. singh, Norbert Elstner

We study the triangular lattice bilayer Heisenberg model with antiferromagnetic interplane coupling $J_\perp$ and nearest neighbour intraplane coupling $J= λJ_\perp$, which can be ferro- or antiferromagnetic, by expansions in $λ$. For negative $λ$ a phase transition is found to an ordered phase at a critical $λ_c=-0.2636 \pm 0.0001$ which is in the 3D classi

Kiran M. Kolwankar, Alexander Punnoose

We study the effect of quenched spatial disorder on the current-carrying steady states of the totally asymmetric simple exclusion process with spatially disordered jump rates. The exact analytical expressions for the steady-state weights, and the current are found for this model in one dimension. We demonstrate how these solutions can be exploited to study a

Boris L. Altshuler, Dmitrii L. Maslov

It is shown that recent experiments indicating a metal-insulator transition in 2D electron systems can be interpreted in terms of a simple model, in which the resistivity is controlled by scattering at charged hole traps located in the oxide layer. The gate voltage changes the number of charged traps which results in a sharp change in the resistivity. The ob

Xindong Wang, X. -G. Zhang

We consider electron transport in a nearly half-metallic ferromagnet, in which the minority spin electrons close to the band edge at the Fermi energy are Anderson-localized due to disorder. For the case of spin-flip scattering of the conduction electrons due to the absorption and emission of magnons, the Boltzmann equation is exactly soluble to the linear or

Jean Desbois, Stéphane Ouvry, Christophe Texier

The Hall conductivity of disordered magnetic systems consisting of hard-core point vortices randomly dropped on the plane with a Poissonian distribution, has a behavior analogous to the one observed experimentally by R.~J.~Haug, R.~R.~Gerhardts, K.~v.~Klitzling and K.~Ploog, with repulsive scatterers \cite {1}. We also argue that models of homogeneous magnet

Claudio Castellano, Marco Zannetti

The phenomenology from the time of the quench to the asymptotic behavior in the phase-ordering kinetics of a system with conserved order parameter is investigated in the Bray-Humayun model and in the Cahn-Hilliard-Cook model. From the comparison of the structure factor in the two models the generic pattern of the overall time evolution, based on the sequence

Jürgen König, Yuval Gefen, Gerd Schön

We study the effect of electron tunneling on the level statistics of quantum dots. While the coupling between individual levels and the electron reservoir leads predominantly to the expected level broadening, the indirect coupling of adjacent levels via the reservoir results in a new asymptotic level statistics and broadening. These features, which are attri

Yukito Iba, George Chikenji, Macoto Kikuchi

A novel family of dynamical Monte Carlo algorithms for lattice polymers is proposed. Our central idea is to simulate an extended ensemble in which the self-avoiding condition is systematically weakened. The degree of the self-overlap is controlled in a similar manner as the multicanonical ensemble. As a consequence, the ensemble --the multi-self-overlap ense

M. Abolfath, M. R. Ejtehadi

We report the application of the nonlinear $σ$ model to study the multi-skyrmion problem in the quantum Hall ferromagnet system. We make use of a first-principle calculation to derive an analytical form for the inter-skyrmionic interaction to show that the ground state of the system can be described by a ferromagnet triangular Skyrme lattice near $ν=1$ where

E. Babaev, H. Kleinert

For an electron gas with a $ δ$-function attraction we investigate the crossover from weak-coupling to strong-coupling superconductivity as well as normal state near the temperature $T^*$, at which the strong coupling produces a pseudogap in the energy spectrum due to the binding of electron pairs. We present curves for the behavior of the superconductive tr

Susumu Shinohara, Yoji Aizawa

Reconnection processes of twin-chains are systematically studied in the quadratic twist map. By using the reversibility and symmetry of the mapping, the location of the indicator points is theoretically determined in the phase space. The indicator points enable us to obtain useful information about the reconnection processes and the transition to global chao

E. M. Shahverdiev

A simple method to perform chaos control without the need of complex numerical and analytical calculations is proposed. The method works for dynamical systems with bounded solutions and in the trivial case of constant Jacobians.

B. Gremaud, S. R. Jain

We show that the spacing distributions of rational rhombus billiards fall in a family of universality classes distinctly different from the Wigner-Dyson family of random matrix theory and the Poisson distribution. Some of the distributions find explanation in a recent work of Bogomolny, Gerland and Schmit. For the irrational billiards, despite ergodicity, we

Andrei Gruzinov

The observed frequency shifts of the high-degree solar fundamental mode are explained using a simple geometrical optics approximation. The predicted fractional frequency shift is proportional to the mean squared velocity of the convection flow at the surface of the Sun and inversely proportional to the group velocity of the mode squared. The data converge to

Romeel Dave&#39;, Lars Hernquist, Neal Katz, David Weinberg

We study the physical origin of the low-redshift Lyman alpha forest in hydrodynamic simulations of four CDM cosmologies. Our main conclusions are insensitive to the cosmological model but depend on our assumption that the UV background declines at low redshift. We find that the expansion of the universe drives rapid evolution of dN/dz (the number of absorber

J. Zhang, S. M. White, M. R. Kundu

We investigate the structure of the solar chromosphere and transition region using full Sun images obtained with the Extreme Ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO) spacecraft. The limb seen in the EIT coronal images (taken in lines of Fe IX/X at 171 Å, Fe XII at 195 Åand Fe XV at 284 Å) is an absorption limb

T. Shahbaz, P. A. Charles, A. R. King

A recent paper by King and Ritter (1998: hereafter KR) proposed that the light curves of soft X-ray transients (SXTs) are dominated by the effect of irradiation of the accretion disc by the central X-rays. This prevents the onset of the cooling wave which would otherwise return the disc to the quiescent state, and so prolongs the outbursts beyond those in dw

Bohdan Paczynski

The red clump giants are potentially very useful as standard candles. There is some controversy about the stability of their I-band absolute magnitude, but it does not seem to be serious. No controversy was anticipated about their colors, with metal rich giants expected to be redder and cooler than the metal poor giants. The purpose of this paper is to point

Terry Bridges, Judith Irwin

The central arcminute of the Perseus cooling flow galaxy, NGC 1275, has been mapped with the JCMT in 12CO(2-1) at 21 arcsec resolution, with detections out to at least 36 arcsec (12 kpc). Within the limits of the resolution and coverage, the distribution of gas appears to be roughly E-W, consistent with previous observations of CO, X-ray, H alpha, and dust e

Georges Paturel, Hélène Di Nella, Jean-Noël Terry et Gilles Theureau

After numerical simulations by E. Praton, we interprete the cocoon-like structure observed for the distribution of galaxies around us as an effect of infall velocities onto clusters. In this view structures like the Cocoon (or even like the Great-Wall) could be interpreted as observationnal artefacts.

Davide Lazzati, Guido Chincarini

We analyze the structure of the X-ray emission of a sample of 22 Abell clusters of galaxies with a cD in their centre, observed with the ROSAT PSPC. Utilizing the multi-scale power of the Wavelet Transform we detect significant (~ 50 h^{-1} kpc) offsets between the large scale centroid and the peak of X-ray emission. Despite the uncertainties on the satellit

D. Burgarella, V. Buat, K. Dohlen, F. Zamkotsian

From the scientific objectives of the Next Generation Space Telescope, this paper tries to constrain the design of the NGST Multi-Object Spectrograph. Several technical alternatives are presented that could address the requirements of the Design Reference Mission.

Alexander Maloney, Vahe Petrosian

We use several quasar samples to determine the density and luminosity evolution of quasars. Combining different samples and accounting for varying selection criteria require tests of correlation and the determination of distributions for multiply truncated data. We describe new non-parametric techniques for accomplishing these tasks, which have been develope

Youngjin Jeong, Cheongho Han, Sung-Hong Park

In current microlensing experiments, the information about the physical parameters of individual lenses are obtained from the Einstein timescales. However, the nature of MACHOs is still very uncertain despite the large number of detected events. This uncertainty is mainly due to the degeneracy of the lens parameters in the measured Einstein timescales. The d

William A. Hiscock

Rapidly rotating white dwarfs in cataclysmic variable systems may be emitting gravitational radiation due to the recently discovered relativistic r-mode instability. Assuming that the four most rapidly rotating known systems are limited in rotation rate by the instability, the amplitude of the emitted gravitational waves is determined at Earth for both known

Valery I. Rupasov

We propose toy models of unconventional magnetic alloys, in which the density of band states, $ρ(ε)$, and hybridization, $t(ε)$, are energy dependent; it is assumed, however, that $t^2(ε)\proptoρ^{-1}(ε)$, and hence an effective electron-impurity coupling $Γ(ε)=ρ(ε)t^2(ε)$ is energy independent. In the renormalization group approach, the physics of the syste

Ernest Ma

In the wake of the SuperKamiokande announcement of atmospheric neutrino oscillations which favor the large mixing of $ν_μ$ with $ν_τ$, there is considerable theoretical activity towards a possible understanding of the solar neutrino deficit also in terms of the mixing of $ν_e$ with the other two neutrinos. A specific dynamical model is presented here for the

Thomas Vojta, Michael Schreiber

We investigate the spreading of damage in the three-dimensional Ising model by means of large-scale Monte-Carlo simulations. Within the Glauber dynamics we use different rules for the order in which the sites are updated. We find that the stationary damage values and the spreading temperature are different for different update order. In particular, random up

H. Ruhl, Y. Sentoku, K. Mima, K. A. Tanaka

Oblique incidence of a $p$-polarized laser beam on a fully ionized plasma with a low density plasma corona is investigated numerically by Particle-In-Cell and Vlasov simulations in two dimensions. A single narrow self-focused current jet of energetic electrons is observed to be projected into the corona nearly normal to the target. Magnetic fields enhance th

K. Ackerstaff

The flavor asymmetry of the light quark sea of the nucleon is determined in the kinematic range 0.02<x<0.3 and 1 GeV^2<Q^2<10 GeV^2, for the first time from semi-inclusive deep-inelastic scattering. The quantity (dbar(x)-ubar(x))/(u(x)-d(x)) is derived from a relationship between the yields of positive and negative pions from unpolarized hydrogen and deuteri

A. I. Karanikas, C. N. Ktorides

Worldline techniques are employed to study the general behaviour of the fermion-fermion collision amplitude at very high energies in a non-abelian gauge field theory for the forward and fixed angle scattering cases. A central objective of this work is to demonstrate the simplicity by which the worldline methodology isolates that sector of the full theory whi

Takayasu Fukuhara, Hiizu Nakanishi

Dynamical stability of the crack front line that propagates between two plates is studied numerically using the simple two-dimensional mass-spring model. It is demonstrated that the straight front line is unstable for low speed while it becomes stable for high speed. For the uniform model, the roughness exponent in the slower speed region is fairly constant

Judith A. McGovern, Michael C. Birse

(New version with some expanded discussion; figures and minor typos corrected.) We have calculated the contribution proportional to the fifth power of the pion mass in the chiral expansion of the nucleon mass in two flavour HBCPT. Only one irreducible two-loop integral enters, and this vanishes. All other corrections in the heavy-baryon limit can be absorbed

Norman K. Glendenning, Christiane Kettner

The work of J. A. Wheeler in the mid 1960&#39;s showed that for smooth equations of state no stable stellar configurations with central densities above that corresponding to the limiting mass of ``neutron stars&#39;&#39; (in the generic sense) were stable against acoustical vibrational modes. A perturbation would cause any such star to collapse to a black ho

Peter Kopietz, Guillermo E. Castilla

We calculate the average conductivity sigma (omega) of interacting electrons in one dimension in the presence of a long-range random potential (forward scattering disorder). Taking the curvature of the energy dispersion into account, we show that weak disorder leads to a transport scattering rate that vanishes as omega^2 for small frequency omega. This impli

A. W. Strong, I. V. Moskalenko

We describe a method for the numerical computation of the propagation of primary and secondary nucleons, primary electrons, and secondary positrons and electrons. Fragmentation and energy losses are computed using realistic distributions for the interstellar gas and radiation fields, and diffusive reacceleration is also incorporated. The models are adjusted

Reinoud J. Slagter

The coupled Einstein-Yang-Mills equations on a time dependent axially symmetric spacetime are investigated, without a priori any conditions on the gauge field. There is numerical evidence for the existence of a regular solution with the desired asymptotic features. Just as in the supermassive abelian counterpart model, the formation of a singularity at finit

H. Castella, R. Zimmermann

The interband polarizations induced by two phase-locked pulses in a semiconductor show strong interference effects depending on the time tau_1 separating the pulses. The four-wave mixing signal diffracted from a third pulse delayed by tau is coherently controlled by tuning tau_1. The four-wave mixing response is evaluated exactly for a two-level system coupl

Ph. Blanchard, M. Pasquini, M. Serva

We introduce a model for a two configurations system, and we study the transition from quantum to classical behaviour. We first consider the effect of the interaction with the environment as an external noise and we show that it produces decoherence and suppression of tunnelling. These features are widely accepted as definition of classicality, while we beli

Sergey S. Safonov

A possibility of describing two-level atom states in terms of positive probability distributions (analog to the symplectic tomography scheme) is considered. As a result the basis of the irreducible representation of a rotation group can be realized by a family of the probability distributions of the spin projection parametrized by points on the sphere. Furth

Maxim Lyutikov

Beam instabilities in the strongly magnetized electron-positron plasma of pulsar magnetospheres are considered. We analyze the resonance conditions and estimate the growth rates of the Cherenkov and cyclotron instabilities of the ordinary (O), extraordinary (X) and Alfvén modes in two limiting regimes: kinetic and hydrodynamic. As a preliminary step, we reco

Peilong Chen

We show that, in a two-dimensional (2d) ideal fluid (also applies to a column of quasi-2d non-neutral plasma in an axial magnetic field), large elliptical vortices in a finite disk are stable. The stability is established by comparison between energy of elliptical and symmetrical states to satisfy a sufficient condition, without dynamical eigen-analysis. Ana

Berndt Müller

This is a review of the parton cascade model (PCM) which provides a QCD-based description of nucleus-nucleus reactions at very high energy. The PCM describes the collision dynamics within the early and dense phase of the reaction in terms of the relativistic, probabilistic transport of perturbative excitations (partons) of the QCD vacuum, combined with the r

E. M. Henley, J. P. Schiffer

Nuclear Physics is the branch of physics that deals with the properties and structure of matter on the hadronic level. In this article we review briefly the history of this field, which has a major role in the development of our understanding of nature. We then proceed to give an outline of a current perspective of the field and of some of the issues that ar

R. Coquereaux, G. E. Schieber

Using the fact that the algebra M := M_N(C) of NxN complex matrices can be considered as a reduced quantum plane, and that it is a module algebra for a finite dimensional Hopf algebra quotient H of U_q(sl(2)) when q is a root of unity, we reduce this algebra M of matrices (assuming N odd) into indecomposable modules for H. We also show how the same finite di

Saharon Shelah

A usual dichotomy is that in many cases, reasonably definable sets, satisfy the CH, i.e. if they are uncountable they have cardinality continuum. A strong dichotomy is when: if the cardinality is infinite it is continuum as in [Sh:273]. We are interested in such phenomena when lambda = aleph_0 is replaced by lambda regular uncountable and also by lambda = be

Peter Komjath, Saharon Shelah

It is consistent that there is a set mapping from the four-tuples of omega_n into the finite subsets with no free subsets of size t_n for some natural number t_n. For any n< omega it is consistent that there is a set mapping from the pairs of omega_n into the finite subsets with no infinite free sets.

Saharon Shelah, Pauli Väisänen

Suppose lambda is a singular cardinal of uncountable cofinality kappa. For a model M of cardinality lambda, let No(M) denote the number of isomorphism types of models N of cardinality lambda which are L_{infty lambda}-equivalent to M. In [Sh:189] inverse kappa-systems A of abelian groups and their certain kind of quotient limits Gr(A)/Fact(A) were considered

Saharon Shelah

We deal with the combinatorial principle Weak Diamond, showing that we always either a local version is not saturated or we can increase the number of colours. Then we point out a model theoretic consequence of Weak Diamond.

Saharon Shelah

Here we deal with the logic of [GuSh 533], which tries to capture polynomial time (for finite models). There it is proved that the logic cannot say much on models with equality only. Here we prove that it cannot say much on models for which we expect it cannot say much, like random enough graphs. This is the result of having a general criterion.

Uri Abraham, Saharon Shelah

Assuming the continuum hypothesis there is an inseparable sequence of length omega_1 that contains no Lusin subsequence, while if Martin&#39;s Axiom and the negation of CH is assumed then every inseparable sequence (of length omega_1) is a union of countably many Lusin subsequences.

Saharon Shelah

We give another proof that for every lambda >= beth_omega for every large enough regular kappa < beth_omega we have lambda^{[kappa]}= lambda, dealing with sufficient conditions for replacing beth_omega by aleph_omega. In section 2 we show that large pcf(a) implies existence of free sets. An example is that if pp(aleph_omega)> aleph_{omega_1} then for every a

Jerrold E. Marsden, George W. Patrick, Steve Shkoller

This paper presents a geometric-variational approach to continuous and discrete mechanics and field theories. Using multisymplectic geometry, we show that the existence of the fundamental geometric structures as well as their preservation along solutions can be obtained directly from the variational principle. In particular, we prove that a unique multisympl

Steve Shkoller

Recently, Holm, Marsden, and Ratiu [1998] have derived a new model for the mean motion of an ideal fluid in Euclidean space given by the equation $\dot{V}(t) + \nabla_{U(t)} V(t) - α^2 [\nabla U(t)]^t \cdot \triangle U(t) = -\text{grad} p(t)$ where $\text{div} U=0$, and $V = (1- α^2 \triangle)U$. In this model, the momentum $V$ is transported by the velocity

Haisheng Li

We give a natural extension of the notion of the contragredient module for a vertex operator algebra. By using this extension we prove that for regular vertex operator algebras, Zhu&#39;s $C_{2}$-finiteness condition holds, fusion rules are finite and the vertex operator algebras themselves are finitely generated.

A. Stoimenow

We collect some examples showing that some Vassiliev invariants are not obtainable from the HOMFLY and Kauffman polynomials in the real sense, namely, that they distinguish knots not distinguishable by the HOMFLY and/or Kauffman polynomial.

Anatoly N. Kochubei

We define analogues of higher derivatives for $F_q$-linear functions over the field of formal Laurent series with coefficients in $F_q$. This results in a formula for Taylor coefficients of a $F_q$-linear holomorphic function, a definition of classes of $F_q$-linear smooth functions which are characterized in terms of coefficients of their Fourier-Carlitz ex

Edward Witten

The theta dependent of pure gauge theories in four dimensions can be studied using a duality of large N gauge theories with string theory on a certain spacetime. Via this duality, one can argue that for every theta, there are infinitely many vacua that are stable in the large N limit. The true vacuum, found by minimizing the energy in this family, is a smoot

A. Gonzalez-Arroyo

We review some of the most important results obtained over the years on the study of Yang-Mills fields on the four dimensional torus at the classical level.

J. A. Nieto

In this work, we consider matroid theory. After presenting three different (but equivalent) definitions of matroids, we mention some of the most important theorems of such theory. In particular, we note that every matroid has a dual matroid and that a matroid is regular if and only if it is binary and includes no Fano matroid or its dual. We show a connectio

Phillial Oh, Jiannis Pachos

We examine the 1+1 dimensional CP(N) model in the large N limit by using the Schroedinger representation. Starting from the Hamiltonian analysis of the model, we present the variational gap equation resulting from the Gaussian trial wave functional. The renormalization of the theory is performed with insertion of mass and energy counter-terms, and the dynami

P. Tran-Ngoc-Bich

We invistigate exact solutions for the two-dimensional quantum field theories called Wess-Zumino-Novikov-Witten (WZNW) models. A WZNW model is a sigma model whose classical fields are applications from a bidimensional space-time (a Riemann surface in the euclidian case) to a Lie group, the target space. We construct (and we compute in genus zero and one) the

N. D. Hari Dass

A systematic investigation is given of finite size effects in $d=2$ quantum gravity or equivalently the theory of dynamically triangulated random surfaces. For Ising models coupled to random surfaces, finite size effects are studied on the one hand by numerical generation of the partition function to arbitrary accuracy by a deterministic calculus, and on the

Elisabeth Kraus

The algebraic method of renormalization is applied to the standard model of electroweak interactions. We present the most important modifications compared to theories with simple groups.

B. Dutta, D. J. Muller, S. Nandi

We consider the phenomenology of GMSB models where the lighter stau is the next to lightest supersymmetric particle. In this situation the dominant signals for supersymmetry at the Tevatron are events where two or three high p_T tau leptons accompanied by large missing transverse energy are produced. This leads to signatures that are very different from the

M. B. Gay Ducati, Victor P. Goncalves

In this work we obtain the DLLA limit of BFKL in the dipole picture and compare it with HERA data. We demonstrate that in leading-logarithmic- approximation, where $α_s$ is fixed, a transition between the BFKL dynamics and the DLLA limit can be obtained in the region of $Q^2 \approx 150 GeV^2$. We compare this result with the DLLA predictions obtained with $

S. M. H. Wong

We examine the effects of the new equilibration scenario of the increasingly strongly interacting parton plasma and of the non-equilibrium environment have on the production of open charm, photon and dilepton at LHC and at RHIC energies. We show that an out-of-equilibrium effect, not shown before, changes significantly the relative yield of the two main part

Chi-Keung Chow, Dan Pirjol, Tung-Mow Yan

We study the properties and couplings of hybrid baryons in the large-$N_c$ expansion. These are color-neutral baryon states which contain in addition to $N_c$ quarks also one constituent gluon. Hybrid baryons with both symmetric and mixed symmetric orbital wave functions are considered. We introduce a Hartree description for these states, similar to the one

H. Fujii, D. Kharzeev

We study the scattering of small color dipoles (e.g., heavy quarkonium states) at low energies. We find that even though the couplings of color dipoles to the gluon field can be described in perturbation theory, at large distances the interaction becomes totally non--perturbative. The structure of the scattering amplitude, however, is fixed by the (broken) c

A. Bialas, K. Zalewski

Recent results on effects of Bose-Einstein symmetrization in a system of independently produced particles are interpreted in terms of statistical physics. For a large class of distributions, the effective sizes of the system in momentum and in configuration space are shown to shrink when quantum interference is taken into account.

F. A. Berends, C. G. Papadopoulos, R. Pittau

In this paper, we present two programs to fit M_W at LEP2 using the best measurable kinematical variables. The theoretical probabilities of observing the final-state kinematical configurations are computed by integrating over the quantities that are not well measured. Therefore, an event-by-event kinematical reconstruction is avoided. M_W is then determined

Ulrich Ellwanger

The correlator of two field strengths is computed from an effective action for Yang Mills theories, which contains both gluons and an auxiliary antisymmetric tensor field for the field strength as local variables. This action allows to relate explicitly many different approaches to confinement, and is computed using Wilsonian renormalization group equations

R. M. Godbole

The phenomenon of beamstrahlung can give rise to potentially dangerous hadronic backgrounds due to minjet production at the future linear colliders as well as at the γγcolliders that are under consideration. In this talk I will review briefly the current estimates of these backgrounds and predictions of the eikonalised minijet model for \siginel. I end by po

K. Terasaki

Two body decays of charm mesons are studied by describing their amplitude in terms of a sum of factorizable and non-factorizable ones. The former is estimated by using a naive factorization while the latter is calculated by using a hard pseudo-scalar-meson approximation. The hard pseudo-scalar-meson amplitude is given by a sum of the so-called equal-time com

S. Chattopadhyaya, Z. Ahammed, Y. P. Viyogi

Using a combination of a preshower detector and a charged particle veto, it is shown that the neural network method is able to provide satisfactory discrimination between photons and hadrons in the case of extremely high particle density produced in the forward region of heavy ion collisions at the LHC energy.

H. P. de Oliveira, I. Damiao Soares

We exhibit a resonance mechanism of amplification of density perturbations in inflationary mo-dels, using a minimal set of ingredients (an effective cosmological constant, a scalar field minimally coupled to the gravitational field and matter), common to most models in the literature of inflation. This mechanism is based on the structure of homoclinic cylind

B. Kleihaus, J. Kunz, A. Sood, M. Wirschins

In Einstein-Maxwell theory black holes are uniquely determined by their mass, their charge and their angular momentum. This is no longer true in Einstein-Yang-Mills theory. We discuss sequences of neutral and charged SU(N) Einstein-Yang-Mills black holes, which are static spherically symmetric and asymptotically flat, and which carry Yang-Mills hair. Further

J. B. Fonseca-Neto, M. J. Reboucas

A class of Riemann-Cartan Gödel-type space-times is examined by using the equivalence problem techniques, as formulated by Fonseca-Neto et al. and embodied in a suite of computer algebra programs called TCLASSI. A coordinate-invariant description of the gravitational field for this class of space-times is presented. It is also shown that these space-times ca

Wenjin Mao, Kevin S. Bedell

We solved the Anderson Lattice Hamiltonian to get the energy bands of a strongly correlated semiconductor by using slave boson mean field theory. The transport properties were calculated in the relaxation-time approximation,and the thermoelectric figure of merit was obtained for the strongly correlated semiconductor and its superlattice structures. We found

D. Goldhaber-Gordon, J. Goeres, M. A. Kastner, Hadas Shtrikman

We demonstrate that the conductance through a single-electron transistor at low temperature is in quantitative agreement with predictions of the equilibrium Anderson model. When an unpaired electron is localized within the transistor, the Kondo effect is observed. Tuning the unpaired electron&#39;s energy toward the Fermi level in nearby leads produces a cro

Oscar Bolina, Domingos H. U. Marchetti

The ground state nature of the Falicov-Kimball model with unconstrained hopping of electrons is investigated. We solve the eigenvalue problem in a pedagogical manner and give a complete account of the ground state energy both as a function of the number of electrons and nuclei and as a function of the total number of particles for any value of interaction U.

R. S. Markiewicz

It is suggested that recent experiments provide evidence for modulations along the charged stripes in the striped phase of the cuprates. Furthermore, 1/8 doping is special because it is associated with a crossover: for lower doping the magnetic stripe width changes; for higher, the hole-doped stripes grow. The crossover is reflected in the doping dependence

P. Azaria, C. Hooley, P. Lecheminant, C. Lhuillier

We study a model of a spin S = 1/2 Heisenberg antiferromagnet on a one dimensional lattice with the local symmetry of the two dimensional kagom{é} lattice. Using three complementary approaches, it is shown that the low energy spectrum can be described by two critical Ising models with different velocities. One of these velocities is small, leading to a stron

Leticia F. Cugliandolo, Jorge Kurchan

The limit of small entropy production is reached in relaxing systems long after preparation, and in stationary driven systems in the limit of small driving power. Surprisingly, for extended systems this limit is not in general the Gibbs-Boltzmann distribution, or a small departure from it. Interesting cases in which it is not are glasses, phase-separation, a

K. Budde, I. F. Lyuksyutov, H. Pfnuer, G. Godzik

The first order phase transitions between a two-dimensional (2d) gas and the 2d solid of the first monolayer have been studied for the noble gases Ar, Kr and Xe on a NaCl(100) surface in quasi-equilibrium with the three-dimensional gas phase. Using linear temperature ramps, we show that the widths of the hysteresis loops of these transitions as a function of

R. Brito, M. H. Ernst

The total energy E(t) in a fluid of inelastic particles is dissipated through inelastic collisions. When such systems are prepared in a homogeneous initial state and evolve undriven, E(t) decays initially as t^{-2} \aprox exp[ - 2ετ] (known as Haff&#39;s law), where τis the average number of collisions suffered by a particle within time t, and ε=1-α^2 measur

Andrea Cavagna, Juan P. Garrahan, Irene Giardina

We consider the p-spin spherical spin-glass model in the presence of an external magnetic field as a general example of a mean-field system where a one step replica symmetry breaking (1-RSB) occurs. In this context we compute the complexity of the Thouless-Anderson-Palmer states, performing a quenched computation. We find what is the general connection betwe

M. J. Martins, B. Nienhuis

Motived by the study of motion in a random environment we introduce and investigate a variant of the Temperley-Lieb algebra. This algebra is very rich, providing us three classes of solutions of the Yang-Baxter equation. This allows us to establish a theoretical framework to study the diffusive behaviour of a Lorentz Lattice gas. Exact results for the geomet

James F. Annett, Jonathan P. Wallington

We derive an appropriate Landau-Ginzburg-Wilson effective action to describe the nearest neighbour attractive Hubbard model. This allows us to discuss both the small V (BCS) limit and the large V (Bose-Einstein) limit within the same framework. The model is particularly interesting as it exhibits both extended s-wave and d-wave solutions as well as an interm

Jian-Sheng Wang

We review the local Monte Carlo dynamics and Swendsen-Wang cluster algorithm. We introduce and analyze a new Monte Carlo dynamics known as transitional Monte Carlo. The transitional Monte Carlo algorithm samples energy probability distribution P(E) with a transition matrix obtained from single-spin-flip dynamics. We analyze the relaxation dynamics master equ

Ryoichi Yamamoto, Akira Onuki

We study a highly supercooled two-dimensional fluid mixture via molecular dynamics simulation. We follow bond breakage events among particle pairs, which occur on the scale of the $α$ relaxation time $τ_α$. Large scale heterogeneities analogous to the critical fluctuations in Ising systems are found in the spatial distribution of bonds which are broken in a

K. Reuter, J. Schardt, J. Bernhardt, H. Wedler

For the example of the SiC(111)-(3x3) reconstruction we show that a holographic interpretation of discrete Low Energy Electron Diffraction (LEED) spot intensities arising from ordered, large unit cell superstructures can give direct access to the local geometry of a cluster around an elevated atom, provided there is only one such prominent atom per surface u

R. E. Prange, R. Narevich, Oleg Zaitsev

Perturbation theory, the quasiclassical approximation and the quantum surface of section method are combined for the first time. This gives a new solution of the the long standing problem of quantizing the resonances generically appearing in classical perturbation theory. Our method is restricted to two dimensions. In that case, however, the results are simp

Julian Juhi-Lian Ting

Within a one-dimensional semi-classical model with a Morse potential the possibility of infrared multi-photon dissociation of vibrationally excited nitrogen oxide was studied. The dissociation thresholds of typical driving forces and couplings were found to be similar, which indicates that the results were robust to variations of the potential and of the def

Wesley N. Colley, Rudolph E. Schild

Since the persuasive determination of the time-delay in Q0957+561, much interest has centered around shifting and subtracting the A and B light-curves to look for residuals due to microlensing. Solar mass objects in the lens galaxy produce variations on timescales of decades, with amplitudes of a few tenths of a magnitude, but MACHO&#39;s (with masses of ord