May 1996 arXiv papers — page 11

Marco Lenci

It is proved that the quantization of the Volkovyski-Sinai model of ideal gas (in the Maxwell-Boltzmann statistics) enjoys at the thermodynamical limit the properties of mixing and ergodicity with respect to the quantum canonical Gibbs state. Plus, the average over the quantum state of a pseudo-differential operator is exactly the average over the classical

B. T. Draine, Joseph C. Weingartner

Irregular dust grains are subject to radiative torques when irradiated by interstellar starlight. It is shown how these radiative torques may be calculated using the discrete dipole approximation. Calculations are carried out for one irregular grain geometry, and three different grain sizes. It is shown that radiative torques can play an important dynamical

Carlos Rodrigo-Blanco

The gravitational potential and the gravitational rotation field generated by a thin-disk mass distribution with exponential density are considered in the case when the force between any two mass elements is not the usual Newtonian one, but some general central force. We use an approximation such that in the Newtonian case the gravitational field generated b

Carlos Rodrigo-Blanco

We consider the gravitational potential and the gravitational rotation field generated by an spherical mass distribution with exponential density, when the force between any two mass elements is not the usual Newtonian one, but some general central force. We invert the usual integral relations and obtain the elemental interaction (between two point-like mass

Julio Navarro, Matthias Steinmetz

We use high resolution N-body/gasdynamical simulations to investigate the effects of a photoionizing UV background on the assembly of disk galaxies in hierarchically clustering universes. We focus on the mass and rotational properties of gas that can cool to form centrifugally supported disks in dark matter halos of different mass. Photoheating can significa

C. Pichon, D. Lynden-Bell

A general method is presented for constructing distribution functions for flat systems whose surface density and Toomre's Q number profile is given. The purpose of these functions is to provide plausible galactic models and assess their critical stability with respect to global non axi-symmetric modes. The derivation may be carried out for an azimuthal v

Michael Hilker, Markus Kissler-Patig

We study the properties of the globular cluster system of the ``old'' merger NGC 5018. We detect a relatively poor globular cluster system, that can be divided into at least two populations based on colors: a small population of blue clusters, aged between several hundred Myr to 6 Gyr, the formation of which was probably induced by the last interacti

F. Matteucci, P. Molaro, G. Vladilo

High redshift DLA systems suggest that the relative abundances of elements might be roughly solar, although with absolute abundances of more than two orders of magnitude below solar. The result comes from observations of the [SII/ZnII] ratio, which is a reliable diagnostic of the true abundance, and from DLA absorbers with small dust depletion and negligible

E. Bergshoeff, R. Kallosh, T. Ortin

We present a new set of supersymmetric stationary solutions of pure N=4,d=4 supergravity (and, hence, of low-energy effective string theory) that generalize (and include) the Israel-Wilson-Perjés solutions of Einstein-Maxwell theory. All solutions have 1/4 of the supersymmetries unbroken and some have 1/2. The full solution is determined by two arbitrary com

J. W. Moffat

We impose in the nonsymmetric gravitational theory, by means of Lagrange multiplier fields in the action, a set of covariant constraints on the antisymmetric tensor field. The canonical Hamiltonian constraints in the weak field approximation for the antisymmetric sector yield a Hamiltonian energy bounded from below. An analysis of the Cauchy evolution, in te

U. Glaessner, S. Guesken, Th. Lippert, G. Ritzenhoefer

The availability of efficient Krylov subspace solvers play a vital role for the solution of a variety of numerical problems in computational science. Here we consider lattice field theory. We present a new general numerical method to compute many Green's functions for complex non-singular matrices within one iteration process. Our procedure applies to ma

R. J. Protheroe, Todor Stanev

Using the propagation of ultra high energy nucleons, photons and electrons in the universal radiation backgrounds, we obtain limits on the luminosity of topological defects scenarios for the origin of the highest energy cosmic rays. The limits are set as function of the mass of the X-particles emitted by the cosmic strings or other defects, the cosmological

C. Wilke, G. Wunner

We present the results of a numerical calculation of the photon splitting rate below the electron-pair creation threshold ($ω\le 2m$) in magnetic fields $B ~{> \atop \sim}~ B_{\rm cr} = m^2 /e = 4.414 \times 10^{9}$ T. Our results confirm asymptotic approximations derived in the low-field ($B < B_{\rm cr}$) and high-field ($B \gg B_{\rm cr}$) limit, and allo

S. Mertens

Binary sequences with low autocorrelations are important in communication engineering and in statistical mechanics as groundstates of the Bernasconi-model. Computer searches are the main tool to construct such sequences. Due to the exponential size $O(2^N)$ of the configuration space, exhaustive searches are limited to short sequences. We discuss an exhausti

A. Galli

We present a new approach for Monte Carlo simulations of lattice quantum spin systems which is able to eliminate the negative sign problem. Its complexity is linear in the volume of the lattice. Its efficiency is tested on a simple 2-dimensional fermionic model.

Per Elmfors, Dario Grasso, Georg Raffelt

We derive general expressions for the neutrino dispersion relation in a magnetized plasma with a wide range of temperatures, chemical potentials, and magnetic field strengths. If the electron and proton chemical potentials vanish, as in the early Universe, there is no magnetization contribution to the neutrino refractive index to leading order in the Fermi c

Ken Dykema

Using Voiculsecu&#39;s free entropy, it is shown that the free group factors L(F_n) lack property C of Popa and that they lack finite multiplicity abelian subalgebras. Property C is an assymptotic commutivity property.

Y Chen, S M Manning

We investigate the gap formation probability of the effective one dimensional gas model proposed the energy level statistics for disordered solids.

Nobuo Furukawa, Fakher F. Assaad, Masatoshi Imada

We study the filling-controlled metal-insulator transition in the two-dimensional Hubbard model near half-filling with the use of zero temperature quantum Monte Carlo methods. In the metallic phase, the compressibility behaves as $κ\propto |μ- μ_c|^{-0.58\pm0.08}$ where $μ_c$ is the critical chemical potential. In the insulating phase, the localization lengt

M. Bordemann, S. Waldmann

In this letter we compute some elementary properties of the Fedosov star product of Weyl type, such as symmetry and order of differentiation. Moreover, we define the notion of a star product of Wick type on every Kähler manifold by a straight forward generalization of the corresponding star product in $\mathbb C^n$: the corresponding sequence of bidifferenti

B. Bakalov, E. Horozov, M. Yakimov

We present methods for obtaining new solutions to the bispectral problem. We achieve this by giving its abstract algebraic version suitable for generalizations. All methods are illustrated by new classes of bispectral operators.

E. Shuryak

Both dilepton and charm production at RHIC are considered to be important signatures for Quark-Gluon Plasma production. Recently it was argued by S.Gavin, P.L.McGaughey,P.V. Ruuskanen and R.Vogt that the background from semileptonic correlated charm decays is so large that it makes dilepton measurements virtually impossible. We show that this conclusion in f

Juergen Schaffner

The phase diagram of nuclear matter is extended to strangeness and antimatter. It offers fascinating features for heavy ion physics and astrophysics. We will discuss some regions of this phase diagram as strange matter at zero temperature, hypermatter at high densities and the antiworld at high densities and strangeness fraction.

T. S. Walhout, R. Cenni, A. Fabrocini, S. Fantoni

We introduce a new approach to highly correlated systems which generalizes the Fermi Hypernetted Chain and Correlated Basis Function techniques. While the latter approaches can only be applied to systems for which a nonrelativistic wave function can be defined, the new approach is based on the variation of a trial hamiltonian within a path integral framework

O. Hanstein, D. Drechsel, L. Tiator

We have analyzed the $M_{1+}^{(3/2)}$ and $E_{1+}^{(3/2)}$ multipole amplitudes of pion photoproduction in the framework of fixed-$t$ dispersion relations. Applying the speed plot technique to our results for these multipoles, we have determined the position and the residues of the $Δ$ (1232) resonance pole. The pole is found at total $c.m.$ energy $W = (121

Bernd Kohler, Paolo Ruggerone, Matthias Scheffler

Helium atom scattering (HAS) studies of the H-covered Mo(110) and W(110) surfaces reveal a twofold anomaly in the respective dispersion curves. In order to explain this unusual behavior we performed density-functional theory calculations of the atomic and electronic structure, the vibrational properties, and the electronic susceptibility of those surfaces. O

Seiji Mukaigawa, Hiroyuki Takata

We study the one loop renormalization in the most general metric-dilaton theory with second derivative only. In constant background dilaton theory, there are two types of gravity background which enable the theory renormalizable at one-loop level. We show this concretely to discuss on the spherical symmetric background.

Stefano De Leo

We introduce {\em half-whole} dimensions for quaternionic matrices and propose a quaternionic version of the Frobenius-Schur theorem which allows us to obtain the proper quaternionic dimensionality for the representations of the Dirac and Duffin-Kemmer-Petiau (DKP) algebras.

Katrin Becker, Melanie Becker

We show that in certain compactifications of ${\cal M}$-theory on eight-manifolds to three-dimensional Minkowski space-time the four-form field strength can have a non-vanishing expectation value, while an $N=2$ supersymmetry is preserved. For these compactifications a warp factor for the metric has to be taken into account. This warp factor is non-trivial i

Q-Han Park, H. J. Shin

Hidden nonabelian symmetries in nonlinear interactions of radiation with matter are clarified. In terms of a nonabelian potential variable, we construct an effective field theory of self-induced transparency, a phenomenon of lossless coherent pulse propagation, in association with Hermitian symmetric spaces $G/H$. Various new properties of self-induced trans

Mirjam Cvetic, Donam Youm

We construct generating solutions for general D-dimensional ($4 \le D \le 9$) rotating, electrically charged, black holes in the effective action of toroidally compactified heterotic (or Type IIA) string. The generating solution is parameterized by the ADM mass, two electric charges and $[{D-1}\over 2]$ angular momenta (as well as the asymptotic values of on

J. L. F. Barbon, M. A. Vazquez-Mozo

We study some properties of target space strings constructed from (2,1) heterotic strings. We argue that world-sheet complexification is a general property of the bosonic sector of such target world-sheets. We give a target space interpretation of this fact and relate it to the non-gaussian nature of free String Field Theory. We provide several one loop calc

S. Dittmaier, D. Schildknecht, G. Weiglein

Carefully analyzing the dependence of the bounds on the Higgs-boson mass $\MH$ derived from the observables $\swbar^2(\LEP)$, $\swbar^2(\SLD)$, $\Gl$, $\MW$, $\GT$, $\Gh$, as well as $\Rb$ and $\Rc$, and considering the uncertainties in $α(\MZ^2)$ and $α_s(\MZ^2)$, we find that a stronger bound than $40\GeV\lsim\MH\lsim 1\TeV$ at the $1σ$ level can hardly be

M. Napsuciale, J. L. Lucio

We analyze the consistency of the Chiral Lagrangian approach to the description of the spin 3/2 interacting theory. We argue that to lowest order in the 1/m expansion, the formalism leads to the appropriated constraints and the theory is free of the so called ``off shell&#34; ambiguities.

F. Palumbo

We consider the possibility that quarks and gluons, due to confinement, have lower scaling dimensions. In such a case there appear naturally new energy scales below which the standard theory is recovered. Arguments are given whereby for dimension $1/2$ of the quarks the theory is unitary also above these energy scales.

Kenneth Lane

We catalog the principal signatures of electroweak and flavor dynamics at $\pbarp$ and $pp$ colliders for use at the 1996 Snowmass Workshop on New Directions in High Energy Physics. The framework for dynamical symmetry breaking we assume is technicolor, with a walking coupling $\atc$, and extended technicolor. The reactions discussed occur mainly at subproce

Matthias Neubert

We discuss two problems in the theory of heavy-quark decays: an understanding of the semileptonic branching ratio of $B$ mesons, and of the lifetime ratio $τ(Λ_b)/τ(B^0)$. We also present a model-independent study of spectator contributions to the lifetimes of beauty hadrons.

De Leo Stefano, Rotelli Pietro

A localized wave packet exhibits under certain conditions zitterbewegung. A similar phenomenon occurs for the chirality of a massive particle. In the case of massive neutrinos, since they are detected via the V-A weak charged currents, this oscillation may even explain the ``missing&#39;&#39; solar neutrino experiments. The neutrino remains a mass eigenstate

A. Corsetti, A. Grau, R. M. Godbole, G. Pancheri

Predictions for total inelastic cross-sections for photon induced processes are discussed in the context of the QCD-inspired minijet model. Large theoretical uncertainties exist, some of them related to the parton distributions of hadrons in impact parameter space. A model for such distribution is presented, based on soft gluon summation. This model incorpor

A. Corsetti, R. M. Godbole, G. Pancheri

In this note we assess the validity and uncertainties in the predictions of the eikonalised mini-jet model for $σ^{inel}_{γγ}$. We are able to find a choice of parameters where the predictions are compatible with the current data. Even for this restricted range of parameters the predictions at the high c.m. energies, which can be reached at the TeV energy $e

G. Montagna, O. Nicrosini, F. Piccinini

A general method for computing ${\cal O} (α^2)$ and higher-order next-to-leading photonic corrections is presented and applied to the precision calculation of the small-angle Bhabha scattering cross section in the phase-space region of interest for the luminosity measurement at LEP. The formulation is based on a proper matching of exact $\cal O (α)$ results

C. D. Froggatt, H. B. Nielsen, D. J. Smith

We examine extensions of the Standard Model (SM), basing our assumptions on what has already been observed; we don&#39;t consider anything fundamentally different, such as grand unification or supersymmetry, which is not directly suggested by the SM itself. We concentrate on the possibility of additional low mass fermions (relative to the Planck mass) and se

Abdellatif Abada, Michael C. Birse, Pengfei Zhuang, Ulrich Heinz

It is found that the extra quantum constraints to the spinor components of the equal-time Wigner function given in a recent paper by Zhuang and Heinz should vanish identically. We point out here the origin of the error and give an interpretation of the result. However, the principal idea of obtaining a complete equal-time transport theory by energy averaging

S. M. Bilenky

Talk presented at the 7th International Workshop on Neutrino Telescopes, Venezia, February 1996.

Abhee K. Dutt-Mazumder, Binayak Dutta-Roy, Anirban Kundu

A novel mechanism for $ρ-ω$ mixing induced by neutron-proton asymmetry in nuclear matter is uncovered and the variation of the mixing angle with the extent of asymmetry is presented.

M. Yoshimura

The basic idea of baryogenesis is lectured to introduce non-experts to this subject. Some recent topics, necessarily subjective in view of short time limitation, are also presented to show how the initial condition for baryogenesis is realized in the new framework of inflation.

Gregorio Bernardi

New results from the H1 and ZEUS collaborations on the measurement of cross-sections at very high Q^2 (up to 25000 GeV^2) and on the proton structure function F_2(x,Q^2) for momentum transfers squared Q^2 >= 1.5 GeV^2 and Bjorken x >= 3.5 10^{-5} are reported, using data collected at HERA mainly in 1994. No deviations from the Standard Model have been observ

James E. Lidsey

The pre--big bang cosmological scenario is studied within the context of the Brans--Dicke theory of gravity. An epoch of superinflationary expansion may occur in the pre--big bang phase of the Universe&#39;s history in a certain region of parameter space. Two models are considered that contain a cosmological constant in the gravitational and matter sectors o

Carlos O. Lousto, N. Sanchez

We study the classical dynamics of a bosonic string in the $D$--dimensional flat Friedmann--Robertson--Walker and Schwarzschild backgrounds. We make a perturbative development in the string coordinates around a {\it null} string configuration; the background geometry is taken into account exactly. In the cosmological case we uncouple and solve the first orde

A. Abrahams, A. Anderson, Y. Choquet-Bruhat, J. W. York

The evolution equations of Einstein&#39;s theory and of Maxwell&#39;s theory---the latter used as a simple model to illustrate the former--- are written in gauge covariant first order symmetric hyperbolic form with only physically natural characteristic directions and speeds for the dynamical variables. Quantities representing gauge degrees of freedom [the s

Ilja Schmelzer

Post-relativistic gravity is a hidden variable theory for general relativity. It introduces the pre-relativistic notions absolute space, absolute time, and ether as hidden variables into general relativity. Evolution is defined by the equations of general relativity and the harmonic coordinate condition interpreted as a physical equation. There are minor dif

Edmond Chow, H. P. Wei, S. M. Girvin, M. Shayegan

Using as a thermometer the temperature dependent magneto-transport of a two-dimensional electron gas, we find that effective temperature scales with current as $T_{\rm e} \sim I^a$, where $a=0.4 \pm 2\%$ in the {\it Shubnikov de-Haas} regime, and $0.53 \pm 2\%$ in both the {\it integer and fractional} quantum Hall effect. This implies the phonon energy emiss

Kun Yang, S. L. Sondhi

We determine the charge and statistical angle of skyrmions in quantum Hall ferromagnets by performing Berry phase calculations based on the microscopic variational wave functions for many-skyrmion states. We find, in contradiction to a recent claim by Dziarmaga, that both the charge and the statistical angle of a skyrmion are independent of its spin (size),

M. C. Faleski, M. C. Marchetti, A. A. Middleton

We present the results of molecular dynamic simulations of a two-dimensional vortex array driven by a uniform current through random pinning centers at zero temperature. We identify two types of flow of the driven array near the depinning threshold. For weak disorder the flux array contains few dislocation and moves via correlated displacements of patches of

G. Vignale, Walter Kohn

The frequency-dependent exchange-correlation potential, which appears in the usual Kohn-Sham formulation of a time-dependent linear response problem, is a strongly nonlocal functional of the density, so that a consistent local density approximation generally does not exist. This problem can be avoided by choosing the current-density as the basic variable in

D. V. Khveshchenko

We consider both disorder and interaction effects on the magnetoresistance and Hall constant of composite fermions in the vicinity of half filled Landau level. By contrast to the standard case of Coulomb interacting two-dimensional electron gas we find logarithmic temperature corrections to the Hall conductivity and the magnetoresistance of composite fermion

Yukitoshi Motome, Nobuyuki Katoh, Nobuo Furukawa, Masatoshi Imada

Effects of nonmagnetic impurity doping in a spin ladder system with a spin gap are investigated by the exact diagonalization as well as by the variational Monte Carlo calculations. Substantial changes in macroscopic properties such as enhancements in spin correlations and magnetic susceptibilities are observed in the low impurity concentration region, which

E. Brézin, S. Hikami

We consider a Hamiltonian $H$ which is the sum of a deterministic part $H_0$ and of a random potential $V$. For finite $N \times N$ matrices, following a method introduced by Kazakov, we derive a representation of the correlation functions in terms of contour integrals over a finite number of variables. This allows one to analyse the level correlations, wher

E. L. Martin, D. Montes

As part of a long term effort to understand pre-main sequence Li burning, we have obtained high resolution spectroscopic observations of 14 late type stars (G0--M1) in the young open cluster IC~4665. Most of the stars have \ha filled-in and \li absorption, as expected for their young age. From the equivalent widths of \ha emission excess (obtained using the

C. Pichon, D. Lynden-Bell

Complete sequences of new analytic solutions of Einstein&#39;s equations which describe thin super massive disks are constructed. These solutions are derived geometrically. The identification of points across two symmetrical cuts through a vacuum solution of Einstein&#39;s equations defines the gradient discontinuity from which the properties of the disk can

Simon D. M. White

I discuss recent theoretical work on the formation and evolution of galaxies paying particular attention to the ability of current models to make detailed comparisons with observations of the galaxy population both nearby and at high redshift. These models suggest that much (perhaps most) star formation in the universe took place in objects that are already

Andrea Ferrara, Yuri Shchekinov

We propose a simple model for the origin and evolution of \lya clouds based on cosmological conductive/cooling fronts. In this model the \lya arises in the interfaces between the IGM and cold clouds that could be tentatively identified with protogalaxies. Most of the properties of the \lya absorbers are reproduced with a very restricted number of assumptions

Luciano Rezzolla

We present results of a linear stability analysis of relativistic detonation fronts, which have been considered as representing phase interfaces in cosmological first order phase transitions. After discussing general stability conditions for detonation fronts, we concentrate on the properties of the fronts with respect to corrugation instabilities and discus

Taihei Yano, Naoteru Gouda

We have investigated the scale-invariant solutions of the BBGKY equations for spatial correlation functions of cosmological density fluctuations and the mean relative peculiar velocity in the strongly nonlinear regime. It is found that the solutions for the mean relative physical velocity depend on the three-point spatial correlation function and the skewnes

Brian Rush, Matthew A. Malkan, Henner H. Fink, Wolfgang Voges

We present the results of ROSAT All-Sky Survey observations of Seyfert and IR-luminous galaxies from the Extended 12 Micron Galaxy Sample and the optically-selected CfA Sample. Roughly half of the Seyferts (mostly Seyfert 1s) have been fitted to an absorbed power-law model, yielding an average gamma of 2.26+-0.11 for 43 Seyfert 1s and 2.45+-0.18 for 10 Seyfe

Carsten Greiner, Berndt Muller

We discuss the classical limit for the long-distance (``soft&#39;&#39;) modes of a quantum field when the hard modes of the field are in thermal equilibrium. We address the question of the correct semiclassical dynamics when a momentum cut-off is introduced. Higher order contributions leads to a stochastic interpretation for the effective action in analogy t

J. Ellis, N. E. Mavromatos, D. V. Nanopoulos

We develop quantization aspects of our Liouville approach to non-critical strings, proposing a path-integral formulation of a second quantization of string theory, that incorporates naturally the couplings of string sources to background fields. Such couplings are characteristic of macroscopic string solutions and/or $D$-brane theories. Resummation over worl

Jan Pisut, Neva Pisutova, Petr Zavada

In an attempt to disentangle the effects of nuclear geometry from those of nuclear geometry we study dependence of longitudinal radius on nucleon numbers of colliding nuclei within a simple model of multiple nucleon- nucleon collisions.We discuss two approaches to resulting simple formula.In the former the data up to S-Au can be described by nuclear geometry

J. -M. Frère, V. A. Novikov, M. I. Vysotsky

We suggest returning to a different presentation of the e+e- \to \bar{f} f data off the Z peak, with the hope of using zeroes of specific amplitudes to enhance the sensitivity to new physics.

S. Aid

Data from electron-proton collisions at a center-of-mass energy of 300 GeV are used for a search for selectrons and squarks within the framework of the minimal supersymmetric model. The decays of selectrons and squarks into the lightest supersymmetric particle lead to final states with an electron and hadrons accompanied by large missing energy and transvers

Detlef Lohse, Michael P. Brenner, Todd F. Dupont, Sascha Hilgenfeldt

The dynamics of single bubble sonoluminescence (SBSL) strongly depends on the percentage of inert gas within the bubble. We propose a theory for this dependence, based on a combination of principles from sonochemistry and hydrodynamic stability. The nitrogen and oxygen dissociation and subsequent reaction to water soluble gases implies that strongly forced a

Michael P. Brenner, Sascha Hilgenfeldt, Detlef Lohse, Rodolfo R. Rosales

Single bubble sonoluminescence is understood in terms of a shock focusing towards the bubble center. We present a mechanism for significantly enhancing the effect of shock focusing, arising from the storage of energy in the acoustic modes of the gas. The modes with strongest coupling are not spherically symmetric. The storage of acoustic energy gives a frame

N. S. Manton, H. Merabet

The symmetric dynamics of two kinks and one antikink in classical (1+1)-dimensional $ϕ^4$ theory is investigated. Gradient flow is used to construct a collective coordinate model of the system. The relationship between the discrete vibrational mode of a single kink, and the process of kink-antikink pair production is explored.

W. Belzig, C. Bruder, Gerd Schoen

A superconductor in contact with a normal metal not only induces superconducting correlations, known as proximity effect, but also modifies the density of states at some distance from the interface. These modifications can be resolved experimentally in microstructured systems. We, therefore, study the local density of states $N(E,x)$ of a superconductor - no

N. Haba, C. Hattori, M. Matsuda, T. Matsuoka

In the context of Calabi-Yau string models we explore the origin of characteristic pattern of quark-lepton masses and the CKM matrix. The discrete $R$-symmetry $Z_K \times Z_2$ is introduced and the $Z_2$ is assigned to the $R$-parity. The gauge symmetry at the string scale, $SU(6) \times SU(2)_R$, is broken into the standard model gauge group at a very larg

Maxim Markevitch, Alexey Vikhlinin

We address the consistency between ASCA and ROSAT spatially-resolved cluster temperature measurements, which is of significant interest given the recent ASCA reports of temperature gradients in several hot clusters. We reanalyze ROSAT PSPC data on A2256 (originally analyzed by Briel & Henry) using the newer calibration and a technique less sensitive to the c

James M. Cline, Kimmo Kainulainen

We compute the three-dimensional effective action for the minimal supersymmetric standard model, which describes the light modes of the theory near the finite-temperature electroweak phase transition, keeping the one-loop corrections from the third generation quarks and squarks. Using the lattice results of Kajantie {\it et al.}\ for the phase transition in

Boris Malomed

An equation to describe nearly one-dimensional traveling-waves patterns is put forward. This is a dispersive generalization of the classical Newell-Whitehead-Segel (NWS) equation. Transverse stability of plane waves is considered within the framework of this equation. It is shown that the dispersion terms drastically alter the stability. A necessary stabilit

J. Hüfner, B. Z. Kopeliovich, J. Nemchik

The integrated cross section for the incoherent photoproduction of vector mesons on nuclei $γ^* A \to VX$, $X\not=A$, is calculated within Glauber theory and as a function of the photon energy. The inverse of the longitudinal momentum transfer is called coherence length $l_c$ and depends on the virtuality and the energy of the photon. Nuclear transmission fa

S. E. Chernyshev, K. V. Shitikova

The effect of projectile shape on cross sections and momentum distributions of fragments from heavy ion reactions is studied. We propose a new approach that implements the underlying symmetries of each isotope with a few parameters directly in the density. Various densities and their nuclear structure are then analyzed in the reactions of $^{12}$C and $^{11}

H. F. Arellano, F. A. Brieva, M. Sander, H. V. von Geramb

The sensitivity of nucleon-nucleus elastic scattering to the off-shell behavior of realistic nucleon-nucleon interactions is investigated when on-shell equivalent nucleon-nucleon potentials are used. The study is based on applications of the full-folding optical model potential for an explicit treatment of the off-shell behavior of the nucleon-nucleon effect

C. Athanassopoulos, L. B. Auerbach, D. Bauer, R. D. Bolton

A search for neutrino oscillations of the type nu_bar_mu to nu_bar_e has been conducted at the Los Alamos Meson Physics Facility using nu_bar_mu from muon decay at rest. Evidence for this transition has been reported previously. This paper discusses in detail the experimental setup, detector operation and neutrino source, including aspects relevant to oscill

John Franks

We consider the rotation set $ρ(F)$ for a lift $F$ of an area preserving homeomorphism $f: \t^2\to \t^2$, which is homotopic to the identity. The relationship between this set and the existence of periodic points for $f$ is least well understood in the case when this set is a line segment. We show that in this case if a vector $v$ lies in $ρ(F)$ and has both

M. Berkooz, R. G. Leigh

We consider the propagation of Type I open superstrings on orbifolds with four non-compact dimensions and $N=1$ supersymmetry. In this paper, we concentrate on a non-trivial Z_2xZ_2 example. We show that consistency conditions, arising from tadpole cancellation and algebraic sources, require the existence of three sets of Dirichlet 5-branes. We discuss fully

B. S. Acharya

We discuss various dual {\it pairs} of $M$-theory compactifications. Each pair consists of a compactification in which the two-brane plays the crucial role in relation to a string theory and a compactification in which the five-brane takes center stage. We show that in many examples such dual pairs are interchanged by the {\it same} duality transformation in

D. V. Antonov

Stochastic quantization is applied to derivation of equations connecting multilocal gauge-invariant correlators in different field theories. They include Abelian Higgs Model, QCD with spinless quarks at T=0 and T>0 and QED, where spin effects are taken into account exactly.

D. V. Antonov

Using stochastic quantization method we derive gauge-invariant equations, connecting multilocal vacuum correlators of nonperturbative field configurations immersed into the quantum background. Three alternative methods of stochastic regularization of these equations are suggested, and the corresponding regularized propagators of a background field are obtain

I. Bakas

We use soliton techniques of the two-dimensional reduced beta-function equations to obtain non-trivial string backgrounds from flat space. These solutions are characterized by two integers (n, m) referring to the soliton numbers of the metric and axion-dilaton sectors respectively. We show that the Nappi-Witten universe associated with the SL(2) x SU(2) / SO

Augusto Sagnotti, Yassen S. Stanev

Open descendants extend Conformal Field Theory to unoriented surfaces with boundaries. The construction rests on two types of generalizations of the fusion algebra. The first is needed even in the relatively simple case of diagonal models. It leads to a new tensor that satisfies the fusion algebra, but whose entries are signed integers. The second is needed

B. -D. Doerfel, St. Meissner

In this paper we continue the investigation of an anisotropic integrable spin chain, consisting of spins $s=1$ and $s=\frac{1}{2}$, started in our paper \cite{meissner}. The thermodynamic Bethe ansatz is analysed especially for the case, when the signs of the two couplings $\bar{c}$ and $\tilde{c}$ differ. For the conformally invariant model ($\bar{c}=\tilde

St. Meissner, B. -D. Doerfel

An anisotropic integrable spin chain, consisting of spins $s=1$ and $s=\frac{1}{2}$, is investigated \cite{devega}. It is characterized by two real parameters $\bar{c}$ and $\tilde{c}$, the coupling constants of the spin interactions. For the case $\bar{c}<0$ and $\tilde{c}<0$ the ground state configuration is obtained by means of thermodynamic Bethe ansatz.

M. Reuter, C. Wetterich

A general framework for the Weyl invariant quantization of Liouville field theory by means of an exact renormalization group equation is proposed. This flow equation describes the scale dependence of the effective average action which has a built-in infrared cutoff. For c<1 it is solved approximately by a truncation of the space of action functionals. We der

N. N. Achasov, V. V. Gubin, V. I. Shevchenko

The potentialities of the production of the scalar $K\bar K$ molecules in the $ϕ$ radiative decays are considered beyond the narrow resonance width approximation. It is shown that $BR(ϕ\rightarrowγf_0(a_0)\rightarrowγππ(πη))\approx (1÷2)\times 10^{-5}\ ,\BR(ϕ\rightarrowγ(f_0+a_0)\rightarrowγK^+K^-)\alt 10^{-6}$ and $BR(ϕ\rightarrowγ(f_0+a_0) \to γK^0\bar K^0

Chris Michael

The status of non-perturbative QCD calculations for mesons with gluonic excitation is presented. Lattice results for the glueball spectrum are reviewed. For hybrid mesons, the heavy quark results are summarised and new results are presented for light quarks. Preliminary results for the spectrum of light-quark hybrid mesons indicate substantial mixing with qu

M. Sadzikowski, P. Wegrzyn

The problem of meson bound states with $N_f$ massive fermions in two dimensional quantum electrodynamics is discussed. We speculate about the spectrum of the lightest particles by means of the effective semiclassical description. In particular, the systems of fundamental fermions with $SU(2)$ and $SU(3)$ flavour symmetries broken by massive terms are investi

Gerhard A. Schuler, Torbjörn Sjöstrand

A real photon has a complicated nature, whereby it may remain unresolved or fluctuate into a vector meson or a perturbative q-qbar pair. In gamma-gamma events, this gives three by three combinations of the nature of the two incoming photons, and thus six distinct event classes. The properties of these classes are partly constrained by the choices already mad

A. Arbuzov, M. Bigi, H. Burkhardt, M. Cacciari

The results concerning the theoretical evaluation of the small-angle Bhabha Scattering cross section obtained during the Workshop on Physics at LEP2 (CERN, Geneva, Switzerland, 1995) by the Working Group ``Event Generators for Bhabha Scattering&#39;&#39; are summarized. The estimate of the theoretical error on the cross section in the luminometry region is u

K. Wang

We incorporate the idea of natural mass matrices into the construction of phenomenologically viable quark mass matrix patterns. The general texture pattern for natural Hermitian mass matrices is obtained and several applications of this result are made.

A. A. Slavnov

Following the line of \cite{AS} we propose an improved algorithm which allows to calculate a D-dimensional fermion determinant integrating the exponent of D+1 dimensional Hermitean bosonic action. For a finite extra dimension the corrections decrease exponentially.

J. Socorro, V. M. Villanueva, Luis O. Pimentel

We study five dimensional cosmological models with four dimensional hypersufaces of the Bianchi type I and V. In this way the five dimensional vacuum field equations $\rm G_{AB} = 0$, led us to four dimensional matter equations $\rm G_{μν}=T_{μν}$ and the matter is interpreted as a purely geometrical property of a fifth dimension. Also, we find that the ener