March 1996 arXiv papers — page 11

Tae-Suk Kim, D. L. Cox

We introduce various exchange interactions in a model Hamiltonian for Ce$^{3+}$ ions in cubic symmetry with three configurations ($f^0$,$f^1$,$f^2$). With the impurity pseudo spin $S_I=1/2$, our Hamiltonian includes: (i) One-channel $S_c=1/2$ Anderson model; (ii) Two-channel $S_c=1/2$ Anderson model; (iii) An unforseen one-channel $S_c=3/2$ Anderson model wi

N. P. Landsman

The common structure of the space of pure states $P$ of a classical or a quantum mechanical system is that of a Poisson space with a transition probability. This is a topological space equipped with a Poisson structure, as well as with a function $p:P\times P-> [0,1]$, with certain properties. The Poisson structure is connected with the transition probabilit

D. V. Khveshchenko

We study temperature dependence of diagonal conductivity at half filled Landau level by means of the theory of composite fermions in the weakly disordered regime $(k_{F}l>>1)$. At low temperatures we find the leading $\log T$ correction resulting from interference between impurity scattering and gauge interactions of composite fermions. The prefactor appears

Goetz S. Uhrig

It is shown that the dynamics of a single $\downarrow$-electron interacting with a band of $\uparrow$-electrons can be calculated exactly in the limit of infinite dimension. The corresponding Green function is determined as a continued fraction. It is used to investigate the stability of saturated ferromagnetism and the nature of the ground state for two gen

H. J. Bussemaker, M. H. Ernst

Lattice gas automata with collision rules that violate the conditions of semi-detailed-balance exhibit algebraic decay of equal time spatial correlations between fluctuations of conserved densities. This is shown on the basis of a systematic microscopic theory. Analytical expressions for the dominant long range behavior of correlation functions are derived u

Ivan G. Avramidi, Giampiero Esposito, Alexander Yu. Kamenshchik

Gauge-invariant boundary conditions in Euclidean quantum gravity can be obtained by setting to zero at the boundary the spatial components of metric perturbations, and a suitable class of gauge-averaging functionals. This paper shows that, on choosing the de Donder functional, the resulting boundary operator involves projection operators jointly with a nilpo

Ofer Aharony, Jacob Sonnenschein, Shimon Yankielowicz

We discuss the relation between M theory and type II string theories. We show that, assuming ``natural'' interactions between membranes and fivebranes in M theory, the known interactions between strings and D-branes in type II string theories arise in appropriate limits. Our discussion of the interactions is purely at the classical level. We remark o

Anton Deitmar

The holomorphic torsion of a compact locally symmetric manifold is expressed as a special value of a zeta function built out of geometric data (closed geodesics) of the manifold.

H. W. Hamber, S. Liu

We develop the general formalism for performing perturbative diagrammatic expansions in the lattice theory of quantum gravity. The results help establish a precise correspondence between continuum and lattice quantities, and should be a useful guide for non-perturbative studies of gravity. The Feynman rules for Regge's simplicial lattice formulation of g

M. R. Adams, J. Harnad, J. Hurtubise

The method of constructing spectral Darboux coordinates on finite dimensional coadjoint orbits in duals of loop algebras is applied to the one pole case, where the orbit is identified with a coadjoint orbit in the dual of a finite dimensional Lie algebra. The constructions are carried out explicitly when the Lie algebra is $\frak{sl}(2,\bold R),\ \frak{sl}(3

O. P. Sushkov

Using semiclassical approximation we consider parity nonconservation (PNC) averaged over compound resonances. We demonstrate that the result of the averaging crucially depends on the properties of residual strong nucleon-nucleon interaction. Natural way to elucidate this problem is to investigate experimentally PNC spin rotation with nonmonachromatic neutron

Axel Gross, Steffen Wilke, Matthias Scheffler

We report six-dimensional quantum dynamical calculations of dissociative adsorption and associative desorption of the system H_2/Pd(100) using an ab-initio potential energy surface. We focus on rotational effects in the steering mechanism, which is responsible for the initial decrease of the sticking probability with kinetic energy. In addition, steric effec

Axel Gross

Due to the improvement of computer power and the development of efficient algorithms it is now possible to combine high-dimensional quantum dynamical calculations of the dissociative adsorption of molecular beams with reliable ab-initio potential energy surfaces (PES). In this brief review two recent examples of such studies of the systems H_2/Cu(111), where

Wolfram Koepf, Dieter Schmersau

In his 1984 proof of the Bieberbach and Milin conjectures de Branges used a positivity result of special functions which follows from an identity about Jacobi polynomial sums that was found by Askey and Gasper in 1973, published in 1976. In 1991 Weinstein presented another proof of the Bieberbach and Milin conjectures, also using a special function system wh

Wolfram Koepf, Dieter Schmersau

Recently, Todorov and Wilf independently realized that de Branges' original proof of the Bieberbach and Milin conjectures and the proof that was later given by Weinstein deal with the same special function system that de Branges had introduced in his work. In this article, we present an elementary proof of this statement based on the defining differentia

Wolfram Koepf

In this article algorithmic methods are presented that have essentially been introduced into computer algebra systems like Mathematica within the last decade. The main ideas are due to Stanley and Zeilberger. Some of them had already been discovered in the last century by Beke, but because of their complexity the underlying algorithms have fallen into oblivi

An. Kavalov, B. Sakita

We present a general method of constructing Winf and winf gauge theories in terms of d+2 dimensional local fields. In this formulation the \Winf gauge theory Lagrangians involve non-local interactions, but the winf theories are entirely local. We discuss the so-called classical contraction procedure by which we derive the Lagrangian of winf gauge theory from

Kasper Olsen

We describe the reduction from four to two dimensions of the SU(2) Donaldson-Witten theory and the dual twisted Seiberg-Witten theory, i.e. the Abelian topological field theory corresponding to the Seiberg--Witten monopole equations.

Vu B Ho, Michael J Morgan

This paper analyses quantum mechanics in multiply connected spaces. It is shown that the multiple connectedness of the configuration space of a physical system can determine the quantum nature of physical observables, such as the angular momentum. In particular, quantum mechanics in compactified Kaluza-Klein spaces is examined. These compactified spaces give

E. C. Marino

Charge and magnetic flux bearing operators are introduced in Chern-Simons theory both in its pure form and when it is coupled to fermions. The magnetic flux creation operator turns out to be the Wilson line. The euclidean correlation functions of these operators are shown to be local and are evaluated exactly in the pure case and through an expansion in the

P. Cea, L. Cosmai, M. Consoli, R. Fiore

We present a detailed discussion of Spontaneous Symmetry Breaking (SSB) in $(λΦ^4)_4$. In the usual approach, inspired by perturbation theory, one predicts a second-order phase transition, the Higgs mass $m_h$, related to the value of the renormalized 4-point coupling, gets smaller when increasing the ultraviolet cutoff and this leads to the generally quoted

J. -G. Zhou, F. Zimmerschied, J. -Q. Liang, H. J. W. Mueller-Kirsten

The significance of zero modes in the path-integral quantization of some solitonic models is investigated. In particular a Skyrme-like theory with topological vortices in (1+2) dimensions is studied, and with a BRST invariant gauge fixing a well defined transition amplitude is obtained in the one loop approximation. We also present an alternative method whic

Jian-Ge Zhou, F. Zimmerschied, J. --Q. Liang, H. J. W. Mueller--Kirsten

The RST model is augmented by the addition of a scalar field and a boundary term so that it is well-posed and local. Expressing the RST action in terms of the ADM formulation, the constraint structure can be analysed completely. It is shown that from the view point of local field theories, there exists a hidden dynamical field in the RST model. Thanks to the

Pawel O. Mazur

The arguments of statistical nature for the existence of constituents of active gravitational masses are presented. The present paper proposes a basis for microscopic theory of universal gravitation. Questions like the relation of cosmological constant and quantum theory, black hole radiance and the nature of inertia are addressed. This paper is the second i

Yosef Nir, Riccardo Rattazzi

Models that combine Abelian horizontal symmetries and spontaneous CP violation can (i) explain the smallness and hierarchy in quark parameters; (ii) satisfactorily suppress supersymmetric contributions to flavor changing neutral current processes; (iii) solve the $μ$-problem; and (iv) suppress supersymmetric contributions to CP violating observables to an ac

C. Boros, Liang Zuo-tang, Meng Ta-chung

Direct consequences on kaon production of the picture proposed in a recent Letter and subsequent publications are discussed. Further evidence supporting the proposed picture is obtained. Comparison with the data for the inclusive cross sections in unpolarized reactions is made. Quantitative results for the left-right asymmetry in single-spin processes are pr

A. M. Stasto

A model for the longitudinal structure function $F_L$ in the region of low $x$ and low $Q^2$ is discussed. It is constructed using the $k_T$ factorization theorem and a photon-gluon fusion mechanism suitably extrapolated to the region of low $Q^2$. A phenomenological model for higher twist is presented, which is based on the assumption that the contribution

B. Badelek, J. Kwiecinski, A. Stasto

A model for the longitudinal structure function $F_L$ at low $x$ and low $Q^2$ is presented, which includes the kinematical constraint $F_L \sim Q^4$ as $Q^2 \rightarrow 0$. It is based on the photon-gluon fusion mechanism suitably extrapolated to the region of low $Q^2$. The contribution of quarks having limited transverse momentum is treated phenomenologic

G. Wilk, Z. Wlodarczyk

Motivated by some recent cosmic ray experiments we study the properties of strange quark matter near flavour equilibrium. Using Fermi-gas model we argue that, contrary to some claims, the geometrical radii of quark matter strangelets are not smaller but rather comparable to those of ordinary nuclei. We propose therefore a scenario of propagation of strangele

J. A. Casas, J. R. Espinosa, M. Quiros

We analyse the stability lower bounds on the Standard Model Higgs mass by carefully controlling the scale independence of the effective potential. We include resummed leading and next-to-leading-log corrections, and physical pole masses for the Higgs boson, M_H, and the top-quark, M_t. Particular attention is devoted to the cases where the scale of new physi

Volker Keiner

We develop a rather simple, formally covariant quark-diquark model of the nucleon. The nucleon is treated as a bound state of a constituent quark and a diquark interacting via a quark exchange. We include both scalar and axial-vector diquarks. The underlying Bethe-Salpeter equation is transformed into a pair of coupled Salpeter equations. The electromagnetic

Joerg Schaldach, Peter Sieber, Dmitri Diakonov, Klaus Goeke

In the presence of fermionic matter the topologically distinct vacua of the standard model are metastable and can decay by tunneling through the sphaleron barrier. This process annihilates one fermion per doublet due to the anomalous non-conservation of baryon and lepton currents and is accompanied by a production of gauge and Higgs bosons. We present a nume

F. del Aguila, M. Zralek

We count the number of CP breaking phases in models with $SU(2)_L\times U(1)_Y$ and $SU(2)_L\times SU(2)_R\times U(1)_{B-L}$ electroweak gauge groups and extended matter contents with some fermion masses vanishing and/or degenerate. Quarks and leptons, including Majorana neutrinos, are treated in a similar way. CP violation is characterized in the mass-eigen

M. Frank, H. Hamidian

We study the one-loop supersymmetric contributions to lepton-flavor violating $Z$ -boson decays in a fully left-right symmetric model. In addition to right-handed scalar neutrinos, the decays could receive important contributions from doubly-charged triplet Higgsinos which couple to leptons only. We find that the decay widths reach present experimental bound

Monoranjan Guchait, D. P. Roy

The like sign dileptons provide the most promising signature for superparticle search in a large category of $R$-parity violating SUSY models. We estimate the like sign dilepton signals at the Tevatron collider, predicted by these models, over a wide region of the MSSM parameter space. One expects an unambiguous signal upto a gluino mass of $200 - 300$ GeV (

F. Karsch, T. Neuhaus, A. Patkós, J. Rank

We study gauge boson propagators in the symmetric and symmetry broken phases of the 3-d, $SU(2)$ gauge-Higgs model. Correlation functions for the gauge fields are calculated in Landau gauge. They are found to decay exponentially at large distances leading to a non-vanishing mass for the gauge bosons. We find that the W-boson screening mass drops in the symme

Lee Samuel Finn

The nature of binary black hole coalescence is the final, uncharted frontier of the relativistic Kepler problem. In the United States, binary black hole coalescence has been identified as a computational ``Grand Challenge'' whose solution is the object of a coordinated effort, just reaching its half-way point, by more than two-score researchers at ne

Anton Deitmar

The equivariant holomorphic torsion of a compact locally symmetric manifold and an automorphism is expressed as a special value of a zeta function built out of geometric data (closed geodesics) of the manifold.

S. Kodiyalam, K. E. Khor, S. Das Sarma

Motivated by our previous work using the Stillinger-Weber potential, which shows that the [$\overline{2}11$] step on 1$\times$1 reconstructed Si(111) has a Schwoebel barrier of 0.61$\pm$0.07 eV, we calculate here the same barrier corresponding to two types of kinks on this step - one with rebonding between upper and lower terrace atoms (type B) and the other

S. Kodiyalam, K. E. Khor, S. Das Sarma

Motivated by the recent investigations on instabilities caused by Schwoebel barriers during growth and their effects on growth or sublimation by step flows, we have investigated, using the Stillinger-Weber potential, how this step edge barrier arises for the two high symmetry steps on 1$\times$1 reconstructed Si(111). Relative to a barrier of 0.97 $\pm$ 0.07

H. T. C. Stoof, M. Bijlsma, M. Houbiers

We present a unified picture of the interaction effects in dilute atomic quantum gases. We consider fermionic as well as bosonic gases and, in particular, discuss for both forms of statistics the fundamental differences between a gas with effectively repulsive and a gas with effectively attractive interatomic interactions, i.e.\ between a gas with either a p

Yukitoshi Motome, Masatoshi Imada

Various types of superfluid-insulator transitions are investigated for two-component lattice boson systems in two dimensions with on-site hard-core repulsion and the component-dependent intersite interaction. The mean-field phase diagram is obtained by the Gutzwiller-type variational technique in the plane of filling and interaction parameters. Various groun

P. B. Sunil Kumar, Madan Rao

We present a novel Monte Carlo simulation of the phase separation dynamics of a model fluid membrane. Such a phase segregation induces shape changes of the membrane and results in local `budding' under favourable conditions. We present a preliminary investigation of the nucleation regime and compute a variety of growth laws. Our study indicates that memb

Herbert H. H. Homeier

Some methods for the convergence acceleration of the Møller-Plesset perturbation series for the correlation energy are discussed. The order-by-order summation is less effective than the Feenberg series. The latter is obtained by renormalizing the unperturbed Hamilton operator by a constant factor that is optimized for the third order energy. In the fifth ord

M. G. Cosenza, A. Parravano

The phenomenon of turbulence is investigated in the context of globally coupled maps. The local dynamics is given by the Chaté-Manneville minimal map previously used in studies of spatiotemporal intermittency in locally coupled map lattices. New features arise in the globally coupled system; for instance, the transition to turbulence takes place discontinuou

Kevin P. Rauch, Scott Tremaine

We demonstrate the existence of an enhanced rate of angular momentum relaxation in nearly Keplerian star clusters, such as those found in the centers of galactic nuclei containing massive black holes. The enhanced relaxation arises because the radial and azimuthal orbital frequencies in a Keplerian potential are equal, and hence may be termed {\em resonant r

C. A. Inman, E. S. Cheng, D. A. Cottingham, D. J. Fixsen

The goal of the second flight of the Medium Scale Anisotropy Measurement (MSAM1-94) was to confirm the measurement of cosmic microwave background radiation (CMBR) anisotropy made in the first flight (MSAM1-92). The CMBR anisotropy and interstellar dust emission signals from the two flights are compared by forming the sum and difference of those portions of t

H. Tadros, G. Efstathiou

We test estimators of the galaxy power spectrum $P(k)$ against simulated galaxy catalogues constructed from N-body simulations and we derive formulae to correct for biases. These estimators are then applied to compute the power spectrum of galaxies in the Stromlo-APM redshift survey. We test whether the amplitude of $P(k)$ depends on galaxy luminosity, but f

H. Di Nella, M. Montuori, G. Paturel, L. Pietronero

All the recent redshift surveys show highly irregular patterns of galaxies on scales of hundreds of megaparsecs such as chains, walls and cells. One of the most powerful catalog of galaxies is represented by the LEDA database that contains more than 36,000 galaxies with redshift. We study the correlation properties of such a samplefinding that galaxy distrib

M. A. Hendry, S. M. Kanbur

The calibration of the Type Ia supernova distances using HST observations of Cepheid variables is discussed. A new maximum likelihood method of calibration is applied to derive the PL relation for a composite sample of Cepheids in the LMC and in the SNIa host galaxies NGC5253 and IC4182. Our results show that the calibration of the Cepheid PL relation is rob

F. R. Bouchet

These lectures notes give an introduction to the fast developing area of research dealing with perturbative descriptions of the gravitational instability in an expanding universe. I just sketch the outlines of some proofs, and many important contributions (and references) were left out. Many untouched aspects are reviewed in \cite{sah_col} which also contain

A. Aragon-Salamanca, R. S. Ellis, K. S. O'Brien

We have obtained very deep near-infrared images in the fields of 10 QSOs whose spectra contain damped Lyman-alpha absorption (DLA) systems with 1.7<z_abs <2.5. The main aim of our investigation is to provide new constraints on the properties of distant galaxies responsible for the DLA absorption. After subtracting the point spread function associated with th

R. G. Gratton, E. Carretta, F. Castelli

We present atmospheric parameters for about 300 stars of different chemical composition, whose spectra will be used to study the galactic enrichment of Fe and light elements. These parameters were derived using an homogenous iterative procedure, which considers new calibrations of colour-\teff\ relations for F, G and K-type stars based on Infrared Flux Metho

Nguyen Quoc Thang

We extend an exact sequence of Colliot-Thelene and Sansuc which connects arithmetic and birational invariants of tori over a number field to one for arbitrary connected linear algebraic groups.

Gerard Laumon

In this paper I construct a geometric transformation for generalized 1-motives which extends the Fourier-Mukai transformation for O-Modules on abelian varieties, the geometric Fourier transformation for D-Modules on vector spaces and the geometric Mellin transformation for D-Modules on tori. In particular, I construct an equivalence of triangulated categorie

D. Comelli, Joao P. Silva

The top quark is well known for the nondecoupling effects it implies in $\rho$ and $R_b$. The recent experimental $R_b$ data exhibits a disagreement with the SM prediction at more than the $3 \sigma$ level. It is tempting to explore whether this might be due to nondecoupling New Physics effects, opposite to those of the top. We investigate this issue in the

Hoi-Kwong Lo, H. F. Chau

We show that all proposed quantum bit commitment schemes are insecure because the sender, Alice, can almost always cheat successfully by using an Einstein-Podolsky-Rosen type of attack and delaying her measurement until she opens her commitment.

N. Armesto, M. A. Braun

Arguments are presented for the odderon intercept being exactly equal to unity. A variational method is presented based on a complete system of one-gluon functions. For the odderon, the highest intercept calculated by this method is $1-(3α_{s}/π)\,0.45$.

J. P. Lupi, A. Restuccia, J. Stephany

We study the interaction of non-Abelian topological $BF$ theories defined on two dimensional manifolds with point sources carrying non-Abelian charges. We identify the most general solution for the field equations on simply and multiply connected two-manifolds. Taking the particular choice of the so-called extended Poincaré group as the gauge group we discus

Giovanni Gallavotti

The fluctuation theorem (FT), the first derived consequence of the {\it Chaotic Hypothesis} (CH) of ref. [GC1], can be considered as an extension to arbitrary forcing fields of the fluctuation dissipation theorem (FD) and the corresponding Onsager reciprocity (OR), in a class of reversible nonequilibrium statistical mechanical systems.

Christian Okonek, Andrei Teleman

In this paper we describe the Seiberg-Witten invariants, which have been introduced by Witten, for manifolds with $b_+=1$. In this case the invariants depend on a chamber structure, and there exists a universal wall crossing formula. For every Kähler surface with $p_g=0$ and $q$=0, these invariants are non-trivial for all $Spin^c(4)$-structures of non-negati

Massimo Campostrini, Andrea Pelissetto, Paolo Rossi, Ettore Vicari

The critical behavior of two-dimensional ${\rm O}(N)$ $σ$ models with $N\leq 2$ on the square, triangular, and honeycomb lattices is investigated by an analysis of the strong-coupling expansion of the two-point fundamental Green&#39;s function $G(x)$, calculated up to 21st order on the square lattice, 15th order on the triangular lattice, and 30th order on t

Frank De Jonghe, Jordi Paris, Walter Troost

Anomalies and BRST invariance are governed, in the context of Lagrangian Batalin-Vilkovisky quantization, by the master equation, whose classical limit is $(S, S)=0$. Using Zimmerman&#39;s normal products and the BPHZ renormalisation method, we obtain a corresponding local quantum operator equation, which is valid to all orders in perturbation theory. The fo

O. Babelon, D. Bernard, F. A. Smirnov

We show how to compute form factors, matrix elements of local fields, in the restricted sine-Gordon model, at the reflectionless points, by quantizing solitons. We introduce (quantum) separated variables in which the Hamiltonians are expressed in terms of (quantum) tau-functions. We explicitly describe the soliton wave functions, and we explain how the restr

Max Tegmark, Joseph Silk, Martin Rees, Alain Blanchard

The minimum mass that a virialized gas cloud must have in order to be able to cool in a Hubble time is computed, using a detailed treatment of the chemistry of molecular hydrogen. With a simple model for halo profiles, we reduce the problem to that of numerically integrating a system of chemical equations. The results agree well with numerically expensive 3D

K. S. Babu, Chris Kolda, John March-Russell

In this paper, we investigate the possibility of explaining both the R_b excess and the R_c deficit reported by the LEP experiments through Z-Z&#39; mixing effects. We have constructed a set of models consistent with a restrictive set of principles: unification of the Standard Model (SM) gauge couplings, vector- like additional matter, and couplings which ar

Catherine Stampfl

The success of density functional theory for the description of the adsorption of atoms on surfaces is well established, and based on recent calculations using gradient corrections, it has been shown that it also describes well the dissociative adsorption of molecules at surfaces - admittedly however, the data base for reactions at surfaces is still somewhat

Gregery T. Buzzard, Franc Forstneric

We construct automorphisms of $\C^n$ which map certain discrete sequences one onto another with prescribed finite jet at each point, thus solving a general Mittag-Leffler interpolation problem for automorphisms. Under certain circumstances, this can be done while also approximating a given automorphism on a compact set.

S. F. Hewson, M. J. Perry

We investigate non-abelian gaugings of WZNW models. When the gauged group is semisimple we are able to present exact formulae for the dual conformal field theory, for all values of the level $k$. The results are then applied to non-abelian target space duality in string theory, showing that the standard formulae are quantum mechanically well defined in the l

G. Delfino, G. Mussardo, P. Simonetti

We approach the study of non--integrable models of two--dimensional quantum field theory as perturbations of the integrable ones. By exploiting the knowledge of the exact $S$-matrix and Form Factors of the integrable field theories we obtain the first order corrections to the mass ratios, the vacuum energy density and the $S$-matrix of the non-integrable the

M. Z. Iofa

One-string-loop (torus topology) corrections to black-string backgrounds corresponding to gauged ${SL(2,R)\times R}/R$ WZW model are calculated using $β$-function equations derived from string-loop-corrected effective action. Loop-corrected backgrounds are used to calculate ADM mass of the black string.

Jari Hakkinen, Hamid Kharraziha

A computer program for evaluating colour factors of QCD Feynman diagrams is presented, and illustrative examples on how to use the program to calculate non trivial colour factors are given. The program and the discussion in this paper is based on a diagrammatic approach to colour factors.

M. Baillargeon, U. Baur, G. Belanger, F. Boudjema

We present an update of the limits expected for anomalous gauge boson couplings in the language of chiral Lagrangian operators at the LHC and the Linear Collider. Both, the $e^+e^-$ and the $γγ$ mode of the Linear Collider are analyzed. With a 500~GeV $e^+e^-$ collider, and an integrated luminosity of 50~--~80~fb$^{-1}$, one reaches the domain of precision m

D. Boyanovsky, I. D. Lawrie, D. S. Lee

A new approach to the dynamics of relaxation and kinetics of thermalization in a scalar field theory is presented that incorporates the relevant time scales through the resummation of hard thermal loops. An alternative derivation of the kinetic equations for the ``quasiparticle&#39;&#39; distribution functions is obtained that allows a clear understanding of

W. K. Baskerville

A quantisation of chiral symmetry within the Skyrme crystal is carried out. The definition of global isospin in the crystal is explored, and found to be ambiguous. However, the state corresponding to a neutron crystal is identified, and the leading quantum correction to the classical mass is computed. The results are compared to those of Klebanov for a cryst

Debrupa Chakraverty, Triptesh De, Binayak Dutta-Roy, Anirban Kundu

In the context of the observed decay $B \rightarrow K^* γ$ the applicability of the Heavy Quark Effective Theory (HQET), treating both b and s as heavy quarks, is examined. We show that the heavy s-quark approximation, as can be found in the literature, is not reliable.

Michael Rueter, H. G. Dosch

If the pomeron is generated by a two gluon exchange there is no a priori reason for a drastic suppression of three gluon exchange with negative parity and charge parity. This would lead to an unacceptably large difference between $p\,p$ and $p\, \bar{p}$ scattering. It is shown that a natural suppression of the $C$=$P$=--1 contribution to high energy scatter

M. Hirsch, H. V. Klapdor-Kleingrothaus, S. G. Kovalenko

A new mechanism for neutrinoless double beta ($\znbb$) decay based on leptoquark exchange is discussed. Due to the specific helicity structure of the effective four-fermion interaction this contribution is strongly enhanced compared to the well-known mass mechanism of $\znbb$ decay. As a result the corresponding leptoquark parameters are severely constrained

Rajiv V. Gavai

Using the finite size scaling theory, we re-examine the nature of the bulk phase transition in the fundamental-adjoint coupling plane of the SU(2) lattice gauge theory at $β_A = 1.25$ where previous finite size scaling investigations of the deconfinement phase transition showed it to be of first order for temporal lattices with four sites. Our simulations on

F. Abe

We have searched for chargino-neutralino production (\chichi) in 1.8 TeV \ppb\sp collisions, followed by their leptonic decays \chione\dk\chizero\lnu\psp and \chitwo\dk\chizero\lplm. These trilepton events are expected within a framework of the Minimal Supersymmetric Standard Model (MSSM). In a 19.1 pb$^{-1}$ data sample collected with the Collider Detector

B. Boisseau, C. Charmousis, B. Linet

We determine the electrostatic self-force at rest in an arbitrary static metric with cylindrical symmetry in the linear approximation in the Newtonian constant. In linearised Einstein theory, we express it in terms of the components of the energy-momentum tensor.

R. Mélin

We analyze the thermal magnetization reversal processes in magnetic grains. Two experiments are carried out: swtiching time and switching field experiments. In both cases, we find that the simulated behavior is coherent with existing experimental data (the streched exponent of the switching time experiment increases with the temperature and is superior to un

M. P. Gelfand, Z. Weihong, R. R. P. Singh, J. Oitmaa

We have carried out a wide range of calculations for the $S=1/2$ Heisenberg model with nearest- and second-neighbor interactions on a two-dimensional lattice which describes the geometry of the vanadium ions in the spin-gap system CaV$_4$O$_9$. The methods used were convergent high-order perturbation expansions (``Ising&#39;&#39; and ``Plaquette&#39;&#39; ex

V. Bayot, E. Grivei, S. Melinte, M. B. Santos

We report low temperature ($T$) heat capacity ($C$) data on a multiple-quantum-well GaAs/AlGaAs sample in the quantum Hall regime. Relative to its low field magnitude, $C$ exhibits up to 10^5-fold enhancement near $ν$=1 where Skyrmions arethe ground state of the confined two-dimensional electrons. We attribute the large $C$ to a Skyrmion-induced, strong coup

D. L. Shepelyansky, O. P. Sushkov

We study the localization length of few interacting particles in a random potential. Concentrating on the case of three particles we show that their localization length is strongly enhanced comparing to the enhancement for two interacting particles.

Ruihong Yue, Heng Fan, Boyu Hou

We use the algebraic nested Bethe ansatz to solve the eigenvalue and eigenvector problem of the supersymmetric $SU_q(n|m)$ model with open boundary conditions. Under an additional condition that model is related to a multicomponent supersymmetric t-J model. We also prove that the transfer matrix with open boundary condition is $SU_q(n|m)$ invariant.

Peter Kleban, Ingo Peschel

We calculate the universal part of the free energy of certain finite two- dimensional regions at criticality by use of conformal field theory. Two geometries are considered: a section of a circle (&#34;pie slice&#34;) of angle ϕand a helical staircase of finite angular (and radial) extent. We derive some consequences for certain matrix elements of the transf

T. Xiang

A momentum-space approach of the density-matrix renormalization-group (DMRG) method is developed. Ground state energies of the Hubbard model are evaluated using this method and compared with exact diagonalization as well as quantum Monte-Carlo results. It is shown that the momentum-space DMRG is a very useful numerical tool for studying the Hubbard model and

Kihong Kim, John W. Wilkins

We extend previous work to consider the effect of the soliton on the density of states and conductivity of quasi-one-dimensional Peierls systems with quantum lattice fluctuations, modeled by a random static disorder. Two features have been verified over an order of magnitude variation in the disorder. (1) The soliton density of states and the leading edges o

Stefan Boettcher, Maya Paczuski

Slowly driven dissipative systems may evolve to a critical state where long periods of apparent equilibrium are punctuated by intermittent avalanches of activity. We present a self-organized critical model of punctuated equilibrium behavior in the context of biological evolution, and solve it in the limit that the number of independent traits for each specie

Sang-Yoon Kim, Kijin Lee

We study period doublings in $N$ $(N=2,3,4, \dots)$ coupled parametrically forced damped pendulums by varying $A$ (the amplitude of the external driving force) and $c$ (the strength of coupling). With increasing $A$, the stationary point undergoes multiple period-doubling transitions to chaos. We first investigate the two-coupled case with $N=2$. For each pe

D. R. Schultz, P. S. Krstic, C. O. Reinhold, J. C. Wells

Presented here is a description of the ionization of hydrogen and hydrogenic ions by antiproton-impact, based on very large scale numerical solutions of the time-dependent Schrödinger equation in three spatial dimensions and on analysis of the topology of the electronic eigenenergy surfaces in the plane of complex internuclear distance. Comparison is made wi

Jean M. Quashnock

If \g--ray bursts are cosmological in origin, the sources are expected to trace the large--scale structure of luminous matter in the universe. I use a new likelihood method that compares the counts--in--cells distribution of \g--ray bursts in the BATSE 3B catalog with that expected from the known large--scale structure of the universe, in order to place a co

Brian D. Fields, Kimmo Kainulainen, Keith A. Olive, David Thomas

We examine in detail how BBN theory is constrained, and what predictions it can make, when using only the most model-independent observational constraints. We avoid the uncertainties and model-dependencies that necessarily arise when solar neighborhood D and \he3 abundances are used to infer primordial D and \he3 via chemical and stellar evolution models. In

Wei Zheng

Based on the IUE SWP spectra obtained between 1978 and 1994, the variations of the UV continuum and the Ly-alpha and C IV emission lines of the broad-line radio galaxy 3C390.3 are studied. The UV continuum between 1220 and 1990 A has varied considerably. In 1991 August, the flux at 1360 A reached a maximum level ~27 times as high as its minimum level. At 185

Alister Graham, Tod R. Lauer, Matthew Colless, Marc Postman

We model the surface brightness profiles of a sample of 119 Abell Brightest Cluster Galaxies (BCG), finding a generalised deVaucouleurs R^{1/n} law, where n is a free parameter, to be appropriate. Departures from the R^{1/4} law are shown to be a real feature of galaxy profiles, not due to observational errors or coupling of n with the other model parameters

Hao Li, Robert Helling, Chao Tang, Ned Wingreen

Protein structures in nature often exhibit a high degree of regularity (secondary structures, tertiary symmetries, etc.) absent in random compact conformations. We demonstrate in a simple lattice model of protein folding that structural regularities are related to high designability and evolutionary stability. We measure the designability of each compact str

S. Mancini, V. I. Man&#39;ko, P. Tombesi

By using a generalization of the optical tomography technique we describe the dynamics of a quantum system in terms of equations for a purely classical probability distribution which contains complete information about the system.

T. Rudolph

An algorithm for quantum computing Hamiltonian cycles of simple, cubic, bipartite graphs is discussed. It is shown that it is possible to evolve a quantum computer into an entanglement of states which map onto the set of all possible paths originating from a chosen vertex, and furthermore to subsequently project out all states not corresponding to Hamiltonia

Yacov Kantor, Mehran Kardar

We consider polymers in which M randomly selected pairs of monomers are restricted to be in contact. Analytical arguments and numerical simulations show that an ideal (Gaussian) chain of N monomers remains expanded as long as M<<N; its mean squared end to end distance growing as r^2 ~ M/N. A possible collapse transition (to a region of order unity) is relate