October 1997 arXiv papers — page 14

C. Barrabès, G. F. Bressange, P. A. Hogan

An example is described in which an asymptotically flat static vacuum Weyl space-time experiences a sudden change across a null hypersurface in the multipole moments of its isolated axially symmetric source. A light-like shell and an impulsive gravitational wave are identified, both having the null hypersurface as history. The stress-energy in the shell is d

R. Parentani

In the absence of a tractable theory of quantum gravity, quantum matter field effects have been so far computed by treating gravity at the Background Field Approximation. The principle aim of this paper is to investigate the validity of this approximation which is not specific to gravity. To this end, for reasons of simplicity and clarity, we shall compare t

G. T. Ter-Kazarian

Suggested theory involves a drastic revision of a role of local internal symmetries in physical concept of curved geometry. Under the reflection of fields and their dynamics from Minkowski to Riemannian space a standard gauge principle of local internal symmetries is generalized. The gravitation gauge group is proposed, which is generated by hidden local int

Robert M. Ziff

It is shown how correlations in the generalized feedback shift-register (GFSR) random-number generator are greatly diminished when the number of feedback taps is increased from two to four (or more) and the tap offsets are lengthened. Simple formulas for producing maximal-cycle four-tap rules from available primitive trinomials are given, and explicit three-

Raffaella Burioni, Davide Cassi, Alberto Pirati, Sofia Regina

We calculate the spectral dimension of a wide class of tree-like fractals by solving the random walk problem through a new analytical technique, based on invariance under generalized cutting-decimation transformations. These fractals are generalizations of the NTD lattices and they are characterized by non integer spectral dimension equal or greater then 2,

T. P. C. van Noije, M. H. Ernst, R. Brito

For a freely evolving granular fluid, the buildup of spatial correlations in density and flow field is described using fluctuating hydrodynamics. The theory for incompressible flows is extended to the general, compressible case, including longitudinal velocity and density fluctuations, and yields qualitatively different results for long range correlations. T

P. Claudin, J. -P. Bouchaud, M. E. Cates, J. P. Wittmer

We investigate in detail two models describing how stresses propagate and fluctuate in granular media. The first one is a scalar model where only the vertical component of the stress tensor is considered. In the continuum limit, this model is equivalent to a diffusion equation (where the rôle of time is played by the vertical coordinate) plus a randomly vary

G. Oshanin, A. Blumen

We study the kinetics of bimolecular, catalytically-activated reactions (CARs) in d-dimensions. The elementary reaction act between reactants takes place only when these meet in the vicinity of a catalytic site; such sites are assumed to be immobile and randomly distributed in space. For CARs we develop a kinetic formalism, based on Collins-Kimball-type idea

Paul J. M. Bastiaansen, Hubert J. F. Knops

A typical problem with Monte Carlo simulations in statistical physics is that they do not allow for a direct calculation of the free energy. For systems at criticality, this means that one cannot calculate the central charge in a Monte Carlo simulation. We present a novel finite size scaling technique for two-dimensional systems on a geometry of LxM, and foc

M. Pleimling, W. Selke

The effect of imperfections on surface critical properties is studied for Ising models with nearest-neighbour ferromagnetic couplings on simple cubic lattices. In particular, results of Monte Carlo simulations for flat, perfect surfaces are compared to those for flat surfaces with random, 'weak' or 'strong', interactions between neighbouring

Gyorgy Szabo, Csaba Toke

A simplified prisoner's game is studied on a square lattice when the players interacting with their neighbors can follow only two strategies: to cooperate (C) or to defect (D) unconditionally. The players updated in a random sequence have a chance to adopt one of the neighboring strategies with a probability depending on the payoff difference. Using Mont

P. Mohanty, E. M. Q. Jariwala, R. A. Webb

We present measurements of the phase coherence time $τ_ϕ$ in six quasi-1D Au wires and clearly show that $τ_ϕ$ is temperature independent at low temperatures. We suggest that zero-point fluctuations of the intrinsic electromagnetic environment are responsible for the observed saturation of $τ_ϕ$. We introduce a new functional form for the temperature depende

P. Mohanty, R. A. Webb

We show that the zero-point fluctuations of the intrinsic electromagnetic environment limit the phase coherence time in all mesoscopic systems at low temperatures. We derive this quantum noise limited dephasing time and its temperature dependence in the crossover to the thermal regime. Our results agree well with most experiments in 1D systems.

Evelyne Tzoukermann, Dragomir R. Radev, William A. Gale

This paper explores morpho-syntactic ambiguities for French to develop a strategy for part-of-speech disambiguation that a) reflects the complexity of French as an inflected language, b) optimizes the estimation of probabilities, c) allows the user flexibility in choosing a tagset. The problem in extracting lexical probabilities from a limited training corpu

Evelyne Tzoukermann, Dragomir R. Radev

This paper addresses issues in part of speech disambiguation using finite-state transducers and presents two main contributions to the field. One of them is the use of finite-state machines for part of speech tagging. Linguistic and statistical information is represented in terms of weights on transitions in weighted finite-state transducers. Another contrib

Markus Kissler-Patig, Jean P. Brodie, Linda L. Schroder, Duncan A. Forbes

We report moderate resolution, high signal-to-noise spectroscopy of globular clusters around NGC 1399, the central cD galaxy in the Fornax cluster. We address issues as diverse as element abundances of globular clusters versus stellar populations in ellipticals, blue horizontal branches in metal-rich globular clusters, broad-band colors as metallicity tracer

Wayne Hayes, Scott Tremaine

Simple ``solar systems'' are generated with planetary orbital radii r distributed uniformly random in log(r) between 0.2 and 50 AU. A conservative stability criterion is imposed by requiring that adjacent planets are separated by a minimum distance of k Hill radii, for values of k ranging from 1 to 8. Least-squares fits of these systems to generalize

Sanjay Reddy, Madappa Prakash, James M Lattimer

We study the charged and neutral current weak interaction rates relevant for the determination of neutrino opacities in dense matter found in supernovae and neutron stars. We establish an efficient formalism for calculating differential cross sections and mean free paths for interacting, asymmetric nuclear matter at arbitrary degeneracy. The formalism is val

D. Marsden, P. R. Blanco, D. E. Gruber, W. A. Heindl

We present the results of observations of the PSR B1509$-$58/MSH 15$-$52 system in X-rays ($2-250$ keV) by the Rossi X-ray Timing Explorer. The spectra of the peak of the pulsed component (radio phase $0.17-0.53$) is fit by a power law of photon index $1.36\pm0.01$, with no evidence of a high energy spectral break seen up to $\sim200$ keV. For the off-pulse

Fred C. Adams, Katherine Freese, Gregory Laughlin, Gregory Tarlé

Motivated by recent experimental proposals to search for extragalactic cosmic rays (including anti-matter from distant galaxies), we study particle propagation through the intergalactic medium (IGM). We first use estimates of the magnetic field strength between galaxies to constrain the mean free path for diffusion of particles through the IGM. We then devel

Slavek M. Rucinski

VLA continuous monitoring of ER Vul during two 11.5 hour sessions in September 1995 in the radio continuum at 3.6 cm (X-band) showed a variation pattern similar to that observed in 1990 and 1991, but at a lower mean flux level. Simultaneous observations with the EUVE satellite in the 70 - 140 A band did not show any significant flaring variability of the sta

K. T. S. Brazier, O. Reimer, G. Kanbach, A. Carraminana

We present a detailed analysis of the high energy gamma-ray source 2EG J0008+7307. The source has a steady flux and a hard spectrum, softening above 2 GeV. The properties of the gamma-ray source are suggestive of emission from a young pulsar in the spatially coincident CTA 1 supernova remnant, which has recently been found to have a non-thermal X-ray plerion

Gregory Laughlin, Fred C. Adams

A number of recently discovered extrasolar planet candidates have surprisingly small orbits, which may indicate that considerable orbital migration takes place in protoplanetary systems. A natural consequence of orbital migration is for a series of planets to be accreted, destroyed, and then thoroughly mixed into the convective envelope of the central star.

Margaret J. Geller, Michael J. Kurtz, ; Gary Wegner, John R. Thorstensen

The ``Century Survey'' (CS hereafter) is a complete redshift survey of a 1$^\circ$-wide strip. It covers 0.03 steradians to a limiting m$_R$ = 16.13. The survey is 98.4% complete and contains 1762 galaxies. Large-scale features in the survey are qualitatively similar to those in other surveys: there are large voids surrounded or nearly surrounded by

Paul Goudfrooij, Ginevra Trinchieri

We present new optical imagery of the X-ray bright elliptical galaxy NGC 5846, the dominant galaxy of a small group of galaxies. A dust lane with a dust mass of 7 10^3 Msun is detected in the central few kpc of NGC 5846. The morphology of the dust features are strikingly similar to that observed for the optical nebulosity AND the X-ray emission. A physical c

G. L. Bryan, M. L. Norman

We compare the results of Eulerian hydrodynamic simulations of cluster formation against virial scaling relations between four bulk quantities: the cluster mass, the dark matter velocity dispersion, the gas temperature and the cluster luminosity. The comparison is made for a large number of clusters at a range of redshifts in three different cosmological mod

Stephen Serjeant, Steve Rawlings, Stephen J. Maddox, Joanne C. Baker

Using complete samples of steep-spectrum quasars, we present evidence for a correlation between radio and optical luminosity which is not caused by selection effects, nor caused by an orientation dependence (such as relativistic beaming), nor a byproduct of cosmic evolution. We argue that this rules out models of jet formation in which there are no parameter

T. Shahbaz, E. Kuulkers

We find a strong correlation between the optical outburst amplitude Delta V and orbital period P_{orb} for the soft X-ray transient sources with orbital periods less than 1 day. By fitting the observed values for 8 X-ray transients we determine an empirical relation that can be used to predict the orbital period of an X-ray transient given only its outburst

Christian R. Kaiser, Jane Dennett-Thorpe, Paul Alexander

This is the second in a series of papers presenting an analytical model for the evolution of FRII radio sources. In this paper we evaluate the expected radio emission from a radio source incorporating energy loss processes for the relativistic electrons. By combining these results with our earlier dynamical model we calculate evolutionary tracks through the

E. Slezak, F. Durret, J. Guibert, C. Lobo

We present two catalogues of galaxies in the direction of the rich cluster \a85. The first one includes 4,232 galaxies located in a region $\pm 1^\circ$ from the cluster centre. It has been obtained from a list of more than 25,000 galaxy candidates detected by scanning a Schmidt photographic plate taken in the \bj band. Positions are very accurate in this ca

J. Richard Bond, James W. Wadsley

We describe large scale structure at high redshift in terms of the Cosmic Web picture for {S,Lambda,O,H}CDM models: how galactic-scale ``peak-patches'', filaments and membranes create an interconnected intergalactic medium. The ideas are applied to our Ly$α$ forest simulations of ``shear-field patches''. We discuss simulation method and desig

R. Tantalo, A. Bressan, C. Chiosi

The gradients in line strength indices such as Mg2 and <Fe> (Carollo & Danziger 1994a,b; Carollo et al. 1993), and their increase toward massive system (Worthey et al. 1992, Faber et al. 1992, Davies et al. 1993, Weiss et al. 1995) observed in elliptical galaxies are customarily considered as indicators of gradients in the chemical abundances of Mg and Fe an

S. A. Levshakov, W. H. Kegel

We show that spatial correlations in a stochastic large scale velocity field in an otherwise smooth intergalactic medium (homogeneous comoving density) superposed on the general Hubble flow, may cause a `line-like&#39; structure in QSO spectra similar to the population of unsaturated Ly-alpha forest lines which usually are attributed to individual clouds wit

Kai Behrend

We prove that the system of Gromov-Witten invariants of the product of two varieties is equal to the tensor product of the systems of Gromov-Witten invariants of the two factors.

Ilya Zakharevich

We discuss an analogue of Riemann-Roch theorem for curves with an infinite number of handles. We represent such a curve X by its Shottki model, which is an open subset U of CP^{1} with infinite union of circles as a boundary. An appropriate bundle on X is ω^{1/2} \otimes L, L being a bundle with (say) constants as gluing conditions on the circles. An admissi

Igor V. Dolgachev

We study stable vector bundles over the modular curve X(p) corresponding to the principal congruence subgroup of the modular group of prime level p which are invariant with respect to its automorphism group.

M. Maul, A. Schafer, E. Mirkes, G. Radel

The asymmetry distributions for several kinematic variables are considered for finding a systematic way to maximize the signal for the extraction of the polarized gluon density. The relevance of mass effects for the corresponding dijet cross section is discussed and the different approximations for including mass effects are compared. We also compare via the

B. Abbott

A measurement of the mass of the W boson is presented which is based on a sample of 5982 W -> e nu decays observed in pbar-p collisions at sqrt(s) = 1.8 TeV with the D0 detector during the 1992-1993 run. From a fit to the transverse mass spectrum, combined with measurements of the Z boson mass, the W boson mass is measured to be M_W = 80.350+-0.140(stat)+-0.

Michael S. Chanowitz

Within the framework of the standard model we observe that there is a significant discrepancy between the most precise $Z$ boson decay asymmetry measurement and the limit from direct searches for Higgs boson production. Using methods inspired by the Particle Data Group we explore the possible effect on fits of the Higgs boson mass. In each case the central v

J. Ellis, I. Jack, D. R. T. Jones, Marek Karliner

We use Asymptotic Pade Approximants (APAP&#39;s) to predict the four- and five-loop β-functions in QCD and N=1 supersymmetric QCD (SQCD), as well as the quark mass anomalous dimensions in Abelian and non-Abelian gauge theories. We show how the accuracy of our previous β-function predictions at the four-loop level may be further improved by using estimators w

G. Dvali, Hong Liu, Tanmay Vachaspati

We propose a new solution to the cosmological monopole problem in which domain walls sweep away the magnetic monopoles and subsequently decay. The solution does not require extensive fine tuning or model building - it works for the prototype SU(5) Grand Unification model. More generally, it shows that defect interactions can lead to ``defect erasure'' in pha

Z. Maassarani

The bosonic su(n) Hubbard model was recently introduced. The model was shown to be integrable in one dimension by exhibiting the infinite set of conserved quantities. I derive the R-matrix and use it to show that the conserved charges commute among themselves. This new matrix is a non-additive solution of the Yang-Baxter equation. Some properties of this mat

M. Faber, J. Greensite, S. Olejnik

We argue that the approximate ``Casimir scaling&#39;&#39; of the string tensions of higher-representation Wilson loops is an effect due to the finite thickness of center vortex configurations. It is shown, in the context of a simple model of the Z(2) vortex core, how vortex condensation in Yang-Mills theory can account for both Casimir scaling in intermediat

Charles F. Dunkl

Calogero-Sutherland models associated to the Weyl groups of type A and B with exchange terms included in the Hamiltonians systems have non-symmetric eigenfunctions, which are products of the ground state with members of a family of orthogonal polynomials. These polynomials can be defined and studied by using the differential-difference operators introduced b

Jiin-Chang Shaw, Ming-Hsien Tu

We construct the supersymmetric extensions of the Darboux-Backlund transformations (DBTs) for the Manin-Radul super KdV hierarchy using the super-pseudo-differential operators. The elementary DBTs are triggered by the gauge operators constructed from the wave functions and adjoint wave functions of the hierarchy. Iterating these elementary DBTs, we obtain no

H. Hamidian

We study Abelian Chern-Simons field theories with matter fields and global SU(N) symmetry in the presence of random weak quenched disorder. In the absence of disorder these theories possess N=2 supersymmetric fixed points and N=1 supersymmetric fixed lines in the infra-red limit. We show that although the presence of disorder forbids any supersymmetry of the

JM Figueroa-O&#39;Farrill, C Koehl, B Spence

In four-dimensional gauge theory there exists a well-known correspondence between instantons and holomorphic curves, and a similar correspondence exists between certain octonionic instantons and triholomorphic curves. We prove that this latter correspondence stems from the dynamics of various dimensional reductions of ten-dimensional supersymmetric Yang-Mill

J. Schneider, H. Wallis

We study the thermodynamical properties of a mesoscopic Fermi gas in view of recent possibilities to trap ultracold atoms in a harmonic potential. We focus on the effects of shell closure for finite small atom numbers. The dependence of the chemical potential, the specific heat and the density distribution on particle number and temperature is obtained. Isot

M. Arneodo, S. Maselli, C. Peroni

The possibility to study elastic and diffractive physics in pp collisions at LHC is investigated. For this purpose we have considered detectors close to the beam in conjunction with the magnetic elements of the accelerator to provide a high precision spectrometer for very forward final state protons. The geometrical acceptance is given and momentum resolutio

Y. Goldin, Y. Avishai

Non - equilibrium tunneling current of an Anderson impurity system subject to both constant and alternating electric fields is studied. A time - dependent Schrieffer - Wolff transformation maps the time - dependent Anderson Hamiltonian onto a Kondo one. Perturbation expansion in powers of the Kondo coupling strength is carried out up to third order, yielding

David B. Fairlie, Tatsuya Ueno

Generalisations of the familiar Euler top equations in three dimensions are proposed which admit a sufficiently large number of conservation laws to permit integrability by quadratures. The usual top is a classical analogue of the Nahm equations. One of the examples discussed here is a seven-dimensional Euler top, which arises as a classical counterpart to t

Y. P. Jing, Yasushi Suto

We perform a detailed analysis of the statistical significance of a concentration of Lyman break galaxies at $z \sim 3$ recently discovered by Steidel et al. (1997), using a series of N-body simulations with $N=256^3$ particles in a $(100\himpc)^3$ comoving box. While the observed number density of Lyman break galaxies at $z\sim3$ implies that they correspon

Andrew Kresch

We consider the operation of intersecting with a locally principal Cartier divisor (i.e., a Cartier divisor which is principal on some neighborhood of its support). We describe this operation explicitly on the level of cycles and rational equivalences and as a corollary obtain a formula for rational equivalence between intersections of two locally principal

Branislav Jurco, Peter Schupp

We give the construction of quantum Lax equations for IRF models and difference versions of Calogero-Moser-Sutherland models introduced by Ruijsenaars. We solve the equations using factorization properties of the underlying face Hopf algebras/elliptic quantum groups. This construction is in the spirit of the Adler-Kostant-Symes method and generalizes our pre

Vwani P. Roychowdhury, Farrokh Vatan

We first present a useful characterization of additive (stabilizer) quantum error-correcting codes. Then we present several examples of We first present a useful characterization of additive (stabilizer) quantum error--correcting codes. Then we present several examples of nonadditive codes. We show that there exist infinitely many non-trivial nonadditive cod

Pavel Exner, Petr Seba

We consider scattering of a three-dimensional particle on a finite family of delta potentials. For some parameter values the scattering wavenctions exhibit nodal lines in the form of closed loops, which may touch but do not entangle. The corresponding probability current forms vortical singularities around these lines; if the scattered particle is charged, t

Jonathan Gratus

This is a copy of the talk given at the conference ``Methods in Field Theory&#39;&#39; at Stara Lesna, The Slovak Republic, Sepemeber 22-26, 1997. An introduction to the noncommutative sphere and a summary of the results of articles q-alg/9703038 \cite{Gratus5}, and q-alg/9708003 \cite{Gratus6} is given. This includes results about the the algebra of scalar,

Mark A. Peterson

The possibility is considered that turbulence is described by differential equations for which uniqueness fails maximally, at least in some limit. The inviscid Burgers equation, in the context of Onsager&#39;s suggestion that turbulence should be described by a negative absolute temperature, is such a limit. In this picture, the onset of turbulence coincides

Bogdan Morariu

The Feynman path integral is used to quantize the symplectic leaves of the Poisson-Lie group SU(2)*. In this way we obtain the unitary representations of U_q(su(2)). This is achieved by finding explicit Darboux coordinates and then using a phase space path integral. I discuss the *-structure of SU(2)* and give a detailed description of its leaves using vario

Zahir A. Daya, V. B. Deyirmenjian, Stephen W. Morris, John R. de Bruyn

We report experiments on convection driven by a radial electrical force in suspended annular smectic A liquid crystal films. In the absence of an externally imposed azimuthal shear, a stationary one-dimensional (1D) pattern consisting of symmetric vortex pairs is formed via a supercritical transition at the onset of convection. Shearing reduces the symmetrie

Kelly Ann Herbst, Franz Gross

The sensitivity of the deuteron form factor to contributions from the excited states of the nucleon is explored using a simple model of the nucleon-nucleon interaction which employs a tower of charged nucleon resonances. The model is manifestly covariant, analytically solvable, and gauge invariant. The consequences of this model are studied in the simplest p

David Goss

Let $\k$ be a global function field in 1-variable over a finite extension of $\Fp$, $p$ prime, $\infty$ a fixed place of $\k$, and $\A$ the ring of functions of $\k$ regular outside of $\infty$. Let $E$ be a Drinfeld module or $T$-module. Then, as in \cite{go1}, one can construct associated characteristic $p$ $L$-functions based on the classical model of abe

John McCuan, David Hoffman

The ends of a complete embedded minimal surface of {\em finite total curvature} are well understood (every such end is asymptotic to a catenoid or to a plane). We give a similar characterization for a large class of ends of {\em infinite total curvature}, showing that each such end is asymptotic to a helicoid. The result applies, in particular, to the genus

Juan Pedro Garrahan, Martin Kruczenski

The collective dynamics of solitons with a coset space G/H as moduli space is studied. It is shown that the collective band for a vibrational state is given by the inequivalent coset space quantization corresponding to the representation of H carried by the vibration.

Theodora Ioannidou

We present soliton and soliton-antisoliton solutions for the integrable chiral model in 2+1 dimensions with nontrivial (elastic) scattering. These solutions can be obtained either as the limiting cases of the ones already constructed by Ward or by adapting Uhlenbeck&#39;s method.

A. Di Giacomo

Evidence is discussed, from lattice simulations, that QCD vacuum is a dual superconductor in the confining phase, and undergoes a phase transition to normal at the deconfining temperature.

Andrzej Czarnecki, Kirill Melnikov

Recent progress in calculating O(alpha_s^2) corrections to inclusive and exclusive semileptonic b-->c transitions is reviewed. The impact of these corrections on the |V_cb| determination from both inclusive and exclusive B decays is discussed.

Tanmay Vachaspati

I describe various aspects of the construction of a dual standard model including how it may be possible to obtain the charge spectrum, the family structure and spin of the known matter particles. I summarize the encouraging features of the model, the open problems and the predictions indicated at this stage.

Juan Carlos D&#39;Olivo, Jose F. Nieves

We calculate the nucleon contribution to the photon self-energy in a plasma, including the effect of the anomalous magnetic moment of the nucleons. General formulas for the transverse and longitudinal components of the self-energy are obtained and we give explicit results in various limits of physical interest. The formulas are relevant for the study of the

T. M. Aliev, N. K. Pak, M. Savci

The radiative B -> tau^+ tau^- gamma decay is investigated in the framework of the Standard Model. When only short (short and long together) distance contributions are taken into account, the Branching Ratio is found as 9.54x10^(-9) (1.52x10^(-8)), for the value of the cut delta = 0.01 imposed on the photon energy.

F. de Campos, S. M. Lietti, S. F. Novaes, R. Rosenfeld

We present the sensitivity limits on the coefficients of a dimension-6 effective operators that parametrizes the possible effects of new physics beyond the Standard Model. Our results are based on the study of the processes $e^+ e^- \to W^+ W^- γ$, $Z Zγ$, and $Zγγ$ at NLC energies. In our calculations, we include all the anomalous interactions involving vec

O. Martin, A. Schaefer, M. Stratmann, W. Vogelsang

We check numerically if Soffer&#39;s inequality for quark distributions is preserved by next-to-leading order QCD evolution. Assuming that the inequality is saturated at a low hadronic scale we estimate the maximal transverse double spin asymmetry for Drell-Yan muon pair production to next-to-leading order accuracy.

Michael A. Doncheski, Stephen Godfrey, K. Andrew Peterson

We studied single $W$ boson production in high energy $eγ$ collisions and the sensitivity of various observables to the $WWγ$ gauge boson coupling by evaluating the helicity amplitudes of all Feynman diagrams which contribute to the final state being studied, including the $W$ decay to final state fermions. We examined $W$ production at 500 GeV and 1 TeV $e^

V. Morénas, A. Le Yaouanc, L. Oliver, O. Pène

In quark models à la Bakamjian and Thomas, that yield covariance and Isgur-Wise scaling of form factors in the heavy quark limit, we compute the decay constants $f^{(n)}$ and $f^{(n)}_{1/2}$ of S-wave and P-wave mesons composed of heavy and light quarks. Heavy quark limit scaling $\sqrt{M} f = Cst$ is obtained, and it is shown that this class of models satis

A Hebecker, P V Landshoff

The structure of the nonperturbative vector meson vertex function complicates the proof of the factorisation theorem for the reaction $γ^*p\to Vp$. It leads to additional contributions but, in a simple model for the vertex function, gauge invariance ensures that they cancel and factorisation is preserved.

A. Bottino, F. Donato, N. Fornengo, S. Scopel

In this note we present an extension of our previous analysis of some preliminary experimental results of the DAMA/NaI Collaboration which might be indicative of a yearly modulation effect. Here we present a direct way for obtaining from the experimental data the relevant cosmological implications for relic neutralinos. We find that some of the configuration

S. V. Goloskokov

It is shown that the $A_{ll}$ asymmetry in diffractive $Q \bar Q$ leptoproduction is not small at HERA energies and dependent on the structure of the pomeron couplings and on the masses of produced quarks. The connection of this asymmetry with the non-forward gluon distribution in the proton is discussed.

Tanmay Vachaspati

In these lectures, I review cosmological phase transitions and the topological aspects of spontaneous symmetry breaking. I then discuss the formation of walls, strings and monopoles during phase transitions including lattice based studies of defect formation and recent attempts to go beyond the lattice. The close connection of defect formation with percolati

Ivan Maksymyk

We examine the subtle differences between two possible frameworks for the calculation of quarkonium production. The differences between the two methods are not a concern when one calculates only to leading order in the relativistic expansion, but when relativistic corrections are included, the two formulations seem at first to be at variance with one another

C. Bernard, T. Blum, C. E. DeTar, U. M. Heller

Quantum chromodynamics with two zero mass flavors is expected to exhibit a phase transition with O(4) critical behavior. Fixing the universality class is important for phenomenology and for facilitating the extrapolation of simulation data to physical quark mass values. At Lattice &#39;96 the Tsukuba and Bielefeld groups reported results from new simulations

C. Best, M. Göckeler, R. Horsley, H. Perlt

We compute the lower moments of the structure functions of $π$ and $ρ$. Of particular interest are the spin-dependent structure functions of the $ρ$ as they give new information about quark binding effects.

P. Boyle, UKQCD Collaboration

We present results of a quenched calculation of the heavy-light and quarkonium spectrum using the tadpole improved clover action. We resolve completely the triplet chi P-states in quarkonium systems, and obtain evidence for fine structure of the heavy-light P-states. Approximate scaling of the hyperfine splittings is observed, producing results that are sign

J. L. Alonso, Ph. Boucaud, V. Martin-Mayor, A. J. van der Sijs

We present a 2+1-dimensional lattice model for the copper oxide superconductors and their parent compounds, in which both the charge and spin degrees of freedom are treated dynamically. The spin-charge coupling parameter is associated to the doping fraction in the cuprates. The model is able to account for the various phases of the cuprates and their propert

A. Belogianni et al

Photons produced in pi p interactions at 280 GeV/c were detected by reconstructing the e+e- pairs produced via the materialisation of the photons in a 1 mm thick lead sheet placed in front of the MWPCs of the OMEGA spectrometer at CERN. A soft photon signal 7.8 +/- 1.5 times the Q.E.D. inner bremsstrahlung prediction was observed confirming the results of a

Michael J. Pfenning, L. H. Ford

We discuss quantum inequalities for minimally coupled scalar fields in static spacetimes. These are inequalities which place limits on the magnitude and duration of negative energy densities. We derive a general expression for the quantum inequality for a static observer in terms of a Euclidean two-point function. In a short sampling time limit, the quantum

K. A. Bronnikov, V. D. Ivashchuk, V. N. Melnikov

A multidimensional model with (at most) one curved factor space and n Ricci-flat internal spaces is considered, with arbitrary numbers of dilatonic scalar fields and antisymmetric forms of both electric and magnetic types, associated with p-branes in theories like M-theory. The problem setting covers, in particular, homogeneous cosmologies, static, spherical

James Isenberg, Alan D. Rendall

We show that there exist maximal globally hyperbolic solutions of the Einstein-dust equations which admit a constant mean curvature Cauchy surface, but are not covered by a constant mean curvature foliation.

Ursula Hamenstaedt

We investigate the cross ratio for closed negatively curved manifolds. As one of several applications, we obtain that for two such homotopy equivalent manifolds M and N, the following is true : If M and N have the same marked length spectrum and if the Anosov splitting for M is C^1 then M and N have the same volume.

John Lott

Let L be a lattice in a connected Lie group. We show that besides a few exceptional cases, the deficiency of L is nonpositive.

P. L. de Andres, K. Reuter, F. J. Garcia-Vidal, D. Sestovic

We analyze BEEM experiments. At low temperatures and low voltages, near the threshold value of the Schottky barrier, the BEEM current is dominated by the elastic component. Elastic scattering by the lattice results in the formation of focused beams and narrow lines in real space. To obtain the current injected in the semiconductor, we compute the current dis

J. -Q. Liang, Y. -B. Zhang, H. J. W. Mueller-Kirsten, Jian-Ge Zhou

A formula suitable for a quantitative evaluation of the tunneling effect in a ferromagnetic particle is derived with the help of the instanton method. The tunneling between n-th degenerate states of neighboring wells is dominated by a periodic pseudoparticle configuration. The low-lying level-splitting previously obtained with the LSZ method in field theory

Joshua E. S. Socolar

A lattice model is presented for investigating the fluctuations in static granular materials under gravitationally induced stress. The model is similar in spirit to the scalar q-model of Coppersmith et al., but ensures balance of all components of forces and torques at each site. The geometric randomness in real granular materials is modeled by choosing rand

H. Krakauer, R. Yu, C. -Z. Wang, K. M. Rabe

Molecular-dynamics simulations of KNbO$_3$ reveal preformed dynamic chain-like structures, present even in the paraelectric phase, that are related to the softening of phonon branches over large regions of the Brillouin zone. The phase sequence of ferroelectric transitions is correctly reproduced, showing that the first-principles effective Hamiltonian used

A. O. Parry, P. S. Swain

We address three problems faced by effective interfacial Hamiltonian models of wetting based on a single collective coordinate \ell representing the position of the unbinding fluid interface. Problems (P1) and (P2) refer to the predictions of non-universality at the upper critical dimension d=3 at critical and complete wetting respectively which are not born

B. Jonas Ohlsson, Mark S. Miller, Mats-Erik Pistol

A dense phase of GaAs wires forms in the early stages of strained growth on GaP,assembling from elongated Stranski-Krastanow islands. The electron diffraction during growth is consistent with long, faceted GaAs islands that are anisotropically deformed without dislocations. The lateral wire period and long shapes are not predicted by published models, though

T. Fukui, N. Kawakami

We investigate a two-leg spin ladder system composed of alternating-spin chains with two-different kind of spins. The fixed point properties are discussed by using spin-wave analysis and non-linear sigma model techniques. The model contains various massive phases, reflecting the interplay between the bond-alternation and the spin-alternation.

A. Mary Selvam

Atmospheric flows exhibit selfsimilar fluctuations on all scales(space-time) ranging from climate(kilometers/years) to turbulence(millimeters/seconds) manifested as fractal geometry to the global cloud cover pattern concomitant with inverse power law form for power spectra of temporal fluctuations. Selfsimilar fluctuations implying long-range correlations ar

Eyal Maoz

Short version: Zaritsky and Lin (1997, ZL97) have recently presented observations which can be interpreted as evidence for an intervening stellar population along the line-of-sight to the LMC, at a distance of ~34 kpc. They suggest that it may belong to a low surface-brightness dwarf galaxy, or to the tidal debris of a disrupted galaxy, and derive an optical

Hartmut Schulz, Stefanie Komossa, Thomas W. Berghoefer, Berto Boer

We present ROSAT observations of the starburst galaxy NGC 2782 (HRI plus a weak PSPC frame) and the ultraluminous infrared galaxy NGC 6240 (PSPC). The (0.1-2.4) keV spectra of both objects appear similar. However, due to better sampling spectral modeling is only warranted in case of NGC 6240 for which both a single thermal Raymond-Smith model (kT = 0.44) or

M. W. Sincell, M. Gehmeyr, D. Mihalas

We calculate the quasi-stationary structure of a radiating shock wave propagating through a spherically symmetric shell of cold gas by solving the time-dependent equations of radiation hydrodynamics on an adaptive grid. We show that this code successfully resolves the shock wave in both the subcritical and supercritical cases and, for the first time, we have