February 1995 arXiv papers — page 6

Sheng-Li Tan

The purpose of this paper is to give a linear and effective height inequality for algebraic points on curves over functional fields. Our height inequality can be viewed as the logarithmic canonical class inequality of a punctured curve over a functional field (a fibered surface minus a section).

Mina Teicher, Boris Moishezon

Computation of the fundamental group of the complement in the complex plane of the branch curve S , of a generic projection of the Veronese surface to the plane is presented. This paper is a continuation of our previous papers: Braid Group Technique I - IV. In I and II we developed algorithms to compute braid monodromy of a brunch curve, provided there exist

Evgenyi A. Ivanov

Starting from the dual action of $(4,4)$ $2D$ twisted multiplets in the harmonic superspace with two independent sets of $SU(2)$ harmonic variables, we present its generalization which hopefully provides an off-shell description of general $(4,4)$ supersymmetric sigma models with torsion. Like the action of the torsionless $(4,4)$ hyper-Kähler sigma models i

F. A. Dilkes, D. G. C. McKeon

The standard formulation of a massive Abelian vector field in $2+1$ dimensions involves a Maxwell kinetic term plus a Chern-Simons mass term; in its place we consider a Chern-Simons kinetic term plus a Stuekelberg mass term. In this latter model, we still have a massive vector field, but now the interaction with a charged spinor field is renormalizable (as o

Youngjai Kiem, Erik Verlinde, Herman Verlinde

We investigate the effect of gravitational back-reaction on the black hole evaporation process. The standard derivation of Hawking radiation is re-examined and extended by including gravitational interactions between the infalling matter and the outgoing radiation. We find that these interactions lead to substantial effects. In particular, as seen by an outs

A. Ceresole, R. D'Auria, S. Ferrara, A. Van Proeyen

We consider duality transformations in N=2, d=4 Yang--Mills theory coupled to N=2 supergravity. A symplectic and coordinate covariant framework is established, which allows one to discuss stringy `classical and quantum duality symmetries' (monodromies), incorporating T and S dualities. In particular, we shall be able to study theories (like N=2 heterotic

Shaojin Qin, Tai-Kai Ng, Zhao-Bin Su

In this letter we report our results in investigating edge effects of open antiferromagnetic Heisenberg spin chains with spin magnitudes $S=1/2, 1,3/2,2$ using the density-matrix renormalization group (DMRG) method initiated by White. For integer spin chains, we find that edge states with spin magnitude $S_{edge}=S/2$ exist, in agreement with Valence-Bond-So

Giulia Ricciardi

We analyze the short and long distance contributions to inclusive $B \rightarrow X_d γ$ decay, paying particular attention to the dependence on the Cabibbo-Kobayashi-Maskawa parameter $V_{td}$. We discuss penguin diagrams with internal $u$ and $c$ quarks in the framework of the effective field theory. We also estimate the size of possible long range contribu

K. G. Chetyrkin, J. H. Kuehn, M. Steinhauser

The three-loop QCD corrections to the $ρ$ parameter from top and bottom quark loops are calculated. The result differs from the one recently calculated by Avdeev et al. As function of the pole mass the numerical value is given by $\drho=\frac{3G_F M_t^2}{8\sqrt{2}π^2}(1- 2.8599 \api - 14.594 (\api)^2 )$.

Gilberto Colangelo

By using the Renormalization Group Equations in Chiral Perturbation Theory, one can calculate the double chiral logs that appear at two loops in any matrix element. We calculate them in the $ππ$ scattering amplitude, where they represent the potentially largest two loop contribution. It is shown that their correction is reasonably small.

Atro Voutilainen

There are two main methodologies for constructing the knowledge base of a natural language analyser: the linguistic and the data-driven. Recent state-of-the-art part-of-speech taggers are based on the data-driven approach. Because of the known feasibility of the linguistic rule-based approach at related levels of description, the success of the data-driven a

Paolo Cea, Luigi Tedesco

We evaluate the thermal corrections to the generalized Gaussian effective potential. We carry out the calculations of the lowest order corrections in the case of self-interacting scalar fields in one and two spatial dimensions, and study the restoration of the symmetry at high temperatures.

Kei-Ichi Kondo

We give another reformulation of the Thirring model (with four-fermion interaction of the current-current type) as a gauge theory and identify it with a gauge-fixed version of the corresponding gauge theory according to the Batalin-Fradkin formalism. Based on this formalism, we study the chiral symmetry breaking of the $D$-dimensional Thirring model ($2<D<4$

Maxim Nazarov, Vitaly Tarasov

We study certain family of finite-dimensional modules over the Yangian $Y(gl_N)$. The algebra $Y(gl_N)$ comes equipped with a distinguished maximal commutative subalgebra $A(gl_n)$ generated by the centres of all algebras in the chain $Y(gl_1)\subset Y(gl_2)\subset...\subset Y(gl_N)$. We study the finite-dimensional $Y(gl_N)$-modules with a semisimple action

Jae-Kwon Kim

For the two dimensional random bond disordered Ising ferromagnet, we measured bulk data of the magnetic susceptibility ($χ$) and correlation length ($ξ$) up to $ξ\simeq 536$, with the use of a novel finite size scaling Monte Carlo technique. Our data are exclusively consistent with normal power-law critical behaviors with only one singular point at criticali

D. B. Fairlie, I. A. B. Strachan

The Hamiltonian structure of the two-dimensional dispersionless Toda hierarchy is studied, this being a particular example of a system of hydrodynamic type. The polynomial conservation laws for the system turn out, after a change of variable, to be associated with the axially symmetric solutions of the 3-dimensional Laplace equation and this enables a genera

M. Kontsevich, Yu. Manin, R. Kaufmann

The operation of tensor product of Cohomological Field Theories (or algebras over genus zero moduli operad) introduced in an earlier paper by the authors is described in full detail, and the proof of a theorem on additive relations between strata classes is given. This operation is a version of the Kuenneth formula for quantum cohomology. In addition, rank o

Paul J. Ellis, Roland Knorren, Madappa Prakash

Based on the Kaplan-Nelson Lagrangian, we investigate kaon condensation in dense neutron star matter allowing for the explicit presence of hyperons. Using various models we find that the condensate threshold is sensitive to the behavior of the scalar density; the more rapidly it increases with baryon density, the lower is the threshold for condensation. The

A. De Pace

The separated isovector spin-longitudinal and spin-transverse responses from a recent (p,n) quasifree experiment at 494 MeV are analyzed in a Glauber theory framework up to two-step contributions. Nuclear correlations are treated in the continuum random phase approximation, accounting for the spreading width of the particle-hole states. A good description of

W. Zhong, David Vanderbilt, K. M. Rabe

We carry out a completely first-principles study of the ferroelectric phase transitions in BaTiO$_3$. Our approach takes advantage of two features of these transitions: the structural changes are small, and only low-energy distortions are important. Based on these observations, we make systematically improvable approximations which enable the parameterizatio

P. Ruggerone, B. Kohler, S. Wilke, M. Scheffler

The large interest in the properties of transition metal surfaces has been recently fostered by inelastic helium atom scattering experiments carried out by Hulpke and Luedecke. Sharp and giant anomalies in the surface phonon dispersion curves along Gamma-H and Gamma-S have been detected on W(110) and Mo(110) at a coverage of one monolayer of hydrogen. At the

Claus Montonen

Lectures presented at the VI Mexican School of Particles and Fields, Villahermosa, 3-7 October, 1994. Contents: 1. Introduction 2. The Symmetry Group Approach to the Quantum Mechanics of Identical Particles 3. How Come Anyons? 4. The Transmutation of Statistics into a Topological Interaction 5. The Chern-Simons Action and Anyon Statistics 6. Nonrelativistic

J. Sucher

In relativistic potential models of quarkonia based on a Dirac-type of equation with a local potential there is a sharp distinction between a linear potential V which is vector-like and one which is scalar-like: There are normalizable solutions for a scalar-like V but not for a vector-like V. It is pointed out that if instead one uses an equation of the no-p

K. Adel, F. J. Ynduráin

We calculate production by vector and axial currents of heavy quark pairs ($c\bar{c}$, $b\bar{b}$, $t\bar{t}$) close to threshold. We take into account strong interaction contributions (including radiative corrections and leading nonperturbative effects) by using the Fermi-Watson final state interaction theorem. We use the results obtained to compare with ex

Alex Kovner, Larry McLerran, Heribert Weigert

We consider the collisions of large nuclei using the theory of McLerran and Venugopalan. The two nuclei are ultra-relativistic and sources of non-abelian Weizsäcker-Williams fields. These sources are in the end averaged over all color orientations locally with a Gaussian weight. We show that there is a solution of the equations of motion for the two nucleus

Xiangdong Ji

I discuss in this talk the physics of the $Q^2$ dependence of the $G_1(x,Q^2)$ structure function sum rule. For $Q^2>3$ GeV$^2$, the $Q^2$ variation is controlled by pure QCD radiative corrections. For $0.5<Q^2<3$ GeV$^2$, the twist-four contribution becomes significant, but stays perturbative. For $Q^2$ below $\sim 0.05$, the sum rule is determined by low-e

Xing Min Wang, Xiaotong Song

The center-of-mass(CM) of a few-body quantum system with a central field is discussed. If the particles are in the designative eigenstates, the CM coordinates of the system can be well-defined. In the CM bag model as well as in other models with central fields, the CM-freedom separation rule and effective nucleon electro-magnetic currents can be presented wi

J. Gluza, M. Zralek

We investigate the reactions $e^-e^- \rightarrow W_i^-W_j^-$ for various gauge bosons production processes in the frame of the standard model with additional right-handed neutrinos and the Left-Right symmetric model. The present bounds on the various model parameters are taken into account. The question of the cross section behaviour for large energy and the

Arild Skjold, Per Osland

In a more general electroweak theory, there could be Higgs particles that are odd under $CP$, and also Higgs-like particles which are not eigenstates of $CP$. We discuss distributions which for the Bjorken process are sensitive to the $CP$ parity. Correlations among momenta of the initial electron and final-state fermions yield this kind of information. We d

F. Hussain, A. N. Ivanov, N. I. Troitskaya

The infinite mass effective theory, when a heavy quark mass tends to infinity, and Chiral perturbation theory at the quark level, based on the extended Nambu -- Jona -- Lasinio model with linear realization of chiral $U(3)\times U(3)$ symmetry, are applied to the calculation of current $s$ -- quark mass corrections to the form factors of the $D\to\bar K~e^+~

M. Flanigan, P. Tamayo

We present an optimized version of a cluster labeling algorithm previously introduced by the authors. This algorithm is well suited for large-scale Monte Carlo simulations of spin models using cluster dynamics on parallel computers with large numbers of processors. The algorithm divides physical space into rectangular cells which are assigned to processors a

Tatsuya Nakada

The Large Hadron Collider (LHC) proposed at CERN will be the ultimate source of B-mesons. With the large number of B-mesons expected at LHC, a real precision test of CP violation in B-meson decays will become possible. There are already several efforts made to explore this possibility and a summary of those activities is presented.

Jaume Garriga

In the context of the open inflationary universe, we calculate the amplitude of quantum fluctuations which deform the bubble shape. These give rise to scalar field fluctuations in the open Friedman-Robertson-Walker universe which is contained inside the bubble. One can transform to a new gauge in which matter looks perfectly smooth, and then the perturbation

Parentani Renaud

The recoils of an accelerated system caused by the transitions characterizing thermal equilibrium are taken into account through the quantum character of the position of the system. The specific model is that of a two level ion accelerated by a constant electric field. The introduction of the wave function of the center of mass position clarifies the role of

Sivan Kartha, James Krumhansl, James Sethna, Lisa Wickham

Defying the conventional wisdom regarding first--order transitions, {\it solid--solid displacive transformations} are often accompanied by pronounced pretransitional phenomena. Generally, these phenomena are indicative of some mesoscopic lattice deformation that ``anticipates&#39;&#39; the upcoming phase transition. Among these precursive effects is the obse

Anthony Zee

I give a brief review of effective field theory, disscussing the contribution of Feza Gürsey in particular and focusing on the literature I am most familiar with.

Linda M. Zeger, Yu-Min Juan, Efthimios Kaxiras, A. Antonelli

We study a new hypothetical form of solid carbon \csc, with a unit cell which is composed of the \cs \ fullerene cluster and an additional single carbon atom arranged in the zincblende structure. Using {\it ab initio} calculations, we show that this new form of solid carbon has lower energy than hyperdiamond, the recently proposed form composed of \cs \ unit

Yumin Juan, Efthimios Kaxiras

We present a study of the equilibrium properties of $sp$-bonded solids within the pseudopotential approach, employing recently proposed generalized gradient approximation (GGA) exchange correlation functionals. We analyze the effects of the gradient corrections on the behavior of the pseudopotentials and discuss possible approaches for constructing pseudopot

F. Dominguez-Adame

Optical absorption spectra of Frenkel excitons in random one-dimensional systems are presented. Two models of inhomogeneous broadening, arising from a Gaussian distribution of on-site energies, are considered. In one case the on-site energies are uncorrelated variables whereas in the second model the on-site energies are pairwise correlated (dimers). We obse

M. Basler, W. Krech, K. Yu. Platov

Within the RSJ model, we performed a theoretical analysis of phase-locking in elementary strongly coupled Josephson junction cells. For this purpose, we developed a systematic method allowing the investigation of phase-locking in cells with small but non-vanishing loop inductance.The voltages across the junctions are found to be locked with very small phase

Andrew Kehler, Mary Dalrymple, John Lamping, Vijay Saraswat

We argue that the resource sharing that is commonly manifest in semantic accounts of coordination is instead appropriately handled in terms of structure-sharing in LFG f-structures. We provide an extension to the previous account of LFG semantics (Dalrymple et al., 1993b) according to which dependencies between f-structures are viewed as resources; as a resu

Richard Crouch

The paper describes a substitutional approach to ellipsis resolution giving comparable results to Dalrymple, Shieber and Pereira (1991), but without the need for order-sensitive interleaving of quantifier scoping and ellipsis resolution. It is argued that the order-independence results from viewing semantic interpretation as building a description of a seman

Atro Voutilainen, Pasi Tapanainen

We are concerned with dependency-oriented morphosyntactic parsing of running text. While a parsing grammar should avoid introducing structurally unresolvable distinctions in order to optimise on the accuracy of the parser, it also is beneficial for the grammarian to have as expressive a structural representation available as possible. In a reductionistic par

Atro Voutilainen, Timo Jarvinen

Is it possible to specify a grammatical representation (descriptors and their application guidelines) to such a degree that it can be consistently applied by different grammarians e.g. for producing a benchmark corpus for parser evaluation? Arguments for and against have been given, but very little empirical evidence. In this article we report on a double-bl

Atro Voutilainen

NPtool is a fast and accurate system for extracting noun phrases from English texts for the purposes of e.g. information retrieval, translation unit discovery, and corpus studies. After a general introduction, the system architecture is presented in outline. Then follows an examination of a recently written Constraint Syntax. An evaluation report concludes t

Ronald Dickman, George Stell

We report extensive Monte Carlo simulations of the Widom-Rowlinson lattice model in two and three dimensions. Our results yield precise values for the critical activities and densities, and clearly place the critical behavior in the Ising universality class.

P. R. Baldwin, G. M. Townsend

We consider solutions to the complex Trkalian equation,~$ \vec{\nabla} \times \vc = \vc ,$ where~$\vc$ is a 3 component vector function with each component in the complex field, and may be expressed in the form~$ \vc = e^{ig} \vec{\nabla} F, $ with~$g$ real and~$F$ complex. We find, there are precisely two classes of solutions; one where~$g$ is a Cartesian v

Gary Steigman, Monica Tosi

The primordial abundances of deuterium and of helium-3, produced during big bang nucleosynthesis, depend sensitively on the baryon density. Thus, the observed abundances of D and \he may provide useful ``baryometers&#39;&#39; provided the evolution from primordial to present (or, presolar nebula) abundances is understood. Inevitably, the derivation of primor

S. Torres, L. Cayon, E. Martinez-Gonzalez, J. L. Sanz

A statistical analysis of texture on the {\it COBE}-DMR first year sky maps based on the genus and spot number is presented. A generalized $χ^2$ statistic is defined in terms of ``observable&#39;&#39; quantities: the genus and spot density that would be measured by different cosmic observers. This strategy together with the use of Monte Carlo simulations of

Scott Tremaine

The nucleus of M31 may be a thick eccentric disk, composed of stars traveling on nearly Keplerian orbits around a black hole or other dark compact object. This hypothesis reproduces most of the features seen in HST photometry of the center of M31; in particular the bright off-center source P1 is the apoapsis of the disk. An eccentric disk can also explain th

L. Rezzolla, J. C. Miller, O. Pantano

We have carried out a study of the hydrodynamics of disconnected quark regions during the final stages of the cosmological quark-hadron transition. A set of relativistic Lagrangian equations is presented for following the evaporation of a single quark drop and results from the numerical solution of this are discussed. A self-similar solution is shown to exis

Andreas Reisenegger, Jordi Miralda-Escude

We use the Zel&#39;dovich approximation and another analytical approximation to calculate the evolution under gravitational instability of the underdense regions of a photoionized intergalactic medium (IGM). We find that over most of the spectrum of a quasar, the optical depth to $\lya$ scattering originates from gas in underdense regions, or voids. This cau

Vincenzo Ancona, Giorgio Ottaviani

Let ${\cal M}_{I\!\! P^3}(c_1,c_2)$ be the moduli space of stable rank-$2$ vector bundles on $I\!\! P^3$ with Chern classes $c_1$, $ c_2$. We prove the following results. 1) Let $0 \le β< γ$ be two integers, ($γ\ge 2)$, such that $2γ-3β>0$; then ${\cal M}_{I\!\! P^3}(0,2γ^2-3β^2)$ is singular (the case $β=0$ was previously proved by M. Maggesi). 2) Let $0 \l

Renata Kallosh, Andrei Linde, Dmitri Linde, Leonard Susskind

There exists a widely spread notion that gravitational effects can strongly violate global symmetries. It may lead to many important consequences. We will argue, in particular, that nonperturbative gravitational effects in the axion theory lead to a strong violation of CP invariance unless they are suppressed by an extremely small factor 10^{-82}. One could

C. Hu, S. Matinyan, B. Muller, A. Trayanov

We discuss the results of numerical simulations of colliding wavepackets in $SU(2)$ Yang--Mills theory. We investigate their behavior as a function of amplitude and momentum distribution. We find regions in our parameter space in which initial wave packets scatter into final configurations with dramatically different momentum distributions. These results con

Yinlong Sun, George Kirczenow

We present self-consistent numerical calculations of the electronic structure of parallel Coulomb-confined quantum wires, based on the Hohenberg-Kohn-Sham density functional theory of inhomogeneous electron systems. We find that the corresponding transverse energy levels of two parallel wires lock together when the wires&#39; widths are similar and their sep

Yu-kui Zhou, Paul Pearce

Functional equations, in the form of fusion hierarchies, are studied for the transfer matrices of the fused restricted $A_{n-1}^{(1)}$ lattice models of Jimbo, Miwa and Okado. Specifically, these equations are solved analytically for the finite-size scaling spectra, central charges and some conformal weights. The results are obtained in terms of Rogers dilog

Javier P. Muniain, Dardo Piriz

The critical behavior of black holes in even and odd dimensional spacetimes is studied based on Bañados-Teitelboim-Zanelli (BTZ) dimensionally continued black holes. In even dimensions it is found that asymptotically flat and anti de-Sitter Reissner-Nordström black holes present up to two second order phase transitions. The case of asymptotically anti-de-Sit

Jan Kiwi

It is shown that a polynomial with a Cremer periodic point has a non-accessible critical point in its Julia set provided that the Cremer periodic point is approximated by small cycles.

D. Uglov, I. Ivanov

We define an $ sl(N) $ analog of Onsager&#39;s Algebra through a finite set of relations that generalize the Dolan Grady defining relations for the original Onsager&#39;s Algebra. This infinite-dimensional Lie Algebra is shown to be isomorphic to a fixed point subalgebra of $ sl(N) $ Loop Algebra with respect to a certain involution. As the consequence of th

A. Klypin, R. Nolthenius, J. Primack

We present a series of four simulations of Cold Dark Matter (CDM) and Cold + Hot Dark Matter (CHDM) cosmologies. We discuss the power spectrum and correlation functions in real and redshift space, with comparisons to the CfA2 and IRAS redshift data, the pairwise velocity of galaxies, and the distribution of hot and cold particles in CHDM simulations. We conf

Robert D. Ryne

We present a new method for obtaining matched solutions of the rms envelope equations. In this approach, the envelope equations are first expressed in Hamiltonian form. The Hamiltonian defines a nonlinear mapping, $\cal M$, and for periodic transport systems the fixed points of the one-period map are the matched envelopes. Expanding the Hamiltonian around a

F. M. Borzumati, G. Kramer

We calculate the inclusive production of charged hadrons in $\pbp$ collisions to next-to-leading order (NLO) in the QCD improved parton model using a new set of NLO fragmentation functions for charged pions and kaons. We predict transverse-momentum distributions and compare them with experimental data from the CERN S$\pbp$S Collider and the Fermilab Tevatron

Ninoslav Brali{ć}, Eduardo Fradkin, Virginia Manias, Fidel A. Schaposnik

We discuss bosonization in three dimensions of an $SU(N)$ massive Thirring model in the low-energy regime. We find that the bosonized theory is related (but not equal) to $SU(N)$ Yang-Mills-Chern-Simons gauge theory. For free massive fermions bosonization leads, at low energies, to the pure $SU(N)$ (level $k=1$) Chern-Simons theory.

Hideo Suganuma, Shoichi Sasaki, Hiroshi Toki, Hiroko Ichie

We study nonperturbative features of QCD using the dual Ginzburg-Landau (DGL) theory, where the color confinement is realized through the dual Higgs mechanism brought by QCD-monopole condensation. The linear confinement potential appears in the QCD-monopole condensed vacuum. We study the infrared screening effect to the confinement potential by the light-qua

Hiroko Ichie, Hideo Suganuma, Hiroshi Toki

We study the pure-gauge QCD phase transition at finite temperatures in the dual Ginzburg-Landau theory, an effective theory of QCD based on the dual Higgs mechanism. We formulate the effective potential at various temperatures by introducing the quadratic source term, which is a new useful method to obtain the effective potential in the negative-curvature re

Hiroshi Toki, Hideo Suganuma, Shoichi Sasaki, Hiroko Ichie

Nonperturbative features of QCD are studied using the dual Ginzburg-Landau (DGL) theory with QCD-monopoles. The linear quark potential appears in the QCD-monopole condensed vacuum. We find that QCD-monopole condensation plays an essential role to the dynamical chiral-symmetry breaking. We also investigate the QCD phase transition at finite temperature in the

W. Beirl, B. A. Berg, B. Krishnan, H. Markum

We present potentials between static charges from simulations of quantum gravity coupled to an SU(2) gauge field on $6^{3}\times 4$ and $8^{3}\times 4$ simplicial lattices. The action consists of the gravitational term given by Regge&#39;s discrete version of the Euclidean Einstein action and a gauge term given by the Wilson action, with coupling constants $

Simonetta Frittelli, Carlos Kozameh, Ted Newman

We reformulate the Einstein equations as equations for families of surfaces on a four-manifold. These surfaces eventually become characteristic surfaces for an Einstein metric (with or without sources). In particular they are formulated in terms of two functions on R4xS2, i.e. the sphere bundle over space-time, - one of the functions playing the role of a co

Vicente Azcoiti, Eduardo Follana, Felix Ritort

We study the chaotic nature of spin glasses against perturbations of the realization of the quenched disorder. This type of perturbation modifies the energy landscape of the system without adding extensive energy. We exactly solve the mean-field case, which displays a very similar chaos to that observed under magnetic field perturbations, and discuss the pos

C. J. Clarke, P. J. Armitage, K. W. Smith, J. E. Pringle

We examine how accretion on to T Tauri stars may be modulated by a time-dependent `magnetic gate&#39; where the inner edge of the accretion disc is disrupted by a varying stellar field. We show that magnetic field variations on time-scales shorter than 10^5 yr can modulate the accretion flow, thus providing a possible mechanism both for the marked photometri

Sharon L. Vadas

We explore the signature of a cold dark matter compensated void in the quasi non-linear regime. We find that this void is entirely a cold spot on the microwave background, in contrast to a non-linear void. On the last scattering surface(LSS), it appears as either a hot or cold spot depending on where this surface cuts the void. In addition, because the usual

Stephen Holland, Gregory G. Fahlman, Harvey B. Richer

We have identified a small globular cluster in M31 located approximately 4 arcseconds northwest of the M31 globular cluster G185. While several multiple globular clusters have been observed in the Magellanic Clouds none have been found in the Galaxy or in M31. We estimate the probability of such a chance line-of-sight alignment occuring near the nucleus of M

Hisao Hayakawa, Kengo Ichiki

An analytical treatment for the sedimentation rate of disordered suspensions is presented in the context of a resistance problem. From the calculation it is confirmed that the lubrication effect is important in contrast to the suggestion by Brady and Durlofsky (Phys.Fluids Vol.31, 717 (1988)). The calculated sedimentation rate agrees well with the experiment

M. Tavani

We address several issues regarding the interpretation of galactic \ggg-ray sources. We consider powerful pulsars in binaries producing X-ray and gamma-ray {\it unpulsed} emission from the shock interaction of relativistic pulsar winds with circumbinary material. Nebular mass outflows from companion stars of binary pulsars can provide the right {\it calorime

Carlos Cassanello, Eduardo Fradkin

We study the behavior of two planes of Quantum Heisenberg Antiferromagnet in the regime in which a Chiral Spin Liquid is stabilized in each plane. The planes are coupled by an exchange interaction of strength $J_3$. We show that in the regime of small $J_3$ (for both ferromagnetic {\it and} antiferromagnetic coupling), the system dynamically selects an \unde

Matthew Wingate, Thomas DeGrand, Sara Collins, Urs M. Heller

We determine the mass and decay constant of the $a_1$ meson using Monte Carlo simulation of lattice QCD. We find $M_{a_1} = 1250 \pm 80$ MeV and $f_{a_1} = 0.30 \pm 0.03 ~({\rm GeV})^2$, in good agreement with experiment.

B. S. Pudliner, V. R. Pandharipande, J. Carlson, R. B. Wiringa

The energies of $^{3}H$, $^{3}He$, and $^{4}He$ ground states, the ${\frac{3}{2}}^{-}$ and ${\frac{1}{2}}^{-}$ scattering states of $^{5}He$, the ground states of $^{6}He$, $^{6}Li$, and $^{6}Be$ and the $3^{+}$ and $0^{+}$ excited states of $^{6}Li$ have been accurately calculated with the Green&#39;s function Monte Carlo method using realistic models of tw

J. D. Hayward

The two-dimensional model which emerges from low-energy considerations of string theory is written down. Solutions of this classical model are noted, including some examples which have nontrivial tachyon field. One such represents the classical backreaction of the tachyon field on the black hole for a two parameter set of tachyon potentials. Assuming the cla

N. L. Balazs, Rupak Chatterjee, A. D. Jackson

We demonstrate that the free motion of any two-dimensional rigid body colliding elastically with two parallel, flat walls is equivalent to a billiard system. Using this equivalence, we analyze the integrable and chaotic properties of this new class of billiards. This provides a demonstration that coin tossing, the prototypical example of an independent rando

L. A. Dickey

Matrix hierarchies are: multi-component KP, general Zakharov-Shabat (ZS) and its special cases, e.g., AKNS. The ZS comprises all integrable systems having a form of zero-curvature equations with rational dependence of matrices on a spectral parameter. The notion of a $τ$-function is introduced here in the most general case along with formulas linking $τ$-fun

H. F. Chau, P. M. Hui, Y. F. Woo

In most models of traffic flow, the car density $p$ is the only free parameter in determining the average car velocity $\langle v \rangle$. The critical car density $p_c$, which is defined to be the car density separating the jamming phase (with $\langle v \rangle = 0$) and the moving phase (with $\langle v \rangle > 0$), is an important physical quantity to

Xingming Chen

The global structure of optically thin hot accretion disks with radial advection included has been investigated. We solve the full energy conservation equation explicitly and construct the radial structure of the disk. It is found that advection is a real cooling process and that there are two solutions co-exist for a given mass accretion rate less than a cr

R. Gavai, D. Kharzeev, H. Satz, G. A. Schuler

We summarize the theoretical description of charmonium and bottonium production in hadronic collisions and compare it to the available data from hadron-nucleon interactions. With the parameters of the theory established by these data, we obtain predictions for quarkonium production at RHIC and LHC energies.

W. Florkowski, M. Abu-Samreh

Using a simple kinetic model we study whether a pion condensate can be formed during the hadronization of the quark-gluon plasma in ultrarelativistic heavy-ion collisions. If hadronization proceeds fast and the pion effective mass is close to zero, some pions condense into the zero momentum state. On the other hand, for the pion effective mass equal to the v

Simonetta Frittelli, Carlos Kozameh, Ted Newman

The following issue is raised and discussed; when do families of foliations by hypersurfaces on a given four dimensional manifold become the null surfaces of some unknown, but to be determined, metric $g_{ab}(x)$? It follows from these results that one can use these surfaces as fundamental variables for GR.

Mingming Wu, Guenter Ahlers, David S. Cannell

We report quantitative experimental results for the intensity of noise-induced fluctuations below the critical temperature difference $ΔT_c$ for Rayleigh-Bénard convection. The structure factor of the fluctuating convection rolls is consistent with the expected rotational invariance of the system. In agreement with predictions based on stochastic hydrodynami

J. Dobaczewski, J. Dudek

Rotation-induced time-odd components in the nuclear mean field are analyzed using the Hartree-Fock cranking approach with effective interactions SIII, SkM*, and SkP. Identical dynamical moments ${{\cal J}^{(2)}}$ are obtained for pairs of superdeformed bands $^{151}$Tb(2)--$^{152}$Dy(1) and $^{150}$Gd(2)--$^{151}$Tb(1). The corresponding relative alignments

Klaus WERNER, Michael HLADIK

We recently introduced new methods to study ultrarelativistic nuclear scattering by providing a link between the string model approach and a thermal description. The string model is used to provide information about fluctuations in energy density. Regions of high energy density are considered to be quark matter droplets and treated macroscopically. At SPS en

Georg Wagner, L. Ya. Glozman, A. J. Buchmann, Amand Faessler

There exists experimental evidence that a dibaryon resonance d&#39; with quantum numbers J^P=0^-,T=0 and mass 2065 MeV could be the origin of the narrow peak in the (π^+ ,π^- ) double charge exchange cross--sections on nuclei. We investigate the six--quark system with these quantum--numbers within the constituent quark model, with linear confinement, effecti

Ruth Gornet

We present a new construction for obtaining pairs of higher-step isospectral Riemannian nilmanifolds and compare several resulting new examples. In particular, we present new examples of manifolds that are isospectral on functions, but not isospectral on one-forms.

I. Bakas, K. Sfetsos

Four-dimensional string backgrounds with local realizations of N = 4 world-sheet supersymmetry have, in the presence of a rotational Killing symmetry, only one complex structure which is an SO(2) singlet, while the other two form an SO(2) doublet. Although N = 2 world-sheet supersymmetry is always preserved under Abelian T-duality transformations, N = 4 brea

Murat Gunaydin

We review the construction of extended ( N=2 and N=4 ) superconformal algebras over triple systems and the gauged WZW models invariant under them. The N=2 superconformal algebras (SCA) realized over Freudenthal triple systems (FTS) admit extension to ``maximal&#39;&#39; N=4 SCA&#39;s with SU(2)XSU(2)XU(1) symmetry. A detailed study of the construction and cl

Moshe Flato, Jacques C. H. Simon, Erik Taflin

In this monograph we prove that the nonlinear Lie algebra representation given by the manifestly covariant Maxwell-Dirac (M-D) equations is integrable to a global nonlinear representation $U$ of the Poincaré group ${\cal P}_0$ on a differentiable manifold ${\cal U}_\infty$ of small initial conditions for the M-D equations. This solves, in particular, the Cau

Michio Jimbo, Rinat Kedem, Hitoshi Konno, Tetsuji Miwa

Correlation functions and form factors in vertex models or spin chains are known to satisfy certain difference equations called the quantum Knizhnik-Zamolodchikov equations. We find similar difference equations for the case of semi-infinite spin chain systems with integrable boundary conditions. We derive these equations using the properties of the vertex op

Ian Hinchliffe, Thomas A. Kaeding

Decays of the D mesons to two pseudoscalars, to two vectors, and to pseudoscalar plus vector are discussed in the context of broken flavor SU(3). A few assumptions are used to reduce the number of parameters. Amplitudes are fit to the available data, and predictions of branching ratios for unmeasured modes are made.

B. Holdom

As described previously, a new massive gauge boson (X) coupling only to the third family produces a tantalizing pattern of deviations away from the standard model. These include increasing Gamma_b/Gamma_h and decreasing the alpha_s(M_Z) extracted from Gamma_h/Gamma_ell . We review the status of these X-Z mixing effects. We then calculate X boson induced vert

G. W. Semenoff, P. Suranyi, L. C. R. Wijewardhana

The possibility that the epsilon expansion can predict the order of phase transitions in three dimensional field theories is examined. For a Hermitean matrix-valued order parameter, the epsilon expansion predicts fluctuation induced first order phase transitions. We analyze two 2+1-dimensional quantum field theories which exhibit spontaneous symmetry breakin

Jan Bartelski, Stanisław Tatur

We present a fit to spin asymmetries which gives polarized quark distributions. These functions are closely related to the ones given by the newest Martin, Roberts and Stirling fit for unpolarized structure functions. The integrals of polarized distributions are discussed and compared with the corresponding quantities obtained from neutron and hyperon $β$-de

Francis Halzen, Bettina Keszthelyi, Enrique Zas

The emission of particles from black holes created in the early Universe has detectable astrophysical consequences. The most stringent bound on their abundance has been obtained from the absence of a detectable diffuse flux of 100 MeV photons. Further scrutiny of these bounds is of interest as they, for instance, rule out primordial black holes as a dark mat