April 1996 arXiv papers — page 8

E. Aurell, G. Boffetta, A. Crisanti, G. Paladin

We discuss the effects of finite perturbations in fully developed turbulence by introducing a measure of the chaoticity degree associated to a given scale of the velocity field. This allows one to determine the predictability time for non-infinitesimal perturbations, generalizing the usual concept of maximum Lyapunov exponent. We also determine the scaling l

Giuseppe Tormen

This review is a short introduction to numerical hydrodynamics in a cosmological context, intended for the non specialist. The main processes relevant to galaxy formation are first presented. The fluid equations are then introduced, and their implementation in numerical codes by Eulerian grid based methods and by Smooth Particle Hydrodynamics is sketched. As

E. L. Martin, R. Rebolo, M. R. Zapatero Osorio

We present optical and near-IR spectroscopy (600--1000 nm) of 8 faint (I$>$18) very red (R--I$>$2.2) objects discovered in a deep CCD survey of the Pleiades (Zapatero-Osorio et al. 1996). We compare them with reliable cluster members like PPl 15 and Teide 1, and with several field very late-type dwarfs (M4--M9.5), which were observed with similar instrumenta

M. R. Zapatero Osorio, R. Rebolo, E. L. Martin

We have obtained deep CCD R and I mosaic imaging of 578 arcmin$^{2}$ within 1$^{\circ}$.5 of the Pleiades' center -- reaching a completeness magnitude I=19.5 -- with the aim of finding free-floating brown dwarfs. Teide~1, the best $bona$ $fide$ brown dwarf discovered so far in the cluster (Rebolo, Zapatero Osorio \& Mart\'ın 1995), arose as a result

Paolo Catelan, Tom Theuns

We discuss the non-linear evolution of the angular momentum L acquired by protostructures, like protogalaxies and protoclusters, due to tidal interactions with the surrounding matter inhomogeneities. The primordial density distribution is assumed to be Gaussian and the non-linear dynamics of the collisionless mass fluid is followed using Lagrangian perturbat

Paolo Catelan, Tom Theuns

The growth of the angular momentum L of protogalaxies induced by tidal torques is reconsidered within the Zel'dovich approximation. We obtain a general expression for the ensemble expectation value of the square of L in terms of the first and second invariant of the inertia tensor of the Lagrangian volume enclosing the protoobject's collapsing mass.

A. Garren, E. Courant, J. Gallardo, R. Palmer

We discuss a preliminary design for a high luminosity 4 TeV center of mass $μ^+\,μ^-$ collider ring.

H. -J. He, Y. -P. Kuang, C. -P. Yuan

We develop a precise power counting rule (a generalization of Weinberg's counting method for the nonlinear sigma model) for the electroweak theories formulated by chiral Lagrangians. Then we estimate the contributions of ``all'' next-to-leading order (NLO) bosonic operators to the amplitudes of the relevant scattering processes which can be measu

Ashoke Sen

We construct several examples where duality transformation commutes with the orbifolding procedure even when the orbifolding group does not act freely, and there are massless states from the twisted sector at a generic point in the moduli space. Often the matching of spectrum in the dual theories is a result of non-trivial identities satisfied by the coeffic

V. Freilikher, E. Kanzieper, I. Yurkevich

Strongly non-Gaussian ensembles of large random matrices possessing unitary symmetry and logarithmic level repulsion are studied both in presence and absence of hard edge in their energy spectra. Employing a theory of polynomials orthogonal with respect to exponential weights we calculate with asymptotic accuracy the two-point kernel over all distance scale,

Daniel Stubbs

In this paper, two methods are employed to investigate for which values of the parameters, if any, the two-dimensional real Landau-Ginzburg equation possesses the Painleve property. For an ordinary differential equation to have the Painleve property all of its solutions must be meromorphic but for partial differential equations there are two inequivalent def

M. Alvarez, J. M. F. Labastida

The general structure of the perturbative expansion of the vacuum expectation value of a Wilson line operator in Chern-Simons gauge field theory is analyzed. The expansion is organized according to the independent group structures that appear at each order. It is shown that the analysis is greatly simplified if the group factors are chosen in a certain way t

A. D. Rogava

Two, the most simple cases of special-relativistic flows of a viscous, incompressible fluid are considered: plane Couette flow and plane Poiseuille flow. Considering only the regular motion of the fluid we found the distribution of velocity in the fluid (velocity profiles) and the friction force, acting on immovable wall. The results are expressed through si

Peter W. Jones, Lesley A. Ward

We construct examples showing that the normalized Lebesgue measure of the conical limit set of a uniformly quasiconformal group acting discontinuously on the disc may take any value between zero and one. This is in contrast to the cases of Fuchsian groups acting on the disc, conformal groups acting discontinuously on the ball in dimension three or higher, un

O. Kechkin, M. Yurova

The constructed $Sp(4,R)/GL(2,R)$ matrix operator defines the family of isotropic geodesic containing vacuum point lines in the target space of the stationary D=4 Einstein--Maxwell--dilaton--axion theory. This operator is used to derive a class of solutions which describes a point center system with nontrivial values of mass, parameter NUT, as well as electr

F. Caravaglios, M. Moretti

We apply the iterative numerical algorithm ALPHA, which automatically generates the N-point Green functions (as recently suggested \cite{alpha}) to the computation of the production rate of four fermions and four fermions plus photon in electron-positron annihilation. The discussion of the physical results is preceded by an introduction on the algorithm.

O. K. Kalashnikov

The phase diagram of the quark-gluon matter evolution is presented for the SU(3)-model with a new phase of heavy deconfined quarks which exists in a rather wide range of temperatures and densities. Fitting the chiral phase transition data to fix the model parameters we establish another (deconfinement) phase transition which separates a new phase from hadron

M. Laine

We compare 4d lattice results for the finite temperature phase transition in the SU(2)+Higgs model with 3d lattice results for the phase transition in the corresponding dimensionally reduced effective theory. While the large errorbars and the lack of a relation of the 4d lattice gauge coupling to continuum physics prevent rigorous conclusions, the results ar

Yoonbai Kim, Kei-ichi Maeda, Nobuyuki Sakai

The nucleation and evolution of bubbles are investigated in the model of an $O(3)$-symmetric scalar field coupled to gravity in the high temperature limit. It is shown that, in addition to the well-known bubble of which the inside region is true vacuum, there exists another decay channel at high temperature which is described by a new solution such that a fa

Ethan Bradford, Craig Hogan

We show that the process of photoionizing a gas of atomic hydrogen and helium by line radiation whose energy is slightly above the helium single-ionization threshold is unstable if the helium fraction by number is less than approximately one half. However, in the two scenarios we consider here, based on the Decaying Dark Matter (DDM) model of cosmological re

Maurice Dubin, Robert K. Soberman

The solar neutrino anomaly, measurements discrepant from predictions of the Standard Solar Model, has existed for over 30 years. Multiple experiments measuring fluxes from several reactions in the hydrogen fusion chain have added to the puzzle. Each of the several elements of the enigma are resolved by recognition of measurements establishing that most of th

Ariel R. Zhitnitsky

We discuss the general method of the calculation of the nucleon matrix elements of an operator associated with nonvalence quarks. The method is based on the QCD sum rules and low energy theorems. As an application of these considerations, we calculate the strange quark matrix element as well as the momentum distribution of the strangeness in the nucleon. We

Harry Contopanagos, Eric Laenen, George Sterman

We present a unified derivation of the resummation of Sudakov logarithms, directly from the factorization properties of cross sections in which they occur. We rederive in this manner the well-known exponentiation of leading and nonleading logarithmic enhancements near the edge of phase space for cross sections such as deeply inelastic scattering, which are i

A. Pordt

We prove that for a general $N$-component model on a $d$-dimensional lattice $\bZ^d$ with pairwise nearest-neighbor coupling and general local interaction obeying a stability bound the linked cluster expansion has a finite radius of convergence. The proof uses Mayer Montroll equations for connected Green functions.

P. Haensel, A. D. Kaminker, D. G. Yakovlev

Neutrino emissivity from the electron $ν\barν$ bremsstrahlung in the liquid layers of the neutron star crusts is studied. Nuclear composition of matter in neutron star crusts is considered for various scenarios of neutron star evolution. For the deep layers of the crust, the compositions of cold catalyzed matter, accreted matter and hot matter ($T \ga 5 \tim

V. E. Zavlin, G. G. Pavlov, Yu. A. Shibanov

We present a detailed investigation of neutron star atmospheres with low magnetic fields, $B < 10^8 -10^{10}$ G, which do not affect opacities and equation of state of the atmospheric matter. We compute the atmospheric structure, emergent spectral fluxes and specific intensities for hydrogen, helium and iron atmospheres in a wide domain of effective temperat

Boris Kastening

The beta function of the vacuum energy density is computed at the four-loop level in massive O(N) symmetric phi^4 theory. Dimensional regularization is used in conjunction with the MSbar scheme and all calculations are in momentum space in the massive theory. The result is beta_v = g N/4+g^3 N(N+2)/96+g^4 N(N+2)(N+8)[12 zeta(3)-25]/1296+o(g^5).

A. Datta, B. -L. Young, X. Zhang

Analyses of the vacuum stability of the electroweak theory indicate that new physics occur at a scale of order of 1 TeV if a light Higgs is discovered at LEP II. In this paper, we parameterize the effects of new physics in the effective Lagrangian approach and examine its implication on the Higgs boson production at LEP II. We consider the effect of higher d

P. Colin, R. G. Carlberg, H. M. P. Couchman

The evolution of the two-point correlation function, xi(r,z), and the pairwise velocity dispersion, sigma(r,z), for both the matter and halo population, in three different cosmological models: (Omega_M,Omega_Lambda)=(1,0), (0.2,0) and (0.2,0.8) are described. If the evolution of xi is parameterized by xi(r,z)=(1+z)^{-(3+eps)}xi(r,0), where xi(r,0)=(r/r_0)^{-

V. Gogohia, B. Lukács, M. Prisznyák

By proposing an Ansatz for the pressure (measured in terms of the bag constant) of the hadronic gas in equilibrium, we have formulated a rather simple method which allows one to analytically investigate the bulk thermodynamic propertities in the vicinity of the phase transition. This makes it also possible to take into account the nonperturbative vacuum effe

P. Hoyer, M. Vänttinen

The momentum distributions of partons in bound nucleons are known to depend significantly on the size of the nucleus. The Fourier transform of the momentum ($\xbj$) distribution measures the overlap between Fock components of the nucleon wave function which differ by a displacement of one parton along the light cone. The magnitude of the overlap thus determi

Oleg M. Braun, Thierry Dauxois, Michel Peyrard

We study surface diffusion in the framework of a generalized Frenkel-Kontorova model with a nonconvex transverse degree of freedom. The model describes a lattice of atoms with a given concentration interacting by Morse-type forces, the lattice being subjected to a two-dimensional substrate potential which is periodic in one direction and nonconvex (Morse) in

C. Castellani, C. Di Castro, F. Pistolesi, G. C. Strinati

We exploit the symmetries associated with the stability of the superfluid phase to solve the long-standing problem of interacting bosons in the presence of a condensate at zero temperature. Implementation of these symmetries poses strong conditions on the renormalizations that heal the singularities of perturbation theory. The renormalized theory gives: For

Jan Ftacnik, Jan Pisut, Neva Pisutova

We point out that dissociation of J/Psi by partons (mostly gluons) present in the intermediate stage of heavy-ion collisions can explain J/Psi suppression observed recently by the NA-50 Collaboration at the CERN-SPS in Pb-Pb interactions. Suppression by intermediate stage gluons represents an additional multiplicative factor to that given by Gerschel-Hufner

G. Papadopoulos

We describe the qualitative properties of p-brane solutions of supergravity theories and present two examples of p-brane solutions, first the dyonic membrane solutions of N=2 D=8 supergravity and second the intersecting M-brane solutions of D=11 supergravity.

Fabio Gavarini

The present work splits in two parts: first, we perform a straightforward generalization of results from [Re], proving autoquasitriangularity of quantum groups $ U_q(\frak{g}) $ and their unrestricted specializations at roots of 1, in particular the function algebra $ F[H] $ of the Poisson group $ H $ dual of $ G $; second, as a main contribution, we prove t

P. V. Moniz

The canonical quantization of $N=1$ and $N=2$ supergravity theories is reviewed in this report. A special emphasis is given to the topic of supersymmetric Bianchi class-A and FRW minisuperspaces, namely in the presence of supermatter fields. The quantization of the general theory (including supermatter) is also contemplated. The issue of quantum physical sta

Yuji Ohta

We discuss N=2 SU(2) Yang-Mills gauge theories coupled with N_f (=2,3) massive hypermultiplets in the weak coupling limit. We determine the exact massive prepotentials and the monodromy matrices around the weak coupling limit. We also study that the double scaling limit of these massive theories and find that the massive N_f -1 theory can be obtained from th

Alon E. Faraggi, Manuel Masip

It was recently suggested that the reported anomalies in $R_b$ and $R_c$ can be interpreted as the effect of a heavy vector boson that couples to quarks and is universally decoupled from leptons. We examine how an extra gauge boson with this property can arise from superstring derived models. In a specific three generation model we show that the $U(1)_{B-L}$

David A. Meyer

Failure to find homogeneous scalar unitary cellular automata (CA) in one dimension led to consideration of only ``approximately unitary&#39;&#39; CA---which motivated our recent proof of a No-go Lemma in one dimension. In this note we extend the one dimensional result to prove the absence of nontrivial homogeneous scalar unitary CA on Euclidean lattices in a

Shin&#39;ichi Nojiri

We obtain a four dimensional exploding universe solution in string theory. The solution is obtained from the string theory in the flat background by using non-abelian $T$-duality and the analytic continuation. In the solution, the radius of the universe is finite for fixed time and the universe is surrounded with the boundary which is composed of the singula

Bohdan Grzadkowski, Zenro Hioki

The process of top-quark pair production at future high-energy $e^+ e^-$ linear colliders has been investigated as a possible test of physics beyond the Standard Model. Non-standard interactions have been assumed both for the production and for the subsequent decay of the top quarks. The energy spectrum of the single lepton $l^\pm$ and the energy correlation

Oleg M. Braun, Thierry~Dauxois, Maxim V. Paliy, Michel Peyrard

Molecular dynamics simulations are used to investigate the atomic mobility and diffusivity of a generalized Frenkel-Kontorova model which takes into account anharmonic (exponential) interaction of atoms subjected to a three-dimensional substrate potential periodic in two dimensions and nonconvex (Morse) in the third dimension. The numerical results are expla

C. J. Benesh, A. C. Hayes, J. L. Friar

In a previous paper, we calculated the fully quantum-mechanical cross section for electromagnetic excitation during peripheral heavy-ion collisions. Here, we examine the sensitivity of that cross section to the detailed structure of the projectile and target nuclei. At the transition energies relevant to nuclear physics, we find the cross section to be weakl

K. Yoshida, M. Matsuo

We discuss damping of the collective rotational motion in $A\sim 150$ superdeformed nuclei by means of a shell model combining the cranked Nilsson mean-filed and the surface-delta two-body residual force. It is shown that, because of the shell structure associated with the superdeformed mean-field, onset energy of the rotational damping becomes $E_x \sim 2-3

O. Scholten, A. Yu. Korchin, V. Pascalutsa, D. Van Neck

We present a relativistic calculation of pion scattering, pion photoproduction and Compton scattering on the nucleon in the energy region of the \Del-resonance (upto 450 MeV photon lab energy), in a unified framework which obeys the unitarity constraint. It is found that the recent data on the cross section for nucleon Compton scattering determine accurately

Marco R. Vervoort

Blackwell games are infinite games of imperfect information. The two players simultaneously make their moves, and are then informed of each other&#39;s moves. Payoff is determined by a Borel measurable function $f$ on the set of possible resulting sequences of moves. A standard result in Game Theory is that finite games of this type are determined. Blackwell

P. B. Ramos, M. J. Martins

We formulate in terms of the quantum inverse scattering method the exact solution of a $spl(2|1)$ invariant vertex model recently introduced in the literature. The corresponding transfer matrix is diagonalized by using the algebraic (nested) Bethe ansatz approach. The ground state structure is investigated and we argue that a Pokrovsky-Talapov transition is

I. J. R. Aitchison, C. D. Fosco, F. D. Mazzitelli

We consider a higher derivative effective theory for an Abelian gauge field in three dimensions, which represents the result of integrating out heavy matter fields interacting with a classical gauge field in a parity-conserving way. We retain terms containing up to two derivatives of $F_{μν}$, but make no assumption about the strength of this field. We then

J. Ambjorn, Y. Watabiki

We propose a non-critical string field theory for $2d$ quantum gravity coupled to ($p$,$q$) conformal fields. The Hamiltonian is described by the generators of the $W_p$ algebra, and the Schwinger-Dyson equation is equivalent to a vacuum condition imposed on the generators of $W_p$ algebra.

Akikazu Hashimoto, Igor R. Klebanov

We calculate the leading order interactions of massless D-brane excitations. Their 4-point functions are found to be identical to those found in type I theory. The amplitude for two massless D-brane fluctuations to produce a massless closed string is found to possess interesting new structure. As a function of its single kinematic invariant, it displays an i

Robert J. Perry

It may be possible to derive a constituent approximation for bound states in QCD using hamiltonian light-front field theory. Cutoffs that violate explicit gauge invariance and Lorentz covariance must be employed. A similarity renormalization group and coupling coherence are used to compute the effective hamiltonian as an expansion in powers of the canonical

M. P. Locher, V. E. Markushin, H. Q. Zheng

Final state interactions in the $S$--wave $ππ$ system (I=0,2) are re-examined on the basis of the Omnès-Mus\-khe\-li\-shvili equation and the coupled channel formalism. The contributions to the pion scalar form factor from $ρ$ and $f_2(1270)$ exchange in the $t$--channel and from the $f_0(980)$ $s$--channel resonance are separately evaluated and the role of

W. Grimus, L. Lavoura

We consider the time dependence of the decays of tagged $D^0$ and $\bar{D}^0$ into CP-conjugate final states $f$ and $\bar{f}$, or into a CP eigenstate $F$. We expand each decay width as $\exp (- Γt)$ times a series in $Γt$, where $Γ$ is the average decay width of the mass eigenstates $D_H$ and $D_L$, and examine the first three terms of the series. We show

Jiri Chyla, Jiri Rames

For theoretically consistent determination of $α_s$ from jet rates in deep inelastic scattering the dependence on $α_s$ of parton distribution functions is in principle as important as that of hard scattering cross--sections. For the kinematical region accessible at HERA we investigate in detail numerical importance of these two sources of the $α_s$ dependen

M. Moretti

Using the recently proposed ALPHA algorithm (and the resulting code) I compute the rate (at tree level) for the process $γγ\rightarrow\barν_e e^- u \bar d$. The bulk of the contribution is due to W pair production and decay. However a non negligible ($\sim10 \%$) contribution comes from other channels, mainly the production and decay of a W and a collinear c

Pilar Hernandez, Raman Sundrum

We propose a new lattice action for non-abelian gauge theories, which will reduce short-range lattice artifacts in the computation of the topological susceptibility. The standard Wilson action is replaced by the Wilson action of a gauge covariant interpolation of the original fields to a finer lattice. If the latter is fine enough, the action of all configur

P. W. Stephenson

We investigate possible problems with universality in lattice gauge theory where a mixed fundamental SU(2) and SO(3)-invariant gauge group is used: the (second order) finite temperature phase transition becomes involved with first order effects with increased SO(3) coupling, and this first order effect has a noticeable coupling dependence for small lattices.

S. Bonazzola, J. Frieben, E. Gourgoulhon, J. A. Marck

Several applications of spectral methods to problems related to the relativistic astrophysics of compact objects are presented. Based on a proper definition of the analytical properties of regular tensorial functions we have developed a spectral method in a general sphericallike coordinate system. The applications include the investigation of spherically sym

Yu. N. Obukhov, E. J. Vlachynsky, W. Esser, R. Tresguerres

The spacetime of the metric-affine gauge theory of gravity (MAG) encompasses {\it nonmetricity} and {\it torsion} as post-Riemannian structures. The sources of MAG are the conserved currents of energy-momentum and dilation, shear and spin. We present an exact static spherically symmetric vacuum solution of the theory describing the exterior of a lump of matt

M. Bianchi, E. Coccia, C. N. Colacino, V. Fafone

We consider the possibility of discriminating different theories of gravity using a recently proposed gravitational wave detector of spherical shape. We argue that the spin content of different theories can be extracted relating the measurements of the excited spheroidal vibrational eigenmodes to the Newman-Penrose parameters. The sphere toroidal modes canno

Martin Engman

We find sharp upper bounds for the multiplicities and the numerical values of all the distinct eigenvalues on a surface of revolution diffeomorphic to the sphere.

Michael E. Fisher, Benjamin P. Lee

To understand the range of close-to-classical critical behavior seen in various electrolytes, generalized Debye-Hueckel theories (that yield density correlation functions) are applied to the restricted primitive model of equisized hard spheres. The results yield a Landau-Ginzburg free-energy functional for which the Ginzburg criterion can be explicitly evalu

John Carroll, Ted Briscoe

We describe an implemented system for robust domain-independent syntactic parsing of English, using a unification-based grammar of part-of-speech and punctuation labels coupled with a probabilistic LR parser. We present evaluations of the system&#39;s performance along several different dimensions; these enable us to assess the contribution that each individ

Giovanni Gallavotti

A reversible version of the Navier Stokes equation is studied. A conjecture emerges stating the equivalence between the reversible equation and the usual Navier Stokes equation. The latter appears as a statement of ensembles equivalence in the limit of infinite Reynolds number, which plays the role of the thermodynamic limit.

Mario Feingold

We show that, in the semiclassical limit and whenever the elements of the Hamiltonian matrix are random enough, the eigenvectors of strongly chaotic time-independent systems in ordered bases can on average be exponentially localized across the energy shell and decay faster than exponentially outside the energy shell. Typically however, matrix elements are st

Sidney van den Bergh

Cepheid variables are used to derive a Virgo cluster distance of 16.0 +/- 1.5 Mpc. In conjunction with the Coma velocity and the well-established Coma/Virgo distance ratio, this yields a Hubble paprameter Ho = 81 +/- 8 km/s/Mpc. By combining this value with an age of the Universe of at least 16.8 +/- 2.1 Gyr, that is derived from the metal-poor globular clus

Ortwin Gerhard

The now substantial evidence for a rotating bar in the inner Galaxy and its dynamical implications are reviewed.

Andreon Stefano

We have looked for differences in the galaxy properties along the Hubble sequence and for the dependence of these properties on the environment, in an absolute magnitude complete sample of 187 galaxies in the Coma cluster. The morphological type of all galaxies was determined from our own high resolution data. We also compared this sample with other publishe

Basilio X. Santiago, Rebecca A. W. Elson, Gerard F. Gilmore

We present V and I photometry for a field 5&#39; from the center of 47 Tuc. The field was imaged with the HST WFPC2 as part of the Medium Deep Survey project. The luminosity function (LF) continually rises in the domain $5 < M_I < 9$ with a slope $Δlog Φ(M) / ΔM \sim 0.15$ and then drops off sharply. We compare our LF with that derived by De Marchi \& Paresc

B. M. Poggianti, G. Barbaro

In order to explain the spectroscopic observations of most of the galaxies in intermediate redshift clusters, bursts of star formation superimposed to the traditional scenario of galactic evolution are needed. The analysis of spectral lines and colours by means of an evolutionary synthesis model, including both the stellar contribution and the emission of th

Ulrich Lindner, Maret Einasto, Jaan Einasto, Wolfram Freudling

We investigate the distribution of normal (faint) galaxies and blue compact galaxies (BCGs) in voids by analyzing their distribution as a function of distance from the void centers and by employing nearest neighbour statistics between objects of various subsamples. We find that galaxies in voids defined by brighter galaxies tend to be concentrated close to t

Xiang-Ping Wu, Bo Qin, Li-Zhi Fang

Current measurements of the Hubble constant $H_0$ on scale less than $\sim100$ Mpc appear to be controversial, while the observations made at high redshift seem to provide a relatively low value. On the other hand, the Hubble expansion is driven by the matter content of the universe. The dynamical analysis on scale of a few $\sim10$ Mpc indicates that the ma

Yoshiaki Sofue

Using the fact that molecular gas is distributed in the inner disk while HI in the outer disk, we have derived most-completely sampled rotation curves by combining HI and CO position-velocity diagrams. We show that inner rotation curves have a steep increase within the central few hundred-pc region. The inner behavior of rotation can be fitted by the Miyamot

Yoshiaki Sofue

Nonthermal radio emission in the galactic center reveals a number of vertical structures across the galactic plane, which are attributed to poloidal magnetic field and/or energetic outflow. Thermal radio emission comprises star forming regions distributed in a thin, dense thermal gas disk. The thermal region is associated with dense molecular gas disk, in wh

A. Berera, M. Strikman, W. S. Toothacker, W. D. Walker

We argue that as the atomic number of the target nucleus $A \to \infty$, the multiplicity of leading particles in hadron-nucleus collisions tends to a finite limit. The limiting multiplicities for various particle production are computed for both proton and pion projectiles. Signatures at finite A are discussed. Data from 100 GeV/c central hadron-nucleus col

M. L. Nekrasov

A generalization of the chiral effective lagrangian of order $p^2$ is proposed which involves the $η&#39;$-meson, its excitation, and the pseudoscalar (PS) glueball. Model-independent constraints are found for the contributions to the lagrangian of the above singlet states. Those allow one to independently identify the nature of these singlet states in the f

Angel Ballesteros, Francisco J. Herranz

A universal $R$-matrix for the non-standard (Jordanian) quantum deformation of $sl(2,\R)$ is presented. A family of solutions of the quantum Yang--Baxter equation is obtained from some finite dimensional representations of this Lie bialgebra quantization of $sl(2,\R)$.

Cenalo Vaz, Louis Witten

Roughly speaking, naked singularities are singularities that may be seen by timelike observers. The Cosmic Censorship conjecture forbids their existence by stating that a reasonable system of energy will not, under reasonable conditions, collapse into a naked singularity. There are however many (classical) counter-examples to this conjecture in the literatur

H. Weigel, L. Gamberg, H. Reinhardt

Nucleon structure functions are studied within the chiral soliton approach to the bosonized Nambu-Jona-Lasinio model. The valence quark approximation is employed which is justified for moderate constituent quark masses ($\sim$ 400 MeV) as the contribution of the valence quark level dominates the predictions of nucleon properties. As examples the unpolarized

H. -W. Hammer, Ulf-G. Meißner, D. Drechsel

We update a recent dispersion--theoretical fit to the nucleon electromagnetic form factors by including the existing data in the time--like region. We show that while the time--like data for the proton can be described consistently with the existing world space--like data, this is not the case for the neutron. Another measurement of the process $e^+ e^- \to

Kemal Oflazer

This paper presents an efficient algorithm for retrieving from a database of trees, all trees that match a given query tree approximately, that is, within a certain error tolerance. It has natural language processing applications in searching for matches in example-based translation systems, and retrieval from lexical databases containing entries of complex

Christian Bauer, Adam F. Falk, Michael Luke

We study logarithms of the form $\ln(m_q/m_b)$ which arise in the inclusive semileptonic decay of a bottom quark to a quark of mass $m_q$. We use the renormalization group to resum the leading radiative corrections to these terms, of the form $m_q^2α_s^n\ln^n(m_q/m_b)$, $m_q^3α_s^{n+1}\ln^n(m_q/m_b)$ and $m_q^4α_s^n\ln^{n+1}(m_q/m_b)$. The first two resummat

A. Fring, V. Kostrykin, R. Schrader

We address the question of whether atomic bound states begin to stabilize in the short ultra-intense field limit. We provide a general theory of ionization probability and investigate its gauge invariance. For a wide range of potentials we find an upper and lower bound by non-perturbative methods, which clearly exclude the possibility that the ultra intense

Kemal Oflazer, Gokhan Tur

This paper presents a constraint-based morphological disambiguation approach that is applicable languages with complex morphology--specifically agglutinative languages with productive inflectional and derivational morphological phenomena. In certain respects, our approach has been motivated by Brill&#39;s recent work, but with the observation that his transf

P. M. Lavrov, S. D. Odintsov, A. A. Reshetnyak

The gauge dependence of the effective action of composite fields for general gauge theories in the framework of the quantization method by Batalin, Lavrov and Tyutin is studied. The corresponding Ward identities are obtained. The variation of composite fields effective action is found in terms of new set of operators depending on composite field. The theorem

Jun-ichi Inoue

We investigate the retrieval phase diagrams of an asynchronous fully-connected attractor network with non-monotonic transfer function by means of a mean-field approximation. We find for the noiseless zero-temperature case that this non-monotonic Hopfield network can store more patterns than a network with monotonic transfer function investigated by Amit et a

M. J. Duff, H. Lu, C. N. Pope

We present a class of black $p$-brane solutions of M-theory which were hitherto known only in the extremal supersymmetric limit, and calculate their macroscopic entropy and temperature.

H. Lu, C. N. Pope, K. W. Xu

We study the general form of the equations for isotropic single-scalar, multi-scalar and dyonic $p$-branes in superstring theory and M-theory, and show that they can be cast into the form of Liouville, Toda (or Toda-like) equations. The general solutions describe non-extremal isotropic $p$-branes, reducing to the previously-known extremal solutions in limiti

T. K. Lee, C. T. Shih

The dispersion of a single hole in the t-J model obtained by the exact result of 32 sites and the results obtained by self-consistent Born approximation and the Green function Monte Carlo method can be simply derived by a mean-field theory with d-RVB and antiferromagnetic order parameters. In addition, it offers a simple explanation for the difference observ

S. -C. Gou, J. Steinbach, P. L. Knight

We propose a scheme for generating vibrational pair coherent states of the motion of an ion in a two-dimensional trap. In our scheme, the trapped ion is excited bichromatically by three laser beams along different directions in the X-Y plane of the ion trap. We show that if the initial vibrational state is given by a two-mode Fock state, the final steady sta

Xiao-Biao Lin

Consider a singularly perturbed system $$εu_t=ε^2 u_{xx} + f(u,x,ε),\quad u\in {\Bbb R}^n,x\in{\Bbb R},t\geq 0. $$ Assume that the system has a sequence of regular and internal layers occurring alternatively along the $x$-direction. These ``multiple wave&#39;&#39; solutions can formally be constructed by matched asymptotic expansions. To obtain a genuine sol

F. Arias de Saavedra, G. Co&#39;, A. Fabrocini, S. Fantoni

Correlated Basis Function theory and Fermi Hypernetted Chain technique are extended to study medium-heavy, doubly closed shell nuclei in j-j coupling scheme, with different single particle wave functions for protons and neutrons and isospin dependent two-body correlations. Central semirealistic interactions are used. Ground state energies, one-body densities

E. Abdalla, R. Mohayaee, A. Zadra

We discuss the issue of screening and confinement of external colour charges in bosonised two-dimensional quantum chromodynamics. Our computation relies on the static solutions of the semi-classical equations of motion. The significance of the different representations of the matter field is explicitly studied. We arrive at the conclusion that the screening

I. Antoniadis, T. R. Taylor

We discuss spontaneous supersymmetry breaking in $N=2$ globally supersymmetric theories describing abelian vector multiplets. The most general form of the action admits, in addition to the usual Fayet-Iliopoulos term, a magnetic Fayet-Iliopoulos term for the auxiliary components of dual vector multiplets. In a generic case, this leads to a spontaneous breakd

D. Ts. Stoyanov

A new version of application Pauli-Villars regularized Green functions in the quantum field theory using higher derivatives is proposed. In this version the regularizing mass $M$ is large but finite. Our approach is demonstrated and discussed on the example of QED. It is shown that in our case there are no ultraviolet divergences and - on the example of the

C. Gomez, R. Hernandez, E. Lopez

The integrable systems associated with Seiberg-Witten geometry are considered both from the Hitchin-Donagi-Witten gauge model and in terms of intermediate Jacobians of Calabi-Yau threefolds. Dual pairs and enhancement of gauge symmetries are discussed on the basis of a map from the Donagi-Witten ``moduli&#39;&#39; into the moduli of complex structures of the

Zheng Huang, Xin-Nian Wang

Since the electromagnetic current for a pion system coincides with the third component of the isovector current, the isospin angular oscillation of a coherent field can be a significant source for the electromagnetic emissions. We study the characteristic dilepton and photon emissions from the classical pion field oscillation in the QCD vacuum. The general a

V. Barger, Kingman Cheung, Paul Langacker

The mixing of a new $Z'$ boson with the $Z$ significantly improves the fit to the LEP precision electroweak data, provided that the $Z'$ couples mainly to quarks. If $M_{Z_2}<200$~GeV, the $s$-channel $Z_2$ production and $(W,Z,\gamma)Z_2$ pair production cross sections at the Tevatron give an excess above QCD of $b\bar b$ and $(W,Z,\gamma)b\bar b$ events, r

Yoshitaka Kuno, Yasuhiro Okada

A search for the lepton-flavor violating $μ^{+}\rightarrow e^{+}γ$ decay using polarized muons is proposed. By measuring the angular distribution of $e^{+}$s with respect to the muon spin direction, in particular antiparallel $e^{+}$s, the serious physics background from $μ^{+}\rightarrow e^{+}ν\overlineνγ$ as well as accidental background from normal muon d