May 1993 arXiv papers — page 5

D. Boyanovsky, R. Holman, D. -S. Lee, J. P. Silva

We calculate the decay rate for a state prepared in a thermal density matrix centered on a metastable ground state. We find a rate that is intrinsically time {\it dependent}, as opposed to the {\it constant} rates of previous works. The rate vanishes at early times, rises to a maximum and eventually falls-off to zero as a consequence of unitary time evolutio

R. Jackiw, V. P. Nair

We describe the relationship between time-ordered and retarded response functions in a plasma. We obtain an expression, including the proper $iε$-prescription, for the induced current due to hard thermal loops in a non-Abelian theory, thus giving the non-Abelian generalization of the Kubo formula. The result is closely related to the eikonal for a Chern-Simo

J. Chýla

The importance of properly taking into account the factorization scheme dependence of parton distribution functions is emphasized. A serious error in the usual handling of this topic is pointed out and the correct procedure for transforming parton distribution functions from one factorisation scheme to another recalled. It is shown that the conventional $\ov

Zoltan Kunszt, Adrian Signer, Zoltán Trócsányi

One loop corrections to the helicity amplitudes of all 2 -> 2 subprocesses are calculated in QCD and in N=1 supersymmetric Yang-Mills theory using two versions of dimensional regularization: the `t~Hooft-Veltman scheme and dimensional reduction. Studying the structure of the soft and collinear singularities, we found universal transition rules for the square

J. Dolejsi, J. Huefner, B. Z. Kopeliovich

We calculate the broadening of the transverse momentum distribution of a quark propagating through nuclear matter. Colour screening plays a fundamental role in that it cuts off quark-nucleon interactions with soft gluons. The mean transverse momentum of the quark acquired along its trajectory, observed via Drell-Yan pairs, is related to it the ratio of the t

V. Barger, M. S. Berger, P. Ohmann

General issues in the renormalization group evolution of fermion masses and mixings is discussed. An effective fixed point in the top quark Yukawa coupling can strongly constrain its value at the electroweak scale. Predictions following from Yukawa coupling unification are affected by threshold corrections at the grand unified scale. The Landau pole translat

Alexandru Nica

We consider a version of the notion of F-inverse semigroup (studied in the algebraic theory of inverse semigroups). We point out that an action of such an inverse semigroup on a locally compact space has associated a natural groupoid construction, very similar to the one of a transformation group. We discuss examples related to Toeplitz algebras on subsemigr

K. A. Mader, H. von Kanel, A. Baldereschi

We present an ab initio full-potential linearized augmented plane-wave (FLAPW) study of the structural and electronic properties of the two bulk unstable compounds FeSi (CsCl structure) and FeSi$_2$ (CaF$_2$ structure) which have recently been grown by molecular beam epitaxy on Si(111). We obtain equilibrium bulk lattice constants of 2.72 Å and 5.32 Å for Fe

Dong-Zi Liu, H. A. Fertig, S. Das Sarma

We develop a theory of photoluminescence using a time-dependent Hartree-Fock approximation that is appropriate for the two-dimensional Wigner crystal in a strong magnetic field. The cases of localized and itinerant holes are both studied. It is found that the photoluminescence spectrum is a weighted measure of the single particle density of states of the ele

Peter Kopietz

We study the half filled Hubbard model on a hypercubic lattice in infinite dimensions in the presence of a staggered magnetic field. An exact Ward-identity between vertex functions and self-energies is derived, that holds in any phase without broken symmetry for all values of $U$. Making the reasonable assumptions that for small enough on-site repulsion $U$

Karen M. Strom, Stephen E. Strom

We have obtained spectra of the reflection nebulosity illuminated by two heavily embedded IRAS sources in the L1641 molecular cloud, Re 50 and IC 430 (V883 Ori). Examination of these spectra in combination with their other properties indicates that these objects are FU Orionis objects. Our spectrum of L1551 IRS 5 confirms the FU Ori classification made for t

James F. Lynch

Random boolean cellular automata are investigated, where each gate has two randomly chosen inputs and is randomly assigned a boolean function of its inputs. The effect of non-uniform distributions on the choice of the boolean functions is considered. The main results are that if the gates are more likely to be assigned constant functions than non-canalyzing

Don N. Page

Hawking's 1974 calculation of thermal emission from a classical black hole led to his 1976 proposal that information may be lost from our universe as a pure quantum state collapses gravitationally into a black hole, which then evaporates completely into a mixed state of thermal radiation. Another possibility is that the information is not lost, but is stored

Nicolas Andruskiewitsch, Jorge Devoto, Alejandro Tiraboschi

We define new quantizations of the Heisenberg group by introducing new quantizations in the universal enveloping algebra of its Lie algebra. Matrix coefficients of the Stone--von Neumann representation are preserved by these new multiplications on the algebra of functions on the Heisenberg group. Some of the new quantizations provide also a new multiplicatio

F. Coester, W. Polyzou

Hamiltonian light-front dynamics of quantum fields may provide a useful approach to systematic non-perturbative approximations to quantum field theories. We investigate inequivalent Hilbert-space representations of the light-front field algebra in which the stability group of the light-front is implemented by unitary transformations. The Hilbert space repres

Sudhakar Panda, Shibaji Roy

It is shown that the two dimensional gravity, described either in the conformal gauge (the Liouville theory) or in the light cone gauge, when coupled to matter possesses an infinite number of twisted $N=2$ superconformal symmetries. The central charges of the $N=2$ algebra for the two gauge choices are in general different. Further, it is argued that the phy

O. F. Dayi

For a class of first order gauge theories it was shown that the proper solution of the BV-master equation can be obtained straightforwardly. Here we present the general condition which the gauge generators should satisfy to conclude that this construction is relevant. The general procedure is illustrated by its application to the Chern-Simons theory in any o

P. Di Francesco, S. Yankielowicz

We give a direct proof of the new "product" expression for the Ramond sector characters of N=2 minimal models recently suggested by E. Witten. Our construction allows us to generalize these expressions to the D and E series of N=2 minimal models, as well as to other N=2 Kazama--Suzuki coset models such as $SU(N)\times SO(2(N-1))/SU(N-1)\times U(1)$.

Nathan Poliatzky

We study a model based on $N$ scalar complex fields coupled to a scalar real field, where all fields are treated classically as c-numbers. The model describes a composite particle made up of $N$ constituents with bare mass $m_0$ interacting both with each other and with themselves via the exchange of a particle of mass $μ_0$. The stationary states of the com

Naoki Sasakura

Carrying out perturbations around a lattice topological field theory in two dimensions, we show that it is on a first order phase transition fixed point with multiplicity ${n(n-1)/2}$, where $n$ is the number of its independent physical observables. We discuss about the order parameters and the finite size effect for the free energy. The finite size effect i

Elizabeth Jenkins

Chiral symmetry and heavy quark symmetry constrain the interactions of mesons containing a single heavy quark with low-momentum pions. Chiral corrections to the Isgur-Wise function for $\bar B_s \rightarrow D_s^{(*)}$ versus $\bar B \rightarrow D^{(*)}$ semileptonic decay, the ratio of heavy meson decay constants $f_{D_s}/ f_D$ or $f_{B_s}/ f_B$, the amplitu

Thomas M. Gould, Erich R. Poppitz

A classical solution to the Yang-Mills theory is given a new semiclassical interpretation in terms of particle scattering. It solves the complex time boundary value problem, which arises in the semiclassical approximation to a multi particle transition probability in the one-instanton sector at fixed energy. The imaginary part of the action of the solution o

J. W. Bos, J. H. Koch

We study the electromagnetic vertex of a nucleon in next-to-leading order chiral perturbation theory (CPT). We consider the case where one of the nucleons at the $γ$NN vertex is off its mass shell. We define relevant measures for the off-shell dependence in the limited kinematical range allowed, and analyze their expansion in the pion mass. The leading nonan

R. S. Chivukula, E. Gates, E. H. Simmons, J. Terning

A slowly running technicolor coupling will affect the size of non-oblique corrections to the $Zb\bar b$ vertex from extended technicolor dynamics. We show that while ``walking technicolor'' reduces the magnitude of the corrections, they generally remain large enough to be seen at LEP.

J. H. K"uhn, E. Mirkes

Hadronic production of nonrelativistic boundstates of $b^{\prime}$ or isosinglet quarks D with suppressed weak decays is investigated for LHC and SSC energies. QCD corrections to production and decay rates are incorporated. Large rates for final states from $η_{b^{\prime}}\rightarrow HZ$ are predicted.

C. F. Baillie, D. A. Johnston

We investigate a dynamically triangulated random surface action that consists of a gaussian term plus the modulus of the intrinsic scalar curvature. We find that the flips are frozen out and the internal geometry is regularized as the coefficient of the latter term is increased. Such a term thus provides a way of interpolating between dynamically triangulate

L. A. Fernandez, A. Munoz Sudupe, J. J. Ruiz-Lorenzo, A. Tarancon

The Coulomb-Higgs phase transition of the four dimensional Z$_8$ gauge model is studied. We find clear first order properties in contradiction with the previously stressed second order behavior. That transition point may be regarded as the end of a transition line of the U(1)-Higgs model with charge $q=8$, that has been also assumed of second order. We show

Herbert Balasin, Herbert Nachbagauer

Using distributional techniques we calculate the energy--momentum tensor of the Schwarzschild geometry. It turns out to be a well--defined tensor--distribution concentrated on the $r=0$ region which is usually excluded from space--time. This provides a physical interpretation for the curvature of this geometry.

Gerard 't Hooft

A formalism previously introduced by the author using tesselated Cauchy surfaces is applied to define a quantized version of gravitating point particles in 2+1 dimensions. We observe that this is the first model whose quantum version automatically discretizes time. But also spacelike distances are discretized in a very special way.

J. Behre, S. Miyashita

The influence of dilution with non--magnetic impurities on the order in the ground state of the $S=1/2$ Heisenberg antiferromagnet is investigated by Quantum Monte Carlo simulations. Data of the spin correlation functions and thermodynamic properties for system sizes up to $L\times L=16\times16$ and for impurity concentrations up to $δ=37.5\%$ are presented.

M. Alvarez, J. M. F. Labastida

The coupling of topological matter to topological Yang-Mills theory in four dimensions is considered and a model is presented. It is shown that, contrary to the two-dimensional case, this coupling leads to a breaking of the topological symmetry. This means that the vacuum expectation values of the observables of the theory loose their invariance under small

Dawei W Dong, Miklos Gyulassy

We study the efficiency of a neural-net filter and deconvolution method for estimating jet energies and spectra in high-background reactions such as nuclear collisions at the relativistic heavy-ion collider and the large hadron collider. The optimal network is shown to be surprisingly close but not identical to a linear high-pass filter. A suitably constrain

Shigemi Ohta

The three-state Potts model is numerically investigated on three-dimensional simple cubic lattices of up to \(128^3\) volume, concentrating on the neighborhood of the first-order phase transition separating the ordered and disordered phases. In both phases clusters of like spins are observed with irregular boundaries. In the ordered phase the two different n

Xiaochun Luo, D. N. Schramm

One of the crucial aspects of density perturbations that are produced by the standard inflation scenario is that they are Gaussian where seeds produced by topological defects tend to be non-Gaussian. The three point correlation function of the temperature anisotropy of the cosmic microwave background radiation (CBR) provides a sensitive test of this aspect o

Hovik Toomassian

(Revised LaTex version).The structure of free field representation and some correlation functions of the SU(3) CFT are considered.

R. K. Kaul

A method to obtain explicit and complete topological solution of SU(2) Chern-Simons theory on $S^3$ is developed. To this effect the necessary aspects of the theory of coloured-oriented braids and duality properties of conformal blocks for the correlators of $SU(2)_k$ Wess-Zumino conformal field theory are presented. A large class of representations of the g

A. Bassetto, L. Griguolo, P. Zanca

We study by non perturbative techniques a vector, axial--vector theory characterized by a parameter which interpolates between pure vector and chiral Schwinger models. Main results are two windows in the space of parameters which exhibit acceptable solutions. In the first window we find a free massive and a free massless bosonic excitations and interacting l

A. Peet, L. Susskind, L. Thorlacius

Static black holes in two-dimensional string theory can carry tachyon hair. Configurations which are non-singular at the event horizon have non-vanishing asymptotic energy density. Such solutions can be smoothly extended through the event horizon and have non-vanishing energy flux emerging from the past singularity. Dynamical processes will not change the am

Alan D. Sokal

Previous theories of dilute polymer solutions have failed to distinguish clearly between two very different ways of taking the long-chain limit: (I) $N \to\infty$ at fixed temperature $T$, and (II) $N \to\infty$, $T \to T_θ$ with $x \equiv N^ϕ(T-T_θ)$ fixed. I argue that the modern two-parameter theory (continuum Edwards model) applies to case II --- not cas

Don N. Page

If a quantum system of Hilbert space dimension $mn$ is in a random pure state, the average entropy of a subsystem of dimension $m\leq n$ is conjectured to be $S_{m,n}=\sum_{k=n+1}^{mn}\frac{1}{k}-\frac{m-1}{2n}$ and is shown to be $\simeq \ln m - \frac{m}{2n}$ for $1\ll m\leq n$. Thus there is less than one-half unit of information, on average, in the smalle

M. Baig, H. Fort, S. Kim, J. B. Kogut

Using finite size scaling and histogram methods we obtain numerical results from lattice simulations indicating the logarithmic triviality of scalar quantum electrodynamics, even when the bare gauge coupling is chosen large. Simulations of the non-compact formulation of the lattice abelian Higgs model with fixed length scalar fields on $L^{4}$ lattices with

J. Harnad, M. -A. Wisse

The isomonodromic deformations underlying the Painlevé transcendants are interpreted as nonautonomous Hamiltonian systems in the dual $\gR^*$ of a loop algebra $\tilde\grg$ in the classical $R$-matrix framework. It is shown how canonical coordinates on symplectic vector spaces of dimensions four or six parametrize certain rational coadjoint orbits in $\gR^*$

Srinandan Dasmahapatra

We present an algorithm for the construction of the branching functions in the vacuum sector for affine Lie algebras based on the string hypothesis solution to a system of Bethe equations for generalized RSOS models. We also mention how the ground state structure and features of the excitation spectra like the Brillouin zone schemes of these models (and thos

G. Amelino-Camelia

The finite temperature effective potential of the Abelian Higgs Model is studied using the self-consistent composite operator method, which sums up the contributions of daisy and superdaisy diagrams. The effect of the momentum dependence of the effective masses is estimated by using a Rayleigh-Ritz variational approximation.

Dan Radu Grigore

We give a definition for the notion of statistics in the lattice-theoretical (or propositional) formulation of quantum mechanics of Birchoff, von Neumann and Piron. We show that this formalism is compatible only with two types of statistics: Bose-Einstein and Fermi-Dirac. Some comments are made about the connection between this result and the existence of ex

B. Zwiebach

In these introductory notes I explain some basic ideas in string field theory. These include: the concept of a string field, the issue of background independence, the reason why minimal area metrics solve the problem of generating all Riemann surfaces with vertices and propagators, and how Batalin-Vilkovisky structures arise from the state spaces of conforma

I. Antoniadis, J. Rizos, K. Tamvakis

We study the cosmological solutions of the one loop corrected superstring effective action, in a Friedmann-Robertson-Walker background, and in the presence of the dilaton and modulus fields. A particularly interesting class of solutions is found which avoid the initial singularity and are consistent with the perturbative treatment of the effective action.

Yoichi Kazama, Hermann Nicolai

A detailed reexamination is made of the exact operator formalism of two-dimensional Liouville quantum gravity in Minkowski spacetime with the cosmological term fully taken into account. Making use of the canonical mapping from the interacting Liouville field into a free field, we focus on the problem of how the Liouville exponential operator should be proper

Ernest Ma, Daniel Ng

If the standard electroweak gauge model is embedded in a larger theory which is supersymmetric and the latter breaks down to the former at some mass scale, then the reduced Higgs potential at the electroweak mass scale may differ from that of the well-known minimal supersymmetric extension. Specifically, if the larger theory is based on $\rm {SU(2)_L \times

Chi-Keung Chow, Mark B. Wise

Heavy quark symmetry relations for $B\rightarrow De\bar ν_e$ and $B\rightarrow D^*e \bar ν_e$ form factors receive corrections suppressed by powers of the charm quark mass. For small up and down quark massed the leading corrections of order $(1/m_c)^{n+2}~n = 0,1,2,...$ have a nonanalytic dependence on the light quark masses of the form $\ell n m_π^2$ for $n

L. Frankfurt, G. A. Miller, M. Strikman

The cross section for coherent nuclear processes in which an incident meson or photon dissociates diffractively into two jets of high relative transverse momentum (between about 1 and 3 GeV/c) is found to be proportional in QCD to $A^2$ in a wide kinematical region. The leading correction to this is a significant positive term $\propto A^{7/3}$ caused by nuc

Tanguy Altherr, David Seibert

We calculate production rates for massless $(u,d)$ and massive $(s,c,b)$ quarks in pure glue and quark gluon plasmas to leading order in the strong coupling constant $g$. The leading contribution comes from gluon decay into $q\bar q$ pairs, using a thermal gluon propagator with finite thermal mass and damping rate. The rate behaves as $α_S^2(\ln 1/α_S)^2 T^4

S. G. Matinyan, E. B. Prokhorenko

The general theory of the branching processes is used for establishing the relation between the parameters $k$ and $\bar n$ of the negative binomial distribution. This relation gives the possibility to describe the overall data on multiplicity distributions in $pp (p\bar p)$-collisions for energies up to 900 GeV and to make several interesting predictions fo

B. Z. Kopeliovich, J. Nemchick, N. N. Nikolaev, B. G. Zakharov

We demonstrate how the virtual photoproduction of vector mesons on nuclei scans the wave function of vector mesons from the large non-perturbative transverse size $ρ\sim R_{V}$ down to the small perturbative size $ρ\sim 1/\sqrt{Q^{2}}$. Thee mechanism of scanning is based on color transparency and QCD predicted spatial wave function of quark-antiquark fluctu

Robert W. Brown, Jin Woo Jun, Shmaryu M. Shvartsman, Cyrus C. Taylor

Four-dimensional heavy-fermion QED is studied in light-cone coordinates with (anti-)periodic field boundary conditions. We carry out a consistent light-cone canonical quantization of this model using the Dirac algorithm for a system with first- and second-class constraints. To examine the role of the zero modes, we consider the quantization procedure in {the

J. L. Hewett, T. G. Rizzo

Possible anomalous couplings of the top-quark to on-shell photons and gluons are constrained by the recent results of the CLEO Collaboration on both inclusive and exclusive radiative $B$ decays. We find that the process \bsg\ can lead to reasonable bounds on both the anomalous electric and magnetic dipole moments of the top-quark, while essentially no limits

Ling-Lie Chau, Ding-Wei Huang

We have derived explicit expressions in the 1-d Ising model for multiplicity distributions $P_{\delξ}(n)$ and factorial moments $F_q(\delξ)$. We identify the salient features of $P_{\delξ}(n)$ that lead to scaling, $F_q(\delξ)=\F_q[F_2]$, and universality. These results compare well with the presently available high-energy data of $\bar{p}p$ and $e^+e^-$ rea

P. F. Gonzalez-Diaz

A gravitational instanton is found that can tunnel into a new more stable vacuum phase where diffeomorphism invariance is broken and pitchfork bifurcations develop. This tunnelling process involves a double sphaleron-like transition which is associated with an extra level of quantization which is above that is contained in quantum field theory.

Daniel Provost, Michel Baranger

Bogomolny's formula for energy-smoothed scars is applied for the first time to a non-specific, non-scalable Hamiltonian, a 2-D anharmonic oscillator. The semiclassical theory reproduces well the exact quantal results over a large spatial and energy range.

Mirek Giersz, Douglas C. Heggie

We study the dynamical evolution of idealised stellar systems by averaging results from many $N$-body simulations, each having modest numbers of stars. For isolated systems with stars of uniform mass, we discuss aspects of evolution up to the point of core collapse: relaxation and its $N$-dependence, the evolution of the density profile, the development of t

Luca Amendola, Stefano Borgani

We analyze the statistical properties of bubble models for the large-scale distribution of galaxies. To this aim, we realize static simulations, in which galaxies are mostly randomly arranged in the regions surrounding bubbles. As a first test, we realize simulations of the Lick map, by suitably projecting the three-dimensional simulations. In this way, we a

H. T. Cho, K. -W. Ng, Achilles D. Speliotopoulos

The burning of a neutron star by strange matter is analyzed using relativistic combustion theory with a planar geometry. It is shown that such burning is probably neither slow combustion nor simple detonation. Fast combustion without detonation is possible under certain circumstances, but would involve very efficient heat transfer mechanisms. It is found, ho

T. Fujita

Let L be an ample line bundle on a log variety (V, D) having only log terminal singularities.The Kodaira energy of such a triple (V, D, L) is defined as follows: κε=-Inf{t\in Q | K(V,D)+tL is big}. Here K(V,D)=K_V+D is the log canonical bundle of (V,D) and "big" means κ=dim V. We first show that the rationality of κε, when it is negative, follows fro

W. T. Giele, E. W. N. Glover, David A. Kosower

We study the production of single isolated leptons at large transverse momentum, $p_T^\ell > M_W/2$. The dominant source of such leptons is production of an on-shell $W$ boson recoiling against a hard jet. Vetoing this jet forces the $W$ boson to be produced off resonance and significantly reduces the standard model cross section, thereby enhancing the disco

Danny Birmingham, Mark Rakowski

Revision contains rewording of selected text

Massimo Campostrini, Paolo Rossi

A general two-dimensional spin model with U$(N)$ invariance, interpolating between $\CPN$ and ${\rm O}(2N)$ models, is studied in detail in order to illustrate both the general features of the $1/N$ expansion on the lattice and the specific techniques devised to extract scaling (field-theoretical) behavior. The continuum version of the model is carefully ana

G. S. Danilov

Multiloop superstring amplitudes are calculated in the explicit form by the solution of Ward identities. A naive generalization of Belavin-Knizhnik theorem to the superstring is found to be incorrect since the period matrix turns out to be depended on the spinor structure over the terms proportional to odd moduli. These terms appear because fermions mix boso

G. Giavarini, C. P. Martin, F. Ruiz Ruiz

We explicitly show that the Landau gauge supersymmetry of Chern-Simons theory does not have any physical significance. In fact, the difference between an effective action both BRS invariant and Landau supersymmetric and an effective action only BRS invariant is a finite field redefinition. Having established this, we use a BRS invariant regulator that define

A. Aurilia, E. Spallucci

In this paper we show that a relativistic membrane admits an equivalent representation in terms of the Kalb-Ramond gauge field $F_{μνρ}=\partial_{\,[\,μ}B_{νρ]}$ encountered in string theory. By `` equivalence '' we mean the following: if $x=X(ξ)$ is a solution of the classical equations of motion derived from the Dirac-Nambu-Goto action, then it is

L. Chekhov

We give the description of discretized moduli spaces (d.m.s.) $\Mcdisc$ introduced in \cite{Ch1} in terms of a discrete de Rham cohomologies for each moduli space $\Mgn$ of a genus $g$, $n$ being the number of punctures. We demonstrate that intersection indices (cohomological classes) calculated for d.m.s. coincide with the ones for the continuum moduli spac

J. X. Lu

A new approach is provided to determine the dilaton--antisymmetric tensor coupling in a supergravity theory by considering the static supersymmetric field configuration around a super extended object, which is consistently formulated in a curved superspace. By this, the corresponding SUSY transformation rules can also be determined for vanishing fermionic fi

H. Awata, S. Odake, J. Shiraishi

A representation of the quantum affine algebra $U_{q}(\widehat{sl}_3)$ of an arbitrary level $k$ is constructed in the Fock module of eight boson fields. This realization reduces the Wakimoto representation in the $q \rightarrow 1$ limit. The analogues of the screening currents are also obtained. They commute with the action of $U_{q}(\widehat{sl}_3)$ modulo

Ted Jacobson, Robert C. Myers

A general formula for the entropy of stationary black holes in Lovelock gravity theories is obtained by integrating the first law of black hole mechanics, which is derived by Hamiltonian methods. The entropy is not simply one quarter of the surface area of the horizon, but also includes a sum of intrinsic curvature invariants integrated over a cross section

A. S. Gorsky, M. B. Voloshin

The amplitude of production of $n$ on-mass-shell scalar bosons by a highly virtual field $ϕ$ is considered in a $λϕ^4$ theory with weak coupling $λ$ and spontaneously broken symmetry. The amplitude of this process is known to have an $n!$ growth when the produced bosons are exactly at rest. Here it is shown that for $n \gg 1/λ$ the process goes through `quan

P. L. White

We discuss the large radiative corrections to the masses of supersymmetric Higgs bosons in the MSSM and in its simplest extension, the NMSSM, with particular attention paid to the bounds on the lightest CP-even Higgs mass found in both models. In the case of the MSSM, these corrections are found to be primarily associated with the effects top quark and stop

L. Reina

We present the results of our recent calculation of $ε^{\prime}/ ε$ at the Next-to-Leading (NLO) order in QCD and QED, in the framework of $\DSone$ Effective Hamiltonians. The operator matrix elements are taken from lattice QCD, at a scale $μ=2\,\,\mbox{GeV}$. NLO corrections seem to lower the value of $ε^{\prime}/ε$, favouring the experimental result of E73

C. E. M. Wagner

I discuss the properties of the minimal supersymmetric extension of the standard model, in the case in which there is a dynamical breakdown of the electroweak symmetry induced by the formation of condensates of the third generation of quarks and their supersymmetric partners. The top quark and Higgs mass predictions derived within this scheme are essentially

C. Weiss, A. Buck, R. Alkofer, H. Reinhardt

Electromagnetic properties of diquarks are investigated in the framework of a color-octet Nambu-Jona-Lasinio model, which describes baryons as bound states of diquarks and quarks. We calculate the electromagnetic form factors of scalar and axial vector diquark bound states using the gauge--invariant proper--time regularization. The nucleon charge radii and m

Y. Koide, F. Fusaoka

A democratic form version of the Rosner-Worah quark mass matrix is discussed from a phenomenological point of view. It is pointed out that an ansatz of "maximal CP violation" can provide reasonable values of the Kobayashi-Maskawa mixings.

Nguyen Hong Chuong, Nguyen Van Hoang

Within the framework of the minimum quadratic Poincare gauge theory of gravity in the Riemann-Cartan spacetime we study the influence of gravitational vacuum energy density (a cosmological constant) on the dynamics of various gravitating systems. It is shown that the inclusion of the cosmological term can lead to gravitational repulsion. For some simple case

Jukka A. Ketoja, Juhani Kurkijarvi

Ge, Rusjan, and Zweifel (J. Stat. Phys. 59, 1265 (1990)) introduced a binary tree which represents all the periodic windows in the chaotic regime of iterated one-dimensional unimodal maps. We consider the scaling behavior in a modified tree which takes into account the self-similarity of the window structure. A non-universal geometric convergence of the asso

Peter L. Biermann

We review recent progress in our understanding of the physics of energetic particles in our Galaxy, in active galaxies such as starburst galaxies, in active galactic nuclei and in the jets and radio hot spots of powerful radio galaxies and radioloud quasars. We propose that cosmic rays originate mainly in three sites, a) normal supernova explosions into the

Rino Bandiera

I present an extension of the thin layer approximation to non-axisymmetric bow shocks. By choosing a suitable set of curvilinear coordinates that matches the geometry of a generally distorted bow shock surface, I derive the fluid equations for the flow. Analytical expansions are given for the matter flow near the bow shock stagnation point. Numerical solutio

Peter L. Biermann, Joseph P. Cassinelli

Based on 1) a conjecture about the mean free path for particle scattering in perpendicular shock geometries, and 2) a model for Wolf Rayet star winds, we argue that explosions of Wolf Rayet stars can lead through diffusive particle acceleration to particle energies up to 3 10^9 GeV. As a test we first demonstrate that the magnetic fields implied by this argu

M. Fukugita, P. J. E. Peebles

Recent observations suggest appreciable star formation activity in early-type galaxies down to redshift $z\sim 0.5$. If so, there is likely to be dust in these galaxies. We consider the possibility that obscuration by dust can reconcile the observed frequency of gravitational lensing of quasar images with the considerably larger rate predicted in a low densi

M. Bellon, B. Machet

We propose a way to reconcile the Standard Model of leptons with a purely vectorial theory. The observed neutrino is predicted to be massless. The unobservability of its partner and the $V-A$ structure of the weak currents are given the same origin.

B. K. Agrawal, A. Ansari

The static path approximation to the path integral representation of partition function provides a natural microscopic basis to deal with thermal fluctuations around mean field configurations. Using this approach for one-dimensional cranking Hamiltonian with quadrupole- quadrupole interaction term we have studied a few properties like energy, level density,

George M. Frichter, J. Piekarewicz

We calculate ground-state properties of a many-quark system in the string-flip model using variational Monte Carlo methods. The many-body potential energy of the system is determined by finding the optimal grouping of quarks into hadrons. This (optimal) assignment problem is solved by using the stochastic optimization technique of simulated annealing. Result

Attila Csoto

Through numerical examples we show that the complex scaling method is suited to explore the pole structure in multichannel scattering problems. All poles lying on the multisheeted Riemann energy surface, including shadow poles, can be revealed and the Riemann sheets on which they reside can be identified.

M. Bellon, S. Boukraa, J-M. Maillard, C-M. Viallet

We introduce a ``pre-Bethe-Ansatz'' system of equations for three dimensional vertex models. We bring to the light various algebraic curves of high genus and discuss some situations where these curves simplify. As a result we describe remarkable subvarieties of the space of parameters.

Edwin Langmann

Unitarily implementable Bogoliubov transformations for charged, relativistic bos\-ons and fermions are discussed, and explicit formulas for the 2-cocycles appearing in the group product of their implementers are derived. In the fermion case this provides a simple field theoretic derivation of the well-known cocycle of the group of unitary Hilbert space opera

T. Elliott

We discuss the upper bound on the lightest CP-even Higgs boson mass in the next-to-minimal supersymmetric standard model within the framework of a low energy renormalisation group analysis. We find $m_h$ < 146 GeV for $m_t$ = 90 GeV, decreasing to $m_h$ < 123 GeV for $m_t$ = 180 GeV.

Ingemar Bengtsson

Riemannian geometry in four dimensions naturally leads to an SL(3) connection that annihilates a basis for self-dual two-forms. Einstein&#39;s equations may be written in terms of an SO(3) connection, with SO(3) chosen as an appropriate subgroup of SL(3). We show how a set of &#34;neighbours&#34; of Einstein&#39;s equations arises because the subgroup may be

K. B. Lauritsen, H. Puhl, H. -J. Tillemans

We have implemented different algorithms for generating Poissonian and vectorizable random lattices. The random lattices fulfil the Voronoi/Delaunay construction. We measure the performance of our algorithms for the two types of random lattices and find that the average computation time is proportional to the number of points on the lattice.

A. Grassi

This work was initially motivated by Miranda&#39;s work on elliptic Weierstrass threefolds. Miranda [Mi] describes a smooth equidimensional (flat) model for any elliptic Weierstrass threefold; such models occur naturally in the study of moduli spaces. In this paper we use minimal model theory to link birational maps of log surfaces (log contractions) to equi

Ezra Getzler

In this paper, we examine the analogy between topological string theory and equivariant cohomology. We also show that the equivariant cohomology of a topological conformal field theory carries a certain algebraic structure, which we call a gravity algebra. (Error on page 9 corrected: BRS current contains total derivatives.)

J. A. Gracey

We write down the anomalous dimensions of the fields of the Nambu--Jona-Lasinio model or chiral Gross Neveu model with a continuous global chiral symmetry for the two cases $U(1)$ $\times$ $U(1)$ and $SU(M)$ $\times$ $SU(M)$ at $O(1/N^2)$ in a $1/N$ expansion.

M. Blau, G. Thompson

We give a derivation of the Verlinde formula for the $G_{k}$ WZW model from Chern-Simons theory, without taking recourse to CFT, by calculating explicitly the partition function $Z_{Σ\times S^{1}}$ of $Σ\times S^{1}$ with an arbitrary number of labelled punctures. By a suitable gauge choice, $Z_{Σ\times S^{1}}$ is reduced to the partition function of an Abel

Hao-wen Xi, J. D. Gunton, Jorge Vinals

Motivated by recent experimental studies of Bodenschatz et al. [E. Bodenschatz, J.R. de Bruyn, G. Ahlers and D.S. Cannell, Phys. Rev. Lett. {\bf 67}, 3078 (1991) ], we present a numerical study of a generalized two dimensional Swift-Hohenberg equation to model pattern formation in Rayleigh-Bénard convection in a non-Boussinesq fluid. It is shown that many of

M. A. Valle Basagoiti

We calculate perturbatively the pressure of a dilute gas of anyons through second order in the anyon coupling constant, as described by Chern-Simons field theory. Near Bose statistics , the divergences in the perturbative expansion are exactly cancelled by a two-body $δ$-function potential which is not required near Fermi statistics. To the order considered,