August 1992 arXiv papers — page 2

S. Kharchev, A. Marshakov, A. Mironov, A. Morozov

We consider the deformations of ``monomial solutions'' to Generalized Kontsevich Model \cite{KMMMZ91a,KMMMZ91b} and establish the relation between the flows generated by these deformations with those of $N=2$ Landau-Ginzburg topological theories. We prove that the partition function of a generic Generalized Kontsevich Model can be presented as a prod

F. Toppan, Y. -Z. Zhang

We present a superconformally invariant and integrable model based on the twisted affine Kac-Moody superalgebra $\hat{osp(2|2)}^{(2)}$ which is the supersymmetrization of the purely bosonic conformal affine Liouville theory recently proposed by Babelon and Bonora. Our model reduces to the super-Liouville or to the super sinh-Gordon theories under certain lim

A. P. de Almeida, J. Frenkel

We study non-perturbatively, via the Schwinger-Dyson equations, the leading infrared behavior of the pressure in the ladder approximation. This problem is discussed firstly in the context of a thermal scalar field theory, and the analysis is then extended to the Yang-Mills theory at high temperatures. Using the Feynman gauge, we find a system of two coupled

M. J. Bowick, L. Chandar, E. A. Schiff, A. M. Srivastava

We have observed the production of strings (disclination lines and loops) via the Kibble mechanism of domain (bubble) formation in the isotropic to nematic phase transition of a sample of uniaxial nematic liquid crystal. The probablity of string formation per bubble is measured to be $0.33 \pm 0.01$. This is in good agreement with the theoretical value $1/ π

Volker Koch, George Bertsch

The effect of collective potentials on pion spectra in ultrarelativistic heavy ion collisions is investigated. We find the effect of these potential to be very small, too small to explain the observed enhancement at low transverse momenta. (7 figures, bill be send on request)

Marcelo Gleiser, Edward W. Kolb

We examine the behavior of the standard-model electroweak phase transition in the early Universe. We argue that close to the critical temperature it is possible to estimate the {\it effective} infrared corrections to the 1-loop potential using well known $\varepsilon$-expansion results from the theory of critical phenomena in 3 spatial dimensions. The theory

Edward Malec, Niall Ó Murchadha

This article gives necessary and sufficient conditions for the formation of trapped surfaces in spherically symmetric initial data defined on a closed manifold. Such trapped surfaces surround a region in which there occurs an enhancement of matter over the average. The conditions are posed directly in terms of physical variables and show that what one needs

Niall Ó Murchadha, Hugh Shanahan

Gravitational instantons, solutions to the euclidean Einstein equations, with topology $R^3 XS^1$ arise naturally in any discussion of finite temperature quantum gravity. This Letter shows that all such instantons (irrespective of their interior behaviour) must have the same asymptotic structure as the Schwarzschild instanton. Using this, it can be shown tha

M. R. Norman

A method is derived for calculating the pairing kernel in exchange mediated superconductors including matrix element effects. Various models for the interaction vertex are considered, including spin exchange, orbital exchange, and quadrupolar exchange. As an example, this formalism is applied to $UPt_3$ using relativistic wavefunctions from a local density b

Daniel Loss, David P. DiVincenzo, G. Grinstein

Within a wide class of ferromagnetic and antiferromagnetic systems, quantum tunneling of magnetization direction is spin-parity dependent: it vanishes for magnetic particles with half-integer spin, but is allowed for integer spin. A coherent-state path integral calculation shows that this topological effect results from interference between tunneling paths.

C. Lucchesi, O. Piguet, S. P. Sorella

We show that the BF theory in any space-time dimension, when quantized in a certain linear covariant gauge, possesses a vector supersymmetry. The generator of the latter together with those of the BRS transformations and of the translations form the basis of a superalgebra of the Wess-Zumino type. We give a general classification of all possible anomalies an

Eugeni Akhmedov, Zurab Berezhiani Goran Senjanovic, Zhijian Tao

We study the phenomenology and cosmology of the Majoron (flavon) models of three active and one inert neutrino paying special attention to the possible (almost) conserved generalization of the Zeldovich-Konopinski-Mahmoud lepton charge. Using Planck scale physics effects which provide the breaking of the lepton charge, we show how in this picture one can inc

A. Nabutovsky, R. Ben-Av

Computations in Dynamical Triangulation Models of Four-Dimensional Quantum Gravity involve weighted averaging over sets of all distinct triangulations of compact four-dimensional manifolds. In order to be able to perform such computations one needs an algorithm which for any given $N$ and a given compact four-dimensional manifold $M$ constructs all possible

T. V. Duong, Ernest Ma

In extensions of the standard model, light scalar particles are often possible because of symmetry considerations. We study the decay of the Z boson into such particles. In particular, we consider for illustration the scalar sector of a recently proposed model of the 17-keV neutrino which satisfies all laboratory, astrophysical, and cosmological constraints.

Yu. Makeenko

I study the large-N reduction a la Eguchi--Kawai in the Kazakov--Migdal lattice gauge model. I show that both quenching and twisting prescriptions lead to the coordinate-independent master field. I discuss properties of loop averages in reduced as well as unreduced models and demonstrate those coincide in the large mass expansion. I derive loop equations for

S. Kharchev, A. Marshakov, A. Mironov, A. Morozov

We introduce {\it conformal multi-matrix models} (CMM) as an alternative to conventional multi-matrix model description of two-dimensional gravity interacting with $c < 1$ matter. We define CMM as solutions to (discrete) extended Virasoro constraints. We argue that the so defined alternatives of multi-matrix models represent the same universality classes in

Amitava Dattta, Manoranjan Guchait, D. P. Roy

Right-handed neutrinos with large Majorana mass occur naturally in the left-right symmetric model. We explore the prospect of such heavy Right-handed Neutrino search Via $W_R$ decay in the Like Sign Dilepton channel at SSC/LHC. The standard model background can be effectively eliminated by suitable lepton $p_T$ and isolation cuts without affecting the signal

A. J. van der Sijs

Recently, a method was proposed and tested to find saddle points of the action in simulations of non-abelian lattice gauge theory. The idea, called `extremization&#39;, is to minimize $\int(\dl S/\dl A_μ)^2$. The method was implemented in an explicitly gauge variant way, however, and gauge dependence showed up in the results. Here we show how extremization c

T. A. Larsson

Conformal fields are a new class of $Vect(N)$ modules which are more general than tensor fields. The corresponding diffeomorphism group action is constructed. Conformal fields are thus invariantly defined.

Jan von Delft, Christopher L. Henley

In some spin tunneling problems, there are several different but symmetry-related tunneling paths that connect the same initial and final configurations. The topological phase factors of the corresponding tunneling amplitudes can lead to destructive interference between the different paths, so that the total tunneling amplitude is zero. In the study of tunne

Albert-László Barabási

We propose a simple discrete model to study the nonequilibrium fluctuations of two locally coupled 1+1 dimensional systems (interfaces). Measuring numerically the tilt-dependent velocity we construct a set of stochastic continuum equations describing the fluctuations in the model The scaling predicted by the equations are studied analytically using dynamic r

J. Fingberg, U. M. Heller, F. Karsch

We determine the critical couplings for the deconfinement phase transition in $SU(2)$ gauge theory on $N_τ\times N_σ^3$ lattices with $N_τ= 8$ and 16 and $N_σ$ varying between 16 and 48. A comparison with string tension data shows scaling of the ratio $T_c / \sqrtσ$ in the entire coupling regime $β=2.30-2.75$, while the individual quantities still exhibit la

G. Savvidy, K. Savvidy

We develop further a new geometrical model of a discretized string, proposed in [1] and establish its basic physical properties. The model can be considered as the natural extention of the usual Feynman amplitude of the random walks to random surfaces. Both amplitudes coinside in the case, when the surface degenarates into a single particle world line. We ex

Ivan K. Kostov, Matthias Staudacher

We find the precise relationship between the loop gas method and the matrix quantum mechanics approach to two-dimensional string theory. The two systems are distinguished by different target spaces ($\Z$ and $\R$, respectively) as far as {\it observables} are concerned. We argue that target space loop correlators should coincide in the two models and demonst

David Land, Eric Carlson

We present a mechanism in which models with two Higgs fields can undergo a two stage phase transition as the temperature falls. The first stage is a conventional second order (or weakly first order) transition in which the symmetry is broken. Shortly thereafter follows a first order transition with barrier penetration, bubble production and loss of thermal e

J. R. Espinosa, M. Quirós

In the minimal supersymmetric standard model (MSSM), when radiative corrections are included, the mass of the $CP=+1$ lightest Higgs boson is bounded by $\sim 110\ GeV$ for $m_t < 150\ GeV$ and a scale of supersymmetry breaking $\sim\ 1\ TeV$. In non-minimal supersymmetric standard models (NMSSM) upper bounds on the mass of the corresponding scalar Higgs bos

G. Cvetič, C. Grosse-Knetter, R. Kögerler

The BESS model is the Higgsless alternative to the standard model of electroweak interaction with nonlinear realized spontaneous symmetry breaking. Since it is non-renormalizable new couplings (not existing in the SM) are induced at each loop order. On the basis of the one loop induced gauge boson self-couplings we calculated the cross sections for the two a

Alfredo Poirier

The theory of Hubbard trees provides an effective classification of non-linear post-critically finite polynomial maps from \C to itself. This note will extend this classification to the case of maps from a finite union of copies of \C to itself. Maps which are post-critically finite and nowhere linear will be characterized by a ``forest&#39;&#39;, which is m

Hermann König

Let X be a Banach space and $1\le p<\infty$. We prove interpolation inequalities of Marcinkiewicz-Zygmund type for X-valued polynomials g of degree $\le n$ on $R$, \[c_p (\sum\limits_{i=1}^{n+1} μ_i \| g(t_i)e^{-t_i^2 /2} \|^p)^{1/p} \le (\int\limits_{\RR}^{} \|g(t)e^{-t^2 /2} \|^p dt)^{1/p} \le d_p (\sum\limits_{i=1}^{n+1} μ_i \|g(t_i)e^{-t_i^2 /2} \|^p)^{1

Hermann König, Niels J. Nielsen

We give necessary and sufficient conditions for interpolation inequalities of the type considered by Marcinkiewicz and Zygmund to be true in the case of Banach space-valued polynomials and Jacobi weights and nodes. We also study the vector-valued expansion problem of $L_p$-functions in terms of Jacobi polynomials and consider the question of unconditional co

O. Aharony, O. Ganor, J. Sonnenschein, S. Yankielowicz

The twisted G/H models are constructed as twisted supersymmetric gauged WZW models. We analyze the case of $G=SU(N)$, $H=SU(N_1)\times ...\times SU(N_n)\times U(1)^r$ with $rank\ G =\ rank\ H$, and discuss possible generalizations. We introduce a non-abelian bosonization of the $(1,0)$ ghost system in the adjoint of $H$ and in G/H. By computing chiral anomal

Eric Smith

The BRST cohomology of 1+1 strings in a free light-cone gauge contains only the two-dimensional tachyon, and excludes all excited states of both matter and ghosts, including the special states that arise in the continuum conformal gauge quantization and in the $c = 1$ matrix models. This exclusion takes place at a very basic level, and therefore may signal s

J. Erler, M. Spalinski

We demonstrate how to find modular discrete symmetry groups for $Z_N$ orbifolds. The $Z_7$ orbifold is treated in detail as a non-trivial example of a $(2,2)$ orbifold model. We give the generators of the modular group for this case which, surprisingly, does not contain $\sltz^3$ as had been speculated. The treatment models with discrete Wilson lines is also

Paolo Aschieri, Leonardo Castellani

We construct a bicovariant differential calculus on the quantum group $GL_q(3)$, and discuss its restriction to $[SU(3) \otimes U(1)]_q$. The $q$-algebra of Lie derivatives is found, as well as the Cartan-Maurer equations. All the quantities characterizing the non-commutative geometry of $GL_q(3)$ are given explicitly.

S. F. Ross, R. B. Mann

We investigate the circumstances under which gravitationally collapsing dust can form a black hole in three-dimensional spacetime.

Nathan Berkovits

The manifestly SU(4)xU(1) super-Poincare invariant free-field N=2 twistor- string action for the ten-dimensional Green-Schwarz superstring is quantized using standard BRST methods. Unlike the light-cone and semi-light-cone gauge-fixed Green-Schwarz actions, the twistor-string action does not require interaction-point operators at the zeroes of the light-cone

Salman Habib

In this paper a quantum mechanical phase space picture is constructed for coarse-grained free quantum fields in an inflationary Universe. The appropriate stochastic quantum Liouville equation is derived. Explicit solutions for the phase space quantum distribution function are found for the cases of power law and exponential expansions. The expectation values

Salman Habib, Henry E. Kandrup

This paper derives and analyzes exact, nonlocal Langevin equations appropriate in a cosmological setting to describe the interaction of some collective degree of freedom with a surrounding ``environment.&#39;&#39; Formally, these equations are much more general, involving as they do a more or less arbitrary ``system,&#39;&#39; characterized by some time-depe

R. B. Mann, S. F. Ross

A method for taking the $D\to 2$ limit of D-dimensional general relativity is constructed, yielding a two-dimensional theory which couples gravitation to conserved stress-energy. We show how this theory is related to those obtained via an alternative dimensional reduction approach.

G. Dev, J. K. Jain

The eigenstates of interacting electrons in the fractional quantum Hall phase typically form fairly well defined bands in the energy space. We show that the composite fermion theory gives insight into the origin of these bands and provides an accurate and complete microscopic description of the strongly correlated many-body states in the low-energy bands. Th

R. M. Neal

The probability of accepting a candidate move in the hybrid Monte Carlo algorithm can be increased by considering a transition to be between windows of several states at the beginning and end of the trajectory, with a state within the selected window being chosen according to the Boltzmann probabilities. The detailed balance condition used to justify the alg

D. L. Cox

Symmetry based selection rules are developed providing minimal criteria for the existence of two-channel Kondo interactions between conduction electrons and the low energy degrees of freedom on U$^{4+}$ and Ce$^{3+}$ in a metal host, assuming that the underlying microscopics are regulated by the Anderson Hamiltonian. An additional dynamic selection rule is i

R. Brooks, D. Cangemi, M. Crescimanno

Einstein Gravity in 2+1 dimensions arises as a consequence of the equations of motion of a gauge model in an external metric. Newton&#39;s constant appears as an order parameter of a spontaneously broken discrete symmetry. Matter is coupled in a straightforward way.

Peter G. O. Freund, Anton V. Zabrodin

Motivated by Harish-Chandra theory, we construct, starting from a simple CDD\--pole $S$\--matrix, a hierarchy of new $S$\--matrices involving ever ``higher&#39;&#39; (in the sense of Barnes) gamma functions.These new $S$\--matrices correspond to scattering of excitations in ever more complex integrable models.From each of these models, new ones are obtained

J. Ambjorn, J. Jurkiewicz, C. F. Kristjansen

We consider a discrete model of euclidean quantum gravity in four dimensions based on a summation over random simplicial manifolds. The action used is the Einstein-Hilbert action plus an $R^2$-term. The phase diagram as a function of the bare coupling constants is studied in the search for a sensible continuum limit. For small values of the coupling constant

Richard Easther, William Moreau

We study the finite temperature effective potential of the Higgs scalar in GUTs with Coleman-Weinberg symmetry breaking. The critical temperature is derived without employing a high temperature approximation to the effective potential, and the limitations of such approximations are discussed.

M. L. Paciello, C. Parrinello, S. Petrarca, B. Taglienti

We study the influence of Gribov copies in the Coulomb gauge on the smeared hadronic correlation functions that are involved in the determination of the B meson decay constant. We find that the residual gauge freedom associated to Gribov copies induces observable noise effects, though at the level of numerical accuracy of our simulation these effects are not

Jeffrey E. Mandula, Michael C. Ogilvie

A new technique for computing the strangeness content of the proton on the lattice is described. It is applied to the calculation of the strange quark contribution to the proton&#39;s spin, specifically to the evaluation of the proton matrix element of the strange quark axial current. Preliminary results are not in disagreement with the EMC experiment. NOTE:

A. A. Migdal

The variety of the phase transitions in Induced QCD are studied. Depending upon the parameters in the scalar field potential, there could be infinite number of fixed points, with different critical behavior. The integral equation for the density of the eigenvalues of the scalar field are generalized to the weak coupling phases, with the gap at the origin. We

Claude Bernard, Amarjit Soni, Ken Yee

This talk was presented to a non-lattice audience at the June, 1992 Paris Workshop on QCD Vacuum Structure. We report on the status of quark and gluon propagators in quenched, gaugefixed lattice QCD. In Landau gauge we find that the effective quark mass in the chiral limit is $M_q \sim 350(40)MeV$. Quark and gluon propagators, the slope of the quark dispersi

M. Goeckeler, A. S. Kronfeld, G. Schierholz, U. -J. Wiese

On the lattice some of the salient features of pure gauge theories and of gauge theories with fermions in complex representations of the gauge group seem to be lost. These features can be recovered by considering part of the theory in the continuum. The prerequisite for that is the construction of continuum gauge fields from lattice gauge fields. Such a cons

G. De Lorenzi, F. Ercolessi

The diffusion of monovacancies in gold has been studied by computer simulation. Multiple jumps have been found to play a central role in the atomic dynamics at high temperature, and have been shown to be responsible for an upward curvature in the Arrhenius plot of the diffusion coefficient. Appropriate saddle points on the potential energy surface have been

Biman B. Nath

It is shown that, for a nontrivial radiative decay channel of the 17-keV neutrino, the photons would distort the microwave background radiation through ionization of the universe. The constraint on the branching ratio of such decays from COBE measurements is found to be more stringent than that from other considerations. The limit on the branching ratio in t

Ronald Anderson, Girish C. Joshi

One of the important ways development takes place in mathematics is via a process of generalization. On the basis of a recent characterization of this process we propose a principle that generalizations of mathematical structures that are already part of successful physical theories serve as good guides for the development of new physical theories. The princ

R. Dijkgraaf, G. Moore, R. Plesser

We derive a compact and explicit expression for the generating functional of all correlation functions of tachyon operators in 2D string theory. This expression makes manifest relations of the $c=1$ system to KP flow and $W_{1+\infty}$ constraints. Moreover we derive a Kontsevich-Penner integral representation of this generating functional.

J. Ambjorn, B. Durhuus, T. Jonsson, G. Thorleifsson

We solve a class of branched polymer models coupled to spin systems and show that they have no phase transition and are either always magnetized or never magnetized depending on the branching weights. By comparing these results with numerical simulations of two-dimensional quantum gravity coupled to matter fields with central charge $c$ we provide evidence t

Damiano Anselmi, Pietro Fre

We show that the BRST quantum version of pure D=4 N=2 supergravity can be topologically twisted, to yield a formulation of topological gravity in four dimensions. The topological BRST complex is just a rearrangement of the old BRST complex, that partly modifies the role of physical and ghost fields: indeed, the new ghost number turns out to be the sum of the

Ian I. Kogan

We discuss the $W_{\infty}$ symmetry in the $2+1$ gauge theory with the Chern-Simons term. It is shown that the generators of this symmetry act on the ground state as the canonical transformations in the phase space. We shall also discuss the analogy between discrete states in $c=1$ string theory and Landau level states in $2+1$ gauge theory with Chern-Simon

A. De Rújula, S. L. Glashow

The observed deficit of $\rm ^8B$ solar neutrinos may call for an improved standard model of the sun or an expanded standard model of particle physics ({\it e.g.,} with neutrino masses and mixing). In the former case, contemporary fluid motions and thermal fluctuations in the sun&#39;s core may modify nuclear reaction rates and restore agreement. To test thi

Zachary Guralnik, Michael Luke, Aneesh V. Manohar

The properties of baryons containing one heavy quark are studied in the Skyrme model, where they are treated as bound states of a heavy meson with an $SU(2)$ chiral soliton. In the large $N_c$ limit, the baryon spectrum is an infinite tower of degenerate states with isospin and spin of the light degrees of freedom $I=s_\ell=0,1,2,\dots$, and total spin $s=\a

Maria Herrero, Ester Ruiz-Morales

We analyze the effects of a strongly interacting symmetry breaking sector of the Standard Model in $γγ-> W_L^+ W_L^-$ and $γγ-> Z_L Z_L$ reactions at TeV energies by using Chiral Lagrangians and Chiral Perturbation Theory. We find significant deviations from the Standard Model predictions for the differential cross sections at high invariant mass of the gaug

Tarun Souradeep, Varun Sahni

We investigate the behaviour of classical and quantum fields in the conical space-time associated with a point mass in 2+1 dimensions. We show that the presence of conical boundary conditions alters the electrostatic field of a point charge leading to the presence of a finite self-force on the charge from the direction of the point mass exactly as if the poi

M. James, L. Perivolaropoulos, T. Vachaspati

We map the parameter space that leads to stable Z-vortices in the electroweak model. For $sin^2 θ_W = 0.23$, we find that the strings are unstable for a Higgs mass larger than 24 GeV. Given the latest constraints on the Higgs mass from LEP, this shows that, if the standard electroweak model is realized in Nature, the Z-vortex (in the bare model) is unstable.

Tarun Souradeep

The origin of seed perturbations in the Universe is studied within the framework of a specific minisuperspace model. It is shown that the `creation&#39; of the Universe as a result of a quantum transition from a flat empty spacetime would lead to a flat FLRW (Friedmann Lema\^ıtre Robertson-Walker) Universe with weak inhomogeneous perturbations at large wavel

Chiara R. Nappi, Andrea Pasquinucci

We explore the thermodynamics of a general class of two dimensional dilatonic black-holes. A simple prescription is given that allows us to compute the mass, entropy and thermodynamic potentials, with results in agreement with those obtained by other methods, when available.

Th. Pruschke, D. L. Cox, M. Jarrell

We present results on thermodynamic quantities, resistivity and optical conductivity for the Hubbard model on a simple hypercubic lattice in infinite dimensions. Our results for the paramagnetic phase display the features expected from an intuitive analysis of the one-particle spectra and substantiate the similarity of the physics of the Hubbard model to tho

Nemanja Kaloper

A special Bianchi I universe is constructed in $~4D~$ string theory. Geometrically it represents a $~3D~$ anti-de-Sitter space crossed with a flat direction whereas in terms of an associated conformal field theory it is an extremal case of a gauged WZWN theory with target the coset $~SU(1,1) \times R^2 / R~$. Some of its properties are discussed.

Edward Witten

A framework for background independent open-string field theory is proposed. The approach involves using the BV formalism -- in a way suggested by recent developments in closed-string field theory -- to implicitly define a gauge invariant Lagrangian in a hypothetical ``space of all open-string world-sheet theories.&#39;&#39; It is built into the formalism th

L. Alvarez-Gaume, J. L. F. Barbon, C. Crnkovic

Using the reduced formulation on large-N Quantum Field Theories we study strings in space-time dimensions higher that one. We present results on possible string susceptibilities, macroscopic loop operators, 1/N -corrections and other general properties of the model.

Tarun Souradeep, Varun Sahni

We asses the contribution to the observed large scale anisotropy of the cosmic microwave background radiation, arising from both gravity waves as well as adiabatic density perturbations, generated by a common inflationary mechanism in the early Universe. We find that for inflationary models predicting power law primordial spectra %$a(t) \propto t^p, p > 1$,

D. B. DeLaney, S. Jadach, C. Shio, G. Siopsis

The Monte Carlo program SSCYFS2 is used in conjunction with available parton distribution functions to calculate the effects of multiple photon radiation on pp scattering at SSC energies. Effects relevant to precision SSC physics such as Higgs discovery and exploration are illustrated.

Alon E. Faraggi

I discuss in detail the construction of realistic superstring standard--like models in the four dimensional free fermionic formulation. The analysis results in a restricted class of models with unique characteristics: (i) Three and only three generations of chiral fermions with their superpartners and the correct Standard Model quantum numbers. (ii) Proton d

Alon E. Faraggi

I investigate the role of nonrenormalizable terms, up to order N=8, in a superstring derived standard--like model. I argue that nonrenormalizable terms restrict the gauge symmetry, at the Planck scale, to be $SU(3)\times SU(2)\times U(1)_{B-L}\times U(1)_{T_{3_R}}$ rather than $SU(3)\times SU(2)\times U(1)_Y$. I show that breaking the gauge symmetry directly

A. Marshakov

I present a short review of our results with S.Kharchev, A.Mironov, A.Morozov and A.Zabrodin on Generalized Kontsevich model which in a sense can be interpreted as unifying ``string field theory&#39;&#39; for $c < 1$ minimal series coupled to 2d gravity. The problem of interpolation between different models is discussed. It is found that this problem is clos

John March-Russell

In the ``Type-II&#39;&#39; regime, $m_{\rm Higgs}\gap m_{\rm gauge}$, the finite-temperature phase transition in spontaneously-broken gauge theories (including the standard model) must be be studied using a renormalization group treatment. Previous studies within the $(4-\ep)$-expansion suggest a 1st-order transition in this regime. We use analogies with exp

Luca Mezincescu, Rafael I. Nepomechie

We review how to construct a large class of integrable quantum spin chains with quantum-algebra symmetry, and how to determine their spectra. (To appear in Louis Witten Festschrift)

F. Lucchin, S. Matarrese, S. Mollerach

A stochastic background of primordial gravitational waves may substantially contribute, via the Sachs--Wolfe effect, to the large--scale Cosmic Microwave Background (CMB) anisotropies recently detected by COBE. This implies a {\it bias} in any resulting determination of the primordial amplitude of density fluctuations. We consider the constraints imposed on

M. Hecht

We present a comparison of Coulomb gauge wave functions from $6/{g^2}=6.0$ quenched simulations with two simulations which include the effects of dynamical fermions: simulations with two flavors of dynamical staggered quarks and valence Wilson quarks at $6/{g^2}=5.6$ and simulations with two flavors of dynamical Wilson quarks and Wilson valence quarks, at $6

John Baez, Micheal Ody, William Richter

We study the purely topological restrictions on allowed spin and statistics of topological solitons in nonlinear sigma models. Taking as space the connected $d$-manifold $X$, and considering nonlinear sigma models with the connected manifold $M$ as target space, topological solitons are given by elements of $pi_d(M)$. Any topological soliton $α\in π_d(M)$ de

J. González, F. Guinea, M. A. H. Vozmediano

The electronic spectrum of sheets of graphite (plane honeycomb lattice) folded into regular polihedra is studied. A continuum limit valid for sufficiently large molecules and based on a tight binding approximation is derived. It is found that a Dirac equation describes the flat graphite lattice. Curving the lattice by insertion of odd numbered rings can be m

F. Guinea, O. Pla, E. Louis

We analyze the dynamical evolution of systems which obey simple growth laws, like diffusion limited aggregation or dielectric breakdown. We show that, if the developing patterns is sufficiently complex, a scale invariant noise spectrum is generated, in agreement with the hypothesis that the system is in a self organized critical state. The intrinsic noise ge

Stefan Åminneborg

Global textures are interesting because they are promising candidates for seeds in the structure formation of the universe. The important configurations are those who will be able to collapse. The type of configurations that I will consider are half knots and true knots. I define a half knot as one that covers more than a half-$S^3$, and a true knot as a con

John Collins

It is shown that the azimuthal dependence of the distribution of hadrons in a quark jet is a probe of the transverse spin of the quark initiating the jet. This results in a new spin-dependent fragmentation function that acts at the twist-2 level. One example of a process where it contributes is semi-inclusive deeply inelastic scattering with a transversely p

L. Houart

We study the sL(3,C) mKDV string theories. We obtain the flows and the string equations. Using the generalized Miura map, we show that we have an unification of these models with the [P,Q]=Q sL(3,C) KDV ones in the framework of open-closed string theories in minimal models backgrounds.

S. Khokhlachev, Yu. Makeenko

We study the lattice gauge model proposed recently by Kazakov and Migdal for inducing QCD. We discuss an extra local Z_N which is a symmetry of the model and propose of how to construct observables. We discuss the role of the large-N phase transition which should occur before the one associated with the continuum limit in order that the model describes conti

Jaume Garriga, Alexander Vilenkin

We evaluate the probability that a loop of string that has spontaneously nucleated during inflation will form a black hole upon collapse, after the end of inflation. We then use the observational bounds on the density of primordial black holes to put constraints on the parameters of the model. Other constraints from the distortions of the microwave backgroun

K. Haglin, C. Gale, V. Emel'yanov

Production of electron-positron pairs with invariant masses less than 300 MeV from thermalized hadronic matter in relativistic heavy ion collisions is calculated using a soft virtual photon approximation. The general theoretical framework is reviewed and extended to include arbitrarily massed and charged reaction partners, which we apply to pions and quarks.

Kenneth A. Ribet

This paper gives a conjectural characterization of those elliptic curves over the field of complex numbers which &#34;should&#34; be covered by standard modular curves. The elliptic curves in question all have algebraic j-invariant, so they can be viewed as curves over Q-bar, the field of algebraic numbers. The condition that they satisfy is that they must b

S. Deser, A. Steif

Spacetimes generated by a lightlike particle source for topologically massive gravity and its limits - Einstein gravity and the pure gravitational Chern-Simons model - are obtained both by solving the field equations and by infinite boosts of static metrics. The resulting geometries are the first known solutions of topologically massive gravity that are asym

C. M. Hull, J. -L. Vazquez-Bello

This paper is concerned with theories describing spinning particles that are formulated in terms of actions possessing either local world-line supersymmetry or local fermionic {\it kappa} invariance. These classical actions are obtained by adding a finite number of spinor or vector coordinates to the usual space-time coordinates. Generalizing to superspace l

D. M. Gitman, A. L. Shelepin

Coherent states $(CS)$ of the $SU(N)$ groups are constructed explicitly and their properties are investigated. They represent a nontrivial generalization of the spining $CS$ of the $SU(2)$ group. The $CS$ are parametrized by the points of the coset space, which is, in that particular case, the projective space $CP^{N-1}$ and plays the role of the phase space

C. Imbimbo

This paper (completed March 1992) is an extensively revised and expanded version of work which appeared July 1991 on the initial incarnation of the hepth bulletin board, and which was published in the Proceedings of the Workshop on String Theory, Trieste, March 1991. Abstract We present a hamiltonian quantization of the $SL(2,R)$ 3-dimensional Chern-Simons t

Xiaoyuan Li, Ernest Ma

A gauge model of generation nonuniversality proposed in 1981 is reexamined in the light of present precision electroweak measurements. Two necessary features of this model are that the tau lifetime should be longer than predicted by the standard model and that the rho parameter measured at the Z peak should have an additional negative contribution. Both tren

J. C. Collins, F. V. Tkachov

An explicit example is presented (a one-loop triangle graph) where dimensional regularization fails to regulate the infra-red singularities that emerge at intermediate steps of studying large-$Q^2$ Sudakov factorization. The mathematical nature of the phenomenon is explained within the framework of the theory of the $As$-operation.

Prakash Mathews, V. Ravindran

We analyse polarised Drell-Yan process using the factorisation method and derive operator definitions for polarised parton distribution functions. We demonstrate that a factorisation analogous to that in the unpolarised Drell-Yan case holds in this process. We study the leading order gluonic contribution to the first moment of polarised Drell-Yan function an

Ph. Boucaud, J-P Leroy, J. Micheli, O. Pène

The $B$-meson decay constant can be measured on the lattice using a $1/m_b$ expansion. To relate the physical quantity to Monte Carlo data one has to know the renormalization coefficient, $Z$, between the lattice operators and their continuum counterparts. We come back to this computation to resolve discrepancies found in previous calculations. We define and

Jonathan J. Halliwell

We consider the problem of extracting physical predictions from the wave function of the universe in quantum cosmological models. We state the features of quantum cosmology an interpretational scheme should confront. We discuss the Everett interpretation, and extensions of it, and their application to quantum cosmology. We review the steps that are normally

Th. Pruschke, D. L. Cox, M. Jarrell

Results for the optical conductivity and resistivity of the Hubbard model in infinite spatial dimensions are presented. At half filling we observe a gradual crossover from a normal Fermi-liquid with a Drude peak at $ω=0$ in the optical conductivity to an insulator as a function of $U$ for temperatures above the antiferromagnetic phase transition. When doped,

R. Kantowski, Caren Marzban

The divergent part of the one-loop off-shell effective action is computed for a single scalar field coupled to the Ricci curvature of 2D gravity ($c ϕR$), and self interacting by an arbitrary potential term $V(ϕ)$. The Vilkovisky-DeWitt effective action is used to compute gauge-fixing independent results. In our background field/covariant gauge we find that

S. P. Gavrilov, D. M. Gitman

A modification of the canonical quantization procedure for systems with time-dependent second-class constraints is discussed and applied to the quantization of the relativistic particle in a plane wave. The time dependence of constraints appears in the problem in two ways. The Lagrangian depends on time explicitly by origin, and a special time-dependent gaug