March 1993 arXiv papers — page 4

Donald Marolf

We study the loop representation of the quantum theory for 2+1 dimensional general relativity on a manifold, $M = {\cal T}^2 \times {\cal R}$, where ${\cal T}^2$ is the torus, and compare it with the connection representation for this system. In particular, we look at the loop transform in the part of the phase space where the holonomies are boosts and study

J. Navarro-Salas, M. Navarro, V. Aldaya

We consider the induced $2$d-gravity in the minisuperspace approach. The general solution to the Wheeler-DeWitt equation is given in terms of different kind of Bessel functions of purely real or imaginary orders. We study the properties of the corresponding probability distribution finding a kind of phase transition at the critical point $ν=0$.

P. E. T. Jørgensen, R. F. Werner

For the $q$-deformed canonical commutation relations $a(f)a^\dagger(g) = (1-q)\,\langle f,g\rangle{\bf1}+q\,a^\dagger(g)a(f)$ for $f,g$ in some Hilbert space ${\cal H}$ we consider representations generated from a vector $Ω$ satisfying $a(f)Ω=\langle f,ϕ\rangleΩ$, where $ϕ\in{\cal H}$. We show that such a representation exists if and only if $\Vertϕ\Vert\leq

J. P. Bouchaud, E. Vincent, J. Hammann

We show that an 'ergodic' time scale can be extracted from the aging experiments on spin-glasses. This is the time for which a significant fraction of the metastable states have been visited. Experiments suggest that the number of metastable states per independent subsystem is $\simeq 10^{12}-10^{14}$. For our insulating spin-glass $({\rm CdCr}_{1.7}

Bruno Eckhardt

Recent developments in the semiclassical analysis of chaotic systems are reviewed and illustrated for Wigner's time delay in elastic scattering of a point particle from three disks in the plane. The convergence of the cycle expanded periodic orbit expression for Wigners time delay is demonstrated. Different regimes in form factor (the Fourier transform o

David A. Egolf, Henry S. Greenside

Using algorithms of Higuchi and of Grassberger and Procaccia, we study numerically how fractal dimensions cross over from finite-dimensional Brownian noise at short time scales to finite values of deterministic chaos at longer time scales for data generated from a Langevin equation that has a strange attractor in the limit of zero noise. Our results suggest

B. Velikson, J. Bascle, T. Garel, H. Orland

We study local energy minima of twenty(L-alanine). The minima are generated using high-temperature Molecular Dynamics and Chain-Growth Monte Carlo simulations, with subsequent minimization. We find that the lower-energy configurations are $ α$-helices for a wide range of dielectric constant values $ (ε= 1,10,80), $ and that there is no noticeable difference

M. I. Polikarpov, U. -J. Wiese, M. A. Zubkov

The partition function of the $4D$ lattice Abelian Higgs theory is represented as the sum over world sheets of Nielsen--Olesen strings. The creation and annihilation operators of the strings are constructed. The topological long--range interaction of the strings and charged particles is shown to exist; it is proportional to the linking number of the string w

Jean-Yves Ollitrault

In the particles produced in a nuclear collision undergo collective flow, the reaction plane can in principle be determined through a global event analysis. We show here that collective flow can be identified by evaluating the reaction plane independently in two separate rapidity intervals, and studying the correlation between the two results. We give an ana

L. Perivolaropoulos, T. Vachaspati

Using an analytic model we show that the predictions of the cosmic string model for the peculiar velocities and the microwave background (MBR) anisotropy depend on similar combinations of string evolution parameters. Normalizing from the COBE detection of MBR anisotropy, and for certain reasonable values of string network evolution parameters, we find that t

Li Ning, Robert E. Ecke

The initial bifurcations in rotating Rayleigh-Bénard convection are studied in the range of dimensionless rotation rate $0 < Ω< 2150$ for an aspect-ratio-2.5 cylindrical cell. We used simultaneous optical shadowgraph, heat transport and local temperature measurements to determine the stability and characteristics of the azimuthally-periodic wall convection s

K. Varga, J. Cseh

We determine the phenomenological cluster--cluster interactions of the algebraic model corresponding to the most often used effective two--nucleon forces for the $^{16}$O + $α$ system.

Attila Csoto

The two--neutron separation energy of $^6$He has been reproduced for the first time in a realistic parameter--free microscopic multicluster model comprising the $α+n+n$ and $t+t$ clusterizations, with $α$ cluster breathing excitations included. The contribution of the $t+t$ channel is substantial. A very thick (0.85 fm) neutron halo has been found in full ag

E. Ivanov, F. Toppan

We present a new supersymmetric integrable model: the $N=2$ superconformal affine Liouville theory. It interpolates between the $N=2$ super Liouville and $N=2$ super sine-Gordon theories and possesses a Lax representation on the complex affine Kac-Moody superalgebra ${\hat {sl(2| 2)^{(1)}}}$. We show that the higher spin $W_{1+\infty}$-type symmetry algebra

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

We consider a biparametric family of BRS invariant regularization methods of SU(N) Chern-Simons theory (the parameters defining the family taking arbitrary values in $\RR^2$) and show that the shift $k\to k + sign(k) N$ of the Chern-Simons parameter $k$ occurs for arbitrary values of the family defining parameters. This supports irrefutably the conjecture th

C. M. Hull

The full non-linear structure of the action and transformation rules for $\W_N$-gravity coupled to matter are obtained from a non-linear truncation of those for $w_ \infty$ gravity. The geometry of the construction is discussed, and it is shown that the defining equations become linear after a twistor-like transform.

Jean-Paul Blaizot, Jean-Yves Ollitrault

We study fermionic excitations in a cold ultrarelativistic plasma. We construct explicitly the quantum states associated with the two branches which develop in the excitation spectrum as the chemical potential is raised. The collective nature of the long wavelength excitations is clearly exhibited. Email contact: ollie@amoco.saclay.cea.fr

Rolf Schimmrigk

The role in string theory of manifolds of complex dimension $D_{crit} + 2(Q-1)$ and positive first Chern class is described. In order to be useful for string theory, the first Chern class of these spaces has to satisfy a certain relation. Because of this condition the cohomology groups of such manifolds show a specific structure. A group that is particularly

M. A. Doncheski, C. S. Kim

Associated production of $J/ψ$ and a $γ$ has recently been proposed as clean probe of the gluon distribution. The same mechanism can be used to probe the polarized gluon content of the proton in polarized proton-proton collisions. We study $J/ψ+ γ$ production at both polarized fixed target and polarized collider energies.

Colin Wilkin

It is argued that the strong energy dependence of the $p\, d \rightarrow \,^{3\!}H\!e\, η$ cross section near threshold is due to a final state interaction between the $η$ meson and the $^3$He nucleus. The large scattering length that this implies is in accord with optical potential predictions and is evidence for a nearby virtual `$\!$`bound&#39;$\!$&#39; s

E. J. Chun, A. Lukas

We analyze the breakdown of SUSY GUTs driven by Nambu--Jona--Lasinio condensates. Starting with the most general gauge invariant and pure Kählerian Lagrangian up to quartic order we solve the one loop gap equation and determine the breaking direction. This is done for various classes of groups and spectra of fundamental particles which especially cover the m

Luis E. Ibanez

Four-dimensional strings with the standard model gauge group $SU(3)\times SU(2)\times U(1)$ give model-dependent predictions for the tree level weak mixing-angle. In the presence of an extra pseudo-anomalous gauged- ${U(1)}_X$, the value of the weak angle may be computed purely in terms of the charges of the massless fermions of the theory, independently of

Sanghyeon Chang, Kiwoon Choi

We examine whether observable majoron emission in double beta decay can be compatible with the big-bang nucleosynthesis (NS) and the observed neutrino flux from SN1987A. It is found that the NS upper bound on $^4$He abundance implies that the majoron-neutrino Yukawa coupling constant $g\leq 9\times 10^{-6}$ and its maximal value is allowed only when the scal

Lawrence Hall, Steven Weinberg

The smallness of fermion masses and mixing angles has recently been been attributed to approximate global $U(1)$ symmetries, one for each fermion type. The parameters associated with these symmetry breakings are estimated here directly from observed masses and mixing angles. It turns out that although flavor changing reaction rates may be acceptably small in

C. F. Baillie, D. A. Johnston

We investigate actions for dynamically triangulated random surfaces that consist of a gaussian or area term plus the {\it modulus} of the gaussian curvature and compare their behavior with both gaussian plus extrinsic curvature and ``Steiner&#39;&#39; actions.

Vanda Silveira, M. D. Maia

The effective action of a (1+2)-dimensional defect is obtained as an expansion in powers of the thickness.Considering non-straight solutions as the zero order term, the corrections to the Nambu action are found to depend on the curvature scalar and on the gaussian curvature .

Michael Frank

We show the possibility and the uniqueness of polar decomposition of elements of arbitrary AW*-algebras inside them. We prove that spectral decomposition of normal elements of normal AW*-algebras is possible and unique inside them. The possibility of spectral decomposition of normal elements does not depend on the normality of the AW*-algebra under considera

D. O. Martinez, W. H. Matthaeus, S. Chen, D. C. Montgomery

We present numerical solutions of the two-dimensional Navier-Stokes equations by two methods; spectral and the novel Lattice Boltzmann Equation (LBE) scheme. Very good agreement is found for global quantities as well as energy spectra. The LBE scheme is, indeed, providing reasonably accurate solutions of the Navier-Stokes equations with an isothermal equatio

Bruno Eckhardt, Gunnar Russberg

The convergence properties of cycle expanded periodic orbit expressions for the spectra of classical and semiclassical time evolution operators have been studied for the open three disk billiard. We present evidence that both the classical and the semiclassical Selberg zeta function have poles. Applying a Padé approximation on the expansions of the full Eule

Wm. T. Ashurst

Computed flame motion through and between swirling eddys exhibits a maximum advancement rate which is related to the time duration of flame motion between eddys. This eddy spatial structure effect upon the apparent turbulent flame speed appears to be similar to the square-root dependence observed in wrinkled flamelet data. The rate-limiting behavior at one e

T. Stanev, P. L. Biermann, T. K. Gaisser

Using the concept developed in earlier papers, that the cosmic rays originate in three different main sites, a) the normal supernova explosions into the interstellar medium, b) the supernova explosions into a stellar wind, and c) powerful radio galaxies, we demonstrate in this paper that the spectrum and chemical abundances above $10^4$ GeV can be well under

V. Alan Kostelecký, V. I. Man&#39;ko, Michael Martin Nieto, D. Rodney Truax

A general technique is outlined for investigating supersymmetry properties of a charged spin-$\half$ quantum particle in time-varying electromagnetic fields. The case of a time-varying uniform magnetic induction is examined and shown to provide a physical realization of a supersymmetric quantum-mechanical system. Group-theoretic methods are used to factorize

Carsten Gundlach

This paper is an application of the ideas of the Born-Oppenheimer (or slow/fast) approximation in molecular physics and of the Isaacson (or short-wave) approximation in classical gravity to the canonical quantization of a perturbed minisuperspace model of the kind examined by Halliwell and Hawking. Its aim is the clarification of the role of the semiclassica

Bernd Bruegmann

This bibliography attempts to give a comprehensive overview of all the literature related to the Ashtekar variables. The original version was compiled by Peter Huebner in 1989, and it has been subsequently updated by Gabriela Gonzalez and Bernd Bruegmann. Information about additional literature, new preprints, and especially corrections are always welcome.

P. Bamert, Z. Kunszt

We discuss a model in which the Standard Model (SM) Higgs sector has been extended by additional real and complex triplets. The $ρ\approx 1$ constraint is satisfied by restricting the potential to have an enlarged $\hisym $ global symmetry. This is fine tuning, which leads to a decreased predictability in next-to-leading order. In this model, however, the tr

E. Alvarez, J. Cespedes, E. Verdaguer

The partition function corresponding to the "polytopic" action, a new action for the gravitational interaction which we have proposed recently, is computed in the simplest two-dimensional geometries of genus zero and one. The functional integral over the Liouville field is approximated by an ordinary integral over the constant zero mode. We study the depende

C. Bachas

I discuss the quantum instability of an electric field in a theory of open strings.

Ashoke Sen

We show that in heterotic string theory compactified on a six dimensional torus, the lower bound (Bogomol&#39;nyi bound) on the dyon mass is invariant under the SL(2,Z) transformation that interchanges strong and weak coupling limits of the theory. Elementary string excitations are also shown to satisfy this lower bound. Finally, we identify specific monopol

N. N. Nikolaev, A. Szczurek, J. Speth, J. Wambach

Quantum filtering of the ejectile wave packet from hard $ep$ scattering on bound nucleons puts stringent constraints on the onset of color transparency in $(e,e&#39;p)$ reactions in nuclei at moderate energies. Based on multiple-scattering theory, we derive a novel formula for nuclear transparency and discuss its energy dependence in terms of a color transpa

Keke Li, Edward Witten

A recent proposal for a background independent open string field theory is studied in detail for a class of backgrounds that correspond to general quadratic boundary interactions on the world-sheet. A short-distance cut-off is introduced to formulate the theory with a finite number of local and potentially unrenormalizable boundary couplings. It is shown tha

Pavel Etingof

The paper introduces a new geometric interpretation of the quantum Knizhnik-Zamolodchikov equations introduced in 1991 by I.Frenkel and N.Reshetikhin. It turns out that these equations can be linked to certain holomorphic vector bundles on the N-th Cartesian power of an elliptic curve. These bundles are naturally constructed by a gluing procedure from a syst

E. Aldrovandi, L. Bonora

We study the Liouville theory on a Riemann surface of genus g by means of their associated Drinfeld--Sokolov linear systems. We discuss the cohomological properties of the monodromies of these systems. We identify the space of solutions of the equations of motion which are single--valued and local and explicitly represent them in terms of Krichever--Novikov

Parentani Renaud

The energy density in Fulling-Rindler vacuum, which is known to be negative &#34;everywhere&#34; is shown to be positive and singular on the horizons in such a fashion as to guarantee the positivity of the total energy. The mechanism of compensation is displayed in detail.

Andrei Bytsenko, Klaus Kirsten, Sergei Odintsov

We calculate the one-loop effective potential of a self-interacting scalar field on the spacetime of the form $\reals^2\times H^2/Γ$. The Selberg trace formula associated with a co-compact discrete group $Γ$ in $PSL(2,\reals )$ (hyperbolic and elliptic elements only) is used. The closed form for the one-loop unrenormalized and renormalized effective potentia

Alon E. Faraggi, Edi Halyo

We propose a new scenario in a class of superstring derived standard--like models that explains the suppression of the left--handed neutrino masses. Due to nonrenormalizable terms and the breaking of the $U(1)_{Z^\prime}$ symmetry a generalized see--saw mechanism takes place. Contrary to the traditional see--saw mechanism in GUTs, the see--saw scale and the

Nemanja Kaloper

A solution of effective string theory in four dimensions is presented which admits interpretation of a rotating black cosmic string. It is constructed by tensoring the three dimensional black hole, extended with the Kalb-Ramond axion, with a flat direction. The physical interpretation of the solution is discussed, with special attention on the axion, which i

A. Sevrin, P. van Nieuwenhuizen

We extend the theory of the gauging of classical quadratically nonlinear algebras without a central charge but with a coset structure, to the quantum level. Inserting the minimal anomalies into the classical transformation rules of the currents introduces further quantum corrections to the classical transformation rules of the gauge fields and currents which

Paul Langacker

The status of solar neutrino experiments and their implications for both nonstandard astrophysics ({\it e.g.,} cool sun models) and nonstandard neutrino properties ({\it e.g.,} MSW conversions) are discussed. Assuming that all of the experiments are correct, the relative rates observed by Kamiokande and Homestake are hard to account for by a purely astrophys

Helene Nadeau, David London

We consider single production of leptoquarks (LQ&#39;s) at $eγ$ colliders, for two values of the centre-of-mass energy, $\sqrt{s}=500$ GeV and 1 TeV. LQ&#39;s with masses essentially up to the kinematic limit can be seen, even for couplings as weak as $O(10^{-3})$-$O(10^{-2})α_{em}$. It is possible to detect LQ&#39;s of mass greater than $\sqrt{s}$ by lookin

Yigal Shamir

We construct a model in which four dimensional chiral fermions arise on the boundaries of a five dimensional lattice with free boundary conditions in the fifth direction. The physical content is similar to Kaplan&#39;s model of domain wall fermions, yet the present construction has several technical advantages. We discuss some aspects of perturbation theory,

Istvan Racz

We consider source-free electromagnetic fields in spacetimes possessing a non-null Killing vector field, $ξ^a$. We assume further that the electromagnetic field tensor, $F_{ab}$, is invariant under the action of the isometry group induced by $ξ^a$. It is proved that whenever the two potentials associated with the electromagnetic field are functionally indepe

Kyung-Hoon Kwon, Doochul Kim

We construct solvable models on the honeycomb lattice by combining three faces of the square lattice solvable models into a hexagon face. These models contain two independent, anisotropy controlling, spectral parameters and their transfer matrices with different spectral parameters commute with each other. At the critical point, the finite-size scaling of th

Ronnie Mainieri, Robert E. Ecke

For one dimensional maps the trajectory scaling functions is invariant under coordinate transformations and can be used to compute any ergodic average. It is the most stringent test between theory and experiment, but so far it has proven difficult to extract from experimental data. It is shown that the main difficulty is a dephasing of the experimental orbit

Andrew T. Sornborger

This study presents a simplified approach to studying the dynamics of global texture collapse. We derive equations of motion for a spherically symmetric field configuration using a two parameter ansatz. Then we analyse the effective potential for the resulting theory to understand possible trajectories of the field configuration in the parameter space of the

Andre Aeppli, Frank Cuypers, Geert Jan van Oldenborgh

Several schemes to introduce finite width effects to reactions involving unstable elementary particles are given and the differences between them are investigated. The effects of the different schemes is investigated numerically for $W$ pair production. In $e^+e^-\to W^+W^-$ we find that the effect of the non-resonant graphs cannot be neglected for $\sqrt{s}

Subir Sachdev

These are lectures presented at the summer course on ``Low Dimensional Quantum Field Theories for Condensed Matter Physicists'', 24 Aug. to 4 Sep. 1992, Trieste, Italy. I review recent work, performed in collaboration primarily with N. Read and Jinwu Ye, on the properties of quantum antiferromagnets in two dimensions. The emphasis is on the properties of the

Alan R. White

The high-energy Regge behavior of gauge theories is studied via the formalism of Analytic Multi-Regge Theory. Perturbative results for spontaneously-broken theories are first organised into reggeon diagrams. Unbroken gauge theories are studied via a reggeon diagram infra-red analysis of symmetry restoration. Massless fermions play a crucial role and the case

E. Bergshoeff, H. J. Boonstra, M. de Roo, S. Panda

We discuss the conditions under which the BRST operator of a $W$-string can be written as the sum of two operators that are separately nilpotent and anticommute with each other. We illustrate our results with the example of the non-critical $W_3$-string. Furthermore, we apply our results to make a conjecture about a relationship between the spectrum of a non

Takayuki Hori

The two dimensional dilaton gravity with the cosmological term and with an even number of matter fields minimally coupled to the gravity is considered. The exact solutions to the Wheeler-DeWitt equation are obtained in an explicit functional form, which contain an arbitrary holomorphic function of the matter fields.

Mark Srednicki

The ground state density matrix for a massless free field is traced over the degrees of freedom residing inside an imaginary sphere; the resulting entropy is shown to be proportional to the area (and not the volume) of the sphere. Possible connections with the physics of black holes are discussed.

Gordon W. Semenoff, Nathan Weiss

We review some of the basic features of the Kazakov-Migdal model of induced QCD. We emphasize the role of $Z_N$ symmetry in determining the observable properties of the model and also argue that it can be broken explicitly without ruining the solvability of induced QCD in the infinite $N$ limit. We outline the sort of critical behavior which the master field

Joe Kiskis, Rajamani Narayanan, Pavlos Vranas

We study the random walk representation of the two-point function in statistical mechanics models near the critical point. Using standard scaling arguments we show that the critical exponent $ν$ describing the vanishing of the physical mass at the critical point is equal to $ν_θ/ d_w$. $d_w$ is the Hausdorff dimension of the walk. $ν_θ$ is the exponent descr

A. A. Tseytlin

We discuss two classes of exact (in $\a&#39;$) string solutions described by conformal sigma models. They can be viewed as two possibilities of constructing a conformal model out of the non-conformal one based on the metric of a $D$-dimensional homogeneous $G/H$ space. The first possibility is to introduce two extra dimensions (one space-like and one time-li

C. Destri, H. J. de Vega

We show how any integrable 2D QFT enjoys the existence of infinitely many non--abelian {\it conserved} charges satisfying a Yang--Baxter symmetry algebra. These charges are generated by quantum monodromy operators and provide a representation of $q-$deformed affine Lie algebras. We review and generalize the work of de Vega, Eichenherr and Maillet on the boot

B. K. Chung, Soonkeon Nam, Q-Han Park, H. J. Shin

Based upon the formalism of conformal field theory with a boundary, we give a description of the boundary effect on fully developed two dimensional turbulence. Exact one and two point velocity correlation functions and energy power spectrum confined in the upper half plane are obtained using the image method. This result enables us to address the infrared pr

Pavel Etingof, Igor B. Frenkel

In this paper we generalize some of these results for loop algebras and groups as well as for the Virasoro algebra to the two-dimensional case. We define and study a class of infinite dimensional complex Lie groups which are central extensions of the group of smooth maps from a two dimensional orientable surface without boundary to a simple complex Lie group

Vittorio Del Duca, Michael E. Peskin, Wai-Keung Tang

We apply the theory of parton-parton total cross sections at large ``s&#34;, due to Lipatov and collaborators, to compute the inclusive cross section for jets which accompany a large ``s&#34; parton scattering process.

K. Langfeld, L. v. Smekal, H. Reinhardt

Massless $ϕ^{4}$-theory is investigated in zero and four space-time dimensions. Path-integral linearisation of the $ϕ^{4}$-interaction defines an effective theory, which is investigated in a loop-expansion around the mean field. In zero dimensions this expansion converges rapidly to the exact potential obtained numerically. In four dimensions its lowest orde

Loyal Durand, Peter N. Maher, Kurt Riesselmann

We use the results of Maher {\em et al.\/} (preceding paper) to construct the matrix of $j=0$ partial-wave two-body and $2\rightarrow3$ scattering amplitudes for the scattering of longitudinally polarized gauge bosons $W_L^\pm$, $Z_L$ and Higgs bosons $H$ correct to two loops in the high-energy, heavy-Higgs limit $\sqrt{s}\gg M_H\gg M_W$. We show explicitly

Peter N. Maher, Loyal Durand, Kurt Riesselmann

We calculate the complete matrix of two-body scattering amplitudes for the scattering of longitudinally polarized gauge bosons $W_L^\pm$, $Z_L$ and Higgs bosons to two loops in the high-energy, heavy-Higgs limit $\sqrt{s}\gg M_H\gg M_W$. Use of the Goldstone boson equivalence theorem reduces the problem to one involving only the scalar fields $w^\pm$, $z$ (t

Riccardo Guida, Kenichi Konishi

We consider the behaviour of fermions in the background of instanton-anti\-instanton type configurations. Several different physics problems, from the high energy electroweak interactions to the study of vacuum structure of QCD and of large orders of perturbation theory are related to this problem. The spectrum of the Dirac operator in such a background is s

S. A. Frolov, A. A. Slavnov

A method for removing fermion doublers in anomaly free chiral gauge theories on the lattice is proposed. It is proven that the resulting continuum theory is gauge invariant and does not require noninvariant counterterms of fine tuning of parameters.

P. Cea, L. Cosmai

We investigate SU(2) gauge theory in a constant chromomagnetic field in three dimensions both in the continuum and on the lattice. Using a variational method to stabilize the unstable modes, we evaluate the vacuum energy density in the one-loop approximation. We compare our theoretical results with the outcomes of the numerical simulations.

Jean-paul Berthias, Bahman Shahid-Saless

We show that the gravitational field equations derived from an action composed of i) an arbitrary function of the scalar curvature and other scalar fields plus ii) connection-independent kinetic and source terms, are identical whether one chooses nonmetricity to vanish and have non-zero torsion or vice versa.

Fong Liu, H. Metiu

We investigate the dynamical evolution of a thermodynamically unstable crystal surface into a hill-and-valley structure. We demonstrate that, for quasi one-dimensional ordering, the equation of motion maps exactly to the modified Cahn-Hilliard equation describing spinodal decomposition. Orderings in two dimensions follow the dynamics of continuum clock model

A. Mailhot, M. L. Plumer, A. Caillé

The results of a detailed histogram Monte-Carlo study of critical-fluctuation effects on the magnetic-field temperature phase diagram associated with the hexagonal Heisenberg antiferromagnet with weak axial anisotropy are reported. The multiphase point where three lines of continuous transitions merge at the spin-flop boundary exhibits a structure consistent

Michael C. Martin, Daniel Koller, L. Mihaly

We have measured the four IR active $C_{60}$ molecular vibrations in $M_{x}C_{60}$ $(M = K, Rb)$ as a function of doping $x$. We observe discontinuous changes in the vibrational spectra showing four distinct phases (presumably $x = 0, 3, 4$, and 6). The $1427cm^{-1}$ and $576cm^{-1}$ modes show the largest changes shifting downward in frequency in four steps

Leon Balents, Mehran Kardar

We study the delocalization by bulk randomness of a single flux line (FL) from an extended defect, such as a columnar pin or twin plane. In three dimensions, the FL is always bound to a planar defect, while there is an unpinning transition from a columnar pin. Transfer matrix simulations confirm this picture, and indicate that the divergence of the localizat

D. M. Beazley, P. S. Lomdahl

We present a new scalable algorithm for short-range molecular dynamics simulations on distributed memory MIMD multicomputer based on a message-passing multi-cell approach. We have implemented the algorithm on the Connection Machine 5 (CM-5) and demonstrate that meso-scale molecular dynamics with more than $10^8$ particles is now possible on massively paralle

Hirokazu Fujisaka, Hideto Shigematsu, Bruno Eckhardt

A new expansion scheme to evaluate the eigenvalues of the generalized evolution operator (Frobenius-Perron operator) $H_{q}$ relevant to the fluctuation spectrum and poles of the order-$q$ power spectrum is proposed. The ``partition function'' is computed in terms of unstable periodic orbits and then used in a finite pole approximation of the continued fract

M. Umemura, A. Loeb, E. L. Turner

The evolution of nonlinear density fluctuations around the Jeans mass shortly after cosmological recombination is analyzed using a 3D hydrodynamics/dark--matter code. The Cosmic Background Radiation (CBR) exerts Compton friction on free electrons due to peculiar velocities. The dynamics therefore depends strongly on the gas ionization history. Under a variet

Michael Dine, Ann E. Nelson

Conventional approaches to supersymmetric model building suffer from several naturalness problems: they do not explain the large hierarchy between the weak scale and the Planck mass, and they require fine tuning to avoid large flavor changing neutral currents and particle electric dipole moments. The existence of models with dynamical supersymmetry breaking,

David J. Gross, Washington Taylor

Many Texo&#39;s have been corrected and a reference added.

J. I. Latorre, C. Manuel, X. Vilasis-Cardona

We present a systematic implementation of differential renormalization to all orders in perturbation theory. The method is applied to individual Feynamn graphs written in coordinate space. After isolating every singularity. which appears in a bare diagram, we define a subtraction procedure which consists in replacing the core of the singularity by its renorm

H. J. de Vega, Luca Mezincescu, Rafael I. Nepomechie

We consider a two-parameter $(\bar c, \tilde c)$ family of quantum integrable Hamiltonians for a chain of alternating spins of spin $s=1/2$ and $s=1$. We determine the thermodynamics for low-temperature $T$ and small external magnetic field $H$, with $T << H$. In the antiferromagnetic $(\bar c > 0, \tilde c > 0)$ case, the model has two gapless excitations.

A. J. Bray, A. D. Rutenberg

We determine the characteristic length scale, $L(t)$, in phase ordering kinetics for both scalar and vector fields, with either short- or long-range interactions, and with or without conservation laws. We obtain $L(t)$ consistently by comparing the global rate of energy change to the energy dissipation from the local evolution of the order parameter. We deri

J. Piekarewicz

We extend a recent calculation of the momentum dependence of the $ρ-ω$ mixing amplitude to the pseudoscalar sector. The $π\!-\!η$ mixing amplitude is calculated in a hadronic model where the mixing is driven by the neutron-proton mass difference. Closed-form analytic expressions are presented in terms of a few nucleon-meson parameters. The observed momentum

R. Paunov

We reexamine the $W_{\infty}$ symmetry of the $sl(N)$ Conformal Affine Toda theories. It is shown that it is possible to reduce (nonuniquely) the zero curvature equation to a Lax equation for a first order pseudodifferential oprator, whose coefficients are the generators of the $W_{\infty}$ algebra. This clarifies the known relation between the Conformal Aff

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

We investigate the phase structure of four-dimensional quantum gravity coupled to Ising spins or Gaussian scalar fields by means of numerical simulations. The quantum gravity part is modelled by the summation over random simplicial manifolds, and the matter fields are located in the center of the 4-simplices, which constitute the building blocks of the manif

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

We measure the fractal structure of four dimensional simplicial quantum gravity by identifying so-called baby universes. This allows an easy determination of the critical exponent $\g$ connected to the entropy of four-dimensional manifolds.

Vadim Kaplunovsky, Jan Louis

We discuss supersymmetry breakdown in effective supergravities such as emerge in the low-energy limit of superstring theory. Without specifying the precise trigger of the breakdown, we analyse the soft parameters in the Lagrangian of the supersymmetrized Standard Model.

J. Lopez, D. Nanopoulos, H. Pois, X. Wang

We study the most promising signals for supersymmetry at LEPII in the context of two well motivated supergravity models: (i) the minimal $SU(5)$ supergravity model including the stringent constraints from proton stability and a not too young Universe, and (ii) a recently proposed string-inspired no-scale flipped $SU(5)$ supergravity model. Our computations s

John N. Bahcall, Pawan Kumar

We show that low-order g-modes with large enough amplitudes to affect significantly the solar neutrino fluxes would produce surface velocities that are $10^4$ times larger than the observed upper limits and hence are ruled out by existing data. We also demonstrate that any large-amplitude, short-period oscillations that grow on a Kelvin-Helmholtz time scale

J. David Brown, James W. York

The authors have recently proposed a ``microcanonical functional integral&#34; representation of the density of quantum states of the gravitational field. The phase of this real--time functional integral is determined by a ``microcanonical&#34; or Jacobi action, the extrema of which are classical solutions at fixed total energy, not at fixed total time inter

Kikuo Harigaya

Effects on C60 by thermal fluctuations of phonons, misalignment of molecules in a crystal, and other intercalated impurities are simulated by disorder potentials. The SSH model for doped C60 is solved with gaussian bond and site disorders. Polarons and dimerizations in lightly doped cases (C60^{-1,-2}) are relatively stable against disorders, indicated by pe

M. Yamanaka, Y. Hatsugai, M. Kohmoto

We study the ground state properties of the bond alternating $S=1/2$ quantum spin chain whose Hamiltonian is H=\sum_j (S_{2j}^x S_{2j+1}^x +S_{2j}^y S_{2j+1}^y +λS_{2j}^z S_{2j+1}^z ) +β\sum_j {\bf S}_{2j-1} \cdot {\bf S}_{2j} . When $β=0$, the ground state is a collection of local singlets with a finite excitation gap. In the limit of strong ferromagnetic c

Kunihiko Kaneko

Traveling waves triggered by a phase slip in coupled map lattices are studied. A local phase slip affects globally the system, which is in strong contrast with kink propagation. Attractors with different velocities coexist, and form quantized bands determined by the number of phase slips. The mechanism and statistical and dynamical characters are studied wit

Fausto Borgonovi, Italo Guarneri

The statistics of S-matrix fluctuations are numerically investigated on a model for irregular quantum scattering in which a classical chaotic diffusion takes place within the interaction region. Agreement with various random-matrix theoretic predictions is discussed in the various regimes (ballistic, diffusive, localized).

Piet Hut

Blue stragglers are natural phenomena in star clusters. They originate through mass transfer in isolated binaries, as well as through encounters between two or more stars, in a complex interplay between stellar dynamics and stellar evolution. While this interplay cannot be modeled quantitatively at present, we will be able to do so in one or two years time.

Kunihiko Kaneko, Junji Suzuki

Motivated by the evolution of complex bird songs, an abstract imitation game is proposed to study the increase of dynamical complexity: Artificial &#34;birds&#34; display a &#34;song&#34; time series to each other, and those that imitate the other&#39;s song better win the game. With the introduction of population dynamics according to the score of the game