arXiv papers from August 1996

C. Zeng, C. L. Henley

We map the ground-state ensemble of antiferromagnetic Ising model of spin-S on a triangular lattice to an interface model whose entropic fluctuations are proposed to be described by an effective Gaussian free energy, which enables us to calculate the critical exponents of various operators in terms of the stiffness constant of the interface. Monte Carlo simu

Remo Garattini

We analyze the possibility of black holes pair creation induced by three dimensional wormholes. Although this spacetime configuration is nowadays hard to suppose, it can be very important in the early universe, when the wormhole spacetime foam representation can be meaningful. We compare our approach with the no-boundary prescription of Hartle-Hawking.

Shoichi Ichinose

Tensor calculation of suffix-contraction is carried out by a C-program. Tensors are represented graphically, and the algorithm makes use of the topology of graphs. Classical and quantum gravity, in the weak-field perturbative approach, is a special interest. Examples of the leading order calculation of some general invariants such as $R_{\mn\ls}R^{\mn\ls}$ a

Shoichi Ichinose, Noriaki Ikeda

We introduce a graphical representation for a global SO(n) tensor $\pl_\m\pl_\n h_\ab$, which generally appears in the perturbative approach of gravity around the flat space: $g_\mn=\del_\mn+h_\mn$. We systematically construct global SO(n) invariants. Independence and completeness of those invariants are shown by taking examples of $\pl\pl h$-, and $ (\pl\pl

Durga P. Choudhury, Balam A. Willemsen, John S. Derov, S. Sridhar

The non-linear microwave surface impedance of patterned YBCO thin films, was measured using a suspended line resonator in the presence of a perpendicular DC magnetic field of magnitude comparable to that of the microwave field. Signature of the virgin state was found to be absent even for relatively low microwave power levels. The microwave loss was initiall

D. Boyanovsky, H. J. de Vega, R. Holman, J. F. J. Salgado

Recent progress in the preheating phenomena for inflationary cosmology is reviewed. We first discuss estimates of the preheating time scale and particle production at the early stages of parametric amplification within the Mathieu and Lam'e approximations and we analyze their precision and limitations. The necessity of self-consistent calculations including

L. Venkataraman, G. Kilcup, J. Grandy

We present a refined calculation of the eta-prime mass using staggered fermions and Wuppertal smeared operators. We use quenched and dynamical configurations of size 16^3x32 with Nf=0, Nf=2 and Nf=4, and compare our results with the expected forms from quenched, partially quenched and unquenched chiral perturbation thoery.

G. Kilcup, D. Pekurovsky, L. Venkataraman

We present results of a study of BK using tadpole improved gauge invariant staggered operators. Using three ensembles of 16^3x32 configurations with varying numbers of dynamical flavors, we observe a small dependence on Nf. Using seven quenched ensembles between beta=5.7 and beta=6.2 we extrapolate to a=0.

R. R. Shcherbakov, Vl. V. Papoyan, A. M. Povolotsky

The model of self-organizing Eulerian walkers is numerically investigated on the square lattice. The critical exponents for the distribution of a number of steps ($\tau_l$) and visited sites ($\tau_s$) characterizing the process of transformation from one recurrent configuration to another are calculated using the finite-size scaling analysis. Two different

Germán Rodrigo

We present the calculation of the decay width of the Z-boson into three jets including complete quark mass effects to second order in the strong coupling constant. The study is done for different jet clustering algorithms such as EM, JADE, E and DURHAM. Because three-jet observables are very sensitive to the quark mass we consider the possibility of extracti

Carlo Rovelli

I suggest that the common unease with taking quantum mechanics as a fundamental description of nature (the "measurement problem") could derive from the use of an incorrect notion, as the unease with the Lorentz transformations before Einstein derived from the notion of observer-independent time. I suggest that this incorrect notion is the notion of observer-

Sandro Ambrosanio, Barbara Mele

The radiative decay of the next-to-lightest neutralino into a lightest neutralino and a photon is analyzed in the MSSM. We find that significant regions of the supersymmetric parameter space with large radiative BR's (up to about 100%) do exist. The radiative channel turns out to be enhanced when the neutralino tree-level decays are suppressed either "kinema

Nikolai Saveliev

In this paper we present our results on the homology cobordism group $\Th$ of the oriented integral homology 3-spheres. We specially emphasize the role played in the subject by the gauge theory including Floer homology and invariants by Donaldson and Seiberg -- Witten.

A. Mezzacappa, A. C. Calder, S. W. Bruenn, J. M. Blondin

We couple two-dimensional hydrodynamics to detailed one-dimensional multigroup flux-limited diffusion neutrino transport to investigate prompt convection in core collapse supernovae. Our initial conditions, time-dependent boundary conditions, and neutrino distributions for computing neutrino heating, cooling, and deleptonization rates are obtained from one-d

E. Keith, Ernest Ma

If baryon-number nonconservation exists in the form of an effective six-quark operator which also changes strangeness by four units, it could have a tremendous impact on the absolute stability of strange quark matter. We show that such an operator is negligible in the supersymmetric standard model with $\lambda_{ijk} u_i^c d_j^c d_k^c$ terms in the superpote

G. Q. Li, C. M. Ko

We study antikaon flow in heavy-ion collisions at SIS energies based on the relativistic transport model (RVUU 1.0). The production of antikaons from both baryon-baryon and pion-baryon collisions are included. Taking into account only elastic and inelastic collisions of the antikaon with nucleons and neglecting its mean-field potential as in the cascade mode

G. Alexanian, V. P. Nair

The Thomas-Fermi screening of non-Abelian gauge fields by fermions or screening of gluon fields in quark matter is discussed. It is described by an effective mass term which is, as with hard thermal loops, related to the eikonal for a Chern-Simons theory and the Wess-Zumino-Witten action.

L. F. Urrutia

The purpose of this contribution is to review some aspects of the loop space formulation of pure gauge theories having the connection defined over a Lie algebra. The emphasis is focused on the discussion of the Mandelstam identities, which provide the basic constraints upon both the classical and the quantum degrees of freedom of the theory. In the case wher

C. Bernard, T. Blum, A. Soni

We present an analysis, using quenched configurations at $6/g^2=$5.7, 5.85, 6.0, and 6.3 of the matrix element $\MP\equiv\langle \bar P_{hl}|\bar h \gamma_\mu (1-\gamma_5)l \bar h \gamma_\mu(1-\gamma_5)l|P_{hl}\rangle$ for heavy-light pseudoscalar mesons. The results are extrapolated to the physical $B$ meson states, $\Bd$ and $\Bs$. We directly compute the

S. L. Adler

We discuss the differing definitions of complex and quaternionic projective group representations employed by us and by Emch. The definition of Emch (termed here a strong projective representation) is too restrictive to accommodate quaternionic Hilbert space embeddings of complex projective representations. Our definition (termed here a weak projective repre

L. F. Urrutia, N. Morales

Starting from the expression for the superdeterminant of $ (xI-M)$, where $M$ is an arbitrary supermatrix , we propose a definition for the corresponding characteristic polynomial and we prove that each supermatrix satisfies its characteristic equation. Depending upon the factorization properties of the basic polynomials whose ratio defines the above mention

Gregory Mahlon, G. L. Kane

We describe a method to help the search for a light stop squark [M(stop) + M(LSP) < M(top)] at the Fermilab Tevatron. Traditional search methods rely upon a series of stringent background-reducing cuts which, unfortunately, leave very few signal events given the present data set. To avoid this difficulty, we instead suggest using a milder set of cuts, combin

Michael Grady

The effect of restricting the plaquette to be greater than a certain cutoff value is studied. The action considered is the standard Wilson action with the addition of a plaquette restriction, which should not affect the continuum limit of the theory. In this investigation, the strong coupling limit is also taken. It is found that a deconfining phase transiti

Ming Lei, Hong Guo

We study the crossover behavior of the Hall resistance between the integer quantum Hall regime and a regime dominated by the Aharonov-Bohm oscillations, in a system of 4-probe quantum dot with an artificial impurity confined inside. In a previous study [M. Lei, N.J. Zhu and Hong Guo, Phys. Rev. B. 52, 16784, (1995)], a peculiar set of symmetry relations betw

W. de Boer, A. Dabelstein, W. Hollik, W. Moesle

A program including all radiative corrections to the MSSM at the same level as the radiative corrections to the SM has been developed and used to perform global fits to all electroweak data from LEP, SLC and the Tevatron and the radiative b->sgamma decay from CLEO. Values of the strong coupling constant at the $M_Z$ scale and $\sin^2\theta_{\overline{MS}}$ a

B. Durhuus, C. Kristjansen

We show that coarse graining arguments invented for the analysis of multi-spin systems on a randomly triangulated surface apply also to the O(n) model on a random lattice. These arguments imply that if the model has a critical point with diverging string susceptibility, then either \g=+1/2 or there exists a dual critical point with negative string susceptibi

Roger Lacasse, the E877 Collaboration

Inclusive double differential multiplicities and rapidity density distributions of hadrons are presented for 10.8 A GeV/c Au+Au collisions as measured at the AGS by the E877 collaboration. The results indicate that large amounts of stopping and collective transverse flow effects are present. The data are also compared to the results from the lighter Si+Al sy

H. J. de Vega, N. Sánchez, F. Combes

The gas clouds of the interstellar medium have a fractal structure, the origin of which has generally been thought to lie in turbulence. The energy of turbulence could come from galactic rotation at large-scale, then cascade down to be dissipated on small-scales by viscosity; it has been suggested that such turbulence helps to prevent massive molecular cloud

D. A. Trifonov

Eigenstates of general complex linear combination of SU(1,1) generators (su^c(1,1) algebraic coherent states (ACS)) are constructed and discussed. In case of quadratic boson representation ACS can exhibit strong both linear and quadratic amplitude squeezing. ACS for a given Lie group algebra contain the corresponding Perelomov CS with maximal symmetry.

L. Frankfurt, M. Sargsian, M. Strikman

The exclusive and inclusive electroproduction off the polarized deuteron is considered at large $Q^2$ and $x \ge 0.5$. It is shown that the use of a polarized target will allow to emphasize smaller than average internucleon distances in the deuteron. As a result, we expect amplification of all the effects (color transparency, relativistic dynamics, etc.) sen

Adam F. Falk

I review the recent proposal that there are new isotriplet heavy baryons with masses approximately 2380 MeV and 5760 MeV. This prediction follows from the application of heavy spin-flavor and light $SU(3)$ symmetries to the observed charmed and bottom baryon states. It also entails assumptions about the spin and parity quantum numbers of the observed states

Jan Govaerts, Jules Deutsch, Pierre M. Van Hove

An anomaly in the time behaviour of the signals observed by the KARMEN Collaboration may be interpreted as the possible decay signature of a 33.9 MeV/c$^2$ mainly sterile neutrino. This note discusses the parameter space still open for the mixing of this hypothetical particle with the neutrinos of known leptonic flavour, considering the experimental results

Abhijit Bhattacharyya, Sanjay K. Ghosh, S. C. Phatak, Sibaji Raha

The variation of kaon mass in dense, charge-neutral baryonic matter at beta-equilibrium has been investigated. The baryon interaction has been included by means of nonlinear Walecka model, with and without hyperons and the interaction of kaons with the baryons has been incorporated through the Nelson-Kaplan model. A self-consistant, one-loop level calculatio

I. Ya. Arefeva, A. P. Zubarev

We consider an interaction representation in the Boltzmann field theory. It describes the master field for a subclass of planar diagrams in matrix models, so called half-planar diagrams. This interaction representation was found in the previous paper by Accardi, Volovich and one of us (I.A.) and it has an unusual property that one deals with a rational funct

Michael P. Reisenberger

An action for simplicial euclidean general relativity involving only left-handed fields is presented. The simplicial theory is shown to converge to continuum general relativity in the Plebanski formulation as the simplicial complex is refined. This contrasts with the Regge model for which Miller and Brewin have shown that the full field equations are much mo

Yuji Koike, N. Nishiyama

We study the $Q^2$ dependence of the chiral-odd twist-3 distribution $e(x,Q^2)$.The anomalous dimension matrix for the corresponding twist-3 operators is calculated in the one-loop level. This study completes the calculation of the anomalous dimension matrices for all the twist-3 distributions together with the known results for the other twist-3 distributio

Mathias van den Bossche, Michel Caffarel

The low-energy physics of the one-dimensional Pair-Hopping (PH) and attractive Hubbard models are expected to be similar. Based on numerical calculations on small chains, several authors have recently challenged this idea and predicted the existence of a phase transition at half-filling and finite positive coupling for the pair-hopping model. We re-examine t

Paolo Rossi, Massimo Campostrini, Ettore Vicari

The general features of the 1/N expansion in statistical mechanics and quantum field theory are briefly reviewed both from the theoretical and from the phenomenological point of view as an introduction to a more detailed analysis of the large-N properties of spin and gauge models possessing the symmetry group $SU(N) \times SU(N)$. An extensive discussion of

S. Moretti, R. Munoz-Tapia, J. B. Tausk

We present a theoretical review of the possibilities offered by heavy flavour tagging in testing QCD features in 4-jet events at LEP1. Attention is focused mainly on the properties of the angular variables which are used in the experimental analyses to measure the colour factors of the strong interactions. We also comment on a possible settlement of the ongo

J. M. Eisenberg

Preequilibrium parton production following an ultrarelativistic nucleus--nucleus collision is studied in terms of the decay of a strong chromoelectric field which generates pairs through the Schwinger mechanism. Back-reaction of the partons with the field is included and a model transport equation containing a collision term is solved for the central rapidit

Werner M. Vieira, Patricio S. Letelier

We clarify some points about the systems considered by Sota, Suzuki and Maeda in Class. Quantum Grav. 13, 1241 (1996). Contrary to the authors' claim for a non-homoclinic kind of chaos, we show the chaotic cases they considered are homoclinic in origin. The power of local criteria to predict chaos is once more questioned. We find that their local, curvature-

A. Ghosh, P. Mitra

Whereas the usual understanding is that the entropy of only a non-extremal black hole is given by the area of the horizon, there are derivations of an area law for extremal black holes in some model calculations. It is explained here how such results can arise in an approach where one sums over topologies and imposes the extremality condition after quantizat

Zhi-zhong Xing

We stress that the observed pattern of flavor mixings can be partly interpreted by the quark mass hierarchy without the assumption of specific quark mass matrices. The quantitatively proper relations between the Kobayashi-Maskawa matrix elements and quark mass ratios, such as $$|V_{cb}| \approx |V_{ts}| \approx \sqrt{2} (\frac{m_s}{m_b} -\frac{m_c}{m_t}) [1

H. Kawai, N. Tsuda, T. Yukawa

A method of defining the complex structure(moduli) for dynamically triangulated(DT) surfaces with torus topology is proposed. Distribution of the moduli parameter is measured numerically and compared with the Liouville theory for the surface coupled to c = 0, 1 and 2 matter. Equivalence between the dynamical triangulation and the Liouville theory is establis

K. Davis

In this article we examine the appearance of tensionless strings in M-Theory. We subsequently interpret these tensionless strings in a String Theory context. In particular, we examine tensionless strings appearing in M-Theory on $S^{1}$, M-Theory on $S^{1} / {\bf Z}_{2}$, and M-Theory on $T^{2}$; we then interpret the appearance of such strings in a String T

Ya. I. Azimov, V. L. Rappoport, V. V. Sarantsev

Phenomenological CP-violating parameters in decays of neutral B-mesons are discussed. Special attention is given to the degree of their measurability. We emphasize important role of the sign of $\Delta m_B$ and suggest how it could be determined experimentally.

J. Abad, M. Rios

The general expression for the local matrix of a quantum chain $L(\theta)$ with the site space in any representation of $su(3)$ is obtained. This is made by generalizing $L(\theta)$ from the fundamental representation and imposing the fulfilment of the Yang-Baxter equation. With these operators and using a generalization of the nested Bethe ansatz, the Bethe

Johan van de Leur

We use the representation theory of the infinite matrix group to show that (in the polynomial case) the $n$--vector $k$--constrained KP hierarchy has a natural geometrical interpretation on Sato's infinite Grassmannian. This description generalizes the the $k$--reduced KP or Gelfand--Dickey hierarchies.

A. De Roeck, E. A. De Wolf

A simple parametrisation of H1 and ZEUS data at HERA is given for the ranges in x and Q^2 of 10^{-4} - 5.10^{-2} and 5 - 250 GeV^2, respectively. This empirical expression is based on a strikingly similar dependence of the average charged particle multiplicity <n> on the centre of mass system energy sqrt{s} in e+e- collisions on the one hand, and the x depen

Jarmo Makela

We formulate a qualitative argument, based on Heisenberg's uncertainty principle, to support the claim that when the effects of matter fields are assumed to overshadow the effects of quantum mechanics of spacetime, the discrete spectrum of black hole radiation, as such as predicted by Bekenstein's proposal for a discrete black hole area spectrum, reduces to

R. S. Dunne, A. J. Macfarlane, J. A. de Azcárraga, J. C. Pérez Bueno

The $q$-calculus for generic $q$ is developed and related to the deformed oscillator of parameter $q^{1/2}$. By passing with care to the limit in which $q$ is a root of unity, one uncovers the full algebraic structure of ${{\cal Z}}_n$-graded fractional supersymmetry and its natural representation.

Kenzo Ishikawa, Nobuki Maeda

Formulation of quantum Hall dynamics using von Neumann lattice of guiding center coordinates is presented. A topological invariant expression of the Hall conductance is given and a new mean field theory of the fractional Hall effect based on flux condensation is proposed. Because our mean field Hamiltonian has the same form as Hofstadter Hamiltonian, it is p

J. A. de Azcárraga, R. S. Dunne, A. J. Macfarlane, J. C. Pérez Bueno

It is shown that fractional $Z_3$-superspace is isomorphic to the $q\to\exp(2\pi i/3)$ limit of the braided line. $Z_3$-supersymmetry is identified as translational invariance along this line. The fractional translation generator and its associated covariant derivative emerge as the $q\to\exp(2\pi i/3)$ limits of the left and right derivatives from the calcu

K. G. Chetyrkin, J. H. Kuhn

We analytically compute quadratic mass corrections of order $\alpha_s^3 m_q^2/s$ to the absorptive part of the (non-diagonal) correlator of two axial vector currents. This allows us to find the correction of order $\alpha_s^3 m_q^2/M^2_W$ to the $\Gamma(W -->hadrons)$ as well as similar corrections to $\Gamma(Z -->hadrons)$.

Kikuo Harigaya

Exciton effects on conjugated polymers and the resulting optical nonlinearities are investigated in soliton lattice systems. The magnitude of the THG at the 10 percent doping increases by the factor about 10^2 from that of the neutral system. The huge increase by the order two is common for several choices of Coulomb interaction strengths, and is seen in ope

O. V. Babourova, B. N. Frolov

The existence of the Pontryagin and Euler forms in a Weyl-Cartan space on the basis of the variational method with Lagrange multipliers are established. It is proved that these forms can be expressed via the exterior derivatives of the corresponding Chern-Simons terms in a Weyl-Cartan space with torsion and nonmetricity.

O. V. Babourova, B. N. Frolov

The Gauss-Bonnet type identity is derived in a Weyl-Cartan space on the basis of the variational method.

Ting-Wai Chiu

Massless fermion field interacting with abelian dynamical gauge field on 2-dimensional random-block lattices are investigated using Hybrid Monte Carlo simulations. Preliminary results of the Wilson loop and the chiral correlation function are in agreement with the continuum Schwinger model.

Yuji Koike, A. Hayashigaki

A new QCD sum rule analysis on the spin-isospin averaged $\rho$, $\omega$ and $\phi$ meson-nucleon scattering lengths is presented. By introducing the constraint relation on the the low energy limit of the vector-current nucleon forward scattering amplitude, we get $a_\rho=-0.47\pm 0.05$ fm, $a_\omega=-0.41\pm 0.05$ fm and $a_\phi=-0.15\pm 0.02$ fm, which su

Yuji Kodama, Jian Ye

We consider the iso-spectral real manifolds of tridiagonal Hessenberg matrices with real eigenvalues. The manifolds are described by the iso-spectral flows of indefinite Toda lattice equations introduced by the authors [Physica, 91D (1996), 321-339]. These Toda lattices consist of $2^{N-1}$ different systems with hamiltonians $H = (1/2) \sum_{k=1}^{N} y_k^2

R. J. Bursill, T. Xiang, G. A. Gehring

We apply a recent adaptation of White's density matrix renormalisation group (DMRG) method to a simple quantum spin model, the dimerised $XY$ chain, in order to assess the applicabilty of the DMRG to quantum systems at non-zero temperature. We find that very reasonable results can be obtained for the thermodynamic functions down to low temperatures using a v

V. M. Canuto, I. Goldman, I. Mazzitelli

We present a selfconsistent model for stellar turbulent convection which is similar in spirit to the CM model (Canuto \& Mazzitelli 1991) since it accounts for the full spectrum of the turbulent eddies rather than only one eddy, as done in the mixing length theory (MLT). The model differs from the CM model in the treatment of the rate of energy input $n_s(k)

J. R. Hiller, S. J. Brodsky

As a precursor to work on QCD, we study the dressed electron in QED nonperturbatively. The calculational scheme uses an invariant mass cutoff, discretized light-cone quantization, a Tamm--Dancoff truncation of the Fock space, and a small photon mass. Nonperturbative renormalization of the coupling and electron mass is developed.

Boris Apanasov

We study deformations of complex hyperbolic surfaces which furnish the simplest examples of: (i) negatively curved K\"ahler manifolds and (ii) negatively curved Riemannian manifolds not having {\it constant} curvature. Although such complex surfaces may share the rigidity of quaternionic/octionic hyperbolic manifolds, our main goal is to show that they enjoy

R A E Fosbury

After the success of the refurbishment mission to HST in December 1993, the telescope has taken its place at the very leading edge of astrophysical research. The breadth and depth of the topics covered at the HST conference in Paris in December 1995 gave us a foretaste of the value of the data archive being accumulated and the supreme importance of future ob

F. Mannucci, D. Thompson, S. V. W. Beckwith

We present the results of a narrowband search for forming galaxies at high redshifts. Given the coverage of 276 square minutes of arc, this is the most extended search for extragalactic emission line objects at near infrared wavelengths. Despite of flux limits down to 1.4E-16 erg cm-2 sec-1 and of a total comoving volume surveyed of 1.4E5 Mpc3 (for a cosmolg

M. Maisack, R. Staubert, K. Otterbein, A. Witzel

We report on Compton Gamma Ray Observatory (CGRO), radio and optical observations of the radio-loud, superluminal quasar NRAO 140. The source is not detected (at a significance of greater than 3 sigma) by any of the CGRO instruments OSSE, Comptel and EGRET. Radio observations simultaneous to the OSSE observation and optical monitoring over three-monthly inte

Tom Banks, Michael Dine

String theory posesses numerous axion candidates. The recent realization that the compactification radius in string theory might be large means that these states can solve the strong CP problem. This still leaves the question of the cosmological bound on the axion mass. Here we explore two schemes for accommodating such light axions in cosmology. In the firs

E. Javier Elizondo

In this article we prove, in a simple way, that for any complete toric variety, and for any Cartier divisor, the ring of global sections of multiples of the line bundle associated to the divisor is finitely generated.

J. W. Moffat

A covariant Lagrangian formulation of a solution to the cosmological constant problem, based on vizualising the fluctuations of the vacuum energy as a non-equilibrium process with stochastic behaviour, is presented. The variational principle yields equations of motion for the cosmological ``constant" $\Lambda$, treated as a dynamical field, together with an

Tom Chou, Marko V. Jaric', Eric D. Siggia

The electrostatic contribution to spontaneous membrane curvature is calculated within Poisson-Boltzmann theory under a variety of assumptions and emphasizing parameters in the physiological range. Asymmetric surface charges, either fixed with respect to bilayer midplane area, or with respect to the lipid-water area both induce curvature but of opposite sign.

The Fermilab E791 Collaboration

We present results of a search for D0-D0bar mixing and doubly-Cabibbo-suppressed decays of the D0 in Fermilab experiment E791, a fixed-target charm hadroproduction experiment. We look for evidence of mixing in the decay chain D* -> pi D0 -> (K pi or K pi pi pi). If the charge of the pion from the D* decay is the same as the charge of the kaon from the D deca

Jan Bischoff, Olaf Lechtenfeld

It is known that the critical N=(2,2) string describes 2+2 dimensional self-dual gravity in a non-covariant form, since it requires the choice of a complex structure in the target, which leaves only U(1,1) Lorentz symmetry. We briefly review picture-changing and spectral flow and show that the world-sheet Maxwell instantons individually break the Lorentz gro

Andre Lukas, Burt A. Ovrut, Daniel Waldram

We study cosmological solutions of type II string theory with a metric of the Kaluza--Klein type and nontrivial Ramond--Ramond forms. It is shown that models with only one form excited can be integrated in general. Moreover, some interesting cases with two nontrivial forms can be solved completely since they correspond to Toda models. We find two types of so

F. Halzen, T. Stanev, G. B. Yodh

Although gamma ray showers are muon-poor, they still produce a number of muons sufficient to make the sources observed by GeV and TeV telescopes observable also in muons. For sources with hard gamma ray spectra there is a relative `enhancement' of muons from gamma ray primaries as compared to that from nucleon primaries. All shower gamma rays above the photo

C. A. Scharf, L. R. Jones, H. Ebeling, E. Perlman

We have embarked on a survey of ROSAT PSPC archival data with the aim of detecting all significant surface brightness enhancements due to sources in the innermost 15 arcmin of the PSPC field of view (0.5-2.0 keV). This project is part of the Wide Angle ROSAT Pointed Survey (WARPS) and is designed primarily to measure the low luminosity, high redshift, X-ray

Shamit Kachru, Eva Silverstein

We describe a class of 4d N=1 compactifications of the $SO(32)$ heterotic/type I string theory which are destabilized by nonperturbatively generated superpotentials. In the type I description, the destabilizing superpotential is generated by a one instanton effect or gaugino condensation in a nonperturbative $SU(2)$ gauge group. The dual, heterotic descripti

Greg Schwarz, Peter H. Hauschildt, Sumner Starrfield, Eddie Baron

We have analyzed the early optically thick ultraviolet spectra of Nova OS And 1986 using a grid of spherically symmetric, non-LTE, line-blanketed, expanding model atmospheres and synthetic spectra with the following set of parameters: $5,000\le$ T$_{model}$ $\le 60,000$K, solar abundances, $\rho \propto r^{-3}$, $\v_{max} = 2000\kms$, $L=6 \times 10^{4}\Lsun

W. Zheng, G. A. Kriss, R. C. Telfer, J. P. Grimes

We construct a composite quasar spectrum from 284 HST FOS spectra of 101 quasars with redshifts z > 0.33. The spectrum covers the wavelengths between 350 and 3000 A in the rest frame. There is a significant steepening of the continuum slope around 1050 A. The continuum between 1050 and 2200 A can be modeled as a power law with alpha = -0.99. For the full sam

E. Knill

This report continues the discussion of unitary error bases and quantum codes begun in "Non-binary Unitary Error Bases and Quantum Codes". Nice error bases are characterized in terms of the existence of certain characters in a group. A general construction for error bases which are non-abelian over the center is given. The method for obtaining codes due to C

John Ellis, Valery A. Khoze, W. J. Stirling

Hadronic antenna patterns provide a tool able to diagnose different patterns of colour flow in large-E_T jet events. They reflect the underlying short-distance dynamics, and are sensitive to colour coherence and interference between the initial- and final-state partons. We discuss how hadronic antenna patterns may be used on large-E_T events from the Fermila

E. Knill

Error operator bases for systems of any dimension are defined and natural generalizations of the bit/sign flip error basis for qubits are given. These bases allow generalizing the construction of quantum codes based on eigenspaces of Abelian groups. As a consequence, quantum codes can be constructed from linear codes over $\ints_n$ for any $n$. The generaliz

Angelo Cacciuto, Enzo Marinari, Giorgio Parisi

We use a constrained Monte Carlo technique to analyze ultrametric features of a 4 dimensional Edwards-Anderson spin glass with quenched couplings J=\pm 1. We find that in the large volume limit an ultrametric structure emerges quite clearly in the overlap of typical equilibrium configurations.

L. Frankfurt, V. Guzey, W. Koepf, M. Sargsian

Coherent electroproduction of vector mesons off $^2$H and $^4$He is considered in the kinematics of deep inelastic scattering. Special emphasis is given to the $-t\sim 0.8-1$ GeV$^2$ region where the cross section is dominated by the interaction of the $q\bar q$ configuration in the $\gamma^*$ with two nucleons. These kinematics provide the unique possibilit

G. C. Branco, D. Emmanuel-Costa, J. I. Silva-Marcos

We do a systematic analysis of the question of calculability of CKM matrix elements in terms of quark mass ratios, within the framework of the hypothesis of universality of strength for Yukawa couplings (USY), where all Yukawa couplings have equal moduli, and the flavor dependence is only in their phases. We use the fact that the limit $m_u=m_d=0$ is special

Patrick Labelle

Nonrelativistic QED bound states are difficult to study because of the presence of at least three widely different scales: the masses, three-momenta ($p_i$) and kinetic energies ($K_i$) of the constituents. Nonrelativistic QED (NRQED), an effective field theory developed by Caswell and Lepage, simplifies greatly bound state calculations by eliminating the ma

N. Evans, S. D. H. Hsu, A. Nyffeler, M. Schwetz

We use the chiral Lagrangian to investigate the global properties of the $N$-flavor QCD vacuum as a function of the $\theta$ parameter. In the case of exact quark degeneracy we find evidence for first order phase transitions at $\theta = \pi \cdot ({\rm odd~ integer})$. The first order transitions are smoothed by quark mass splittings, although interesting e

N. J. Cerf, C. Adami

We derive entropic Bell inequalities from considering entropy Venn diagrams. These entropic inequalities, akin to the Braunstein-Caves inequalities, are violated for a quantum mechanical Einstein-Podolsky-Rosen pair, which implies that the conditional entropies of Bell variables must be negative in this case. This suggests that the satisfaction of entropic B

Michel Dubois-Violette, Richard Kerner

We recall the definition of $q$-differential algebras and discuss some representative examples. In particular we construct the $q$-analog of the Hochschild coboundary. We then construct the universal $q$-differential envelope of a unital associative algebra and study its properties. The paper also contains general results on $d^N=0$.

A. V. Semenov

We consider the general problem of derivation of the Feynman rules for the matrix elements in momentum representation from the given Lagrangian in coordinate space invariant under the transformation of some gauge group. LanHEP package presented in this paper allows to define in a convenient way the gauge model Lagrangian in canonical form and then to generat

U. S. Schwarz, K. Swamy, G. Gompper

We study the dependence of the phase behavior of ternary amphiphilic systems on composition and temperature. Our analysis is based on a curvature elastic model of the surfactant film with sufficiently large spontaneous curvature and sufficiently negative saddle-splay modulus that the stable phases are the lamellar phase and a droplet microemulsion. In additi

Jian Wang, Hong Guo

The frequency dependent conductance of a two-dimensional quantum wire is computed using a current conserving formalism. The correction to the dc-conductance due to a time-dependent potential is related to the local partial density of states which we compute numerically. The current conservation is explicitly confirmed by computing the global density of state

A. Aste, G. Scharf

The scalar two-loop master diagram is revisited in the massive cases needed for the computation of boson and fermion propagators in QED and QCD. By means of the causal method it is possible in a straightforward manner to express the propagators as double integrals. In the case of vacuum polarization both integrations can be carried out in terms of polylogari

D. Nanopoulos

After a quick tour through the present status of the Standard Model, an attempt is made to set up a framework to discuss some presently available exotica, including $R_b$ and the CDF $ee\gamma\gamma+E_T\hskip-13pt/\ $ ``event." Supersymmetry seems to be a key player in establishing a paradigm shift beyond the Standard Model. (XI Topical Workshop on Proton-an

Philip R. Page

We introduce strong and electromagnetic interaction selection rules for the two-body decay and production of exotic J^{PC} = 0^{+-}, 1^{-+}, 2^{+-}, 3^{-+} hybrid mesons, four-quark states and glueballs. The rules arise from symmetrization in states. Examples include various decays to eta' eta, eta pi, eta' pi and pi^{\pm} pi^0. The symmetrization rules can

Hans J. Witt

We show here that quadruple lenses can be useful laboratories to probe whether the potential of the lensing galaxy is purely elliptical or whether an additional distortion is present in the deflector plane. For this test we only have to know the relative image positions of the quadruple lens system and the (relative) center of light position of the lensing g

Carlos Simpson

We look at homotopy-coherent diagrams of spaces (after Segal, Leitch, Vogt, Mather, Cordier) over a Grothendieck site; we call these ``flexible presheaves''. After some preliminary materiel, we define the ``flexible sheaf'' condition. This descent condition (known to Thomason) is the same as what Jardine called being ``flasque'' with respect to the presheave

M. De Francia, H. Falomir, M. Loewe

We introduce the chemical potential in a system of massless fermions in a bag by impossing boundary conditions in the Euclidean time direction. We express the fermionic mean number in terms of a functional trace involving the Green's function of the boundary value problem, which we study analytically. Numerical evaluations are made, and an application to a s

E. Breitmoser, H. Arenhoevel

Coherent eta photoproduction on the deuteron is studied in the $S_{11}$ resonance region neglecting eta rescattering and two-body processes. For the elementary reaction on the nucleon, we have considered the dominant $S_{11}(1535)$ resonance and as background the nucleon pole terms as well as $\rho$ and $\omega$ meson exchange. We have studied the influence

Savely G. Karshenboim

Radiative corrections to the Zemach contribution of the hydrogen hyperfine splitting are calculated. Their contributions amount to $-0.63(3)$ ppm to the HFS. The radiative recoil corrections are estimated to be $0.09(3)$ ppm and heavy particle vacuum polarization shifts the HFS by $0.10(2)$ ppm. The status of the nuclear-dependent contributions are considere