October 1994 arXiv papers — page 5

J. Schechter, H. Weigel

We impose the requirement that the isovector axial vector current for the soliton sector of the chiral quark model transforms correctly under particle conjugation. This forces us to choose an otherwise arbitrary ordering of collective space operators in such a way that the next--to--leading $1/N_C$ correction to $g_A$ vanishes.

Bernd A. Kniehl, Michael Spira

We present the two-loop ${\cal O}(α_sG_Fm_t^2)$ correction to the $b\bar b$ decay rate of the Stan\-dard-Model Higgs boson, assuming that the $t$ quark is much heavier than the Higgs boson. Apart from the universal correction connected with the renormalizations of the wave function and the vacuum expectation value of the Higgs field, this involves vertex cor

J. L. Hewett

The charm physics program accessible to a Tau-Charm Factory is summarized. Semileptonic, leptonic, hadronic, rare and forbidden charm decay modes are discussed, as well as \dmix\ mixing and CP violation in the charm sector. The theoretical expectations in the Standard Model and beyond as well as the experimental capabilities of a Tau-Charm Factory are examin

Claus Vohwinkel

I investigate the time step dependence of Monte Carlo simulations for coordinate-spaces consisting of several patches. It is shown that a naive kinetic term does not necessarily converge to the same spectrum as a Hamiltonian calculation. Then an improved kinetic term is presented which allows one to connect the Monte Carlo and Rayleigh-Ritz results of interm

M. Asorey, J. G. Esteve, F. Falceto, J. Salas

We compute by Monte Carlo numerical simulations the critical exponents of two-dimensional scalar field theories at the $λϕ^6$ tricritical point. The results are in agreement with the Zamolodchikov conjecture based on conformal invariance.

Michael Creutz

I review the problem of formulating chiral symmetry in lattice gauge theory. I discuss recent approaches involving an infinite tower of additional heavy states to absorb Fermion doublers. For hadronic physics this provides a natural scheme for taking quark masses to zero without requiring a precise tuning of parameters. A mirror Fermion variation provides a

O. Bertolami, P. V. Moniz

Retrieval of classical behaviour in quantum cosmology is usually discussed in the framework of {\em midi}superspace models in the presence of scalar fields and the inhomogeneous modes corresponding either to gravitational or scalar fields. In this work, we propose an alternative model to study the decoherence of homogeneous and isotropic geometries where the

V. M. Villalba

In the present article we obtain, by separation of variables, an exact solution to the Dirac equation with anomalous momentum for an electrically neutral massless particle in a Bertotti-Robinson universe. We discuss the phenomenom of particle creation in this model.

Michel Dubois-Violette, Peter W. Michor

In commutative differential geometry the Frölicher-Nijenhuis bracket computes all kinds of curvatures and obstructions to integrability. In \cit!{3} the Frölicher-Nijenhuis bracket was developped for universal differential forms of non-commutative algebras, and several applications were given. In this paper this bracket and the Frölicher-Nijenhuis calculus w

M. Schoene, R. Kaschner, G. Seifert

Using the Car-Parrinello technique, ab initio molecular dynamics simulations are performed for liquid NaSn alloys in five different compositions (20, 40, 50, 57 and 80 % sodium). The obtained structure factors agree well with the data from neutron scattering experiments. The measured prepeak in the structure factor is reproduced qualitatively for most compos

H. Schinz, F. Schwabl

Employing mode-coupling theory we show that the amplitude of the spin wave frequency scaling function for the isotropic Heisenberg Hamiltonian is universal. Theoretical and experimental values for Fe, Ni, Co, EuO, and EuS agree quite well. Recent measurements of the longitudinal line width in Ni are explained quantitatively.

S. J. B. Einchcomb, A. J. McKane

We formulate the stochastic dynamics of a particle subject to internal non-white (coloured) noise in terms of path-integrals. In the simplest case, where the noise is exponentially correlated, the weak-noise limit is characterised by optimum paths which are given by third order differential equations. In contrast to systems subject to white noise or external

S. J. B. Einchcomb, A. J. McKane

The evaluation of the path-integral representation for stochastic processes in the weak-noise limit shows that these systems are governed by a set of equations which are those of a classical dynamics. We show that, even when the noise is colored, these may be put into a Hamiltonian form which leads to better insights and improved numerical treatments. We con

Atsushi Yamagata

A nearest neighbour spin pair of the quasi-two-dimensional three-state Potts model interacts with the strength $J(>0)$ in the $xy$-plane and with $λJ$ $(0\le λ\ll 1)$ in the $z$-axis. The phase transition is of second-order when $λ= 0$ and is of first-order when $λ> 0$. The dimensional crossover occurs with a change of the order of the phase transition. We s

Jian Ma, P. Alméras, R. J. Kelley, H. Berger

$Pb_{0.4}Bi_{1.6}Sr_2CaCu_2O_{8+x}$ ($Bi(Pb)-$2212) single crystal samples were studied using transmission electron microscopy (TEM), $ab-$plane ($ρ_{ab}$) and $c-$axis ($ρ_c$) resistivity, and high resolution angle-resolved ultraviolet photoemission spectroscopy (ARUPS). TEM reveals that the modulation in the $b-$axis for $Pb(0.4)-$doped $Bi(Pb)-$2212 is do

Marc Kamionkowski

If stars at the lower end of the main sequence are responsible for the microlensing events observed in the Galactic bulge, then light from the lensing star contributes to the observed brightness. The background and lensing stars generally have different colors, and the relative brightness changes during the microlensing event. Therefore, microlensing light c

Neta A. Bahcall, Mirt Gramann, Renyue Cen

The distributions of peculiar velocities of rich clusters and of groups of galaxies are investigated for different cosmological models and are compared with observations. Four cosmological models are studied: standard ($Ω=1$) CDM, low-density ($Ω=0.3$) CDM, HDM ($Ω=1$), and PBI ($Ω=0.3$), all COBE normalized. We find that rich clusters of galaxies exhibit a

Gary Steigman

The early, hot, dense, expanding Universe was a primordial reactor in which the light nuclides D, 3He, 4He and 7Li were synthesized in astrophysically interesting abundances. The challenge to the standard hot big bang model (Big Bang Nucleosynthesis = BBN) is the comparison between the observed and predicted abundances, the latter which depend only on the un

E. Pierpaoli, S. Bonometto

We calculate the linear evolution for a class of mixed dark matter models, where the hot component derives from the decay of a heavier particle (CntHDM models). These models differ from ordinary mixed models based on massive neutrinos (CHDM models), for which the hot component has a phase space distribution which derives from a thermal one. In CntHDM models

Keith A. Olive, Robert T. Rood, David N. Schramm, James Truran

We consider the galactic evolutionary history of \he3 in models which deplete deuterium by as much as a factor of 2 to $\sim$ 15 from its primordial value to its present day observed value in the ISM. We show that when \he3 production in low mass stars (1 -- 3 $M_\odot$) is included over the history of the galaxy, \he3 is greatly over-produced and exceeds th

Garrelt Mellema, Adam Frank

The status of numerical hydrodynamical models for Planetary Nebulae is reviewed. Since all of the numerical work is based on the interacting winds model, we start with a description of this model and give an overview of the early analytical and numerical models. Subsequently we address the numerical models which include radiation effects, first of all the on

R. Triay

The key point limits to define the {\it statistical model} describing the data distribution. Hence, it turns out that the characteristics related to the so-called. Inverse Tully-Fisher relation and the Direct relation are maximum likelyhood (ML) estimators of different statistical models, and we obtain coherent distance estimates as long as the same model is

Guillermo Fernández del Busto

The purpose of this note is to give an (esentially optimal) effective version of Matsusaka's Big theorem for smooth projective surfaces.

David A. Cox

In ${\bf C}^{n+1}$, one can show that the residue of $n+1$ homogeneous forms of the same degree equals the integral of a certain $(n,n)$ form over ${\bf P}^n$. Furthermore, the Jacobian of the forms has nonzero residue equal to a certain intersection number. In this paper, we generalize these results to an arbitrary projective toric variety. In particular, w

J. P. Rodriguez

The thermally driven confinement-deconfinement transition exhibited by lattice quantum electrodynamics in two space dimensions is re-examined in the context of the statistical gauge-fields common to anyon superconductors and to spin-liquids. Particle-hole excitations in both systems are bound by a confining string at temperatures below the transition tempera

Martin Lemoine, Roger Ferlet

We discuss the observational status of the interstellar lithium isotopic ratio and its significance with respect to the galactic evolution of lithium.

D. Belitz, M. N. Wybourne

A connection is proposed between the anomalous thermal transport properties of amorphous solids and the low-frequency behavior of the Eliashberg function. By means of a model calculation we show that the size and frequency dependence of the phonon mean-free-path that has been extracted from measurements of the thermal conductivity in amorphous solids leads t

Adam F. Falk

I discuss the recent controversy over the semileptonic branching ratio of the $B$ meson, pointing out that it is only the combination of this quantity with the reported charm multiplicity in $B$ decays which is in serious conflict with theoretical calculations. I consider possible solutions to the problem. (Invited talk presented at the Eighteenth Johns Hopk

D. Garcia, R. A. Jimenez, J. Sola

Within the framework of the MSSM, we compute the complete set of electroweak one-loop supersymmetric quantum effects on the width $Γ_Z$ of the $Z$-boson in the on-shell renormalization scheme. Numerical analyses of the corrections to the various partial widths into leptons and quarks are presented. On general grounds, the average size of the electroweak SUSY

George Leibbrandt, Jimmy Williams

A new integration technique for multi-loop Feynman integrals, called the matrix method, is developed and then applied to the divergent part of the overlapping two-loop quark self-energy function $\,iΣ\,$ in the light- cone gauge. It is shown that the coefficient of the double-pole term is strictly local, even off mass-shell, while the coefficient of the sing

D. Garcia, R. A. Jimenez, J. Sola

We address the computation of Γ_Z and of the intriguing quantity R_b in the MSSM including full treatment of the Higgs sector. For a pseudoscalar Higgs mass m_{A^0}>70\,GeV and CDF limits on m_t, the bounds on R_b at 1σlevel leave no room to the MSSM to solve the `R_b crisis' for any combination of the parameters, not even admitting the possibility of a

C. T. Traxler, H. Vija, M. H. Thoma

We compute the photon production rate of a quark-gluon plasma (QGP) at finite quark chemical potential $μ$ using the Braaten-Pisarski method, thus continuing the work of Kapusta, Lichard, and Seibert who did the calculation for $μ=0$.

K. Burzynski, P. Magierski, J. Dobaczewski, W. Nazarewicz

A role of the multipole interaction in the description of the $\triangle I$=4 staggering phenomenon is investigated in a model consisting of a single-$j$ shell filled by identical nucleons. Exact diagonalization of the quadrupole-plus-hexadecapole Hamiltonian shows that the hexadecapole-hexadecapole interaction can produce a $\triangle I$=4 periodicity in th

P. Braun-Munzinger, J. Stachel, J. P. Wessels, N. Xu

The rather complete data set of hadron yields from central Si + A collisions at the Brookhaven AGS is used to test whether the system at freeze-out is in thermal and hadro-chemical equilibrium. Rapidity and transverse momentum distributions are discussed with regards to the information they provide on hydrodynamic flow.

Stephen Cornell

Extensive simulations are performed of the diffusion-limited reaction A$+$B$\to 0$ in one dimension, with initially separated reagents. The reaction rate profile, and the probability distributions of the separation and midpoint of the nearest-neighbour pair of A and B particles, are all shown to exhibit dynamic scaling, independently of the presence of fluct

Andrei L. Kataev

We describe several problems related to the studies of the effects of radiative QCD corrections in the phenomenological and theoretical considerations thus summarizing the work of the QCD part of the Symposium on "Radiative Corrections: Status and Outlook".

Ted Jacobson, Shankar Venkataramani

We prove that, under certain conditions, the topology of the event horizon of a four dimensional asymptotically flat black hole spacetime must be a 2-sphere. No stationarity assumption is made. However, in order for the theorem to apply, the horizon topology must be unchanging for long enough to admit a certain kind of cross section. We expect this condition

C. R. Chinn, Ch. Elster, R. M. Thaler, S. P. Weppner

The optical model potentials for nucleon-nucleus elastic scattering at $65$~MeV are calculated for $^{12}$C, $^{16}$O, $^{28}$Si, $^{40}$Ca, $^{56}$Fe, $^{90}$Zr and $^{208}$Pb in first order multiple scattering theory, following the prescription of the spectator expansion, where the only inputs are the free NN potentials, the nuclear densities and the nucle

Kevin Haglin

The $ω$ and $ϕ$ mesons are exceptionally narrow in vacua being about 8 and 4 MeV. At finite temperature they will scatter with other hadrons in their approach to equilibrium and thereafter. These dynamics induce broadening to the already unstable vector mesons which is calculated in the framework of relativistic kinetic theory. A rather complete set of low-l

J. Caro, E. Ruiz Arriola, L. L. Salcedo

We present the first calculation of the $\hbar^4$-Wigner--Kirkwood corrections to a relativistic system of fermions in the presence of external scalar and vector potentials. The method we propose allows to compute efficiently semiclassical corrections to one body operators such as mean energies and local densities. It also preserves gauge invariance and prod

A. S. Rinat, M. F. Taragin

Using hadron dynamics we calculate nuclear transparencies for protons, knocked-out in high-$Q^2$, semi-inclusive reactions. Predicted transparencies are, roughly half a standard deviation above the NE18 data. The latter contain the effects of binned proton missing momenta and mass, and of finite detector acceptances. In order to test sensitivity we compare c

David J. Balding, David C. Torney

Consider a collection of objects, some of which may be `bad', and a test which determines whether or not a given sub-collection contains no bad objects. The non-adaptive pooling (or group testing) problem involves identifying the bad objects using the least number of tests applied in parallel. The `hypergeometric' case occurs when an upper bound on t

P. J. Arias, A. Restuccia

It is shown that the Topological Massive and ``Self-dual'' theories, which are known to provide locally equivalent descriptions of spin 1 theories in 2+1 dimensions, have different global properties when formulated over topologically non-trivial regions of space-time. The partition function of these theories, when constructed on an arbitrary Riemanni

Marcia E. Wehlau

Using the superspace formalism, we compute for the two-dimensional N=1 supersymmetric non-linear $σ$-model, the order $(α^{\prime})^{2}$ $(R_{mnpq})^2$ (three-loop) correction to the central charge via the operator product expansion of the supercurrent with itself. The contribution vanishes, in agreement with previous results obtained from the usual $σ$-mode

A. L. Larsen, N. Sanchez

We perform string quantization in anti de Sitter (AdS) spacetime. The string motion is stable, oscillatory in time with real frequencies $ω_n= \sqrt{n^2+m^2α'^2H^2}$ and the string size and energy are bounded. The string fluctuations around the center of mass are well behaved. We find the mass formula which is also well behaved in all regimes. There is a

V. Aldaya, M. Calixto, J. Guerrero

The assumption that the Weinberg rotation between the gauge fields associated with the third component of the ``weak isospin" ($T_3$) and the hypercharge ($Y$) proceeds in a natural way from a global homomorphism of the $SU(2)\otimes U(1)$ gauge group in some locally isomorphic group (which proves to be $U(2)$), imposes strong restrictions so as to fix t

N. N. Khuri

In this paper we consider non-relativistic quantum mechanics on a space with an additional internal compact dimension, i.e. $R^3\otimes S^1$ instead of $R^3$. More specifically we study potential scattering for this case and the analyticity properties of the forward scattering amplitude, $T_{nn}(K)$, where $K^2$ is the total energy and the integer n denotes

Alexander Turbiner

Polynomial relations between the generators of $q$--deformed Heisenberg algebra invariant under the quantization and $q$-deformation are discovered. One of the examples of such relations is the following: if two elements $a$ and $b$, obeying the relation \[ ab - q ba = p, \] where $p, q$ are any complex numbers, then for any $p,q$ and natural $n$ \[ (aba)^n

Zvonimir Hlousek, Donald Spector

This talk summarizes our recent work establishing an algebraic, model-independent basis for the existence of \B bounds and \B equations for topologically non-trivial solitons and instantons. Our arguments use supersymmetry in an essential way to understand both supersymmetric and non-supersymmetric theories. Our arguments are constructive and work in nearly

M. P. Fry

The renormalized fermionic determinant of QED in 3 + 1 dimensions, $\mbox{det}_{ren}$, in a static, unidirectional, inhomogeneous magnetic field with finite flux can be calculated from the massive Euclidean Schwinger model's determinant, $\mbox{det}_{Sch}$, in the same field by integrating $\mbox{det}_{Sch}$, over the fermion's mass. Since $\mbox{det

A. Pordt

In this talk methods for a rigorous control of the renormalization group (RG) flow of field theories are discussed. The RG equations involve the flow of an infinite number of local partition functions. By the method of exact beta-function the RG equations are reduced to flow equations of a finite number of coupling constants. Generating functions of Greens f

A. H. Chamseddine

This is a brief review where some basic elements of non-commutative geometry are given. The rules and ingredients that enter in the construction of the standard model and grand unification models in non-commutative geometry are summarized. A connection between some space-time supersymmetric models and non-commutative geometry is made. The advantages and prob

R. Gianvittorio, A. Restuccia, J. Stephany

In this letter a new gauge invariant, metric independent action is introduced from which Witten's Topological Quantum Field Theory may be obtained after gauge fixing using standard BRST techniques. In our model the BRST algebra of transformations, under which the effective action is invariant, close off-shell in distintion with what occurs in the one pro

Chang-Ho Kim, Young-Jai Park, Kee Yong Kim, Yongduk Kim

We study the four-dimensional {\it N}=8 maximal supergravity in the context of Lie superalgebra SU(8/1). All possible successive superalgebraic truncations from four-dimensional {\it N}=8 theory to {\it N}=7, 6, $\cdots$, 1 supergravity theories are systematically realized as sub-superalgebra chains of SU(8/1) by using the Kac-Dynkin weight techniques.

J. A. Gracey

Using the full conformal bootstrap method an analytic expression is given in d-dimensions for the anomalous dimension of the fermion at O(1/N^3) in a large N expansion of the Nambu--Jona-Lasinio model with SU(2) x SU(2) continuous chiral symmetry.

Yigal Shamir

A model of random triangulations of a domain in $R^{(4)}$ is presented. The global symmetries of the model include SL(4) transformations and translations. If a stable microscopic scale exists for some range of parameters, the model should be in a translation invariant phase where SL(4) is spontaneously broken to O(4). In that phase, SL(4) Ward identities imp

Chanju Kim, Yoonbai Kim

There has been considerable interest in the possible cosmic string configurations and Y. Yang has recently derived intriguing obstructions to the existence of cylindrically symmetric solutions in the Bogomol'nyi critical phase of the Einstein-Maxwell-Higgs system. In this comment, we would like to mention some earlier results and recent progress which we

Alfred S. Goldhaber, T. Goldman

We suggest that the quark-confining force is related by crossing symmetry to a color-singlet glueball ${\cal G}$ which is well described as a loop of one quantum of color magnetic flux. Electron pair annihilation as high as $\approx 2 GeV$ above the $Υ$ mass could produce $Υ\rightarrow \ell^+\ell^-$ accompanied by ${\cal G}$ or one of its excited states.

L. Susskind, M. Burkardt

Spontaneous breaking of chiral symmetry is discussed in the light-cone framework. The essential ingredient is an infinite number of constituents near zero light-cone momentum. These high (light-cone) energy degrees of freedom freeze out and leave behind some explicit symmetry breaking in the low (light-cone) energy effective Hamiltonian. Connections with Reg

L. Susskind, P. Griffin

A light-front renormalization group analysis is applied to study matter which falls into massive black holes, and the related problem of matter with transplankian energies. One finds that the rate of matter spreading over the black hole's horizon unexpectedly saturates the causality bound. This is related to the transverse growth behavior of transplankia

A. Soni

Lattice results for heavy light matrix elements are reviewed and some of their implications are very briefly discussed. Despite the fact that in most cases the lattice results for weak matrix elements at the moment have only a modest accuracy of about 20--30\% they already have important phenomenological repercussions; e.g.\ for $V_{td}/V_{ts}$, $x_s/x_d$ an

L. P. Grishchuk

A theory of quantum-mechanical generation of cosmological perturbations is considered. The conclusion of this study is that if the large-angular-scale anisotropy in the cosmic microwave background radiation is caused by the long-wavelength cosmological perturbations of quantum mechanical origin, they are, most likely, gravitational waves, rather than density

J. M. Combes, P. D. Hislop

We prove the existence of localized states at the edges of the bands for the two-dimensional Landau Hamiltonian with a random potential, of arbitrary disorder, provided that the magnetic field is sufficiently large. The corresponding eigenfunctions decay exponentially with the magnetic field and distance. We also prove that the integrated density of states i

D. Cule, Y. Shapir

The dynamics of the random-phase sine-Gordon model, which describes 2D vortex-glass arrays and crystalline surfaces on disordered substrates, is investigated using the self-consistent Hartree approximation. The fluctuation-dissipation theorem is violated below the critical temperature T_c for large time t>t* where t* diverges in the thermodynamic limit. Whil

A. Hoffmann, P. Lemmens, L. Winkeler, G. Guentherodt

By means of electronic Raman scattering we investigated the symmetry of the energy gap Delta(k), its temperature dependence and its variation with doping of well characterized Bi2Sr2CaCu2O8+delta single crystals. The oxygen content delta was varied between the under- and the overdoped regime by subsequently annealing the same single crystal in Ar and O2, res

Peter Neu, Roland Speicher

A model of a randomly disordered system with site-diagonal random energy fluctuations is introduced. It is an extension of Wegner's $n$-orbital model to arbitrary eigenvalue distribution in the electronic level space. The new feature is that the random energy values are not assumed to be independent at different sites but free. Freeness of random variabl

Peter Neu, Roland Speicher

We introduce a generalization of Wegner's $n$-orbital model for the description of randomly disordered systems by replacing his ensemble of Gaussian random matrices by an ensemble of randomly rotated matrices. We calculate the one- and two-particle Green's functions and the conductivity exactly in the limit $n\to\infty$. Our solution solves the CPA-e

Peter Neu, Alois Würger

A new relaxation mechanism is shown to arise from overdamped two-level systems above a critical temperature $T^*\approx 5$ K, thus yielding an explanation for experimental observations in dielectric glasses in the temperature range between $T^*$ and the relaxation peak at 50 K. Using the distribution function of the tunnelling model for the parameters of the

M. Di Stasio, X. Zotos

We study the level statistics of a non-integrable one dimensional interacting fermionic system characterized by the GOE distribution. We calculate numerically on a finite size system the level spacing distribution $P(s)$ and the Dyson-Mehta $Δ_3$ correlation. We observe that its low energy spectrum follows rather the Poisson distribution, characteristic of a

S. Fujimoto, N. Kawakami

The one-dimensional Kondo lattice model is investigated by using bosonization techniques and conformal field theory. In the half-filled band, the charge and spin gaps open for the anti-ferromagnetic Kondo coupling. Away from half-filling, the paramagnetic metallic state is characterized by the fixed point of Tomonaga-Luttinger liquid with the {\it large} Fer

Owen Rambow, Aravind Joshi

The central role of the lexicon in Meaning-Text Theory (MTT) and other dependency-based linguistic theories cannot be replicated in linguistic theories based on context-free grammars (CFGs). We describe Tree Adjoining Grammar (TAG) as a system that arises naturally in the process of lexicalizing CFGs. A TAG grammar can therefore be compared directly to an Me

Adam G. Riess, William H. Press, Robert P. Kirshner

We present an empirical method which uses visual band light curve shapes (LCS) to estimate the luminosity of type Ia supernovae (SN Ia). This method is first applied to a ``training set'' of 8 SN Ia light curves with independent distance estimates to derive the correlation between the LCS and the luminosity. We employ a linear estimation algorithm of

A. Ferrara, E. Corbelli

We study thermoreactive and acoustic instabilities in a diffuse gas, photoionized and heated by a radiation field. The analysis of the thermal instability by Field (1965) is extended to include the effects of the hydrogen recombination reaction, which, in general, is found to be a stabilizing agent for the condensation mode. This effect is stronger when the

Cheongho Han, Andrew Gould

We show that the statistical error, $σ_τ$, in estimating the optical depth, $τ$, due to microlensing is substantially higher than the naive Poisson estimate: $σ_τ = \sqrt{η/ N} τ$, where $N$ is the number of detections and $1.65 \leq η\lsim 3$. We construct a ``microlensing map'' using an observationally well-constrained barred bulge model and compar

Howard Georgi, Lev Kaplan, David Morin, Andreas Schenk

We investigate the effects of top quark compositeness on various physical parameters, and obtain lower limits on the compositeness scale from electroweak precision data. We consider corrections to top quark decay rates and other physical processes. Our results depend sensitively on whether the left-handed top is composite. A considerable enhancement of $t \b

B. Coluzzi

We study the 4d Heisenberg spin glass model with Gaussian nearest-neighbor interactions. We use finite size scaling to analyze the data. We find a behavior consistent with a finite temperature spin glass transition. Our estimates for the critical exponents agree with the results from epsilon-expansion.

Kostas Skenderis

We show that any BRST invariant quantum action with open or closed gauge algebra has a corresponding local background gauge invariance. If the BRST symmetry is anomalous, but the anomaly can be removed in the antifield formalism, then the effective action possesses a local background gauge invariance. The presence of antifields (BRST sources) is necessary. A

F. Tzschichholz, H. J. Herrmann

We consider a two dimensional lattice model to describe the opening of a crack in hydraulic fracturing. In particular we consider that the material only breaks under tension and the fluid has no pressure drop inside the crack. For the case in which the material is completely homogeneous (no disorder) we present results for pressure and elastic energy as a fu

N. Brambilla, G. M. Prosperi

The derivation of the $ q \bar q $ and the $ 3q $ potential for two dynamical quarks in a Wilson--loop context is reviewed. Some improvements are introduced. Only the usual assumptions in the evaluation of the Wilson loop integrals and expansions in the quark velocities are required for the result. It is shown that under the same assumptions it is possible t

Scott Koranda, Bruce Allen

We examine stochastic temperature fluctuations of the cosmic background radiation (CBR) arising via the Sachs-Wolfe effect from gravitational wave perturbations produced in the early universe. We consider spatially flat, perturbed FRW models that begin with an inflationary phase, followed by a mixed phase containing both radiation and dust. The scale factor

Giuseppe Santoro, Marco Airoldi, Nicola Manini, Erio Tosatti

A model for correlated electrons in a lattice with local additional spin--1 degrees of freedom inducing constrained hopping, is studied both in the low density limit and at quarter filling. We show that in both 1D and 2D two particles form a bound state even in presence of a repulsive U<U_c. A picture of a dilute Bose gas, leading to off-diagonal long range

R. Jakob, P. Kroll, M. Raulfs

We report results on the $π$-$γ$ transition form factor obtained within the hard scattering approach including transverse momentum effects and Sudakov corrections. The results clearly favor distribution amplitudes close to the asymptotic form, $\sim x_1x_2$, and disfavor distribution amplitudes which are strongly concentrated in the end-point regions. This o

I. V. Andreev, M. Plümer, B. R. Schlei, R. M. Weiner

We compare and analyse Bose-Einstein correlation data for $π^+ p$ and $K^+ p$ collisions at $\sqrt{s}=22\ GeV$ obtained by the NA22-Collaboration and data for $p\bar{p}$ collisions at $\sqrt{s}=630\ GeV$ obtained by the UA1-Minimum-Bias-Collaboration. Using a parametrization for a longitudinally expanding source, we observe that correlation lengths and radii

R. Anni, G. Co', P. Pellegrino

The model independent procedure of extracting charge density distributions from elastic electron scattering data is investigated. The charge density distributions are expanded on an orthonormal basis and the parameters of the expansions are fixed by the comparison with the experimental data. Two bases with different analytical properties (Fourier-Bessel and

A. Bianconi, S. Jeschonnek, N. N. Nikolaev, B. G. Zakharov

We demonstrate that the final state $p$-$n$ interaction in the reaction of electrodissociation of the deuteron at large $Q^{2}$ in a static external field leads to the apparent reacceleration of neutrons. The shift of the neutron velocity from the velocity of the deuteron beam is related to the quantum-mechanical forward-backward asymmetry of the missing mom

Marco Martens, Charles Tresser

We prove that for continuous maps on the interval, the existence of an n-cycle, implies the existence of n-1 points which interwind the original ones and are permuted by the map. We then use this combinatorial result to show that piecewise affine maps (with no zero slope) cannot be infinitely renormalizable.

Atish Bagchi, Charles Wells

Traditional treatments of formal logic provide: 1. A syntax for formulas. 2. An inference relation between sets of formulas. 3. A rule for assigning meaning to formulas (semantics) that is sound with respect to the inference relation. First order logic, the logic and semantics of programming languages, and the languages that have been formulated for various

G. Delfino, G. Mussardo, P. Simonetti

A non-perturbative method based on the Form Factor bootstrap approach is proposed for the analysis of correlation functions of 2-D massless integrable theories and applied to the massless flow between the Tricritical and the Critical Ising Models.

K. Fredenhagen, M. R. Gaberdiel, S. M. Rueger

A Haag-Ruelle scattering theory for particles with braid group statistics is developed, and the arising structure of the Hilbert space of multiparticle states is analyzed.

F. Barbarin, E. Ragoucy, P. Sorba

New realizations of finite W algebras are constructed by relaxing the usual constraint conditions. Then, finite W algebras are recognized in the Heisenberg quantization recently proposed by Leinaas and Myrheim, for a system of two identical particles in d dimensions. As the anyonic parameter is directly associated to the W-algebra involved in the d=1 case, i

Emilio Elizalde, Sergei D. Odintsov, August Romeo

\noindent{\large\bf Abstract.} We develop a general formalism to study the renormalization group (RG) improved effective potential for renormalizable gauge theories ---including matter-$R^2$-gravity--- in curved spacetime. The result is given up to quadratic terms in curvature, and one-loop effective potentials may be easiliy obtained from it. As an example,

A. A. Btsenko, A. D. Odintsov, S. Zerbini

The one-loop effective action for D-dimensional quantum gravity with negative cosmological constant, is investigated in space-times with compact hyperbolic spatial section. The explicit expansion of the effective action as a power series of the curvature on hyperbolic background is derived, making use of heat-kernel and zeta-regularization techniques. It is

K. -I. Izawa

The cosmological term prevents perturbation based on derivative expansion in Einstein gravity. We consider quantum theory of gravitation invariant under volume-preserving diffeomorphism and Weyl transformation, which is suitable for derivative expansion.

I. M. Dremin

The study of the singularities and zeros of the generating functions of multiplicity distributions is advocated. Some hints from well known probability distributions and experimental data are given. The statistical mechanics analogies provoke to look for a signature of phase transitions. The program of further experimental studies of the singularities is for

B. Ananthanarayan, D. Toublan, G. Wanders

The pion-pion scattering amplitudes provided by second-order chiral perturbation theory are confronted with known rigorous constraints derived from the axioms of quantum field theory. We mainly test constraints restricting the $\pi^0$-$\pi^0$ $S$- and $D$-wave amplitudes in the unphysical interval $0\leq s\leq 4m_\pi^2$. These constraints impose significant

M. Ciuchini

We present an updated theoretical prediction of $\epse$, using the next-to-leading $\DSone$ effective hamiltonian and lattice QCD matrix elements. The CP violating phase is costrained by using both the experimental values of $\ep$ and $x_d$, assuming the theoretical determination of $f_B$. Predictions of $\cosδ$ and $\sin 2β$ are also obtained in this way. F

M. Ciuchini

Theoretical predictions for the branching ratios of the $B \rightarrow X_s\,γ$ and $B \rightarrow K^*\,γ$ decays are calculated in the Standard Model and in the (type II) two-Higgs-doublet model. Both the complete leading and the partially known next-to-leading order QCD corrections are included. The uncertainties due to the regularization scheme dependence

Michelangelo MANGANO

We review heavy quark and quarkonium production in high energy hadronic collisions. We discuss the status of the theoretical calculations and their uncertainties. We then compare the current theoretical results with the most recent measurements from the tevatron collider experiments.

Chul Hi Park, D0 Collaboration

We have studies the performance characteristics of approximately 4000 Visible Light Photon Counters(VLPC) over a range of operating temperatures and biases. We will describe the characterization procedure and present the measured gain, noise and the relative quantum efficiency for the devices. We will also discuss the general operation of the devices and the

R. M. Avakian, G. Oganessyan

It has been shown by one of the authors$^1$ that in isotropic spherical coordinates there is a relation between the mass of a static spherical gravitating body and the pressure distribution inside it. In this paper the result is generalized for the case of stationary axisymmetric configurations.