August 1996 arXiv papers — page 6

M. Weigt, A. Engel

The coupling space of perceptrons with continuous as well as with binary weights gets partitioned into a disordered multifractal by a set of $p=γN$ random input patterns. The multifractal spectrum $f(α)$ can be calculated analytically using the replica formalism. The storage capacity and the generalization behaviour of the perceptron are shown to be related

Jacques Bros, Detlev Buchholz

The problem of extracting the modes of Goldstone bosons from a thermal background is reconsidered in the framework of relativistic quantum field theory. It is shown that in the case of spontaneous breakdown of an internal bosonic symmetry a recently established decomposition of thermal correlation functions contains certain specific contributions which can b

Hsiang-nan Li, Hoi-Lai Yu

We combine the resummations for radiative corrections and for the heavy quark expansion to study the inclusive radiative decay $B \to X_sγ$. The infrared renormalon ambiguity is also taken into account. Including both theoretical and experimental uncertainties, we determine the allowed domain for the HQET parameters ${\bar Λ}$ and $λ_1$ centered at ${\bar Λ}

K. A. Kiers, W. van Dijk

We formulate scattering in one dimension due to the coupled Schrödinger equation in terms of the $S$ matrix, the unitarity of which leads to constraints on the scattering amplitudes. Levinson's theorem is seen to have the form $η(0) = π(n_b + 1/2 n - 1/2 N)$, where $η(0)$ is the phase of the $S$ matrix at zero energy, $n_b$ the number of bound states wit

L. C. Kwek, C. H. Oh, K. Singh

We consider a modified version of the coproduct for $\U(\su_q(2))$ and show that in the limit when $q \rightarrow 1$, there exists an essentially non-cocommutative coproduct. We study the implications of this non-cocommutativity for a system of two spin-$1/2$ particles. Here it is shown that, unlike the usual case, this non-trivial coproduct allows for symme

Shin-ichi Sasa

Phase equations describing the evolution of large scale modulation of spatially periodic patterns in two dimensional systems are derived by employing the renormalization group method. A general formula for phase diffusion coefficients is given under certain conditions.

G. Q. Li, C. M. Ko

Lambda flow in Ni+Ni collisions at SIS energies is studied in the relativistic transport model (RVUU 1.0). It is found that for primordial lambdas the flow is considerably weaker than proton flow. The inclusion of final-state interactions, especially the propagation of lambdas in mean-field potential, brings the lambda flow close to that of protons. An accur

B. R. Schlei, N. Xu

Within a theoretical study using both HYLANDER and RQMD, we revisit Bose-Einstein correlation measurements of 200AGeV S+S and 160AGeV Pb+Pb. Transverse flow does not show up in the Bose-Einstein measurements. The decrease of the effective transverse radius parameters with increasing transverse average momentum of the particle pair is largely due to the effec

G. A. Chekomazov, M. H. Urin

The description of the direct nucleon decay of high-spin subbarrier one-particle states in near-magic nuclei is attempted using a simple optical model and the simplest version of the coupled-channel approach. The branching ratios for the direct decay of the several single-neutron states in $^{209}Pb$ and $^{91}Zr$ to the ground state and to the low-lying col

H. M. Hofmann, G. M. Hale

We report on a consistent, microscopic calculation of the bound and scattering states in the 4He system employing a realistic nucleon-nucleon potential in the framework of the resonating group model (RGM). We present for comparison with these microscopic RGM calculations the results from a charge-independent, Coulomb-corrected R-matrix analysis of all types

George Khimshiashvili, Alexander Ushveridze

We investigate average gradient degree of normal random polynomials of fixed algebraic degree n. In particular, for polynomials of two variables, asymptotics of the average gradient degree for large values of n is determined.

M. Henningson, G. Moore

We consider compactifications of the heterotic string on $K3 \times T2$ so that the resulting theory in $d = 4$ space-time dimensions has $N = 2$ supersymmetry. The gravitational and gauge coupling constants of the low-energy effective theory receive threshold corrections from loops of super-heavy string states. We calculate these corrections for the case wh

M. Alimohammadi, M. Khorrami

By using the path integral method , we calculate the Green functions of field strength of Yang-Mills theories on arbitrary nonorientable surfaces in Schwinger-Fock gauge. We show that the non-gauge invariant correlators consist of a free part and an almost $x$-independent part. We also show that the gauge invariant $n$-point functions are those corresponding

Elisabeth Kraus, Klaus Sibold

We outline the renormalization of the standard model to all orders of perturbation theory in a way which does not make essential use of a specific subtraction scheme but is based on the Slavnov-Taylor identity. Physical fields and parameters are used throughout the paper. The Ward-identity for the global gauge invariance of the vertex functions is formulated

Karsten Bormann, Frank Antonsen

The free energy due to the vacuum fluctuations of matter fields on a classical gravitational background is discussed. It is shown explicitly how this energy is calculated for a non-minimally coupled scalar field in an arbitrary gravitational background, using the heat kernel method. The treatment of (self-)interacting fields of higher spin is outlined, using

Frank Antonsen, Karsten Bormann

We demonstrate how to obtain explicitly the propagators for quantum fields residing in curved space-time using the heat kernel for which a new construction procedure exists. Propagators are determined for the case of Rindler, Friedman-Robertson-Walker, Schwarzschild and general conformally flat metrics, both for scalar, Dirac and Yang-Mills fields. The calcu

O. Kechkin, M. Yurova

The action of the isometry subgroup which preserves the trivial values of the fields is studied for the stationary D=4 Einstein--Maxwell--Dilaton--Axion theory. The technique for generation of charges and the corresponding procedure for construction of new solutions is formulated. A solution describing the double rotating dyon with independent values of all

I. Ya. Aref'eva

A construction of master field describing multicolour QCD is presented. The master fields for large N matrix theories satisfy to standard equations of relativistic field theory but fields are quantized according $q$-deformed commutation relations with $q=0$. These commutation relations are realized in the Boltzmannian Fock space. The master field for gauge t

J. Bartels, A. DeRoeck, H. Lotter

We present a numerical estimate of the $γ^* γ^*$ total cross section at LEP and at the designed $e^+e^-$ Next Linear Collider (NLC), based upon the BFKL Pomeron. We find for the linear collider that the event rate is substantial provided electrons scattered under small angles can be detected, and a measurement of this cross section provides an excellent test

Bodo Lampe

I present the highlights of a long review on polarization in deep inelastic scattering. Some new results are discussed at the end of the talk.

Stefano Forte, Richard D. Ball, Giovanni Ridolfi

We discuss the determination of polarized parton distributions from a next-to-leading order analysis of recent experimental data. We extract the first moment of the polarized quark and gluon distribution and assess the corresponding uncertainties, with special regard to those related to scheme dependence.

Xiao-yuan Li, Ernest Ma

Because of the existence of cubic scalar couplings, there are in general nondecoupling effects at tree level in the scalar sector of any theory with two or more very different mass scales. We show this explicitly in the minimal nonsupersymmetric SU(5) model of grand unification. We show also how tree-level decoupling is guaranteed if supersymmetry is imposed

Hyun-Chul Kim

The recent investigation on various form factors of the nucleon is reviewed in the framework of the SU(3) chiral quark-soliton model. The results for the electromagnetic and scalar form factors are in remarkable agreement with experimental and empirical data. The strange vector form factors are also discussed with the effect of the kaon cloud being considere

C. A. Dominguez, M. S. Fetea, M. Loewe

The temperature corrections to the current algebra Gell-Mann, Oakes, and Renner (GMOR) relation in $SU(2)\otimes SU(2)$ are investigated in the framework of QCD sum rules. There are no corrections at leading order in the quark masses. At the next to leading order we find corrections of the form $m_{q}^2\; T^{2}$, which are small except near the critical temp

M. Dasgupta, B. R. Webber

We estimate the power corrections (infrared renormalon contributions) to the coefficient functions for the transverse, longitudinal and asymmetric fragmentation functions in $e^+e^-$ annihilation, using a method based on the analysis of one-loop Feynman graphs containing a massive gluon. The leading corrections have the expected $1/Q^2$ behaviour, but the gl

M. Anselmino, E. Andreeva, V. Korotkov, F. Murgia

The physics of polarized nucleon--nucleon collisions originating from an internal polarized target in the HERA proton beam is investigated. Based on 240 pb^-1 integrated luminosity at 40 GeV c.m. energy, statistical sensitivities are given over a wide (x_F, p_T) range for a variety of inclusive and exclusive final states. By measuring single spin asymmetries

H. W. Griesshammer

Magnetically charged vortex defects are shown to arise in canonically quantised modified axial gauge QCD_{3+1} on a torus. This gauge -- being an Abelian projection -- keeps only the eigenphases as dynamical variables of the Wilson line in x_3-direction. A mismatch between the identification of large gauge transformations before and after gauge fixing is ind

Glennys R. Farrar

The light gaugino scenario predicts that the lighter chargino mass is less than m_W, gluino and lightest neutralino masses are <~ 1 GeV, and the dominant decay mode of charginos and non-LSP neutralinos is generically to three jets. The excess &#34;4j&#34; events observed by ALEPH in e+ e- annihilation at 133 GeV may be evidence that m(C_1) = 53 GeV. If so, m

L. L. Jenkovszky, E. S. Martynov, F. Paccanoni

It is shown that the dipole pomeron model of single diffraction dissociation -- contrary to the case of the supercritical pomeron -- is compatible with the inequality $σ^{SD}\leqσ^{tot}$, imposed by unitarity, provided the triple pomeron coupling satisfies certain conditions. With the adopted approximation the model considered as a parcticular solution of th

A. Pap, P. Suranyi

A lattice theory of scalar bosons in the fundamental representation of the gauge group $SU(N_c)$ and of the global symmetry group $SU(N_f)$ is shown to induce a standard gauge theory only at large $N_f$. The system is in a deconfined phase at strong scalar self-coupling and any finite $N_f$. The requirement of convergence of the effective gauge action impose

Eric Myers, Michael F. Bruist

We describe an explicitly discrete model of the process of DNA branch migration. The model matches the existing data well, but we find that branch migration along long strands of DNA ($N \simge 40$~bp) is also well modeled by continuum diffusion. The discrete model is still useful for guiding future experiments.

A. Duncan, E. Eichten, S. Perrucci, H. Thacker

Limits on the size of quenched chiral logs in the pion mass for Wilson fermions are investigated. The smallness of chiral logs is shown to be a result of the suppression of the hairpin diagram for small $p^2$, such that the value of the hairpin on the pion mass shell is much smaller than the physical $m_{η&#39;}^2$. A direct calculation of the topological su

B. Bunk

Subspace iterations are used to minimise a generalised Ritz functional of a large, sparse Hermitean matrix. In this way, the lowest $m$ eigenvalues are determined. Tests with $1 \leq m \leq 32$ demonstrate that the computational cost (no. of matrix multiplies) does not increase substantially with $m$. This implies that, as compared to the case of a $m=1$, th

A. Donini, V. Giménez, G. Martinelli, G. C. Rossi

We discuss the application of the MPSTV non-perturbative method \cite{NPM} to the operators relevant to kaon decays. This enables us to reappraise the long-standing question of the $ΔI=1/2$ rule, which involves power-divergent subtractions that cannot be evaluated in perturbation theory. We also study the mixing with dimension-six operators and discuss its i

J. W. Maluf

We calculate the total gravitational energy and the gravitational energy density of the de Sitter space using the definition of localized energy that arises in the framework of the teleparallel equivalent of general relativity. We find that the gravitational energy can only be defined within the cosmological horizon and is largely concentrated in regions far

Bernd Bruegmann

We present first results obtained with a 3+1 dimensional adaptive mesh code in numerical general relativity. The adaptive mesh is used in conjunction with a standard ADM code for the evolution of a dynamically sliced Schwarzschild spacetime (geodesic slicing). We argue that adaptive mesh is particularly natural in the context of general relativity, where apa

J. W. Maluf, E. F. Martins, A. Kneip

In the teleparallel equivalent of general relativity the energy density of asymptotically flat gravitational fields can be naturaly defined as a scalar density restricted to a three-dimensional spacelike hypersurface $Σ$. Integration over the whole $Σ$ yields the standard ADM energy. After establishing the reference space with zero gravitational energy we ob

Jin-Ho Cho, Hyuk-jae Lee

The quantization of the gravitational Chern-Simons coefficient is investigated in the framework of $ISO(2,1)$ gauge gravity. Some paradoxes involved are cured. The resolution is largely based on the inequivalence of $ISO(2,1)$ gauge gravity and the metric formulation. Both the Lorentzian scheme and the Euclidean scheme lead to the coefficient quantization, w

Robert Shrock, Shan-Ho Tsai

We study the $q$-state Potts antiferromagnet with $q=3$ on the honeycomb lattice. Using an analytic argument together with a Monte Carlo simulation, we conclude that this model is disordered for all $T \ge 0$. We also calculate the ground state entropy to be $S_0/k_B = 0.507(10)$ and discuss this result.

R. W. Reid, S. K. Bose, B. Mitrovic

Via Monte Carlo studies of the frustrated XY or classical planar model we demonstrate the possibility of a finite (nonzero) temperature spin/gauge glass phase in two dimensions. Examples of both periodic and quasiperiodic two dimensional lattices, where a high temperature paramagnetic phase changes to a spin/gauge glass phase with the lowering of temperature

Enzo Granato

Numerical simulations of the current-voltage characteristics of an ordered two-dimensional Josephson junction array at an irrational flux quantum per plaquette are presented. The results are consistent with an scaling analysis which assumes a zero temperature vortex glass transition. The thermal correlation length exponent characterizing this transition is f

David Sherrington

A brief introductory overview in general terms is given of concepts, issues and applications of the paradigm of rugged landscapes in the contexts of physics and biology.

Stephan Haas, Fu-Chun Zhang, Frederic Mila, T. M. Rice

Recent experiments on La_2Cu_{1-x}Li_xO_4 show that although the doped holes remain localized near the substitutional Li impurities, magnetic order is rapidly suppressed. An examination of the spin texture around a bound hole in a CuO_2 plane shows that the formation of a skyrmion is favored in a wide range of parameters, as was previously proposed in the co

R. Allub, B. Alascio

We use a model previously formulated based on the double exchange mechanism and diagonal disorder to calculate magnetization and conductivity for La_{1-x}Sr_xMnO_3 type crystals as a function of temperature. The model represents each Mn^{4+} ion by a spin S=1/2, on which an electron can be added to produce Mn$^{3+}$. We include a hopping energy $t,$ two stro

M. Baehr, M. Winkelmann, P. Vorderwisch, M. Steiner

Inelastic neutron scattering measurements were performed on the ferromagnetic chain system CsNiF_3 in the collinear antiferromagnetic ordered state below T_N = 2.67K. The measured spin wave dispersion was found to be in good agreement with linear spin wave theory including dipolar interactions. The additional dipole tensor in the Hamiltonian was essential to

Francis Bond, Kentaro Ogura, Satoru Ikehara

This paper proposes an analysis of classifiers into four major types: UNIT, METRIC, GROUP and SPECIES, based on properties of both Japanese and English. The analysis makes possible a uniform and straightforward treatment of noun phrases headed by classifiers in Japanese-to-English machine translation, and has been implemented in the MT system ALT-J/E. Althou

S. Doebereiner, N. Junkes, S. J. Wagner, H. Zinnecker

We present results from a sensitive high-resolution X-ray observation of the nearby active galaxy Centaurus A (NGC 5128) with the ROSAT HRI. The 65~ksec X-ray image clearly distinguishes different components of the X-ray emission from Cen A: the nucleus and the jet, the diffuse galaxy halo, and a number of individual sources associated with the galaxy. The l

Nir J. Shaviv, Arnon Dar

Photoexcitation and ionization of partially ionized heavy atoms in highly relativistic flows by interstellar photons, followed by their reemission in radiative recombination and decay, boost star-light into beamed $γ$ rays along the flow direction. Repeated excitation/decay of highly relativistic baryonic ejecta from merger or accretion induced collapse of n

P. E. Christopoulou, A. J. Holloway, W. Steffen, C. G. Mundell

New observations using narrow band imaging, long-slit spectroscopy and MERLIN observations of the nuclear region of the Seyfert galaxy NGC~4051 have been made. An edge brightened, triangular region of ionized gas extending 420 pc from the centre of the galaxy has been detected. Long-slit spectra of this ionised gas, taken at 1.5\arcsec\ from the core, show t

Martin G. Haehnelt, Michael Rauch, Matthias Steinmetz

Estimates of the linear extent of heavy-element absorption systems along the line-of-sight to a QSO often assume that the cloud is photoionized and that the temperature takes the equilibrium value where photo-heating balances line cooling. We show that rather small deviations from this photoionization equilibrium temperature caused by additional heating proc

Mark Andrea A. de Cataldo

We make precise the structure of the first two reduction morphisms associated with codimension two nonsingular subvarieties of quadrics $\Q{n}$, $n\geq 5$. We give a coarse classification of the same class of subvarieties when they are assumed to be not of log-general-type. Keywords: Adjunction Theory, classification, codimension two, conic bundles, low codi

Mark Andrea A. de Cataldo

Let $X$ be a codimension two nonsingular subvariety of a nonsingular quadric $\Q{n}$ of dimension $n\geq 5$. We classify such subvarieties when they are scrolls. We also classify them when the degree $d\leq 10$. Both results were known when $n=4$. Keywords: Classification; liaison; low codimension; low degree; quadric; scroll; vector bundle

Mark Andrea A. de Cataldo

We prove that there are only finitely many families of codimension two nonsingular subvarieties of quadrics $\Q{n}$ which are not of general type, for $n=5$ and $n\geq 7$. We prove a similar statement also for the case of higher codimension. The case $n=6$ has been recently settled by Fania-Ottaviani. Keywords: Codimension two, Grassmannians, Lifting, Low co

Mark Andrea A. de Cataldo

By means of an {\it ad hoc} modification of the so-called ``Castelnuovo-Harris analysis&#34; we derive an upper bound for the genus of integral curves on the three dimensional nonsingular quadric which lie on an integral surface of degree $2k$, as a function of $k$ and the degree $d$ of the curve. In order to obtain this we revisit the Uniform Position Princ

Chung Kao, David Atwood, Amarjit Soni

Parity violation induced by the chromo-anapole form factor of the bottom quark, generated from weak corrections, is studied in polarized hadron collisions. The forward-backward asymmetry in the bottom quark pair production at polarized $pp$ and $p\bar{p}$ colliders is evaluated in the Standard Model and in a Two Higgs Doublet Model to examine the effects of

Uros Seljak

Polarization induced by cosmological scalar perturbations leads to a typical anisotropy pattern, which can best be analyzed in Fourier domain. This allows one to unambiguously distinguish cosmological signal of polarization from other foregrounds and systematics, as well as from polarization induced by non-scalar perturbations. The precision with which polar

Simon C. Benjamin, Neil F. Johnson

We calculate analytically the exact dynamical response of a droplet of N interacting electrons in a quantum dot with an arbitrarily time-dependent parabolic confinement potential ω(t) and a perpendicular magnetic field. We find that, for certain frequency ranges, a sinusoidal perturbation acts like an attractive effective interaction between electrons. In th

R. Santos, A. Barroso, L. Bruecher

We calculate the decay width for the process $H^+ \to h^0 W^+$ up to order $g^4$ in the framework of the Two Higgs Doublet Model. We argue that for some reasonable choice of the free parameters the contribution from the one-loop graphs can be as large as 40%.

Atsushi Nakayashiki

We shall give an elementary and rigorous proof of the Thomae formula for ${\bf Z}_N$ curves which was discovered by Bershadsky and Radul. Instead of using the determinant of the Laplacian we use the traditional variational method which goes back to Riemann, Thomae, Fuchs. In the proof we made explicit the algebraic expression of the chiral Szegö kernels and

R. Brent Tully, Marc A. W. Verheijen, Michael J. Pierce, Jia-Sheng Huang

The Ursa Major Cluster has received remarkably little attention, although it is as near as the Virgo Cluster and contains a comparable number of HI-rich galaxies. In this paper, criteria for group membership are discussed and data are presented for 79 galaxies identified with the group. Of these, all 79 have been imaged at B,R,I bands with CCDs, 70 have been

Kei-Ichi Kondo

In two space-time dimensions, we write down the exact and closed Schwinger-Dyson equation for the gauged Thirring model which has been proposed recently by the author. The gauged Thirring model is a natural gauge-invariant extension of the Thirring model and reduces to the Schwinger model (in the Abelian case) in the strong four-fermion coupling limit. The e

Sergei V. Ketov, Christine Unkmeir, Sven-Olaf Moch

We present the N=4 superspace constraints for the two-dimensional (2d) off-shell (4,4) supergravity with the superfield strengths expressed in terms of a (4,4) twisted (scalar) multiplet TM-I, as well as the corresponding component results, in a form suitable for applications. The constraints are shown to be invariant under the N=4 super-Weyl transformations

M. Hotta, I. Joichi, Sh. Matsumoto, M. Yoshimura

In many physical situations the behavior of a quantum system is affected by interaction with a larger environment. We develop, using the method of influence functional, how to deduce the density matrix of the quantum system incorporating the effect of environment. After introducing characterization of the environment by spectral weight, we first devise schem

Carl H. Albright

Many of the ingredients are explored which are needed to develop a super- symmetric SO(10) x U(1)_F grand unified model based on the Yukawa structure of a model previously constructed in collaboration with S. Nandi to explain the quark and lepton masses and mixings in a particular neutrino scenario. The U(1)_F family symmetry can be made anomaly-free with th

Simon Labrunie, Robert Conte

We study the discretisation of the Chazy class III equation by two means: a discrete Painlevé test, and the preservation of a two-parameter solution to the continuous equation. We get that way a best discretisation scheme.

Simon Labrunie, Robert Conte

We develop a method, based on Darboux&#39; and Liouville&#39;s works, to find first integrals and/or invariant manifolds for a physically relevant class of dynamical systems, without making any assumption on these elements&#39; form. We apply it to three dynamical systems: Lotka--Volterra, Lorenz and Rikitake.

P. Severa

Simple Hamiltonian systems, such as mathematical pendulum or Euler equations for rigid body, are solved without computation. It is nothing but a joke but maybe you will find it nice.

Ali Mostafazadeh

Adiabatic $U(2)$ geometric phases are studied for arbitrary quantum systems with a three-dimensional Hilbert space. Necessary and sufficient conditions for the occurrence of the non-Abelian geometrical phases are obtained without actually solving the full eigenvalue problem for the instantaneous Hamiltonian. The parameter space of such systems which has the

V. Vedral, M. A. Rippin, M. B. Plenio

We consider the effects of local interactions upon quantum mechanically entangled systems. In particular we demonstrate that non-local correlations cannot increase through local operations on any of the subsystems, but that through the use of quantum error correction methods, correlations can be maintained. We provide two mathematical proofs that local gener

L. M. Pismen

Striped Turing patterns and solitary band and disk structures are constructed using a three-variable multiscale model with cubic nonlinearity and global control. The existence and stability conditions of regular structures are analysed using the equation of motion of curved boundaries between alternative states of the short-range component. The combined pict

L. M. Pismen

An interphase boundary may be immobilized due to nonlinear diffractional interactions in a feedback optical device. This effect reminds of the Turing mechanism, with the optical field playing the role of a diffusive inhibitor. Two examples of pattern formation are considered in detail: arrays of kinks in 1d, and solitary spots in 2d. In both cases, a large n

Andrew Cumming, W. C. Haxton

Recent solar neutrino experiments have shown that both $ϕ(^8$B) and the neutrino flux ratio $ϕ(^7$Be)/$ϕ(^8$B) are substantially below their standard solar model values, leading some to discount the possibility of an astrophysical solution to the solar neutrino puzzle. We test this conclusion phenomenologically and find that the discrepancies can be signific

G. Mart&#39;inez-Pinedo, A. P. Zuker, A. Poves, E. Caurier

Complete diagonalizations in the pf major shell, lead to very good agreement with the experimental data (level schemes, transitions rates, and static moments) for the A=47 and A=49 isotopes of Ca, Sc, Ti, V, Cr, and Mn. Gamow-Teller and M1 strength functions are calculated. The necessary monopole modifications to the realistic interactions are shown to be cr

I. G. Alekseev, V. P. Kanavets, B. V. Morozov, D. N. Svirida

Recent measurements of spin-rotation parameters in elastic $π^+ p$ scattering are in marked disagreement with predictions of the Carnegie-Mellon$-$Berkeley and Karlsruhe-Helsinki analyses. Using the method of Barrelet, we show how this discrepancy can be removed. We then show how this Barrelet transformation alters the partial-wave amplitudes. The effect of

Thomas R. Hemmert, Barry R. Holstein, Germar Knoechlein, Stefan Scherer

We investigate the spin-independent part of the virtual Compton scattering (VCS) amplitude off the nucleon within the framework of chiral perturbation theory. We perform a consistent calculation to third order in external momenta according to Weinberg&#39;s power counting. With this calculation we can determine the second- and fourth-order structure-dependen

C. M. Naon, M. C. von Reichenbach, M. L. Trobo

We apply a recently proposed path-integral approach to non-local bosonization to a Thirring-like system modeling non-relativistic massless particles interacting with localized fermionic impurities. We consider forward scattering processes described by symmetric potentials including interactions between charge, current, spin and spin-current densities. In the

I. V. Volovich

We discuss an application of the known in QCD large $N$ expansion to strings and supermembranes in the strong coupling. In particular we use the recently obtained master field describing $ SU(\infty)$ gauge theory to argue that quantum extreme black holes obey quantum Boltzmann (infinite) statistics. This supports a topological argument by Strominger that bl

John D. Barrow, Mariusz P. Dabrowski

We present new exact solutions of the low-energy-effective-action string equations with both dilaton $ϕ$ and axion $H$ fields non-zero. The background universe is of Kantowski-Sachs type. We consider the possibility of a pseudoscalar axion field $h$ ($H=e^ϕ(dh)^{*}$) that can be either time or space dependent. The case of time-dependent $h$ reduces to that o

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

We investigate the behavior of softly broken $N=2$ SQCD at non-zero bare theta angle $θ_0$, using superfield spurions to implement the SUSY breaking. We find a first-order phase transition as $θ_0$ is varied from zero to $2 π$, in agreement with a prediction of `t Hooft. The low-energy theta angle $θ_{eff}$, which determines the effective charges of dyonic e

Edson Stedile, Rogerio Duarte

It is pointed out that any conformally transformed of a flat space-time metric $\ball g_{ij} = f(x)\;η_{ij}$ is a solution to Witten&#39;s equation of Chern-Simons gravity, which holds outside matter in (2+1) dimensions. It is also shown that a simultaneous exterior solution to both Witten&#39;s and Einstein&#39;s equations, yields the lensing effect of an i

A. Yu. Kamenshchik, S. L. Lyakhovich

We introduce and study a new discrete basis of gravity constraints by making use of harmonic expansion for closed cosmological models. The full set of constraints is splitted into area-preserving spatial diffeomorphisms, forming closed subalgebra, and Virasoro-like generators. Operatorial Hamiltonian BFV-BRST quantization is performed in the framework of per

Philip C. Argyres, M. Ronen Plesser, Alfred D. Shapere

We determine the exact global structure of the moduli space of $N{=}2$ supersymmetric $SO(n)$ and $\USp(2n)$ gauge theories with matter hypermultiplets in the fundamental representations, using the non-renormalization theorem for the Higgs branches and the exact solutions for the Coulomb branches. By adding an $(N{=}2)$--breaking mass term for the adjoint ch

Hiroyuki Hata, Hajime Oda

Causality is studied in the covariant formulation of free string field theory (SFT). We find that, though the string field in the covariant formulation is a functional of the ghost coordinates as well as the space-time coordinate and the latter contains the time-like oscillators with negative norm, the condition for the commutator of two open string fields t

Akikazu Hashimoto

Method for computing scattering amplitudes of open strings with Dirichlet boundary on one end and Neumann boundary condition on the other is described. Vertex operator for these states are constructed using twist fields which have been studied previously in the context of Ashkin-Teller model and strings on orbifolds. Using these vertex operators, we compute

Barak Kol, Arvind Rajaraman

For an extreme charged black hole some scalars take on a fixed value at the horizon determined by the charges alone. We call them fixed scalars. We find the absorption cross section for a low frequency wave of a fixed scalar to be proportional to the square of the frequency. This implies a strong suppression of the Hawking radiation near extremality. We comp

L. Micu

The decay constants of pseudoscalar mesons are calculated in a relativistic quark model which assumes that mesons are made of a valence quark antiquark pair and of an effective vacuum like component. The results are given in terms of quark masses and of some free parameters entering the expression of the internal wave functions of the mesons. By using the pi

L. L. Jenkovszky, E. S. Martynov, F. Paccanoni

Recent $HERA$ data on the photoproduction of vector mesons are analysed within a &#34;soft&#34;, dipole pomeron model. We argued that the data on $σ^{γ\rightarrow J/ψ}_{el}$ is consistent with a soft pomeron, the apparent rapid increase resulting from the non-asymptotic effects due to the delayed asymptotics of $σ_{el}$ with respect to $σ_{tot}$.

Youichi Yamada

We study the relation between different renormalization schemes for the parameter $\tanβ$ in the Minimal Supersymmetric Standard Model. The contributions of the third-generation quark-squark loops to the differences between $\tanβ$&#39;s in several schemes are discussed. Their numerical differences are typically within several %.

Agustin Nieto

Effective-field-theory methods are used to study the high T limit of QCD. These methods unravel the contributions to the free energy of QCD at high temperature from the scales T, gT, and g^2 T. The free energy is explicitly computed to order g^5. Implications for the application of perturbative QCD to the quark-gluon plasma are also discussed.

Matthias Burkardt

Numerical results for the calculation of the (rest-frame) $Q\bar{Q}$ potential, for light-front quantized $QCD_{2+1}$ on a $\perp$ lattice are presented. Both in the longitudinal as well as the $\perp$ spatial directions one obtains linear confinement. The resulting potential is almost rotational symmetric.

B. W. Harris

A new next-to-leading order Monte Carlo program for the calculation of fully differential heavy quark cross sections in electroproduction is described. A comparison between the theoretical predictions and the latest charm production data from H1 and ZEUS at HERA is presented.

B. W. Harris, J. F. Owens

A new next-to-leading order Monte Carlo program for the calculation of fully differential jet cross sections in photoproduction is described. The contributions from both resolved and direct components are included. A comparison between the theoretical predictions and ZEUS data is presented.

A. C. B. Antunes, L. J. Antunes

The problem of three different masses bound by harmonic oscillator potentials is solved exactly. It is shown that Jacobi coordinates cannot, in general, decouple this system into two three-dimensional oscillators but this decoupling can always be obtained in terms of the normal coordinates. The condition for the decoupling in Jacobi coordinates is given. It

G. Grunberg

The connection between renormalons and power corrections is discussed in the case the effective coupling constant has an infrared fixed point of perturbative origin.

Thomas Schaefer

We study flavor mixing and the axial anomaly in QCD at zero and finite temperature. Using the instanton liquid model, we show that the strength of the anomaly is essentially unchanged near the critical temperature for chiral symmetry restoration. We demonstrate that nevertheless, chiral symmetry restoration has important consequences for the eta and eta prim

Steven Gottlieb

Progress on the calculation of the spectrum from lattice calculations is reviewed. Particular emphasis is placed on discussing our ability to control possible systematic errors coming from finite volume, and extrapolations in quark mass and lattice spacing. Recent approaches based on improved actions are compared.

J. Cox, W. Franzki, J. Jersak, C. B. Lang

We examine selected properties of the gauge-ball spectrum and fermionic variables in the vicinity of the recently discussed non-Gaussian fixed point of 4D compact U(1) lattice gauge theory within the quenched approximation. Approaching the critical point from within the confinement phase, our data support scaling of $T1^{+-}$ gauge-ball states in units of th

Artan Borici, Philippe de Forcrand

Quenched light hadron masses are measured on blocked lattices, using 6 different lattice discretizations of the Dirac operator. Results are compared with those of unblocked lattices, allowing for a ``ranking&#39;&#39; of the Dirac discretizations.

J. Fingberg

We investigate the effect of a non-perturbative gluon condensate on the spectrum of bound states of extremely heavy quarks using Non-Relativistic-QCD (NRQCD). Simulations are done with an improved gluon action on small lattices. We compare our numerical results with perturbative calculations to test the consistency.

Wolfgang Bock

A variety of different combinations of improved gluon and fermion actions is tested for quenched hadron spectroscopy