September 1995 arXiv papers — page 7

Richard Easther, Kei-ichi Maeda, David Wands

In this paper we examine the classical evolution of a cosmological model derived from the low-energy tree-level limit of a generic string theory. The action contains the metric, dilaton, central charge and an antisymmetric tensor field. We show that with a homogeneous and isotropic metric, allowing spatial curvature, there is a formal equivalence between thi

Shoichi Ichinose, Noriaki Ikeda

A general approach to anomaly in quantum field theory is newly formulated by use of the propagator theory in solving the heat-kernel equation. We regard the heat-kernel as a sort of the point-splitting regularization in the space(-time) manifold. Fujikawa's general standpoint that the anomalies come from the path-integral measure is taken. We obtain some

R. Chatterjee

We compute the exact partition function, the universal ground state degeneracy and boundary state of the 2-D Ising model with boundary magnetic field at off-critical temperatures. The model has a domain that exhibits states localized near the boundaries. We study this domain of boundary bound state and derive exact expressions for the ``$g$ function'&#39

Carl R. Schmidt

A high energy $e^+e^-$ linear collider (NLC) is an excellent tool for studying the properties of the top quark. In this talk I review some of the theory of top quark production and decay in $e^+e^-$ collisions both at threshold and in the continuum. I also report on the results of phenomenological analyses of $t\bar t$ production at the NLC.

M. Nielsen, L. A. Barreiro, C. O. Escobar, R. Rosenfeld

QCD sum rules are used to calculate the contribution of short-distance single-quark transition $s\rightarrow d γ$, to the amplitudes of the hyperon radiative decay, $Ω^-\rightarrow Ξ^-γ$. We re-evaluate the Wilson coefficient of the effective operator responsible for this transition. We obtain a branching ratio which is comparable to the unitarity limit.

D. J. Broadhurst, R. Delbourgo, D. Kreimer

A knot-theoretic explanation is given for the rationality of the quenched QED beta function. At the link level, the Ward identity entails cancellation of subdivergences generated by one term of the skein relation, which in turn implies cancellation of knots generated by the other term. In consequence, each bare three-loop diagram has a rational Laurent expan

S. Wallon

Considering the BFKL and DGLAP QCD evolution equations for structure functions, we discuss the possibility of unifying them in the whole $x$ and $Q^2$ range. We emphasize that the main problem is related to the constraint of angular ordering of the radiation, and the cancellation of the related collinear singularities for inclusive processes. At the leading

T. Kobayashi, S. Kitamura, T. Kon

In the framework of the minimal supersymmetric standard model and the $R$-parity breaking model, we investigate various production processes of the supersymmetric partner at HERA energies. Our emphasis is paid upon the scalar top quark, the partner of top quark, characterized by its lighter mass than the top quark and other scalar quarks in a model. We propo

D. -U. Jungnickel

Dynamical chiral symmetry breaking is described within the linear sigma model of QCD coupled to quarks. The main technical tool used for this intrinsically non--perturbative problem is an exact renormalization group equation for the quantum effective action. It is demonstrated that realistic values for phenomenological quantities like the pion decay constant

Hartmut Wittig

The status of lattice calculations for heavy quark systems is reviewed, focussing on weak matrix elements for leptonic and semi-leptonic decays of heavy mesons. After an assessment of the main systematic errors, results for the decay constants $f_D$ and $f_B$, the $B$ parameter describing $B - \bar{B}$ mixing, the Isgur-Wise function and the spectroscopy of

Dae Sung Hwang, Gwang-Hee Kim

We calculate the ratio $f_{B_s}/f_{B_d}$ by following the Oakes&#39; method which is based on chiral symmetry breaking, but we improve his calculation by performing the calculation of the factor $<0|{\bar{b}}γ_5s|B_s>$/$<0|{\bar{b}}γ_5d|B_d>$ in the mock meson model. In this calculation we improved the mock meson model by using the value of the parameter $β$

R. Narayanan, H. Neuberger, P. Vranas

The massless vector Schwinger model with $N_f=1,2,3,4$ number of flavors is studied on the lattice using the overlap formalism. A full Monte Carlo simulation yields values for the bilinear fermion condensate that are in agreement with the exact solution of the continuum Schwinger model with an added Thirring interaction.

C. Bernard, T. Blum, A. De, T. DeGrand

Results for $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$, and their ratios are presented. High statistics quenched runs at $β=5.7$, $5.85$, $6.0$, and $6.3$, plus a run still in progress at $β=6.52$ make possible a preliminary extrapolation to the continuum. The data allows good control of all systematic errors except for quenching, although not all of the error estim

A D Kennedy, Robert Edwards, Hidetoshi Mino, Brian Pendleton

We discuss the analytic computation of autocorrelation functions for the generalized Hybrid Monte Carlo algorithm applied to free field theory and compare the results with numerical results for the $O(4)$ spin model in two dimensions. We explain how the dynamical critical exponent $z$ for some operators may be reduced from two to one by tuning the amount of

Seyong Kim, Shigemi Ohta

We discuss preliminary results from our quenched light hadron mass calculation on a $48^3 \times 64$ lattice at the coupling of $β= 6.5$. Staggered quarks with masses of $m_q = 0.01, 0.005, 0.0025$ and $0.00125$ are used.

S. Gowdy

A gallium arsenide detector was tested with a beam of 70GeV pions at the {\sf SPS} at CERN. The detector utilises a novel biasing scheme which has been shown to behave as expected. The detector has a pitch of 50$μ$m and therefore an expected resolution of 14.5$μ$m. The measured resolution was approximately 14$μ$m. By using a non-linear charge division algori

J. David Brown, Donald Marolf

This work closes certain gaps in the literature on material reference systems in general relativity. It is shown that perfect fluids are a special case of DeWitt&#39;s relativistic elastic media and that the velocity--potential formalism for perfect fluids can be interpreted as describing a perfect fluid coupled to a fleet of clocks. A Hamiltonian analysis o

Frank Wilczek

After surveying the quantum kinematics and dynamics of statistical transmutation, I show how this concept suggests a phase diagram for the two-dimensional matter in a magnetic field, as a function of quantum statistics. I discuss the fundamental properties of quasiparticles in the different phases, and briefly suggest {\it gedanken\/} -- but not manifestly i

Yue-lin Shen, Mo-lin Ge

We investigate Wilczeck&#39;s mutual fractional statistical model at the field- theoretical level. The effective Hamiltonian for the particles is derived by the canonical procedure, whereas the commutators of the anyonic excitations are proved to obey the Zamolodchikov-Faddeev algebra. Cases leading to well known statistics as well as Laughlin&#39;s wave fun

Hu Cheng, Mo-lin Ge, Jiushu Shao

The dynamics of two-level systems in an external periodic field are investigated in general. The necessary conditions of localization are obtained through analysing the time-evolving matrix. It is found that localization is possible if not only is the dynamics of the system periodic, but also its period is the same as that of the external potential. A model

Mo-lin Ge, Y. W. Wang, K. Xue

Based on the RTT relation for a given rational $R$-matrix the {\em Yangian} and truncated {\em Yangian} are discussed. The former can be used to generate the long-range interaction models, whereas the latter can be related to the Goryachev-Chaplygin(GC) gyrostat. The trigonometric extension of the Goryachev-Chaplygin gyrostat has also been shown.

Mo-lin Ge, Yiwen Wang

The generalized Sutherland-Romer models and Yan models with internal spin degrees are formulated in terms of the Polychronakos&#39; approach and RTT relation associated to the Yang-Baxter equation in consistent way. The Yangian symmetry is shown to generate both models. We finally introduce the reflection algebra K(u) to the long range models.

Attila Szolnoki, Gyorgy Szabo

We consider a two-dimensional lattice gas model with repulsive nearest- and next-nearest-neighbor interactions that evolves in time according to anisotropic Kawasaki dynamics. The hopping of particles along the principal directions is governed by heat baths at different temperatures. The stationary states of this non-equilibrium model are studied using a gen

Jordi Miralda-Escude

This paper is intended as an introduction to the theory of weak lensing. A review of the inversion formula introduced by Kaiser and Squires is presented. We then prove the formula of the aperture densitometry method in a simple way that allows a clear understanding of where the various terms come from. This is particularly useful to quantitatively measure ma

J. H. Knapen, J. E. Beckman, J. Cepa, N. Nakai

We present new J=1-0 12-CO observations along the northern spiral arm of the grand-design spiral galaxy M100 (NGC 4321), and study the distribution of molecular hydrogen as derived from these observations, comparing the new data with a set of data points on the southern arm published previously. We compare these measurements on both spiral arms and on the in

Andrew A. de Laix, Rober J. Scherrer

We examine Gaussian isocurvature hot dark matter (massive neutrino) models for large-scale structure in which the initial density perturbations are produced in the baryons with a power--law spectrum $P_B(k) = Ak^{n_B}$. We calculate the linearly-evolved power spectrum and cosmic microwave fluctuations. We find that models with only isocurvature perturbations

Edward L. Wright

Calculations of the rate of local Primordial Black Hole explosions often assume that the PBH&#39;s can be highly concentrated into galaxies, thereby weakening the Page-Hawking limit on the cosmological density of PBH&#39;s. But if the PBH&#39;s are concentrated by a factor exceeding $c/(H_\circ R_\circ) \approx 4 \times 10^5$, where $R_\circ = 8.5$ kpc is th

K. K. McLeod, G. H. Rieke

Some recent observations of nearby quasars with HST have apparently failed to detect host galaxies. We review the HST observations as well as near infrared ground-based observations of the same objects. We find that the quasar hosts can be detected in the HST data if they are smoothed sufficiently to reveal low surface brightness. The smooth hosts are very d

Fabien Malbet

Recent adaptive optics systems in astronomy achieve high-angular resolution. With the extreme stability of the images, detection at very low fluxes can be reached using a coronograph at the diffraction limit of the telescopes. This paper is an overview of the issues of stellar coronography used at the diffraction limit. Image formation through such a system

Xiangdong Ji

This paper has been withdrawn by the author.

S. Carlip

I review a new (and still tentative) approach to black hole thermodynamics that seeks to explain black hole entropy in terms of microscopic quantum gravitational boundary states induced on the black hole horizon.

C. Bachas

I discuss the breaking of space-time supersymmetry when magnetic monopole fields are switched on in compact dimensions.

E. Gotsman, E. Levin, U. Maor

The formulae for shadowing corrections in deep inelastic leptoproduction of vector mesons are presented. These formulae are also applicable for photoproduction of vector mesons constituted of heavy quarks. Our results are conveniently presented by the definition of a damping factor giving the reduction of the calculated cross sections due to shadowing. Our c

Hyun-Chul Kim, Maxim V. Polyakov, Klaus Goeke

We investigate the singlet $g_T^{(0)}$ and isovector $g_T^{(3)}$ tensor charges of the nucleon, which are deeply related to the first moment of the leading twist transversity quark distribution $h_1(x)$, in the SU(2) chiral quark-soliton model. With rotational $O(1/N_c)$ corrections taken into account, we obtain $g_T^{(0)}=0.69$ and $g_T^{(3)}=1.45$ at a low

E. Maina, M. Pizzio

QCD corrections to $e^+e^- \ra WW \ra q_1 \bar q_1 q_2 \bar q_2$ are computed and presented in a form which allows to impose realistic cuts on the structure of the observed events. QCD radiation substantially modifies the jet--jet invariant mass distributions from which the value of the $W$ mass will be extracted. When the range of allowed jet--jet masses is

George Kastrinakis

At low temperature and for finite spin scattering in a weakly disordered metal, for a certain value, predicted from our theory, of the material-dependent paramagnon interaction, the total conductivity becomes highly sensitive to the orbital effects of a finite magnetic field. As a consequence, positive giant magnetoresistance and giant corrections to the Hal

P. G. Grinevich

In our paper we construct a new infinite family of symmetries of the Whitham equations (averaged Korteveg-de-Vries equation). In contrast with the ordinary hydrodynamic-type flows these symmetries are nonhomogeneous (i.e. they act nontrivially at the constant solutions), are nonlocal, explicitly depend upon space and time coordinates and form a noncommutativ

Boucif Abdesselam

We show how to adapt the Gelfand-Zetlin basis for describing the atypical representation of ${\cal U}_{\displaystyle{q}}(sl(N))$ when $q$ is root of unity. The explicit construction of atypical representation is presented in details for $N=3$.

Tomasz Brzezinski

We show that certain embeddable homogeneous spaces of a quantum group that do not correspond to a quantum subgroup still have the structure of quantum quotient spaces. We propose a construction of quantum fibre bundles on such spaces. The quantum plane and the general quantum two-spheres are discussed in detail.

J. Schnack, H. Feldmeier

Statistical properties of Fermionic Molecular Dynamics are studied. It is shown that, although the centroids of the single--particle wave--packets follow classical trajectories in the case of a harmonic oscillator potential, the equilibrium properties of the system are the quantum mechanical ones. A system of weakly interacting fermions as well as of disting

S. Bellucci, S. Krivonos, A. Sorin

We consider the nonlinear algebras $W(sl(4),sl(3))$ and $W(sl(3|1),sl(3))$ and find their realizations in terms of currents spanning conformal linearizing algebras. The specific structure of these algebras, allows us to construct realizations modulo null fields of the $W_3$ algebra that lies in the cosets $W(sl(4),sl(3))/u(1)$ and $W(sl(3|1),sl(3))/u(1)$. Su

Dmitri V. Vassilevich

We prove gauge-independence of one-loop path integral for on-shell quantum gravity obtained in a framework of modified geometric approach. We use projector on pure gauge directions constructed via quadratic form of the action. This enables us to formulate the proof entirely in terms of determinants of non-degenerate elliptic operators without reference to an

C. Muñoz

We study the structure of the soft SUSY-breaking terms obtained from large classes of 4-D Strings under the assumption of dilaton/moduli dominance in the process of SUSY-breaking. In particular, we first analyze in detail the dilaton-dominated limit because of its finiteness properties and phenomenological predictivity, and second, we consider the new featur

D. A. Jenkins, I. I. Strakovsky

Pion-photoproduction data is examined to check for the nucleon-helicity conservation predicted by asymptotic QCD. The differential cross section shows agreement with constituent-counting rules, and polarization data is not in disagreement with conservation of nucleon helicity. However large uncertainties in the polarization measurements do not allow a conclu

K. J. Eskola, B. Müller, Xin-Nian Wang

Screening of initial parton production due to the presence of on-shell partons in high-energy heavy-ion collisions is discussed. It is shown that the divergent cross sections in the calculation of parton production can be regulated self-consistently without an {\it ad hoc} cut-off, and that the resultant parton production and transverse energy production rat

V. Keiner

We present a simple covariant constituent diquark-quark model for the nucleon. The nucleon is assumed to be composed of a scalar diquark and a quark which interact via a quark exchange. Starting from the Bethe-Salpeter equation, the instantaneous approximation leads to a diquark-quark Salpeter equation. In the Mandelstam formalism, the electromagnetic form f

Kurt Langfeld

We study an extended Gross-Neveu model with $N_f$ quark flavors and with an additional SU(2) (global color) degree of freedom of the quarks. The four fermion interaction in the color channel is mediated by a random color matrix with fixed strength. The effective potential for the quark condensate and the scalar correlation function is investigated in the lar

E. Focht, J. Jersak, J. Paul

The 3D Yukawa model with U(1) chiral symmetry is investigated in a broad interval of parameters using the Binder method. Critical exponents of the Wilson-Fisher (magnetic) and Gross-Neveu (chiral) universality classes are measured. The model is dominated by the chiral universality class. However at weak coupling we observe a crossover between both classes, m

V. Azcoiti, G. Di Carlo, A. Galante, A. F. Grillo

We present a detailed analysis, in the framework of the MFA approach, of the critical behaviour of the lattice Schwinger model with Wilson fermions on lattices up to $24^2$, through the study of the Lee-Yang zeros and the specific heat. We find compelling evidence for a critical line ending at $κ= 0.25$ at large $β$. Finite size scaling analysis on lattices

W. Franzki, J. Jersák

We investigate the tricritical point in the lattice fermion--gauge--scalar model with U(1) gauge symmetry. In the vicinity of this point, in the phase with the broken chiral symmetry, we observe the scaling behavior of the chiral condensate and of the masses of composite fermion and composite scalar, indicating the existence of an interesting continuum limit

V. Azcoiti, G. Di Carlo, A. Galante, A. F. Grillo

We measure chiral susceptibilities in the Coulomb phase of noncompact QED$_4$ in $8^4, 10^4$ and $12^4$ lattices. The MFA approach allows simulations in the chiral limit which are therefore free from arbitrary mass extrapolations. Using the critical couplings extracted from these calculations, we study the critical behaviour of the chiral condensate, which w

A. Di Giacomo

We review recent results from lattice on topological aspects of QCD: most of the results refer to monopoles and to instantons. We discuss in detail the evidence for condensation of monopoles in the vacuum and confinement of colour by dual superconductivity, and the major role of monopoles in dynamics (monopole dominance). As for instantons we review the $U(1

C. Christou, A. Di Giacomo, H. Panagopoulos, E. Vicari

We analyze the properties of a class of improved lattice topological charge density operators, constructed by a smearing-like procedure. By optimizing the choice of the parameters introduced in their definition, we find operators having (i) a much better statistical behavior as estimators of the topological charge density on the lattice, i.e. much less noisy

F. X. Lee, R. M. Woloshyn, H. D. Trottier

Calculations of the chiral condensate on the lattice using staggered fermions and the Lanczos algorithm are presented. Four gauge fields are considered: the quenched non-Abelian field, an Abelian projected field, and monopole and photon fields further decomposed from the Abelian field. Abelian projection is performed in maximal Abelian gauge and in Polyakov

Guenter Baum

An overview of the SMC data taking and the polarized deep inelastic scattering experiment is given. The new data on the deuteron extend the kinematic range and have considerably reduced statistical and systematic errors. The evaluation of the first moment of the spin dependent structure function is presented and the result for the Bjorken sum rule from SMC d

Kevin Leung, Reinhold Egger, C. H. Mak

Transport of single-channel spinless interacting fermions (Luttinger liquid) through a barrier has been studied by numerically exact quantum Monte Carlo methods. A novel stochastic integration over the real-time paths allows for direct computation of nonequilibrium conductance and noise properties. We have examined the low-temperature scaling of the conducta

Rajiv R. P. Singh, Martin P. Gelfand

Using a recently developed method for calculating series expansions of the excitation spectra of quantum lattice models, we obtain the spin-wave spectra for square lattice, $S=1/2$ Heisenberg-Ising antiferromagnets. The calculated spin-wave spectrum for the Heisenberg model is close to but noticeably different from a uniformly renormalized classical (large-$

G. M. Buendia, M. A. Novotny

We present a study of a classical ferrimagnetic model on a square lattice in which the two interpenetrating square sublattices have spins one-half and one. This model is relevant for understanding bimetallic molecular ferrimagnets that are currently being synthesized by several experimental groups. We perform exact ground-state calculations for the model and

Kai Nagel

This paper shows how particle hopping models fit into the context of traffic flow theory. Connections between fluid-dynamical traffic flow models, which derive from the Navier-Stokes-equations, and particle hopping models are shown. In some cases, these connections are exact and have long been established, but have never been viewed in the context of traffic

Yu Shi

Some conceptual issues in the semi-classical approaches to giant magnetoresistance in magnetic multilayers are discussed.

Robert M. Losee

Academic disciplines, often divided into hard and soft sciences, may be understood as &#34;donor disciplines&#34; if they produce more concepts than they borrow from other disciplines, or &#34;borrower disciplines&#34; if they import more than they originate. Terms used to describe these concepts can be used to distinguish between hard and soft, donor and bo

G. J. Chaitin

The latest in a series of reports presenting the information-theoretic incompleteness theorems of algorithmic information theory via algorithms written in specially designed versions of LISP. Previously in this LISP code only one-character identifiers were allowed, and arithmetic had to be programmed out. Now identifiers can be many characters long, and arit

Douglas M. Kelly, John H. Lacy

We present accurate new wavenumbers for a set of 13 mid-infrared fine-structure lines. The wavenumbers were determined from observations of the planetary nebula NGC 7027 and of the red supergiant Alpha Scorpii. Most of the new wavenumbers are good to within 0.0025%, or 8 km/s. We provide details on the measurements and present an analysis of the errors. In a

Igor V. Igumenshchev, Xingming Chen, Marek A. Abramowicz

Two-dimensional accretion flows near black holes have been investigated by time-dependent hydrodynamical calculations. We assume that the flow is axisymmetric and that radiative losses of internal energy are negligible, so that the disc is geometrically thick and hot. Accretion occurs due to the overflow of the effective potential barrier near the black hole

C. M. Baugh

We test the hypothesis that elliptical galaxies are formed by violent mergers in a universe with hierarchical structure formation. Within the framework of a semi-analytic scheme for galaxy formation, we predict the distribution of morphological types with redshift and compare the colours of elliptical galaxies in different environments.

S. P. Ellingsen, R. P. Norris, P. M. McCulloch

We have used the Australia Telescope Compact Array (ATCA) to search for continuum emission toward three strong 6.7-GHz methanol maser sources. For two of the sources, G339.88-1.26 and NGC 6334F (G351.42+0.64), we detect continuum emission closely associated with the methanol masers. A further three clusters of masers showed no radio continuum emission above

R. L. Jaffe

We study the operator description of the gluon spin contribution ($Γ$) to the nucleon&#39;s spin as it is measured in deep inelastic processes. $Γ$ can be related to the forward matrix element of a local gluon operator in $A^+=0$ gauge. In quark models the nucleon contains ambient color electric and magnetic fields. The latter are thought to be responsible f

Florian Nill, Kornel Szlachanyi

Given a finite dimensional C^*-Hopf algebra H and its dual H^ we construct the infinite crossed product A=... x H x H^ x H ... and study its superselection sectors in the framework of algebraic quantum field theory. A is the observable algebra of a generalized quantum spin chain with H-order and H^-disorder symmetries, where by a duality transformation the r

T. R. Kirkpatrick, D. Belitz

The stability of antiferromagnetic long-range order against quenched disorder is considered. A simple model of an antiferromagnet with a spatially varying Neel temperature is shown to possess a nontrivial fixed point corresponding to long-range order that is stable unless either the order parameter or the spatial dimensionality exceeds a critical value. The

M. Crisafulli, A. Donini, V. Lubicz, G. Martinelli F. Rapuano

We present results for the kaon $B$-parameter $B_K$ from a sample of $200$ configurations using the Wilson action and $460$ configurations using the SW-Clover action, on a $18^3 \times 64$ lattice at $β=6.0$. We compare results obtained by renormalizing the relevant operator with different ``boosted&#34; values of the strong coupling constant $α_s$. In the c

Cecile Monthus, Chistophe Texier

We give the exact solution to the problem of a random walk on the Bethe lattice through a mapping on an asymmetric random walk on the half-line. We also study the continuous limit of this model, and discuss in detail the relation between the random walk on the Bethe lattice and Brownian motion on a space of constant negative curvature.

H. -J. He, Y. -P. Kuang, C. -P. Yuan

We formulate the equivalence theorem as a theoretical criterion for sensitively probing the electroweak symmetry breaking mechanism, and develop a precise power counting method for the chiral Lagrangian formulated electroweak theories. Armed with these, we perform a systematic analysis on the sensitivities of the scattering processes $W^\pm W^\pm \rightarrow

Hal Tasaki

We present the first rigorous examples of non-singular Hubbard models which exhibit ferromagnetism at zero temperature. The models are defined in arbitrary dimensions, and are characterized by finite-ranged hoppings, dispersive bands, and finite on-site Coulomb interaction U. The picture, which goes back to Heisenberg, that sufficiently large Coulomb interac

H. Kleinert, W. Janke

Variational perturbation expansions have recently been used to calculate directly the strong-coupling expansion coefficients of the anharmonic oscillator. The convergence is exponentially fast with superimposed oscillations, as recently observed empirically by the authors. In this note, the observed behavior is explained and used to determine accurately the

B. M. Zupnik

A noncommutative algebra of the complex $q$-twistors and their differentials is considered on the basis of the quantum $GL_q (4)\times SL_q (2)$ group. Real and pseudoreal $q$-twistors are discussed too. We consider the quantum-group self-duality equation in the framework of the local gauge algebra of differential forms on $q$-twistor spaces. Quantum deforma

N. Soic, S. Blagus, M. Bogovac, S. Fazinic

In a kinematically complete measurement of the $^{7}$Li($^{7}$Li,$α$$^{6}$He)$^4$He reaction at $E_{i}$ = 8 MeV it was observed that the $^{10}$Be excited states at 9.6 and 10.2 MeV decay by $^{6}$He emission. The state at 10.2 MeV may be a member of a rotational band based on the 6.18 MeV 0$^+$ state.

John McCuan

We consider embedded ring-type surfaces (that is, compact, connected, orientable surfaces with two boundary components and Euler-Poincaré characteristic zero) in ${\bold R}^3$ of constant mean curvature which meet planes $Π_1$ and $Π_2$ in constant contact angles $γ_1$ and $γ_2$ and bound, together with those planes, an open set in ${\bold R}^3$. If the plan

Winfried Just, Arnold W. Miller, Marion Scheepers, Paul J. Szeptycki

We continue to investigate various diagonalization properties for sequences of open covers of separable metrizable spaces introduced in Part I. These properties generalize classical ones of Rothberger, Menger, Hurewicz, and Gerlits-Nagy. In particular, we show that most of the properties introduced in Part I are indeed distinct. We characterize two of the ne

Arnold W. Miller, Juris Steprāns

For x and y sequences of real numbers define the inner product (x,y) = x(0)y(0) + x(1)y(1)+ ... which may not be finite or even exist. We say that x and y are orthogonal iff (x,y) converges and equals 0. Define l_p to be the set of all real sequences x such that |x(0)|^p + |x(1)|^p + .. converges. For Hilbert space, l_2, any family of pairwise orthogonal seq

K. Intriligator, N. Seiberg

We review some of the recent work on the dynamics of four dimensional, supersymmetric gauge theories. The kinematics are largely determined by holomorphy and the dynamics are governed by duality. The results shed light on the phases of gauge theories. Some results and interpretations which have not been published before are also included.

Ilya L. Shapiro

The main part of this presentation is a review of the previous original works on the perturbative covariant approach to the $2$-dimensional quantum gravity. We discuss the renormalization of the two-dimensional dilaton gravity in a harmonic gauge, the form of the quantum corrections to the classical potential, and the conditions of Weyl invariance in a theor

S. Naftulin, S. D. Odintsov

We discuss lowering the order of the two-dimensional scalar-tensor $R^2$ quantum gravity, by mapping the most general version of the model to a multi-dilaton gravity, which is essentially the sigma-model coupled with Jackiw-Teitelboim-like gravity. In the continuation of our previous research, we calculate the divergent part of the one-loop effective action

T. N. Tomaras

We report on the status of our search for quasi-topological solitons of various dimensions in realistic field theoretical models of condensed matter and of elementary particle physics.

S. M. Kuzenko, S. L. Lyakhovich, A. Yu. Segal, A. A. Sharapov

To describe a massive particle with fixed, but arbitrary, spin on $d=4$ anti-de Sitter space $M^4$, we propose the point-particle model with configuration space ${\cal M}^6 = M^{4}\times S^{2}$, where the sphere $S^2$ corresponds to the spin degrees of freedom. The model possesses two gauge symmetries expressing strong conservation of the phase-space counter

A. A. Natale

We estimate the cross-section for glueball production in peripheral heavy-ion collisions through two-photon and double-Pomeron exchange, at energies that will be available at RHIC and LHC. Glueballs will be produced at large rates, opening the possibility to study decays with very small branching ratios. In particular, we discuss the possibility of observing

G. C. Cho, Y. Kizukuri, N. Oshimo

We discuss the constraints on the mass of the lighter top squark from \bbbar\ mixing in the minimal supersymmetric standard model. A light top squark whose mass is less than half of the $Z^0$-boson mass has not yet been excluded from direct search experiments at LEP. However, the existence of the light top squark may exceedingly enhance \bbbar\ mixing, owing

J. A. Gracey

The large N_f self consistency method is applied to the computation of perturbative information in the operator product expansion used in deep inelastic scattering. The O(1/N_f) critical exponents corresponding to the anomalous dimensions of the twist 2 non-singlet and singlet operators are computed analytically as well as the non-singlet structure functions

Alexander Kusenko

A metastable state, or a false vacuum, is not an eigenstate of the Hamiltonian in quantum field theory. Its energy density has a non-zero imaginary part equal to its decay width. Therefore, supersymmetry cannot be exact in the false vacuum. We calculate the size of this effect using the path integral approach.

Massimo Campostrini, Attilio Cucchieri, Tereza Mendes, Andrea Pelissetto

In this talk we present the exact solution of the most general one-dimensional $O(N)$-invariant spin model taking values in the sphere $S^{N-1}$, with nearest-neighbour interactions, and we discuss the possible continuum limits. All these results are obtained using a high-temperature expansion in terms of hyperspherical harmonics. Applications in higher dime

Sergio Caracciolo, Robert G. Edwards, Tereza Mendes, Andrea Pelissetto

We have computed the four-loop contribution to the beta-function and to the anomalous dimension of the field for the two-dimensional lattice $N$-vector model. This allows the determination of the second perturbative correction to various long-distance quantities like the correlation lengths and the susceptibilities. We compare these predictions with new Mont

Alan D. Sokal

This article is a pedagogical review of Monte Carlo methods for the self-avoiding walk, with emphasis on the extraordinarily efficient algorithms developed over the past decade. Many more details can be found in hep-lat/9405016.

Jesús Salas, Alan D. Sokal

We study the dynamic critical behavior of a Swendsen--Wang--type algorithm for the Ashkin--Teller model. We find that the Li--Sokal bound on the autocorrelation time ($τ_{{\rm int},{\cal E}} \ge {\rm const} \times C_H$) holds along the self-dual curve of the symmetric Ashkin--Teller model, but this bound is apparently not sharp. The ratio $τ_{{\rm int},{\cal

Gustavo Mana, Tereza Mendes, Andrea Pelissetto, Alan D. Sokal

We introduce a new and very convenient approach to multi-grid Monte Carlo (MGMC) algorithms for general nonlinear $σ$-models: it is based on embedding an $XY$ model into the given $σ$-model, and then updating the induced $XY$ model using a standard $XY$-model MGMC code. We study the dynamic critical behavior of this algorithm for the two-dimensional $O(N)$ $

Maarten Golterman, Yigal Shamir

We describe a conceptually simple, but important test for the overlap approach to the construction of lattice chiral gauge theories. We explain the equivalence of the overlap formula with a certain waveguide model for a simple set of gauge configurations (the trivial orbit). This equivalence is helpful in carrying out the test, and casts serious doubts on th

Massimo Campostrini, Paolo Rossi, Ettore Vicari

We consider a definition of the QCD running coupling constant $α(μ)$ related to Wilson loops of size $r{\times}t$ with arbitrary fixed $t/r$. The schemes defined by these couplings are very close to the $\overline{\rm MS}$ scheme for all values of $t/r$; in the $t/r\to\infty$ limit, the ``$q\bar q$ force&#39;&#39; scheme is recovered. We propose a definition

Massimo Campostrini, Andrea Pelissetto, Paolo Rossi, Ettore Vicari

We report progress in the computation and analysis of strong-coupling series of two- and three-dimensional ${\rm O}(N)$ $σ$ models. We show that, through a combination of long strong-coupling series and judicious choice of observables, one can compute continuum quantities reliably and with a precision at least comparable with the best available Monte Carlo d

W. Kerler, C. Rebbi, A. Weber

We show that the two phases of the 4-dimensional compact U(1) lattice gauge theory are characterized by the existence or absence of an infinite current network, defining ``infinite&#39;&#39; on a finite lattice in a manner appropriate to the chosen boundary conditions. In addition for open and fixed boundary conditions we demonstrate the effects of inhomogen

Yigal Shamir

I review the ongoing attempts to define chiral gauge theories using the lattice regularization.

Patricia McBride, Sheldon Stone

The decay mode $B_s\toψ\overline{K}^*$ is suggested as a very good way to measure the $B_s$ mixing parameter $x_s$. These decays can be gathered using a $ψ\to\ell^+\ell^-$ trigger. This final state has a well resolved four track decay vertex, useful for good time resolution and background rejection.

S. Abachi

The global topologies of inclusive three-- and four--jet events produced in $\pp$ interactions are described. The three-- and four--jet events are selected from data recorded by the DØdetector at the Tevatron Collider operating at a center--of--mass energy of $\sqrt{s} = 1800$ GeV. The measured, normalized distributions of various topological variables are c