May 1996 arXiv papers — page 10

Yuri G. Prokhorov

We prove that the linear system $|-1/3K_X| on a non-singular Fano fivefold $X$ of index 3 contains an irreducible divisor with only canonical singularities.

Michael Birkel, Subir Sarkar

We constrain proposed phenomenological models for a vacuum energy which decays with the expansion of the universe from considerations of standard big bang nucleosynthesis. Several such models which attempt to solve the cosmological age problem are disfavored or even ruled out.

I. Dasgupta, A. R. Levi, V. Lubicz, C. Rebbi

We present a complete set of Fortran 90 modules that can be used to write very compact, efficient, and high level QCD programs. The modules define fields (gauge, fermi, generators, complex, and real fields) as abstract data types, together with simpler objects such as SU(3) matrices or color vectors. Overloaded operators are then defined to perform all possi

Li Hua Yu

Applying a technique developed recently [1,2] for an harmonic oscillator coupled to a bath of harmonic oscillators, we present an exact solution for the tunneling problem in an Ohmic dissipative system with inverted harmonic potential. The result shows that while the dissipation tends to suppress the tunneling, the Brownian motion tends to enhance the tunnel

A. E. Koshelev

We relate the frequency of the plasma resonance in layered superconductors with the frequency dependent superconducting response along the c-direction. We demonstrate that the sharp resonance can persist even when the global superconducting coherence in this direction is absent provided the resonance frequency is larger than the typical frequency of interlay

B. Abdesselam, D. Arnaudon, M. Bauer

Quantum groups at roots of unity have the property that their centre is enlarged. Polynomial equations relate the standard deformed Casimir operators and the new central elements. These relations are important from a physical point of view since they correspond to relations among quantum expectation values of observables that have to be satisfied on all phys

Franco Bagnoli, Paolo Palmerini, Raul Rechtman

Probabilistic cellular automata are prototypes of non equilibrium critical phenomena. This class of models includes among others the directed percolation problem (Domany Kinzel model) and the dynamical Ising model. The critical properties of these models are usually obtained by fine-tuning one or more control parameters, as for instance the temperature. We p

Robert de Mello Koch, João P. Rodrigues

In this paper, colorless bilocal fields are employed to study the large $N$ limit of both fermionic and bosonic vector models. The Jacobian associated with the change of variables from the original fields to the bilocals is computed exactly, thereby providing an exact effective action. This effective action is shown to reproduce the familiar perturbative exp

János Pach, Joel Spencer

Let $d_1\leq d_2\leq\ldots\leq d_{n\choose 2}$ denote the distances determined by $n$ points in the plane. It is shown that $\min\sum_i (d_{i+1}-d_i)^2=O(n^{-6/7})$, where the minimum is taken over all point sets with minimal distance $d_1 \geq 1$. This bound is asymptotically tight.

Chaz Schlindwein

Shelah shows that certain revised countable support (RCS) iterations do not add reals. His motivation is to establish the independence (relative to large cardinals) of Avraham's problem on the existence of uncountable non-constuctible sequences all of whose proper initial segments are constructible, Friedman's problem on whether every 2-coloring of $

Subir Ghosh

The possibility of composite systems arising out of a point charge interacting with a Nielsen-Olesen vortex in 2+1-dimensions is investigated. It is shown that classical bounded orbits are possible for certain ranges of parameters. Long lived metastable states are shown to exist, in a semi-classical approach, from the study of the effective potential. Loss o

Dan Radu Grigore

We provide a new proof of a important theorem in the Lagrangian formalism about necessary and sufficient conditions for a second-order variational system of equations to follow from a first-order Lagrangian.

Jose D. Edelstein, Carlos Nunez

We study the connection between $N=2$ supersymmetry and a topological bound in a two-Higgs-doublet system with an $SU(2)\times U(1)_Y\times U(1)_{Y^{\prime}}$ gauge group. We derive the Bogomol'nyi equations from supersymmetry considerations showing that they hold provided certain conditions on the coupling constants, which are a consequence of the huge

T. Barnes, T. E. Browder, S. F. Tuan

We argue that an experimental search for an $η_c'$, the first radial excitation of the $η_c(2980)$, may be carried out using the two photon process $e^+e^- \to e^+e^- γγ\ra e^+e^-η_c'$. We estimate the partial width $Γ_{γγ}(η_c')$ and the branching fraction $B(η_c' \to h)$, where $h$ is an exclusive hadronic channel, and find that for $h = K^

N. D. Antunes, L. M. A. Bettencourt

We study the full out-of-thermal-equilibrium dynamics of a relativistic classical scalar field through a symmetry breaking phase transition. In these circumstances we determine the evolution of the ensemble averages of the correlation length and topological defect densities. This clarifies many aspects of the non-perturbative dynamics of fields in symmetry b

A. DeRoeck, M. Klein, Th. Naumann

We discuss how the proton structure function F2 is described in the HERA kinematic range by double asymptotic expressions for low x and large Q^2. From a NLO double asymptotic approximation of recent data from the H1 experiment at HERA we extract the strong coupling constant alpha_S(M^2_Z)=0.113+/-0.002(stat)+/-0.007(syst). The additional theoretical error c

L. E. Gordon, J. K. Storrow

We calculate the cross section for inclusive prompt photon production in $γγ$ collisions, i.e. the reaction $e^+e^-\to γγ\to γX$, in next-to-leading order QCD. We show that at LEP2 energies this cross section is measurable and is sensitive to the gluon distribution of the photon, $g^γ$, which is currently very poorly constrained by data.

Maria Girone, Matthias Neubert

The decay rate of the $τ$ lepton into hadrons of invariant mass smaller than $Q\ggΛ_{\rm QCD}$ can be calculated in QCD using the OPE. Using experimental data on the hadronic mass distribution, the running coupling constant $α_s(Q^2)$ is extracted in the range $0.85~\mbox{GeV}<Q<m_τ$, where its value changes by about a factor~2. At $Q=m_τ$, the result is $α_

G. L. Fogli, E. Lisi, D. Montanino

We present a systematic analysis of the three-flavor Mikheyev-Smirnov-Wolfenstein (MSW) oscillation solutions to the solar neutrino problem, in the hypothesis that the two independent neutrino square mass differences, $δm^2$ and $m^2$, are well separated: $δm^2 \ll m^2$. At zeroth order in $δm^2/m^2$, the relevant variables for solar neutrinos are $δm^2$ and

Dimitris Kominis

In Topcolor theories the mass of the top quark is generated dynamically by new strong interactions coupling to the third generation fermions. This leads to potentially observable effects in flavor-changing neutral current processes involving heavy flavored mesons, as well as in the production of heavy quarks at high-energy colliders. Recent theoretical devel

A. D. Martin

We review the latest information that is available about the parton distributions of the proton, paying particular attention to the determination of the gluon. We briefly describe the various processes that have been advocated to be a measure of the gluon. We discuss the importance of the gluon to the description of the structure function F2 at small x, with

S. Frixione, M. L. Mangano

We present a next-to-leading order QCD calculation of the production rates of jets containing heavy quarks. This calculation is performed using the standard Snowmass jet algorithm; it therefore allows a comparison with similar results known at next-to-leading order for generic jets. As an application, we present results for the inclusive transverse energy of

H. L. Lai, W. K. Tung

The recently reported CDF and D0 inclusive jet cross-sections are compared, using a uniform theoretical NLO QCD calculation to account for the different kinematic coverages of the pseudo-rapidity variable in the two experiments. The two data sets are found to be in good agreement. With a 2-3\% relative overall normalization adjustment, the data sets appear t

Andreas Jaster

Some time ago Kaplan proposed a new model for the description of chiral fermions on the lattice by adding an extra dimension for the fermions. A variant of this proposal was introduced by Shamir and can be used to describe vector-like theories in even dimensions. We used this model for the simulation of the massive Schwinger model at different gauge coupling

A. Donini, M. Guagnelli

We present the first results obtained with a Hybrid Molecular Dynamics algorithm applied to an $N=1$ SU(2) Super-Yang--Mills on the lattice. We derive the Hamilton equations of motion for the system with Wilson gluinos and present preliminary results on small lattices.

Alan D. Rendall

It is shown that in a class of maximal globally hyperbolic spacetimes admitting two local Killing vectors, the past (defined with respect to an appropriate time orientation) of any compact constant mean curvature hypersurface can be covered by a foliation of compact constant mean curvature hypersurfaces. Moreover, the mean curvature of the leaves of this fol

Razvan Gelca

The results in the paper are related to the classification problem for invariant subspaces of multiplication operators in several variables. The main results consist of characterizations, in the two dimensional case, of ideals of polynomials and analytic functions which are closed in the relative topology induced by Bergman spaces on certain domains. This pr

M. Greven, R. J. Birgeneau, U. -J. Wiese

We study antiferromagnetic spin--1/2 Heisenberg ladders, comprised of $n_c$ chains ($2 \leq n_c \leq 6$) with ratio $J_{\bot}/J_{\|}$ of inter-- to intra--chain couplings. From measurements of the correlation function we deduce the correlation length $ξ(T)$. For even $n_c$, the static structure factor exhibits a peak at a temperature below the corresponding

Y Chen, S M Manning

In this paper we revisit the smallest-eigenvalue distribution of the Laguerre ensembles by presenting in closed form certain integrals obtained previously. With this information we compute, using Dyson&#39;s continuum approximation, the two-smallest-eigenvalue distribution of the Laguerre ensemble. High-order contributions to the free energies describing the

Beate Paulus, Peter Fulde, Hermann Stoll

Cohesive energies for twelve cubic III-V semiconductors with zincblende structure have been determined using an ab-initio scheme. Correlation contributions, in particular, have been evaluated using the coupled-cluster approach with single and double excitations (CCSD). This was done by means of increments obtained for localized bond orbitals and for pairs an

G. Zarand L. Udvardi

The effect of local density of states (LDOS) fluctuations on the dynamics of a Kondo impurities in a small metallic point contact (PC) is studied. To estimate the spatial and energy dependent LDOS fluctuations we investigate a model PC by means of a transfer matrix formalism. For small PC&#39;s in the nanometer scale we find that near to the orifice strong L

Tobias Brandes, Bodo Huckestein, Ludwig Schweitzer

We investigate the dynamics of electrons in the vicinity of the Anderson transition in $d=3$ dimensions. Using the exact eigenstates from a numerical diagonalization, a number of quantities related to the critical behavior of the diffusion function are obtained. The relation $η= d-D_{2}$ between the correlation dimension $D_{2}$ of the multifractal eigenstat

Fred Popowich

A generation algorithm based on an active chart parsing algorithm is introduced which can be used in conjunction with a Shake and Bake machine translation system. A concise Prolog implementation of the algorithm is provided, and some performance comparisons with a shift-reduce based algorithm are given which show the chart generator is much more efficient fo

Jochen Doerre

We study the computational complexity of the parsing problem of a variant of Lambek Categorial Grammar that we call {\em semidirectional}. In semidirectional Lambek calculus $\SDL$ there is an additional non-directional abstraction rule allowing the formula abstracted over to appear anywhere in the premise sequent&#39;s left-hand side, thus permitting non-pe

Manny Rayner, David Carter, Pierrette Bouillon

We describe how substantial domain-independent language-processing systems for French and Spanish were quickly developed by manually adapting an existing English-language system, the SRI Core Language Engine. We explain the adaptation process in detail, and argue that it provides a fairly general recipe for converting a grammar-based system for English into

Sujan K. Dhar, Anirban Sain, Rahul Pandit

We propose and verify a wave-vector-space version of generalized extended self similarity and broaden its applicability to uncover intriguing, universal scaling in the far dissipation range by computing high-order ($\leq 20\/$) structure functions numerically for: (1) the three-dimensional, incompressible Navier Stokes equation (with and without hyperviscosi

S. Alexiou

In this work we study in detail the NeVII 2s3p-2s3s singlet line, which was also the object of a recent experiment. The standard perturbative impact theory predictions are tested against a fully non-perturbative semiclassical impact calculation, taking into account dipole and quadrupole interactions. Potentially very significant problems with the standard pe

S. Alexiou

The modern era in spectral line broadening began with the understanding that the slow(quasistatic) ion and fast(impact) electron perturbers could be treated separately. The problem remained of unifying these two theoretical limits. A scheme for this unification is presented here that has at its foundation a fundamental observation that is supported by analyt

D. J. Fixsen, E. S. Cheng, J. M. Gales, J. C. Mather

We have refined the analysis of the data from the FIRAS (Far InfraRed Absolute Spectrophotometer) on board the COBE (COsmic Background Explorer). The FIRAS measures the difference between the cosmic microwave background and a precise blackbody spectrum. We find new tighter upper limits on general deviations from a blackbody spectrum. The RMS deviations are l

Francesco Sylos Labini, Luciano Pietronero

We discuss how luminosity and space distribution of galaxies are naturally linked in view of their multifractal properties. In particular we show that the mass (luminosity) function corresponding to a multifractal distribution in a given observed volume, consists of a power law followed by an exponential cut-off. This implies that the amplitude $ϕ^*$ of the

Juri Poutanen, Marek Sikora, Mitchell C. Begelman, Pawel Magdziarz

We show that the sharp cutoff in the hard X-ray spectrum of NGC 4151, unusual for Seyfert 1 galaxies, can be reconciled with the average Seyfert 1 spectrum if we assume that the central source is completely hidden from our line of sight by the thick part of the accretion disk or by the broad emission line clouds. The observed X-ray radiation is produced by s

Andrew Ulmer

The two-point correlation function, $ξ$, of Lyman-alpha forest is found to be large, $ξ= 1.8^{+1.6}_{-1.2}$, > 90% confidence level, on the scale of 250-500 km/s for a sample of absorbers (0 < z < 1.3) assembled from HST Key Project Observations. This correlation function is stronger than at high redshift (z > 1.7) where $ξ\approx 0.2$ for velocities > 250 k

Jane C. Charlton, Christopher W. Churchill

To understand which parts of galaxies give rise to the variety of observed MgII absorption profiles seen in QSO spectra, we have embarked upon a program to generate simulated absorption profiles as they would arise from the many typical galactic structures we see today. Here, we present preliminary results for a clumpy, rotating disk which has been sampled b

W. Steffen, A. J. Holloway, A. Pedlar

The emission-lines in the active galaxy IRAS\,0421+0400 show a dramatic ($\sim$\,900\kms) increase in the velocity spread at the position of radio hot-spots which are located at the beginning of extended radio lobes. We study a simple geometric model of an opening outflow which reproduces the structure found in the long-slit emission-line spectrum of the hot

Simon P. Driver, Warrick J. Couch, Steven Phillipps, Rogier A. Windhorst

We infer the redshift distribution of the faint blue galaxy excess (FBE) at B=23.5 by subtracting the predicted distribution of giant/normal galaxies from the observed N(z) distribution for all types. This is possible because of the recent deep {\it Hubble Space Telescope} (HST) WFPC2 morphological number counts which have convincingly demonstrated that litt

Joao Magueijo, Andreas Albrecht, Pedro Ferreira, David Coulson

We investigate how the qualitative structure of Doppler peaks in the angular power spectrum of the cosmic microwave anisotropy is affected by basic assumptions going into theories of structure formation. We define the concepts of ``coherent&#39;&#39; and ``incoherent&#39;&#39; fluctuations, and also of ``active&#39;&#39; and ``passive&#39;&#39; fluctuations.

J. Stephany

Topologically non trivial effects appearing in the discussion of duality transformations in higher genus manifolds are discussed in a simple example, and their relation with the properties of Topological Field Theories is established.

Franz Embacher

The Hawking minisuperspace model (closed FRW geometry with a homogeneous massive scalar field) provides a fairly non-trivial testing ground for fundamental problems in quantum cosmology. We provide evidence that the Wheeler-DeWitt equation admits a basis of solutions that is distinguished by analyticity properities in a large scale factor expansion. As a con

C. Athanassopoulos, L. B. Auerbach, R. L. Burman, I. Cohen

A search for $\bar\nu_{\mu}\to \bar\nu_{e}$ oscillations has been conducted at the Los Alamos Meson Physics Facility by using $\bar\nu_\mu$ from $\mu^+$ decay at rest. The $\bar\nu_e$ are detected via the reaction $\bar\nu_e\,p \rightarrow e^{+}\,n$, correlated with a $\gamma$ from $np\rightarrow d\gamma$ ($2.2\,{\rm MeV}$). The use of tight cuts to identify

Capp Yess, Sergei F. Shandarin, Karl B. Fisher

We present percolation analyses of Wiener Reconstructions of the IRAS 1.2 Jy Redshift Survey. There are ten reconstructions of galaxy density fields in real space spanning the range $β= 0.1$ to $1.0$, where $β={Ω^{0.6}}/b$, $Ω$ is the present dimensionless density and $b$ is the bias factor. Our method uses the growth of the largest cluster statistic to char

F. Perez-Bernal, J. M. Arias, A. Frank, R. Lemus

The vibrational excitations of ozone, including both bending and stretching vibrations, are studied in the framework of a symmetry-adapted algebraic approach. This method is based on the isomorphism between the U(2) algebra and the one-dimensional Morse oscillator, and the introduction of point group symmetry techniques. The use of symmetry-adapted interacti

J. M. Aroca, H. Fort, R. Gambini

We show how the Hamiltonian lattice loop representation can be cast straightforwardly in the path integral formalism. The procedure is general for any gauge theory. Here we present in detail the simplest case: pure compact QED. We also analyze the non-Abelian Yang-Mills theory. The lattice loop path integral approach allows to knit together the power of stat

Andrei Okounkov

We extend some results about shifted Schur functions to the general context of shifted Macdonald polynomials. We obtain two explicit formulas for these polynomials: a $q$-integral representation and a combinatorial formula. Our main tool is a $q$-integral representation for ordinary Macdonald polynomials. We also discuss duality for shifted Macdonald polynom

J. A. de Azcarraga, A. M. Perelomov, J. C. Perez Bueno

Newly introduced generalized Poisson structures based on suitable skew-symmetric contravariant tensors of even order are discussed in terms of the Schouten-Nijenhuis bracket. The associated `Jacobi identities&#39; are expressed as conditions on these tensors, the cohomological contents of which is given. In particular, we determine the linear generalized Poi

Giovanni Gallavotti

Dissipative Euler and Navier Stokes equations are discussed with the aim of proposing several experiments apt to test the equivalence of dynamical ensembles and the chaotic hypothesis.

Franz Embacher

We formulate a &#39;&#39;minimal&#39;&#39; interpretational scheme for fairly general (minisuperspace) quantum cosmological models. Admitting as few exact mathematical structure as is reasonably possible at the fundamental level, we apply approximate WKB-techniques locally in minisuperspace in order to make contact with the realm of predictions, and propose

Z. Maassarani, D. Serban

We consider the supersymmetric approach to gaussian disordered systems like the random bond Ising model and Dirac model with random mass and random potential. These models appeared in particular in the study of the integer quantum Hall transition. The supersymmetric approach reveals an osp(2/2)_1 affine symmetry at the pure critical point. A similar symmetry

Ivan Cherednik

A systematic study of the representation theory of double affine Hecke algebras and related harmonic analysis is started in this paper. Continuing the previous papers we use the technique of intertwining operators to create Macdonald polynomials, estimate their denominators, generalize the classical representations of p-adic affine Hecke algebras in the spac

A. R. Calderbank, E. M Rains, P. W. Shor, N. J. A. Sloane

A group theoretic framework is introduced that simplifies the description of known quantum error-correcting codes and greatly facilitates the construction of new examples. Codes are given which map 3 qubits to 8 qubits correcting 1 error, 4 to 10 qubits correcting 1 error, 1 to 13 qubits correcting 2 errors, and 1 to 29 qubits correcting 5 errors.

Pablo M. Llatas

We show that the most general stationary electrically charged black-hole solutions of the heterotic string compactified on a (10-D)-torus (where D > 3) can be obtained by using the solution generating transformations of Sen acting on the Myers and Perry metric. The conserved charges labeling these black-hole solutions are the mass, the angular momentum in al

Benjamin Grinstein, I. Z. Rothstein

We investigate the errors due to the use of unphysical values of light quark masses in lattice extractions of $α_s$. A functional form for the pion mass dependence of the quarkonium mass splittings ($Δm$) is given as an expansion in $m_π/(4πf_π)$ and $m_πr_B$, where $r_B$ is the quarkonium Bohr radius. We find that, to lowest order,$Δm\simeq A+B m_π^2$, wher

R. D. Benguria, M. C. Depassier

We consider the bifurcation problem $u&#39;&#39; + λu = N(u)$ with two point boundary conditions where $N(u)$ is a general nonlinear term which may also depend on the eigenvalue $λ$. We give a variational characterization of the bifurcating branch $λ$ as a function of the amplitude of the solution. As an application we show how it can be used to obtain simpl

John Bechhoefer, Brad Johnson

We show that the linear-stability analysis of the birth of Faraday waves on the surface of a fluid is simplified considerably when the fluid container is driven by a triangle waveform rather than by a sine wave. The calculation is simple enough to use in an undergraduate course on fluid dynamics or nonlinear dynamics. It is also an attractive starting point

Bao-An Li, Z. Z. Ren, C. M. Ko, S. J. Yennello

Within the framework of an isospin-dependent Boltzmann-Uehling-Uhlenbeck (BUU) model using initial proton and neutron densities calculated from the nonlinear relativistic mean-field (RMF) theory, we compare the strength of transverse collective flow in reactions $^{48}Ca+^{58}Fe$ and $^{48}Cr+^{58}Ni$, which have the same mass number but different neutron/pr

Bao-An Li, C. M. Ko, G. Q. Li

The strength of transverse flow is examined as a function of transverse momentum $p_t$ using a simple, transversely moving thermal model and a more realistic, relativistic transport model (ART). It is shown that the $p_t$ dependence reveals useful information about the collective flow that is complementary to that obtained from the standard in-plane transver

N. Minkov, S. B. Drenska, P. P. Raychev, R. P. Roussev

The SU$_q$(2) rotator model is used for describing the $\beta_1$- and $\gamma_1$-bands of even-even rare earth and actinide collective nuclei. Good results are obtained in nuclei with valence pair number $N>10$. It is shown that in the excited bands the violation of the exact SU(2) symmetry is generally stronger than in the ground state bands, indicating the

V. S. Uma Maheswari, L. Satpathy

Stability of droplets of $ud$ matter, {\it viz} udilets, is studied using non-relativistic and relativistic bag models. It is found that there is a strong possibility for forming hypercharged metastable udilets with charge fraction $Z/A \ge 1$ in semicentral relativistic heavy ion collisions. It is then speculated that protons hadronised from these hyperchar

Beata Randrianantoanina

We prove that if $X$ is a complex strictly monotone sequence space with $1$-unconditional basis, $Y \subseteq X$ has no bands isometric to $\ell_2^2$ and $Y$ is the range of norm-one projection from $X$, then $Y$ is a closed linear span a family of mutually disjoint vectors in $X$. We completely characterize $1$-complemented subspaces and norm-one projection

Pradipta Bandyopadhyay, Sudeshna Basu

In this work, we obtain some necessary and some sufficient conditions for a space to be nicely smooth, and show that they are equivalent for separable or Asplund spaces. We obtain a sufficient condition for the Ball Generated Property (BGP), and conclude that Property $(II)$ implies the BGP, which, in turn, implies the space is nicely smooth. We show that th

Alexander Koldobsky

We say that an even continuous function $H$ on the unit sphere $Ω$ in $R^n$ admits the Blaschke-Levy representation with $q>0$ if there exists an even function $b\in L_1(Ω)$ so that $H^q(x)=\int_Ω|(x,ξ)|^q b(ξ)\ dξ$ for every $x\in Ω.$ This representation has numerous applications in convex geometry, probability and Banach space theory. In this paper, we pre

Jan Saxl, Saharon Shelah, Simon Thomas

We classify those sequences $\langle S_{n} \mid n \in \mathbb{N} \rangle$ of finite simple nonabelian groups such that the full product $\prod_{n} S_{n}$ has property (FA).

Barton Zwiebach

In string field theory an infinitesimal background deformation is implemented as a canonical transformation whose hamiltonian function is defined by moduli spaces of punctured Riemann surfaces having one special puncture. We show that the consistency conditions associated to the commutator of two deformations are implemented by virtue of the existence of mod

Ashok Das, Shibaji Roy

We study the ``ordinary&#39;&#39; Scherk-Schwarz dimensional reduction of the bosonic sector of the low energy effective action of a hypothetical M-theory on $S^1 \times S^1 \cong T^2$. We thus obtain the low energy effective actions of type IIA string theory in both ten and nine space-time dimensions. We point out how to obtain the O(1, 1) invariance of the

N. A. Papadopoulos, J. Plass

An extension of the Connes--Lott model is proposed. It is also within the framework of the A.Connes construction based on a generalized Dirac--Yukawa operator and the K--cycle $(H,D)$, with $H$ a fermionic Hilbert space. The basic algebra $A$ which may be considered as representing the non--commutative extension, plays a less important role in our approach.

H. M. Bosselmann, N. A. Papadopoulos

We consider the notion of a connection on a principal bundle $P(M,G)$ from the point of view of the action of the tangential group $TG$. This leads to a new definition of a connection and allows to interpret gauge transformations as effect of the $TG$ action.

Noureddine Mohammedi

A class of non-linear sigma models possessing a new symmetry is identified. The same symmetry is also present in Chern-Simons theories. This hints at a possible topological origin for this class of sigma models. The non-linear sigma models obtained by non-Abelian duality are a particular case in this class.

N. Dorey, C. Fraser, T. J. Hollowood, M. A. C. Kneipp

The Goddard, Nuyts and Olive conjecture for electric-magnetic duality in Yang-Mills theory with an arbitrary gauge group G is extended by including a non-vanishing vacuum angle $θ$. This extended S-duality conjecture includes the case when the unbroken gauge group is non-abelian and a definite prediction for the spectrum of dyons results.

G. Delfino, P. Simonetti

The one and two-particle form factors of the energy operator in the two-dimensional Ising model in a magnetic field at $T=T_c$ are exactly computed within the form factor bootstrap approach. Together with the matrix elements of the magnetisation operator already computed in ref.\,\cite{immf}, they are used to write down the large distance expansion for the c

S. Meljanac, M. Stojic, D. Svrtan

We describe a unified approach to calculating the partition functions of a general multi-level system with a free Hamiltonian. Particularly, we present new results for parastatistical systems of any order in the second quantized approach. Anyonic- like systems are briefly discussed.

Niels Tuning, Herman Verlinde

We compute the effect of quantum mechanical backreaction on the spectrum of radiation in a dynamical moving mirror model, mimicking the effect of a gravitational collapse geometry. Our method is based on the use of a combined WKB and saddle-point approximation to implement energy conservation in the calculation of the Bogolyubov coefficients, in which we ass

J. D. Kim, I. G. Koh

Two-particle scattering amplitudes for integrable relativistic quantum field theory in 1+1 dimensions can normally have at most singularities of poles and zeros along the imaginary axis in the complex rapidity plane. It has been supposed that single particle amplitudes of the exact boundary reflection matrix exhibit the same structure. In this paper, single

A. H. Bilge, T. Dereli, Ş. Koçak

We show that self-dual 2-forms in 2n dimensional spaces determine a $n^2-n+1$ dimensional manifold ${\cal S}_{2n}$ and the dimension of the maximal linear subspaces of ${\cal S}_{2n}$ is equal to the (Radon-Hurwitz) number of linearly independent vector fields on the sphere $S^{2n-1}$. We provide a direct proof that for $n$ odd ${\cal S}_{2n}$ has only one-d

Michael K. Murray

Recently K. Lee, E.J. Weinberg and P. Yi in CU-TP-739, hep-th/9602167, calculated the asymptotic metric on the moduli space of (1, 1, ..., 1) BPS monopoles and conjectured that it was globally exact. I lend support to this conjecture by showing that the metric on the corresponding space of Nahm data is the same as the metric they calculate.

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

Using chiral perturbation theory and the large-$N_c$ expansion, we obtain expressions for the $η&#39;$ mass and $η- η&#39;$ mixing in terms of low-energy chiral Lagrangian parameters. This is accomplished through an intermediate step of `matching&#39; the topological susceptibility in the large-$N_c$ and chiral Lagrangian descriptions. By inserting the value

Marta Losada

Using dimensional reduction we construct an effective 3D theory of the Minimal Supersymmetric Standard Model at finite temperature. The final effective theory is obtained after three successive stages of integration out of massive particles. We obtain the full 1-loop relation between the couplings of the reduced theory and the underlying 4D couplings and mas

F. J. Ynduráin

A number of internal inconsistencies, misleading conclusions and lack of completeness in the analyses of the small $x$ deep inelastic data in recent papers of HERA physicists, particularly in a very recent one by the H1 collaboration are pointed out. It is also shown that, when an analysis without prejudice is carried over, the situation is very different fr

P. Kroll, M. Raulfs

The pion wave function is discussed in the light of the recent CLEO data on the pion gamma transition form factor. It turns out that the wave function is close to the asymptotic form whereas wave functions strongly concentrated in the end-point regions are disfavoured. Consequences for other exclusive quantities, as for instance the pion&#39;s electromagneti

S. Kumano

We give a brief overview of nuclear parton distributions. First, the EMC effect is discussed together with possible interpretations such as nuclear binding and $Q^2$ rescaling. Next, we explain shadowing descriptions: vector-meson-dominance-type and parton-recombination models. Nuclear dependence of $Q^2$ evolution should be interesting in testing whether or

M. Beneke, G. Buchalla, I. Dunietz

We use the heavy quark expansion to investigate the width difference $ΔΓ_{B_s}$ between the $B_s$ mass eigenstates. The corrections of ${\cal O}(Λ_{QCD}/m_b)$ and ${\cal O}(m_s/m_b)$ to the leading order expression in the operator product expansion are derived and estimated to yield a sizable reduction of the leading result for $ΔΓ_{B_s}$ by typically $30\%$

Lawrence J. Hall

Three aspects of supersymmetric theories are discussed: electroweak symmetry breaking, the issues of flavor, and gauge unification. The heavy top quark plays an important, sometimes dominant, role in each case. Additional symmetries lead to extensions of the standard model which can provide an understanding for many of the outstanding problems of particle ph

Joachim Hein, Jochen Heitger

We determine the interface tension of the finite-temperature electroweak phase transition in a numerical investigation of the SU(2)--Higgs model on a four-dimensional lattice with temporal extension $L_t=3$. In this simulation the chosen parameters correspond to a Higgs boson mass of about 16 GeV. As a result the interface tension shows only small scaling vi

Marco Cavaglia`, Vittorio de Alfaro

Recently the low-energy effective string theory has been used by Gasperini and Veneziano to elaborate a very interesting scenario for the early history of the universe (``birth of the universe as quantum scattering&#39;&#39;). Here we investigate the gauge fixing and the problem of the definition of a global time parameter for this model, and we obtain the p

Reginald T. Cahill, Christopher M. Klinger

At present we have only the very successful but phenomenological Einstein geometrical modelling of the spacetime phenomenon. This geometrical model provides a `container&#39; for other theories, in particular the quantum field theories. Here we report progress in developing a {\em Heraclitean Quantum System}. This is a particular pregeometric theory for spac

Karol I. Wysokinski

The derivation of the Eliashberg -- type equations for a superconductor with strong correlations and electron--phonon interaction has been presented. The proper account of short range Coulomb interactions results in a strongly anisotropic equations. Possible symmetries of the order parameter include s, p and d wave. We found the carrier concentration depende

C. B. Hanna, A. H. MacDonald

We investigate spontaneous interlayer phase coherence and the occurrence of the quantum Hall effect in triple-layer electron systems. Our work is based on a simple tight-binding model that greatly facilitates calculations and whose accuracy is verified by comparison with recent experiments. By calculating the ground state in an unrestricted Hartree-Fock appr

Yu. A. Danilov, A. V. Rozhkov, V. L. Safonov

New phenomenological approach for the description of elementary collective excitations is proposed. The crystal is considered to be an anisotropic space-time vacuum with a prescribed metric tensor in which the information on electromagnetic crystalline fields is included. The quasiparticles in this space are supposed to be described by the equations structur

M. L. Plumer, A. Mailhot

The results of finite-size scaling analysis of histogram Monte-Carlo simulations on the stacked triangular XY antiferromagnet with anisotropic near-neighbor exchange interactions are presented. With ferromagnetic interplane coupling ten times stronger than the antiferromagnetic intraplane interaction ($J_\| / J_\bot = -10$), a weak first-order transition is

T. T. Chou, Chen Ning Yang, L. H. Yu

The coordinate-momentum double distribution function $ρ({\bf r}, {\bf p}) d^{3}rd^{3}p$ is calculated in the local density approximation for bosons with positive scattering length $a$ in a trap. The calculation is valid to the first order of $a$. To clarify the meaning of the result, it is compared for a special case with the double distribution function $ρ_

N. Lemke, I. A. Campbell

We demonstrate numerically that for Ising spins on square lattices with ferromagnetic second neighbour interactions and random near neighbour interactions, two dimensional Ising spin glass order with a non-zero freezing temperature can occur. We compare some of the physical properties of these spin glasses with those of standard spin glasses in higher dimens

Friedhelm Schoenfeld, Arno P. Kampf, Erwin Mueller-Hartmann

We present the results for a model calculation of resonant two-magnon Raman scattering in a spin density wave (SDW) antiferromagnet. The resonant enhancement of the two-magnon intensity is obtained from a microscopic analysis of the photon-magnon coupling vertex. By combining magnon-magnon interactions with `triple resonance` phenomena in the vertex function