November 1994 arXiv papers — page 6

Alexander Braverman

Let g be a semisimple Lie algebra over an algebraically closed field k of characteristic 0. Let V be a simple finite-dimensional g-module and let y\in V be a highest weight vector. It is a classical result of B. Kostant that the algebra of functions on the closure of the orbit of y under the simply connected group which corresponds to g is quadratic (i.e. th

M. Martinis, V. Mikuta-Martinis, J. Črnugelj

We study a Centauro-type phenomenon in high-energy heavy-ion collisions by assuming that pions are produced semiclassically both directly and in pairs through the isovector channel. The leading-particle effect and the factorization property of the scattering amplitude in the impact-parameter space are used to define the classical pion field. By analyzing the

M. Martinis, V. Mikuta-Martinis, A. Švarc, J. Črnugelj

Assuming that leading particles in high-energy hadronic and nuclear collisions become sources of a classical pion field, we show that the direct production of pions favors Centauro (mainly charged) events and that the production of pions through the $ ρ$-type channel favors anti-Centauro (mainly neutral) events. We also observe a strong negative neutral-char

J. R. Cudell

I report on recent progress in the study of mass generation in non-abelian gauge theories, and concentrate on the origin of constituent masses in QCD. I argue that a consistent formalism has been developed to describe chiral symmetry breaking via multiplicatively renormalisable Dyson-Schwinger equations. Its main consequence is the existence of a critical va

Thomas G. Rizzo

The recent observation by the CLEO Collaboration of the inclusive decay $b\to sγ$ with a branching fraction consistent with the expectations of the Standard Model is used to constrain the parameter space of the Left-Right Symmetric Model. Two scenarios are considered: ($i$) equal left- and right- handed Cabibbo-Kobayashi-Maskawa mixing matrices, $V_L=V_R (~{

Sally Dawson

A basic introduction to the physics of the Standard Model Higgs boson is given. We discuss Higgs boson production in $e^+e^-$ and hadronic collisions and survey search techniques at future accelerators. The Higgs bosons of the minimal SUSY model are briefly considered. Indirect limits from triviality arguments, vacuum stability and precision measurements at

R. M. Godbole, B. Mukhopadhyaya, M. Nowakowski

We investigate the possibility of probing the triplet Higgs boson sector via single charged Higgs production in the process $e^+ e^- \to H^+ l ν_l$, at high energy electron-positron colliders, using the tree level $H^+W^-Z$ coupling which is a unique feature of such models. We find that even LEP-200 can give nontrivial information upto $M_{H^{\pm}} \simeq 12

A. G. Grozin, G. P. Korchemsky

We consider properties of the structure functions of inclusive heavy meson decays $B\to X_c$ and treat the $c$ quark mass as a free parameter. We show that in two extreme cases of heavy and light $c$ quark the structure functions of heavy--heavy and heavy--light transitions are given by a Fourier transform of the matrix elements of Wilson lines containing a

A. P. Burichenko, D. Yu. Ivanov

Corrections $\sim α^2 $ to the positronium decay rate, induced by one--loop vacuum polarization diagram, are calculated. Their relative values are $0.4468(3)(α/π)^2$ for para- and $0.960(3)(α/π)^2$ for orthopositronium.

Dima Bardin, Dietrich Lehner, Tord Riemann

A cross-section calculation for the Standard Model reaction $e^+e^- \rightarrow (Z^0Z^0) \rightarrow f_1\bar{f_1}f_2\bar{f_2}$ including the effects of the finite $Z^0$~width and initial state radiative corrections is presented. The angular phase space integrations are performed analytically, leaving the invariant masses for numerical integration. Semi-analy

D. P. Roy

I start with a brief introduction to the elementary particles and their interactions, Higgs mechanism and supersymmetry. The major physics objectives of the Tevatron and LHC colliders are identified. The status and prospects of the top quark, charged Higgs boson and superparticle searches are discussed in detail, while those of the neutral Higgs boson(s) are

Abhay Ashtekar, Jerzy Lewandowski

A general framework for integration over certain infinite dimensional spaces is first developed using projective limits of a projective family of compact Hausdorff spaces. The procedure is then applied to gauge theories to carry out integration over the non-linear, infinite dimensional spaces of connections modulo gauge transformations. This method of evalua

J. C. Talstra, S. P. Strong, P. W. Anderson

We discuss new possibilities for Off-Diagonal Long Range Order (ODLRO) in spin chains involving operators which add or delete sites from the chain. For the Heisenberg and Inverse Square Exchange models we give strong numerical evidence for the hidden ODLRO conjectured by Anderson \cite{pwa_conj}. We find a similar ODLRO for the XY model (or equivalently for

Diptiman Sen, R. K. Bhaduri

We use the Thomas-Fermi method to examine the thermodynamics of particles obeying Haldane exclusion statistics. Specifically, we study Calogero-Sutherland particles placed in a given external potential in one dimension. For the case of a simple harmonic potential (constant density of states), we obtain the exact one-particle spatial density and a {\it closed

M. Abplanalp, C. Berger, G. Czapek, U. Diggelmann

This work is part of an ongoing project to develop a Superheated Superconducting Granule (SSG) detector for cold dark matter and neutrinos. The response of SSG devices to nuclear recoils has been explored irradiating SSG detectors with a 70MeV neutron beam. The aim of the experiment was to test the sensitivity of Sn, Al and Zn SSG detectors to nuclear recoil

F. W. J. Hekking, L. I. Glazman, Gerd Schoen

It is shown that the low energy spectrum of mesoscopic superconductors coupled by Josephson interaction can be probed by two-electron tunneling from a normal electrode. The Andreev reflection in the NS junction of a normal-superconductor-superconductor double junction (NSS transistor) provides a unique spectroscopic tool to probe the coherent Cooper pair tun

D. Boyanovsky, D. Jasnow, J. Llambias, F. Takakura

The response and nonconserved dynamics of a two-phase interface in the presence of a temperature gradient oriented normally to the interface are considered. Two types of boundary conditions on the order parameter are considered, and the structure of the effective free energy and the Langevin equation for the collective coordinate specifying the interface pos

Hiroyuki Mori

The persistent current and charge stiffness of a one-dimensional Luttinger liquid on a ring threaded by a magnetic flux are calculated by Monte Carlo simulation. By changing the random impurity potential strength and the electron-electron interaction, we see a crossover behavior between weak and strong impurity limits. For weak impurity potentials, interacti

M. J. M. de Jong, L. W. Molenkamp

Hydrodynamic electron flow is experimentally observed in the differential resistance of electrostatically defined wires in the two-dimensional electron gas in (Al,Ga)As heterostructures. In these experiments current heating is used to induce a controlled increase in the number of electron-electron collisions in the wire. The interplay between the partly diff

Subir Sachdev, Andrey V. Chubukov, Alexander Sokol

We consider two-dimensional Fermi liquids in the vicinity of a quantum transition to a phase with commensurate, antiferromagnetic long-range order. Depending upon the Fermi surface topology, mean-field spin-density-wave theory predicts two different types of such transitions, with mean-field dynamic critical exponents $z=1$ (when the Fermi surface does not c

J. C. Talstra, F. D. M. Haldane

In this letter we develop a method to construct all the integrals of motion of the $SU(p)$ Haldane-Shastry model of spins, equally spaced around a circle, interacting through a $1/r^2$ exchange interaction. These integrals of motion respect the Yangian symmetry algebra of the Hamiltonian.

Gregor Erbach

In this paper, we present an alternative approach to multiple inheritance for typed feature structures. In our approach, a feature structure can be associated with several types coming from different hierarchies (dimensions). In case of multiple inheritance, a type has supertypes from different hierarchies. We contrast this approach with approaches based on

Hagen Langer

DATR is a declarative representation language for lexical information and as such, in principle, neutral with respect to particular processing strategies. Previous DATR compiler/interpreter systems support only one access strategy that closely resembles the set of inference rules of the procedural semantics of DATR (Evans & Gazdar 1989a). In this paper we pr

Kenji Ono, Kazuo Sumita, Seiji Miike Research, Development Center

We have developed an automatic abstract generation system for Japanese expository writings based on rhetorical structure extraction. The system first extracts the rhetorical structure, the compound of the rhetorical relations between sentences, and then cuts out less important parts in the extracted structure to generate an abstract of the desired length. Ev

Harald Lesch, Masashi Chiba

We show that the relatively strong magnetic fields ($\ge 1 μ$G) in high redshift objects can be explained by the combined action of an evolving protogalactic fluctuation and electrodynamic processes providing the magnetic seed fields. Three different seed field mechanisms are reviewed and incorporated into a spherical "top-hat" model and tidal torque

Ofer Lahav

We attempt to de-mistify Artificial Neural Networks (ANNs) by considering special cases which are related to other statistical methods common in Astronomy and other fields. In particular we show how ANNs generalise Bayesian methods, multi-parameter fitting, Principal Component Analysis (PCA), Wiener filtering and regularisation methods. Examples of morpholog

Avi Naim

There is an obvious need for automated classification of galaxies, as the number of observed galaxies increases very fast. We examine several approaches to this problem, utilising {\em Artificial Neural Networks} (ANNs). We quote results from a recent study which show that ANNs can classsify galaxies morphologically as well as humans can.

Gerard Gilmore

Correlations between stellar kinematics and chemical abundances are fossil evidence for evolutionary connections between Galactic structural components. Extensive stellar surveys show that the only tolerably clear distinction between galactic components appears in the distributions of specific angular momentum. Here the stellar metal-poor halo and the metal-

Gerard Gilmore

There are many fundamental aspects of Galactic structure and evolution which can be studied best or exclusively with high quality three dimensional kinematics. Amongst these we note as examples determination of the orientation of the stellar velocity ellipsoid, and the detection of structure in velocity-position phase space. The first of these is the primary

David B. Jaffe

Let S be a surface in CP^3, having only nodes as singularities. Let pi: S~ --> S be a minimal resolution of singularities. A set N of nodes on S is EVEN if there exists a divisor Q on S~ such that 2Q ~ pi^{-1}(N). Suppose that S has degree 6. It is known (Basset) that S cannot have 67 or more nodes. It is also known (Barth) that S can have 65 nodes. It is no

Lesley L. Smith, Pankaj Jain, Douglas W. McKay

The Landau gauge Schwinger-Dyson Equation for the quark self-energy is solved in the quenched ladder approximation for several cases of one- and two-quark-generations. The exchanges of Standard Model gluons and Higgs bosons are taken into account. It is found that Higgs boson exchange dominates the quark self-energy for sufficiently large input quark masses

David D. Palmer, Marti A. Hearst

Labeling of sentence boundaries is a necessary prerequisite for many natural language processing tasks, including part-of-speech tagging and sentence alignment. End-of-sentence punctuation marks are ambiguous; to disambiguate them most systems use brittle, special-purpose regular expression grammars and exception rules. As an alternative, we have developed a

C. Ciliberto, A. Lopez, R. Miranda

Let $C \subset P^{g-1}$ be a smooth canonical curve of genus $g \geq 3$. The purpose of this article is to further develop a method to classify varieties having $C$ as their curve section, using Gaussian map computations. In a previous article a careful analysis of the degeneration to the cone over the hyperplane section was made for _prime_ Fano threefolds,

J. Sexton, D. Weingarten

We construct a systematic expansion for full QCD. The leading term gives the valence (quenched) approximation.

Gerald Dunne

An algebraic restriction of the nonabelian self-dual Chern-Simons-Higgs systems leads to coupled abelian models with interesting mass spectra. The vacua are characterized by embeddings of $SU(2)$ into the gauge algebra, and in the broken phases the gauge and real scalar masses coincide, reflecting the relation of these self-dual models to $N=2$ SUSY. The mas

Paolo Catelan, Francesco Lucchin, Sabino Matarrese, Lauro Moscardini

The problem of solving perturbatively the equations describing the evolution of self-gravitating collisionless matter in an expanding universe considerably simplifies when directly formulated in terms of the gravitational and velocity potentials: the problem can be solved {\it exactly}, rather than approximately, even for cosmological models with arbitrary d

R. D. Ball, P. E. Haagensen, J. I. Latorre, E. Moreno

We compute critical exponents in a $Z_2$ symmetric scalar field theory in three dimensions, using Wilson's exact renormalization group equations expanded in powers of derivatives. A nontrivial relation between these exponents is confirmed explicitly at the first two orders in the derivative expansion. At leading order all our results are cutoff independe

Ernest Ma

A simple 3 X 3 neutrino mass matrix is proposed to accommodate both the solar and atmospheric neutrino deficits. This scenario can be realized naturally by a radiative mechanism for the generation of neutrino masses. It also goes together naturally with electroweak baryogenesis and cold dark matter in a specific model.

J. A. de Azcarraga, P. P. Kulish, F. Rodenas

Some physical aspects of $q$-deformed spacetimes are discussed. It is pointed out that, under certain standard assumptions relating deformation and quantization, the classical limit (Poisson bracket description) of the dynamics is bound to contain unusual features. At the same time, it is argued that the formulation of an associated $q$-deformed field theory

R. Kenna, A. C. Irving

We study the distribution of partition function zeroes for the $XY$--model in two dimensions. In particular we find the scaling behaviour of the end of the distribution of zeroes in the complex external magnetic field plane in the thermodynamic limit (the Yang--Lee edge) and the form for the density of these zeroes. Assuming that finite--size scaling holds,

Metin Gurses, Atalay Karasu

We show that the integrable subclassess of a class of third order non-autonomous equations are identical with the integrable subclassess of the autonomous ones.

Yukari Ito, Miles Reid

This is the final draft, containing very minor proof-reading corrections. Let G in SL(n,\C) be a finite subgroup and \fie: Y -> X = \C^n/G any resolution of singularities of the quotient space. We prove that crepant exceptional prime divisors of Y correspond one-to-one with ``junior'' conjugacy classes of G. When n = 2 this is a version of the McKay correspo

Redouane Fakir

An observer, situated several thousand light-years away from a radio pulsar, finds himself embedded in the diffraction pattern resulting from the propagation of the radio waves through the irregular interstellar medium. The observer's movement relative to the pattern causes an apparent scintillation of the pulsar. A binary star, situated close to the pul

M. Jimbo, R. Kedem, T. Kojima, H. Konno

The $\XXZ$ spin chain with a boundary magnetic field $h$ is considered, using the vertex operator approach to diagonalize the Hamiltonian. We find explicit bosonic formulas for the two vacuum vectors with zero particle content. There are three distinct regions when $h\geq0$, in which the structure of the vacuum states is different. Excited states are given b

T. Csorgo, B. Lorstad, J. Zimanyi

Model-independent considerations are presented for the calculation of Bose-Einstein correlation functions and momentum distributions which describe boson-emitting systems containing a central part surrounded by a large halo. If the characteristic geometrical size of the halo is sufficiently large, the contributions of central part and the halo to the invaria

Gregory Mills, Hannes Jonsson

A practical method for finding free energy barriers for transitions in high-dimensional classical and quantum systems is presented and used to calculate the dissociative sticking probability of H2 on a metal surface within transition state theory (TST). The reversible work involved in shifting the system confined to a hyperplane from the reactant region towa

J. Hietarinta, B. Grammaticos, A. Ramani

In a recent publication we proposed an extension of Hirota's bilinear formalism to arbitrary multilinearities. The trilinear (and higher) operators were constructed from the requirement of gauge invariance for the nonlinear equation. Here we concentrate on the trilinear case, and use singularity analysis in order to single out equations that are likely t

Wim van Saarloos, Martin van Hecke, Robert Holyst

We discuss the front propagation in ferroelectric chiral smectics (SmC*) subjected to electric and magnetic fields applied parallel to smectic layers. The reversal of the electric field induces the motion of domain walls or fronts that propagate into either an unstable or a metastable state. In both regimes, the front velocity is calculated exactly. Dependin

S. C. Erwin, G. V. Krishna, E. J. Mele

The low-temperature structure of A1C60 (A=K, Rb) is an ordered array of polymerized C60 chains, with magnetic properties that suggest a non-metallic ground state. We study the paramagnetic state of this phase using first-principles electronic-structure methods, and examine the magnetic fluctuations around this state using a model Hamiltonian. The electronic

Vadim B. Kuznetsov

We construct a class of representations of the quadratic $R$-matrix algebra given by the reflection equation with the spectral parameter, $$ R{\,}(u-v)\,T^{(1)}(u)\,R{\,}(u+v)\,T^{(2)}(v)= T^{(2)}(v)\,R{\,}(u+v)\,T^{(1)}(u)\,R{\,}(u-v), $$ in terms of certain ordinary difference operators. These operators turn out to act as parameter shifting operators on th

M. Lawrence Glasser

It appears that, along with many of my friends and colleagues, I had been brainwashed by the great and tragic lives of Abel and Galois to believe that no general formulas are possible for roots of equations higher than quartic. This seemed to be confirmed by the brilliant and arduous solution of the general quintic by Hermite. Yet, below we find a formula gi

Beata Randrianantoanina

Let $X$ be a (real or complex) rearrangement-in\-va\-riant function space on $\Om$ (where $\Om = [0,1]$ or $\Om \subseteq \bbN$) whose norm is not proportional to the $L_2$-norm. Let $H$ be a separable Hilbert space. We characterize surjective isometries of $X(H).$ We prove that if $T$ is such an isometry then there exist Borel maps $a:\Om\to\bbK$ and $σ:\Om

Daniela Garajeu, Richard Grimm, Serge Lazzarini

Starting from flat two-dimensional gauge potentials we propose the notion of ${\cal W}$-gauge structure in terms of a nilpotent BRS differential algebra. The decomposition of the underlying Lie algebra with respect to an $SL(2)$ subalgebra is crucial for the discussion conformal covariance, in particular the appearance of a projective connection. Different $

R. Bonisch

From the global chiral SU(2)*U(1) that appears in the electroweak Left-Right Model in the fundamental representation, a continuous transition to the representation of the minimal Standard Model is considered in the Cartan subalgebra of the right-handed sector. The connecting parameter is the splitting of U(1)_R quantum numbers. It is a deformation parameter,

L. Martina, O. K. Pashaev, G. Soliani

We represent the two - dimensional planar classical continuous Heisenberg spin model as a constrained Chern-Simons gauged nonlinear Schrödinger system. The hamiltonian structure of the model is studied, allowing the quantization of the theory by the gauge invariant approach. A preliminary study of the quantum states is displayed and several physical conseque

Beatriz Gato-Rivera, Jose Ignacio Rosado

The "minimal matter + scalar" system can be embedded into the twisted N=2 topological algebra in two ways: a la DDK or a la KM. Here we present some results concerning the topological descendants and their DDK and KM realizations. In particular, we prove four "no-ghost" theorems (two for null states) regarding the reduction of the topological

Ioannis Bakas

We examine the properties and symmetries of the lowest order effective theory of 4-dim string backgrounds with axion and dilaton fields and zero cosmological constant. The dimensional reduction yields an O(2,2) current group of transformations in the presence of two commuting Killing symmetries. Special emphasis is placed on the identification of the T and S

A. Andrasi

This is about new unexpected features of the Mandestam-Leibbrandt prescription found as applied to spacelike Wilson lines. The regularization parameter $ ω$ in the M-L denominator for the spurious poles has to be kept throughout the calculation till the very end or else the integrals do not make sense. We get various `ambiguous' terms of the form $ ω^{-{

P. Kosi{ń}ski, J. Lukierski, P. Ma{ś}lanka, J. Sobczyk

The $κ$-deformed $D=4$ Poincar{é} superalgebra written in Hopf superalgebra form is transformed to the basis with classical Lorentz subalgebra generators. We show that in such a basis the $κ$-deformed $D=4$ Poincare superalgebra can be written as graded bicrossproduct. We show that the $κ$-deformed $D=4$ superalgebra acts covariantly on $κ$-deformed chiral s

Lech Szymanowski

I discuss the construction of the effective action for QCD suitable for the description of high-energy and small momentum transfer diffractive processes.

Alexander Braverman, Dennis Gaitsgory

In this paper we discuss a generalization of the classica PBW-theorem to the case of Koszul algebras. Our result is a slight generalization of that obtained by A.Polischuk and L.Positselsky, but the proof is different and uses deformation theory.

Andrei Linde, Dmitri Linde, Arthur Mezhlumian

We investigate the distribution of energy density in a stationary self-reproducing inflationary universe. We show that the main fraction of volume of the universe in a state with a given density $ρ$ at any given moment of time $t$ in synchronous coordinates is concentrated near the centers of deep exponentially wide spherically symmetric holes in the density

Charles A. Nelson

The Lorentz structure of the tau lepton's charged-current can almost be completely determined by use of stage-two spin-correlation functions for the $\{ρ^{-},ρ^{+}\}$ and $\{a_1^{-},a_1^{+}\}$ decay modes It is possible to test for a ``(V-A) + something'' structure in the ${J^{Charged}}_{Lepton}$ current, so as to bound the scales $Λ$ for ``new p

Ina Sarcevic, Peter Valerio

We present results on rapidity and transverse momentum distributions of inclusive charm quark production in hadronic and heavy-ion collisions at RHIC and LHC energies, including the next-to-leading order, $O(α_s^3)$, radiative corrections and the nuclear shadowing effect. We determine the hadronic and the {\it effective} (in-medium) K-factor for the differen

Roger Decker, Markus Finkemeier

We have calculated the radiative corrections to the decay $\tau\to \pi(K) \nu_\tau$, taking to account internal bremsstrahlung and structure dependent radiation in the radiative decay and point meson, hadronic structure dependent and short distance contributions in the virtual corrections. We display the spectra of the photon energy and of the pion-photon in

A. Djouadi, M. Drees

We calculate the decay rate of scalar and pseudoscalar Higgs bosons into a pair of gluinos, within the Minimal Supersymmetric Standard Model. In the theoretically and experimentally allowed light gluino window, $\mg \sim $ 3--5 GeV, gluino pairs can completely dominate the decays of the light scalar Higgs boson and play a prominent role in the decay of the p

R. Bonisch

In the two Higgs doublet model, perturbativity breaks down below the Planck scale: For top mass values 170-180 GeV, the Yukawa coupling reaches the pole below 1000 TeV, if the ratio of vev&#39;s v_u/v_d is below 1. We discuss top condensate scenarios for 150 GeV < m_top < 200 GeV, showing that a version with two composite Higgses is a viable option. Within e

Xiangdong Ji, MIT

Infrared renormalons and $1/Q^2$ power corrections in deep-inelastic sum rules are studied. The renormalization of operators with power divergence are discussed. The higher-twist terms in the operator product expansion are shown to account for the residual soft contributions survived from the Kinoshita-Lee-Nauenberg type of cancellation in Feynman diagrams.

J. Bijnens, G. Colangelo, G. Ecker, J. Gasser

We present the matrix elements for the semileptonic kaon decays $K_{l2\gamma}$ , $K_{l2l^+l^-}$, $K_{l2l'^+l'^-}$,$K_{l3}$, $K_{l3\gamma}$ and $K_{l4}$ at next-to-leading order, and $K_{e5}$ at leading order in Chiral Perturbation Theory and compare the predictions with experimental data. For $K_{l4}$ decays we estimate yet higher orders in order to reduce t

Y. Sumino

We review the recent developments of studies on $e^+ e^- \to t\bar{t}$ in the threshold region. It has been shown that the top threshold cross sections will be able to provide many important and interesting physics. Due to the large mass and the large decay width of top quark, there will appear a number of unique features at top threshold. First, theoretical

E. Di Salvo, L. A. Kondratyuk, P. Saracco

We start from a field-theoretical model of zero range approximation to derive three-dimensional relativistic two- and three-body equations on a null plane. We generalize those equations to finite range interactions. We propose a three-body null-plane equation whose form is different from the one presented earlier in the framework of light-cone dynamics. We d

Hsiang-nan Li, Hoi-Lai Yu

Resummation of large QCD radiative corrections, including leading and next-to-leading logarithms, in pion electromagnetic form factor is reviewed. Similar formalism is applied to exclusive processes involving heavy mesons, and leads to Sudakov suppression for the semi-leptonic decay $B\toπlν$. It is found that, with the inclusion of Sudakov effects, perturba

Alakabha Datta

We study the vector and axial vector form factors in the heavy to light transitions in charmed baryon decays using HQET. We calculate the 1/m_c corrections to the form factors and show that these corrections can be significant. We also consider applications to semi-leptonic and hadronic decays of charmed baryons.

L. N. Lipatov, A. Berera

We examine the generalized leading-logarithmic approximation (LLA) equations for compound states of n-reggeized gluons. It is shown that in multi-color QCD, when $N_c \rightarrow \infty$, these equations have a sufficient number of conservation laws to be exactly solvable. Holomorphic factorization of the wave functions is used to reduce the corresponding qu

M. Faber, H. Markum, S. Olejnik, W. Sakuler

We update our numerical investigation of topological structures around static quarks in pure gauge QCD by results of the first runs including dynamical quarks. Simulations were performed on an $8^3\times4$ lattice, with $SU(3)$ Wilson action, with 3 flavours of quarks of equal mass, both in the confinement and deconfinement phase. In the confinement phase we

Norbert Schultka, Efstratios Manousakis

We investigate the influence of the Chern-Simons term coupled to the three-dimensional $x-y$ model. This term endows vortices with an internal angular momentum and thus gives them arbitrary statistics. The Chern-Simons term for the $x-y$ model takes an integer value which can be written as a sum over all vortex lines of the product of the vortex charge and t

Esteban Calzetta, Juan Jose Gonzalez

In this paper we present a Friedmann-Robertson-Walker cosmological model conformally coupled to a massive scalar field where the WKB approximation fails to reproduce the exact solution to the Wheeler-DeWitt equation for large Universes. The breakdown of the WKB approximation follows the same pattern than in semiclassical physics of chaotic systems, and it is

Massimo Fioroni, Giorgio Immirzi

We explain the collapse of the wavefunction with the notion that, in a measurement, the system observed nucleates a first order phase transition in the measuring device. The possible final states differ by the values of macroscopic observables, and their relative phase is therefore unobservable. The process is irreversible, but needs no separate postulate.

Andreas Schadschneider

The Hubbard model with an additional bond-charge interaction $X$ is solved exactly in one dimension for the case $t=X$ where $t$ is the hopping amplitude. In this case the number of doubly occupied sites is conserved. In the sector with no double occupations the model reduces to the $U=\infty$ Hubbard model. In arbitrary dimensions the qualitative form of th

T. Giamarchi, B. S. Shastry

We consider a one-dimensional Hubbard model in the presence of disorder. We compute the charge stiffness for a mesoscopic ring, as a function of the size $L$, which is a measure of the permanent currents. We find that for finite disorder the permanent currents of the system with repulsive interactions are larger than those of the system with attractive inter

I. Vattulainen

The aim of this Thesis is to present five new tests for random numbers, which are widely used {\em e.g.} in computer simulations in physics applications. The first two tests, the cluster test and the autocorrelation test, are based on analogies to the two-dimensional Ising model. The next two, the random walk test and the $n$-block test, are based on studies

V. L. Pokrovsky

A lot of controversy appeared recently in measurements of different properties of High-$T_c$-superconductor YBCO. A part of data supports d-wave hypothesis whereas other one contradicts it. We suggest to reconcile visibly controversial experimental data by an assumption that orthorombicity is not small for electronic properties of YBCO, and naturally mixes s

P. Sitko, L. Jacak

We find the RPA correlation energy and collective modes of the systems of composite fermions corresponding to the fillings of $1/3$, $1/5$, $2/5$ in the fractional quantum Hall effect. It is verified that transmutations to composite fermions do not change the ground-state energy.

H. J. Schulz

Functional integral methods provide a way to define mean--field theories and to systematically improve them. For the Hubbard model and similar strong--correlation problems, methods based in particular on the Hubbard--Stratonovich transformation have however been plagued by difficulties to formulate the problem in a spin--rotation invariant way. Here a formal

Salman Habib

Some recent investigations of the thermal equilibrium properties of kinks in a $1+1$-dimensional, classical $Φ^4$ field theory are reviewed. The distribution function, kink density, correlation function, and certain thermodynamic quantities were studied both theoretically and via large scale simulations. A simple double Gaussian variational approach within t

Yong Baek Kim, Patrick A. Lee, Xiao-Gang Wen, P. C. E. Stamp

Taking into account the transverse gauge field fluctuations, which interact with composite fermions, we examine the finite temperature compressibility of the fermions as a function of an effective magnetic field $ΔB = B - 2 n_e hc/e$ ($n_e$ is the density of electrons) near the half-filled state. It is shown that, after including the lowest order gauge field

Satoshi Tojo

We propose a paradigm for concurrent natural language generation. In order to represent grammar rules distributively, we adopt categorial unification grammar (CUG) where each category owns its functional type. We augment typed lambda calculus with several new combinators, to make the order of lambda-conversions free for partial / local processing. The concur

Daniel Provost, Paul Brumer

A uniform semiclassical propagator is used to time evolve a wavepacket in a smooth Hamiltonian system at energies for which the underlying classical motion is chaotic. The propagated wavepacket is Fourier transformed to yield a scarred eigenstate.

John S. Gallagher, Rosemary F. G. Wyse

Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and g

Heino Falcke

Sgr A* is the unique 1 Jy flat spectrum radio point source located at the dynamical center of the Galaxy and in the very center of the central star cluster. Due to its unusual appearance it has long been speculated that this source is powered by a supermassive black hole. The enormous increase in observational data obtained for Sgr A* in recent years has ena

S. Campana, L. Stella, S. Mereghetti, M. Colpi

Rapidly rotating magnetic neutron stars in eccentric binary systems containing an early type star provide a unique opportunity to investigate the interplay between radio pulsar, stellar wind and accretion phenomena. We summarise the radio pulsar-dominated and the accretion-dominated regimes, discussing how the transition from one regime to another can take p

W. N. Brandt, A. C. Fabian, K. Nandra, C. S. Reynolds

We present spatial, temporal and spectral analyses of ROSAT Position Sensitive Proportional Counter (PSPC) observations of the Seyfert 1 galaxies Ark 564, NGC 985, Kaz 163, Mrk 79 and RX J2256.6+0525. Ark 564 is a powerful narrow-line Seyfert 1 with strong Fe II emission. Several similar narrow-line Seyfert 1 galaxies have recently been found to have remarka

Caryl Gronwall, David C. Koo

We explore the nature of the evolution of faint field galaxies by assuming that the local luminosity function is not well defined. We use a non-negative least squares technique to derive a near optimal set of local luminosity functions for different spectral types of galaxies by fitting to the observed optical and near-infrared counts, B-R colors, and redshi

C. Alcock, R. A. Allsman, T. S. Axelrod, D. P. Bennett

We report the discovery of 45 beat Cepheids in the Large Magellanic Cloud (LMC) using the MACHO Project photometry database. The variables which are pulsating simultaneously in two radial modes are shown to break cleanly into two period-ratio groups, providing the first unambiguous evidence that the second overtone is indeed excited in real Cepheids. Thirty

Ramesh Narayan, Insu Yi, Rohan Mahadevan

The enigmatic radio source Sagittarius A* at the centre of our Galaxy appears to be a low-luminosity version of active galactic nuclei in other galaxies. By analogy with active galactic nuclei models, it has been proposed that Sgr A* may be a massive accreting black holes. The black hole hypothesis is, however, problematic because no model of Sgr A* has been

Ramesh Narayan, Insu Yi

We describe new optically thin solutions for rotating accretion flows around black holes and neutron stars. These solutions are advection dominated, so that most of the viscously dissipated energy is advected radially with the flow. We model the accreting gas as a two temperature plasma and include cooling by bremsstrahlung, synchrotron, and Comptonization.

Nina Byers

The contributions of Emmy Noether to particle physics fall into two categories. One is given under the rubric of Noether&#39;s theorem, and the other may be described as her important contributions to modern mathematics. These are discussed along with an historical account of her work and what its impact has been. In addition a brief biography is given. (To

C. P. Korthals Altes, N. J. Watson

We discuss a novel form of CP violation in the standard model. It takes place at temperatures of the order of the electroweak transition, when two regions with different values of the Wilson line are juxtaposed. This CP violation is maximal. A sufficient condition is simply the existence of a long-lived metastable state; this can occur for fewer than three g

Peter Grassberger, Rainer Hegger

We point out that a newly introduced recursive algorithm for lattice polymers has a much wider range of applicability. In particular, we apply it to the simulation of off-lattice polymers with Lennard-Jones potentials between non-bonded monomers and either delta or harmonic potentials between bonded monomers. Our algorithm allows particularly easy calculatio

F. E. Close, P. R. Page

An analytic calculation of the breaking of excited chromoelectric flux-tubes is performed in an harmonic oscillator approximation and applied to predict the dynamics of all $J^{PC}$ low-lying gluonic excitations of mesons (hybrids). Widths, branching ratios and production dynamics of some recently discovered $J^{PC} = 1^{-+}, 0^{-+}$ and $1^{--}$ mesons are