May 1996 arXiv papers — page 2

Arjendu K. Pattanayak, Paul Brumer

Phase space representations of the dynamics of the quantal and classical cat map are used to explore quantum--classical correspondence in a K-system: as $\hbar \to 0$, the classical chaotic behavior is shown to emerge smoothly and exactly. The quantum dynamics near the classical limit displays both exponential separation of adjacent distributions and long ti

Bhuvnesh Jain

The stable clustering hypothesis is a key analytical anchor on the nonlinear dynamics of gravitational clustering in cosmology. It states that on sufficiently small scales the mean pair velocity approaches zero, or equivalently, that the mean number of neighbours of a particle remains constant in time at a given physical separation. In this paper we use N-bo

Alexander Vilenkin, Serge Winitzki

The problem of making predictions in eternally inflating universe that thermalizes by bubble nucleation is considered. A recently introduced regularization procedure is applied to find the probability distribution for the ensemble of thermalized bubbles. The resulting probabilities are shown to be independent of the choice of the time parametrization. This f

Luis C. Ho

An unprecedentedly large number of LINERs has been discovered in a recently completed optical spectroscopic survey of nearby galaxies, allowing several statistical properties of the host galaxies and of the line-emitting regions to be examined reliably for the first time. As a consequence of the many detections and some revised classifications, the detailed

Luis C. Ho, Alexei V. Filippenko

Recent high-resolution observations with the Hubble Space Telescope (HST) reveal that star clusters of extraordinary luminosity and compactness are commonly found in a variety of starburst systems. There has been much speculation that these clusters represent present-day analogs of young globular clusters. Using the HIRES echelle spectrograph on the Keck 10

S. Bonazzola, E. Gourgoulhon

Contents: 1. Introduction 2. Spontaneous symmetry breaking 2.1 Review of classical results about Maclaurin/Jacobi ellipsoids 2.2 Spontaneous breaking of symmetry: a general phenomenom 2.3 Previous results for compressible Newtonian stars 2.4 Generation of gravitational waves 2.5 Finding the equilibrium configurations of a rotating star in the Newtonian regim

G. Parzen

A treatment is given of the orbit dynamics for linear unstable motion that allows for the zeros in the beta function and makes no assumptions about the realness of the betatron and phase functions. The phase shift per turn is shown to be related to the beta function and the number of zeros the beta function goes through per turn. The solutions of the equatio

Rajan Gupta, Tanmoy Bhattacharya

We present estimates of the masses of light quarks using lattice data. Our main results are based on a global analysis of all the published data for Wilson, Sheikholeslami-Wohlert (clover), and staggered fermions, both in the quenched approximation and with $n_f=2$ dynamical flavors. We find that the values of masses with the various formulations agree after

J. I. Katz, David R. Nelson

We develop a finite temperature theory for the susceptibility and electrostriction of isotropic substances in which permanent electric dipoles are restrained from free rotation by elastic forces. All parameters are constrained by the measured susceptibility and elastic constants. When applied to polyurethane, the predicted electrostriction is approximately c

Lov K. Grover

Imagine a phone directory containing N names arranged in completely random order. In order to find someone's phone number with a 50% probability, any classical algorithm (whether deterministic or probabilistic) will need to look at a minimum of N/2 names. Quantum mechanical systems can be in a superposition of states and simultaneously examine multiple names

A. Klypin

The purpose of these lectures is to give a short introduction into a very vast field of numerical simulations for cosmological applications. I focus on major features of the simulations: the equations, main numerical techniques, effects of resolution, and methods of halo identification.

T. H. Koornwinder, N. M. Muller

We generalise the quantum double construction of Drinfel'd to the case of the (Hopf) algebra of suitable functions on a compact or locally compact group. We will concentrate on the *-algebra structure of the quantum double. If the conjugacy classes in the group are countably separated, then we classify the irreducible *-representations by using the conne

Sergey Arkhipov

We introduce the techniques of semiregular bimodules over a Lie algebra with respect to a Lie subalgebra. Using this techniques in the case of affine Lie algebras we introduce twisting functors on the categories of modules. These functors are enumerated by elements of the affine Weyl group corresponding to the chosen affine Lie algebra and map Verma modules

G. Yepes, R. Kates, A. Khokhlov, A. Klypin

We numerically simulate some of the most critical physical processes in galaxy formation: The supernova feedback, in conjunction with gasdynamics and gravity, plays a crucial role in determining how galaxies arise within the context of a model for large-scale structure. Our treatment incorporates a multi-phase model of the interstellar medium and includes th

J. Fernando Barbero G.

We study in this paper a new approach to the problem of relating solutions to the Einstein field equations with Riemannian and Lorentzian signatures. The procedure can be thought of as a "real Wick rotation". We give a modified action for general relativity, depending on two real parameters, that can be used to control the signature of the solutions

P. Pronin, K. Stepanyantz

We present master formulas for the divergent part of the one-loop effective action for an arbitrary (both minimal and nonminimal) operators of any order in the 4-dimensional curved space. They can be considered as computer algorithms, because the one-loop calculations are then reduced to the simplest algebraic operations. Some test applications are considere

A. A. Bytsenko, Guido Cognola, Sergio Zerbini

The one-loop effective action for a massive self-interacting scalar field is investigated in $4$-dimensional ultrastatic space-time $ R \times H^3/Γ$, $H^3/Γ$ being a non-compact hyperbolic manifold with finite volume. Making use of the Selberg trace formula, the $ζ$-function related to the small disturbance operator is constructed. For an arbitrary gravitat

Fabian H. L. Essler

An open supersymmetric t-J chain with boundary fields is studied by means of the Bethe Ansatz. Ground state properties for the case of an almost half-filled band and a bulk magnetic field are determined. Boundary susceptibilities are calculated as functions of the boundary fields. The effects of the boundary on excitations are investigated by constructing th

S. P. Hong, H. Doh, S. H. Suck Salk

We present both the gauge theoretic description and the numerical calculations of the Berry phases with the real eigenstates, involving one with a many-body system as a background and the other with no such background. We demonstrate that for the former the sign of the Berry phase factor for a spin $\f{1}{2}$ particle (hole) coupled to a slow subsystem (phon

M. Bershadsky, K. Intriligator, S. Kachru, D. R. Morrison

Using ``Tate's algorithm,'' we identify loci in the moduli of F-theory compactifications corresponding to enhanced gauge symmetry. We apply this to test the proposed F-theory/heterotic dualities in six dimensions. We recover the perturbative gauge symmetry enhancements of the heterotic side and the physics of small $SO(32)$ instantons, and discov

Nicolas J. Cerf, Chris Adami

We present a quantum information theory that allows for a consistent description of entanglement. It parallels classical (Shannon) information theory but is based entirely on density matrices (rather than probability distributions) for the description of quantum ensembles. We find that quantum conditional entropies can be negative for entangled systems, whic

C. Adami, N. J. Cerf

A practical measure for the complexity of sequences of symbols (``strings'') is introduced that is rooted in automata theory but avoids the problems of Kolmogorov-Chaitin complexity. This physical complexity can be estimated for ensembles of sequences, for which it reverts to the difference between the maximal entropy of the ensemble and the actual e

Arvind, K. S. Mallesh, N. Mukunda

We describe a generalisation of the well known Pancharatnam geometric phase formula for two level systems, to evolution of a three-level system along a geodesic triangle in state space. This is achieved by using a recently developed generalisation of the Poincare sphere method, to represent pure states of a three-level quantum system in a convenient geometri

A. Isar, A. Sandulescu, W. Scheid

The Lindblad master equation for an open quantum system with a Hamiltonian containing an arbitrary potential is written as an equation for the Wigner distribution function in the phase space representation. The time derivative of this function is given by a sum of three parts: the classical one, the quantum corrections and the contribution due to the opening

Paul J. Ellis, James M. Lattimer, M. Prakash

Immediately after they are born, neutron stars are characterized by an entropy per baryon of order unity and by the presence of trapped neutrinos. If the only hadrons in the star are nucleons, these effects slightly reduce the maximum mass relative to cold, catalyzed matter. However, if negatively charged particles in the form of hyperons, a kaon condensate,

G. Amelino-Camelia, J. Ellis, N. E. Mavromatos, D. V. Nanopoulos

Within a Liouville approach to non-critical string theory, we discuss space-time foam effects on the propagation of low-energy particles. We find an induced frequency-dependent dispersion in the propagation of a wave packet, and observe that this would affect the outcome of measurements involving low-energy particles as probes. In particular, the maximum pos

Taro Kashiwa, Naoki Tanimura

Discussions are made on the relationship between physical states and gauge independence in QED. As the first candidate take the LSZ-asymptotic states in a covariant canonical formalism to investigate gauge independence of the (Belinfante's) symmetric energy-momentum tensor. It is shown that expectation values of the energy-momentum tensor in terms of tho

Wen-Jui Huang

A previously unnoticed connection between the Lax descriptions and the superextensions of the KdV hierarchy is presented. It is shown that the two different Lax descriptions of the KdV hierarchy come out naturally from two different bihamiltonian superextensions of the KdV hierarchy. Some implications of this observation are briefly mentioned.

A. K. Mishra, G. Rajasekaran

We formulate a theory of generalized Fock spaces which underlies the different forms of quantum statistics such as ``infinite'', Bose-Einstein and Fermi-Dirac statistics. Single-indexed systems as well as multi-indexed systems that cannot be mapped into single-indexed systems are studied. Our theory is based on a three-tiered structure consisting of

Tetsuya Shiromizu, Masahiro Morikawa

Weak first-order phase transitions proceed with percolation of new phase. The kinematics of this process is clarified from the point of view of subcritical bubbles. We examine the effect of small subcritical bubbles around a large domain of asymmetric phase by introducing an effective geometry. The percolation process can be understood as a perpetual growth

C. C. Lassig, G. C. Joshi

Using the framework of Nambu's generalised mechanics, we obtain a new description of constrained Hamiltonian dynamics, involving the introduction of another degree of freedom in phase space, and the necessity of defining the action integral on a world sheet. We also discuss the problem of quantising Nambu mechanics.

Ori J. Ganor

When $N$ five-branes of M-theory coincide the world-volume theory contains tensionless strings, according to Strominger's construction. This suggests a large $N$ limit of tensionless string theories. For the small $E_8$ instanton theories, the definition would be a large instanton number. An adiabatic argument suggests that in the large $N$ limit an effe

Tom Banks, Michael R. Douglas, Nathan Seiberg

Last week, A. Sen found an explicit type I string compactification dual to the eight-dimensional F-theory construction with SO(8)^4 nonabelian gauge symmetry. He found that the perturbations around the enhanced symmetry point were described by the mathematics of the solution of N=2, d=4 SU(2) gauge theory with four flavors, and argued more generally that glo

A. Djouadi, H. Haber, P. Igo-Kemenes, P. Janot

Report of the Higgs Working Group to appear in the Proceedings of the Workshop "Physics with $\ee$ Linear Colliders", Annecy-Gran Sasso-Hamburg, Feb. 4 - Sept. 1, 1995, P.M. Zerwas (editor).

Manuel Drees, Tao Han

Four double-parton scattering processes are examined at the Fermilab Tevatron energy. With optimized kinematical cuts and realistic parton level simulation for both signals and backgrounds, we find large samples of four-jet and three-jet+one-photon events with signal to background ratio being 20\%-30\%, and much cleaner signals from two-jet+two-photon and tw

Taekoon Lee

We calculate the one-loop QCD correction for inclusive jet cross section and Drell-Yan process in a general low-energy effective Lagrangian for composite quarks and leptons.

W. Buchmuller, D. Haidt

Recent data on the structure function F_2(x,Q^2) at small values of x are analysed and compared with theoretical expectations. It is shown that the observed rise at small x is consistent with a logarithmic increase, growing logarithmically also with Q^2. A stronger increase, which may be incompatible with unitarity when extrapolated to asymptotically small v

Martin Luescher, Stefan Sint, Rainer Sommer, Peter Weisz

The dominant cutoff effects in lattice QCD with Wilson quarks are proportional to the lattice spacing a. In particular, the isovector axial current satisfies the PCAC relation only up to such effects. Following a suggestion of Symanzik, they can be cancelled by adding local O(a) correction terms to the action and the axial current. We here address a number o

Claus Lämmerzahl

The role of the equivalence principle in the context of non-relativistic quantum mechanics and matter wave interferometry, especially atom beam interferometry, will be discussed. A generalised form of the weak equivalence principle which is capable of covering quantum phenomena too, will be proposed. It is shown that this generalised equivalence principle is

Claude LeBrun

Among all conformal classes of Riemannian metrics on ${\Bbb CP}_2$, that of the Fubini-Study metric is shown to have the largest Yamabe constant. The proof, which involves perturbations of the Seiberg-Witten equations, also yields new results on the total scalar curvature of almost-Kähler 4-manifolds.

Joel L. Lebowitz

The observed general time-asymmetric behavior of macroscopic systems -- embodied in the second law of thermodynamics -- arises naturally from time-symmetric microscopic laws due to the great disparity between macro and micro-scales. More specific features of macroscopic evolution depend on the nature of the microscopic dynamics. In particular, short range in

T. Xiang, J. M. Wheatley

The quasiparticle dispersion in the one-hole t-t'-t"-J model is studied. Both the finite-size diagonalization and the self-consistent Born approximation calculations have been performed and compared. The quasiparticle band structures in the hole and electron doped high-Tc cuprates are qualitatively different. In the hole doped compounds, the band max

Klaus Kroy, Erwin Frey

We derive the linear force-extension relation for a wormlike chain of arbitrary stiffness including entropy elasticity, bending and thermodynamic buckling. From this we infer the plateau modulus $G^0$ of an isotropic entangled solution of wormlike chains. The entanglement length $L_e$ is expressed in terms of the characteristic network parameters for three d

P. W. Leung, K. C. Chiu, K. J. Runge

We study the nature of the ground state of the quantum dimer model proposed by Rokhsar and Kivelson by diagonalizing the Hamiltonian of the model on square lattices of size $L\times L$, where $L\leq 8$, with periodic boundary conditions. Finite-size scaling studies of the columnar order parameter and the low lying excitation spectrum show no evidence of a di

Takashi Hotta, Satoshi Fujimoto

We investigate the spin and charge susceptibilities of the two-dimensional Hubbard model based upon the perturbative calculation in the strength of correlation $U$. For $U$ comparable to a bare bandwidth, the charge susceptibility decreases near the half-filling as hole-doping approaches zero. This behavior suggesting the precursor of the Mott-Hubbard gap fo

Hyeonjin Doh, Sung-Ho Suck Salk

Using the Hubbard model Hamiltonian in a mean field level, we examine the variation of antiferromagnetic strength with applied magnetic field. It is demonstrated that minima in the antiferromagnetic strength exist at the the even integer denominator values of rational number for magnetic flux per plaquette. The undulatory behavior of antiferromagnetic streng

Christer Samuelsson

A method is given that "inverts" a logic grammar and displays it from the point of view of the logical form, rather than from that of the word string. LR-compiling techniques are used to allow a recursive-descent generation algorithm to perform "functor merging" much in the same way as an LR parser performs prefix merging. This is an improvem

Christer Samuelsson

A general, practical method for handling sparse data that avoids held-out data and iterative reestimation is derived from first principles. It has been tested on a part-of-speech tagging task and outperformed (deleted) interpolation with context-independent weights, even when the latter used a globally optimal parameter setting determined a posteriori.

Christer Samuelsson

The design of an LR parser based on interleaving the atomic symbol processing of a context-free backbone grammar with the full constraints of the underlying unification grammar is described. The parser employs a set of reduced constraints derived from the unification grammar in the LR parsing step. Gap threading is simulated to reduce the applicability of em

C. M. Gaskell

Analysis of spectra of the quasar 3C 390.3 covering a period of over 20 yr shows that the blueshifted peak of H beta has been changing its radial velocity at an almost constant rate during this time. The radial velocity has increased by over 1500 km/s. The lower limit to the period of radial velocity changes is 210 yr. Although very long periods cannot be ex

S. N. Nazin, V. M. Lipunov, I. E. Panchenko, K. A. Postnov

We present a WWW-version of the {\it Scenario Machine} - a computer code designed to calculate the evolution of close binary stellar systems. The Internet users can directly access to the code and calculate binary evolutionary tracks with parameters at the user's will. The program is running on the {\it Pentium} server of the Division of the Relativistic

F. Patat, R. Barbon, E. Cappellaro M. Turatto

Following recent claims regarding possible errors in the photometry of SNe carried out at Asiago observatory during the 70's, which produced very blue $(B-V)$ color at maximum for some objects, we present the result of new CCD photometry of the sequences around 16 type Ia supernovae. Except for a few cases, e.g. SN1970J and SN1972J for which a large zero

Christopher W. Churchill, Charles C. Steidel, Steven S. Vogt

(Abridged) We present HIRES/Keck spectra having resolution 6 km/s of Mg II 2796 absorption profiles which arise in the gas associated with 15 identified galaxies over the redshift range 0.5 < z < 0.9. Using non-parametric rank correlation tests, we searched for correlations of the absorption strengths, saturation, and line-of-sight kinematics with the galaxy

S. P. Bhavsar, R. J. Splinter

In this work we demonstrate the ability of the Minimal Spanning Tree to duplicate the information contained within a percolation analysis for a point dataset. We show how to construct the percolation properties from the Minimal Spanning Tree, finding roughly an order of magnitude improvement in the computer time required. We apply these statistics to Particl

M. Turatto, S. Benetti, E. Cappellaro, I. J. Danziger

Observations of the peculiar type Ia SN~1991bg in NGC~4374 collected at ESO--La Silla and Asiago are presented and discussed. The broad--band light curves in the early months have a narrower peak and a luminosity decline faster than other SNIa while the R and I light curves do not show the secondary peak. The SN is intrinsically very red (\bv$_{max}=0.74$) a

Konrad Bernlöhr

Measuring the angles of muons and electrons in air showers is proposed as a method for studying the primary cosmic-ray mass composition near the knee of the cosmic-ray energy spectrum at a few $10^{15}$ eV. Conventional tracking detectors at existing air shower arrays could serve this purpose, like the CRT detectors at the HEGRA array. When the average radia

Salvatore Capozziello, Ruggiero de Ritis, Alma Angela Marino

We construct a cosmological toy model in which a step-function ``cosmological constant&#39;&#39; is taken into consideration beside ordinary matter. We assume that $Λ$ takes two values depending on the epoch, and matter goes from a radiation dominated era to a dust dominated era. The model is exactly solvable and it can be compared with recent observations.

C. M. Gaskell

Some quasars show Doppler shifted broad emission line peaks. I give new statistics of the occurrence of these peaks and show that, while the most spectacular cases are in quasars with strong radio jets inclined to the line of sight, they are also almost as common in radio-quiet quasars. Theories of the origin of the peaks are reviewed and it is argued that t

Victor Matveev, Robert Shrock

We report some new results on the complex-temperature (CT) singularities of $q$-state Potts models on the square lattice. We concentrate on the problematic region $Re(a) < 0$ (where $a=e^K$) in which CT zeros of the partition function are sensitive to finite lattice artifacts. From analyses of low-temperature series expansions for $3 \le q \le 8$, we establi

A. Pineda

The leading nonperturbative effects to the fine and hyperfine splitting were calculated some time ago. Recently, they have been used in order to obtain realistic numerical results for the lower levels in bottomonium systems. We point out that a contribution of the same order $O(Λ_{QCD}^4/m^3 α_s^2)$ has been overlooked. We calculate it in this paper.

F. del Aguila, J. A. Aguilar-Saavedra

We find a minimal set of constraints which are independent of the choice of weak quark basis and necessary and sufficient for CP conservation for four quark families, including also the case of degenerate quark masses. These invariant conditions are written in the mass eigenstate basis as a function of the fermion masses and charged current mixings. CP viola

Michal Horodecki, Pawel Horodecki, Ryszard Horodecki

We provide necessary and sufficient conditions for separability of mixed states. As a result we obtain a simple criterion of separability for $2\times2$ and $2\times3$ systems. Here, the positivity of the partial transposition of a state is necessary and sufficient for its separability. However, it is not the case in general. Some examples of mixtures which

J. Kim, J. Lopez, D. Nanopoulos, R. Rangarajan

We calculate the one-loop supersymmetric electroweak-like and QCD-like corrections to the top-quark pair-production cross section at the Tevatron, including the important effects of non-degenerate top-squarks and left-right top-squark mixing. The largest electroweak effects yield a negative shift in the cross section and are enhanced right below the threshol

Vadim Zeitlin

Spontaneous magnetization in the Maxwell QED$_{2+1}$ at finite fermion density is studied. It is shown that at low fermion densities the one-loop free energy has its minimum at some nonvanishing value of the magnetic field. The magnetization is due to the asymmetry of the fermion spectrum of the massive QED$_{2+1}$ in an external magnetic field.

Ivar Zapata, Roland Bartussek, Fernando Sols, Peter Hänggi

We argue that the phase across an asymmetric dc SQUID threaded by a magnetic flux can experience an effective ratchet (periodic and asymmetric) potential. Under an external ac current, a rocking ratchet mechanism operates whereby one sign of the time derivative of the phase is favored. We show that there exists a range of parameters in which a fixed sign (an

Oliver Rudolph

A formulation of the consistent histories approach to quantum mechanics in terms of generalized observables (POV measures) and effect operators is provided. The usual notion of `history&#39; is generalized to the notion of `effect history&#39;. The space of effect histories carries the structure of a D-poset. Recent results of J.D. Maitland Wright imply that

D. Fargion, A. Salis

Inverse Compton Scattering (ICS) by a relativistic electron beam jet at GeV energies (emitted by a compact object as a NS, BH,...), a NSJ, onto thermal BBR photons (from a nearby stellar companion) may originate a collinear gamma jet (GJ). Due to the binary system interaction the GJ precession would blaze suddenly toward the observer leading to a GRB event.

Morimitsu Tanimoto

We have studied CP violation originated by the phase of the neutrino mixing matrix in the long baseline neutrino oscillation experiments. The direct measurements of CP violation is the difference of the transition probabilities between CP-conjugate channels. In those experiments, the CP violating effect is not suppressed if the highest neutrino mass scale is

A. S. Cârstea, D. Grecu

A class of rational solutions of Toda lattice satisfying certain Backlund transformations and a class of mixed rational-soliton solutions (quasisolitons) in wronskian formare obtained using the method of Ablowitz and Satsuma. Also an extended class of rational solutions are found using an appropriate recursion relation. They are also solutions of Boussinesq

Andrei Okounkov, Grigori Olshanski

The classical algebra $Λ$ of symmetric functions has a remarkable deformation $Λ^*$, which we call the algebra of shifted symmetric functions. In the latter algebra, there is a distinguished basis formed by shifted Schur functions $s^*_μ$, where $μ$ ranges over the set of all partitions. The main significance of the shifted Schur functions is that they deter

C. Quesne, N. Vansteenkiste

The representation theory of deformed oscillator algebras, defined in terms of an arbitrary function of the number operator~$N$, is developed in terms of the eigenvalues of a Casimir operator~$C$. It is shown that according to the nature of the $N$ spectrum, their unitary irreducible representations may fall into one out of four classes, some of which contai

H. T. Koelink

The generic Hecke algebra for the hyperoctahedral group, i.e. the Weyl group of type B, contains the generic Hecke algebra for the symmetric group, i.e. the Weyl group of type A, as a subalgebra. Inducing the index representation of the subalgebra gives a Hecke algebra module, which splits multiplicity free. The corresponding zonal spherical functions are ca

S. Khoroshkin, D. Lebedev, S. Pakuliak

The traces over infinite dimensional representations of the central extended Yangian double for the product of operators which intertwine these representations are calculated. For the special combinations of the intertwining operators the traces are identified with form factors of local operators in SU(2)-invariant Thirring model. This identification is base

Narcisse Randrianantoanina

Let $\M$ be a von Neumann algebra with a faithful normal trace $\T$, and let $H^\infty$ be a finite, maximal, subdiagonal algebra of $\M$. Fundamental theorems on conjugate functions for weak$^*$\!-Dirichlet algebras are shown to be valid for non-commutative $H^\infty$. In particular the conjugation operator is shown to be a bounded linear map from $L^p(\M,

F. M. de Carvalho Filho

Based on the covariant background field method, we calculate the ultraviolet counter\-terms up to two-loop order and discuss the renormalizability of the three-dimensional non-linear sigma models with arbitrary Riemannian manifolds as target spaces. We investigate the bosonic model and its supersymmetric extension. We show that at the one-loop level these mo

F. Zimmerschied

The Lagrangian field-antifield formalism of Batalin and Vilkovisky (BV) is used to investigate the application of the collective coordinate method to soliton quantisation. It is shown how Noether identities and local symmetries of the Lagrangian arise when collective coordinates are introduced in order to avoid divergences related to zero modes. This transfo

I. Andrić, V. Bardek, L. Jonke

We consider the large-$N$ Sutherland model in the Hamiltonian collective-field approach based on the $1/N$ expansion. The Bogomol&#39;nyi limit appears and the corresponding solutions are given by static-soliton configurations. They exist only for $ł<1$, i.e. for the negative coupling constant of the Sutherland interaction. We determine their creation energi

B. Geyer, L. N. Granda, S. D. Odintsov

We discuss the phase structure of the NJL model in curved spacetime with magnetic field using $1/N$-expansion and linear curvature approximation. The effective potential for composite fields $\barψψ$ is calculated using the proper-time cut-off in the following cases: a) at non-zero curvature, b) at non-zero curvature and non-zero magnetic field, and c) at no

L. Bonora, L. P. Colatto, C. P. Constantinidis

In analogy with the Liouville case we study the $sl_3$ Toda theory on the lattice and define the relevant quadratic algebra and out of it we recover the discrete $W_3$ algebra. We define an integrable system with respect to the latter and establish the relation with the Toda lattice hierarchy. We compute the the relevant continuum limits. Finally we find the

Paul Sutcliffe

Using Seiberg-Witten theory it is known that the dynamics of N=2 supersymmetric SU(n) Yang-Mills theory is determined by a Riemann surface. In particular the mass formula for BPS states is given by the periods of a special differential on this surface. In this note we point out that the surface can be obtained from the quotient of a symmetric n-monopole spec

G. Marmo, G. Vilasi

Canonical coordinates for the Schrödinger equation are introduced, making more transparent its Hamiltonian structure. It is shown that the Schrödinger equation, considered as a classical field theory, shares with Liouville completely integrable field theories the existence of a {\sl recursion operator} which allows for the infinitely many conserved functiona

A. Rossi

We present a generalization of the resonant neutrino conversion in matter, including a random component in the matter density profile. The study is focused on the effect of such matter perturbations upon both large and small mixing angle MSW solutions to the solar neutrino problem. This is carried out both for the active-active $ν_e \ra ν_{μ,τ}$ as well as a

A. Djouadi

I discuss the physics prospects at future high--energy $e^+ e^-$ linear colliders. After summarizing some aspects of these future machines, I will review a few topics in the Standard Model which can be studied at these colliders: top quark, $W/Z$ vector bosons and Higgs particles physics. A brief discussion on the exploration of extensions of the Standard Mo

John Ellis, Klaus Geiger, Henryk Kowalski

We extend a quantum kinetic approach to the description of hadronic showers in space, time and momentum space to deep-inelastic $ep$ collisions, with particular reference to experiments at HERA. We follow the history of hard scattering events back to the initial hadronic state and forward to the formation of colour-singlet pre-hadronic clusters and their dec

As. Abada, M. B. Gavela, O. Pène

Massless neutrinos are exchanged in a neutron star, leading to long range interactions. Many body forces of this type follow and we resum them. Their net contribution to the total energy is negligible as compared to the star mass. The stability of the star is not in danger, contrary to recent assertions.

Michio Hashimoto

We show that isospin/SU(3) breaking terms can be introduced to the anomalous VVP coupling in the hidden local symmetry scheme without changing Wess-Zumino-Witten term in the low-energy limit. We make the analysis for anomalous processes of 2-body and 3-body decays; radiative vector meson decays(V \to Pγ), conversion decays of photon into a lepton pair(V \to

A. Bassetto

We summarize several basic features concerning canonical equal time quantization and renormalization of Yang--Mills theories in light--cone gauge. We describe a ``two component&#34; formulation which is reminiscent of the light--cone hamiltonian perturbation rules. Finally we review the derivation of the one--loop Altarelli--Parisi densities, using the corre

M. Roth, A. Denner

We provide high-energy approximations for all one-loop scalar 3- and 4-point functions and the corresponding tensor integrals that appear in scattering processes with four external on-shell particles. Our expressions are valid if all kinematical invariants are much larger than the internal and external masses. They contain all leading-order terms of the inte

D. Indumathi, Wei Zhu

We construct a dynamical model for the parton distributions in a nucleus by perturbative evolution of input distributions from a low starting scale. These input distributions are obtained by modifications of the corresponding free nucleon ones; the modifications being determined by standard nuclear physics considerations. The model gives good agreement with

Paolo Privitera

The potentiality of an experiment measuring the muon polarization in $K^+\rightarrowπ^0μ^+ν_μ$ at a $ϕ$ factory is discussed, with particular attention to the possibility of revealing unexpected violation of Time reversal invariancethrough the transverse polarization component. An experimental method is proposed which is based on the reconstruction of the $K

A. Culatti, G. Degrassi, F. Feruglio, A. Masiero

We analyse the contribution of new heavy virtual fermions to the $e^+e^- \rightarrow W^+W^-$ cross section. We find that there exists a relevant interplay between trilinear and bilinear oblique corrections. The result strongly depends on the chiral or vector--like nature of the new fermions. As for the chiral case we consider sequential fermions: one obtains

Masato Jimbo, Hidekazu Tanaka, Tadashi Kon, Toshiaki Kaneko

We introduce a new method to treat Majorana fermions and interactions with fermion-number violation on the GRACE system which has been developed for the automatic computation of the matrix elements for the processes of the standard model. Thus we have constructed a system for the automatic computation of cross-sections for the processes of the minimal SUSY s

H. G. Ballesteros, L. A. Fernandez, V. Martin-Mayor, A. Munoz Sudupe

We study the behavior of the antiferromagnetic RP$^2$ model in $d=3$. The vacuum structure is analyzed in the critical and low temperature regions, paying special attention to the spontaneous symmetry breaking pattern. Near the critical point we observe a full breakdown of the O(3) symmetry of the action. Several methods for computing critical exponents are

B. A. Berg, W. Beirl, B. Krishnan, H. Markum

We analyze Regge quantum gravity coupled to SU(2) gauge theory on $4^3\times 2$, $6^{3}\times 4$ and $8^{3}\times 4$ simplicial lattices. It turns out that the window of the well-defined phase of the gravity sector where geometrical expectation values are stable extends to negative gravitational couplings as well as to gauge couplings across the deconfinemen

A. P. Heinson

Top quarks are produced at the Tevatron proton-antiproton collider at Fermilab and at the Large Hadron (proton-proton) Collider at CERN in two ways: as quark-antiquark pairs, and singly. For each mode, the cross sections and future experimental yields are presented. I then discuss some precision measurements that can be made using the anticipated large data

Roberto De Pietri

Using Penrose binor calculus for $SU(2)$ ($SL(2,C)$) tensor expressions, a graphical method for the connection representation of Euclidean Quantum Gravity (real connection) is constructed. It is explicitly shown that: {\it (i)} the recently proposed scalar product in the loop-representation coincide with the Ashtekar-Lewandoski cylindrical measure in the spa

A. A. Coley, R. J. van den Hoogen, R. Maartens

The Full (non--truncated) Israel--Stewart theory of bulk viscosity is applied to dissipative FRW spacetimes. Dimensionless variables and dimensionless equations of state are used to write the Einstein--thermodynamic equations as a plane autonomous system and the qualitative behaviour of this system is determined. Entropy production in these models is also di

R. J. van den Hoogen, A. A. Coley

The truncated Israel-Stewart theory of irreversible thermodynamics is used to describe the bulk viscous pressure and the anisotropic stress in a class of spatially homogeneous viscous fluid cosmological models. The governing system of differential equations is written in terms of dimensionless variables and a set of dimensionless equations of state is utiliz

A A Coley, R J van den Hoogen

Isotropic and spatially homogeneous viscous fluid cosmological models are investigated using the truncated Israel-Stewart theory of irreversible thermodynamics to model the bulk viscous pressure. The governing system of differential equations is written in terms of dimensionless variables and a set of dimensionless equations of state is then utilized to comp

C J S Clarke, J A Vickers, J P Wilson

A new method is presented for assigning distributional curvature, in an invariant manner, to a space-time of low differentiability, using the techniques of Colombeau&#39;s `new generalised functions&#39;. The method is applied to show that curvature of a cone is equivalent to a delta function. The same is true under small enough perturbations.