May 1998 arXiv papers — page 16

M. P. Bellon, C. -M. Viallet

For any discrete time dynamical system with a rational evolution, we define an entropy, which is a global index of complexity for the evolution map. We analyze its basic properties and its relations to the singularities and the irreversibility of the map. We indicate how it can be exactly calculated.

M. Beccaria, G. Montagna, F. Piccinini, F. M. Renard

The virtual massive gauge boson effects on several observables in the process of charged fermion pairs production at $e^+e^-$ colliders are computed up to the TeV energy range in the Standard Model, working in the ``$Z$-peak subtracted'' representation. It is shown that these effects increase regularly with energy, approaching the typical ten percent

Muneto Nitta

We derive the moduli space for the global symmetry in N=1 supersymmetric theories. We show, at the generic points, it coincides with the space of quasi-Nambu-Goldstone (QNG) bosons, which appear besides the ordinary Nambu-Goldstone (NG) bosons when global symmetry G breaks down spontaneously to its subgroup H with preserving N=1 supersymmetry. At the singula

Han-Ying Guo, Ke Wu, Wei Zhang

Using the well-known Chern-Weil formula and its generalization, we systematically construct the Chern-Simons forms and their generalization induced by torsion as well as the Nieh-Yan (N-Y) forms. We also give an argument on the vanishing of integration of N-Y form on any compact manifold without boundary. A systematic construction of N-Y forms in D=4n dimens

Damien Challet, Yi-Cheng Zhang

We investigate further several properties of the minority game we have recently introduced. We explain the origin of the phase transition and give an analytical expression of $σ^2/N$ in the $N\ll2^M$ region. The ability of the players to learn a given payoff is also analyzed, and we show that the Darwinian evolution process tends to a self-organized state, i

Ferenc Igloi, Enrico Carlon

The surface and bulk properties of the two-dimensional Q > 4 state Potts model in the vicinity of the first order bulk transition point have been studied by exact calculations and by density matrix renormalization group techniques. For the surface transition the complete analytical solution of the problem is presented in the $Q \to \infty$ limit, including t

Ken-ichi Hikasa, Takaaki Nagano

Some mechanisms of supersymmetry breaking result in splitting of the third generation sfermions from the other sfermions. We show that the three-body decay branching ratio of the lighter chargino gives a sensitive probe of the sfermion mass spectrum if the chargino has a large gaugino component.

Dagmar Bruss

A generalization of the quantum cryptographic protocol by Bennett and Brassard is discussed, using three conjugate bases, i.e. six states. By calculating the optimal mutual information between sender and eavesdropper it is shown that this scheme is safer against eavesdropping on single qubits than the one based on two conjugate bases. We also address the que

Sean A. Hayward

A new framework is proposed for general dynamic wormholes, unifying them with black holes. Both are generically defined locally by outer trapping horizons, temporal for wormholes and spatial or null for black and white holes. Thus wormhole horizons are two-way traversible, while black-hole and white-hole horizons are only one-way traversible. It follows from

K. Naito, K. Yoshida, Y. Nemoto, M. Oka

Dynamical breaking of chiral symmetry in effective models of QCD is studied. Introducing a cut-off function or a non-local interaction, the Noether current must be modified and thus the Ward-Takahashi identity and the PCAC relation are modified accordingly. We point out that the pion decay constant must be defined consistently with the Noether current so tha

Michio Hashimoto

A new formula for the composite Higgs boson mass is given, based on the Ward-Takahashi identity and the Schwinger-Dyson(SD) equation. In this formula the dominant asymptotic solution of the SD equation yields a correct answer, in sharp contrast to the Partially Conserved Dilatation Current(PCDC) approach where the sub- and sub-sub-dominant solutions should b

Manuel Drees, E. Ma, P. N. Pandita, D. P. Roy

We point out that present experimental limits from searches for neutral Higgs bosons at LEP already imply stringent lower bounds on the mass of the charged Higgs boson in the Minimal Supersymmetric Standard Model (MSSM); these bounds are especially severe for low values of \tanb ($\tanb \leq 3$), where the $H^+ \bar{t} b$ coupling is large. However, these in

Jean P. Brodie, Linda L. Schroder, John P. Huchra, Andrew C. Phillips

Keck spectroscopy of 5 proto-globular cluster candidates in NGC 1275 has been combined with HST WFPC2 photometry to explore the nature and origin of these objects and discriminate between merger and cooling flow scenarios for globular cluster formation. The objects we have studied are not HII regions, but rather star clusters, yet their integrated spectral p

Jiin-Chang Shaw, Ming-Hsien Tu

The supersymmetric version of the Miura and Bäcklund transformations associated with the supersymmetric Gelfand-Dickey bracket are investigated from the point of view of the Kupershmidt-Wilson theorem.

J. Machta

Computational devices may be supplied with external sources of information (oracles). Quantum oracles may transmit phase information which is available to a quantum computer but not a classical computer. One consequence of this observation is that there is an oracle which is of no assistance to a classical computer but which allows a quantum computer to solv

Antoine Suarez

We discuss a number of comments on quant-ph/9801061, and propose to introduce the concept of 'Causal Indistinguishability'. The incompatibility between Quantum Mechanics and Nonlocal Causality appears to be unavoidable: upholding of Quantum Mechanics by experiment would mean to live with influences backward in time, just as we are now living with suc

V. Buzek, G. Drobny, R. Derka, G. Adam

Knowing and guessing, these are two essential epistemological pillars in the theory of quantum-mechanical measurement. As formulated quantum mechanics is a statistical theory. In general, a priori unknown states can be completely determined only when measurements on infinite ensembles of identically prepared quantum systems are performed. But how one can est

Philippe Matherat, Marc-Thierry Jaekel

As revealed by discussions of principle on energy dissipation by computers, logic imposes constraints on physical systems designed for a logical function. We define a notion of logical dissipation for a finite automaton. We discuss the constraints associated with physical implementation of automata and exhibit the role played by modularity for testability. A

Richard Jozsa, Michal Horodecki, Pawel Horodecki, Ryszard Horodecki

Suppose that a quantum source is known to have von Neumann entropy less than or equal to S but is otherwise completely unspecified. We describe a method of universal quantum data compression which will faithfully compress the quantum information of any such source to S qubits per signal (in the limit of large block lengths).

Robert R. Tucci

We show how to express the information contained in a Quantum Bayesian (QB) net as a product of unitary matrices. If each of these unitary matrices is expressed as a sequence of elementary operations (operations such as controlled-nots and qubit rotations), then the result is a sequence of operations that can be used to run a quantum computer. QB nets have b

Robert R. Tucci

We present a new algorithm for reducing an arbitrary unitary matrix into a sequence of elementary operations (operations such as controlled-nots and qubit rotations). Such a sequence of operations can be used to manipulate an array of quantum bits (i.e., a quantum computer). We report on a C++ program called "Qubiter" that implements our algorithm. Q

B. Segev, J. C. Wells

The two-center Dirac equation for an electron in the external electromagnetic field of two colliding heavy ions in the limit in which the ions are moving at the speed of light is exactly solved and nonperturbative amplitudes for free electron-positron pair production are obtained. We find the condition for the applicability of this solution for large but fin

C. G. Bao

Inherent nodal surfaces existing in the wavefunctions of intrashell states of 4-valence-electron atoms have been investigated. The decisive effect of these surfaces has been demonstrated, the ordering of low-lying levels has been predicted, a primary classification scheme has been proposed, the existence of three rotation bands has been suggested.

S. Goedecker, C. Umrigar

The exchange-correlation energy in Kohn-Sham density functional theory is expressed as a functional of the electronic density and the Kohn-Sham orbitals. An alternative to Kohn-Sham theory is to express the energy as a functional of the reduced first-order density matrix or equivalently the natural orbitals. In the former approach the unknown part of the fun

M. E. Bracco, G. Krein, M. Nielsen

The binding energy of nuclear matter including exchange and pionic effects is calculated in a quark-meson coupling model with massive constituent quarks. As in the case with elementary nucleons in QHD, exchange effects are repulsive. However, the coupling of the mesons directly to the quarks in the nucleons introduces a new effect on the exchange energies th

Ch. Elster, W. Schadow, A. Nogga, W. Gloeckle

The Faddeev equations for the three body bound state are solved directly as three dimensional integral equation without employing partial wave decomposition. The numerical stability of the algorithm is demonstrated. The three body binding energy is calculated for Malfliet-Tjon type potentials and compared with results obtained from calculations based on part

Boris Tomasik, Ulrich Heinz

We present a model study of single-particle spectra and two-particle Bose-Einstein correlations for opaque sources. We study the transverse mass dependence of the correlation radii R_\perp, R_\parallel and R_0 in the YKP parametrization and find a strong sensitivity of the temporal radius parameter R_0^2 to the source opacity. A simple comparison with the pu

David B. Fairlie, Tatsuya Ueno

We give a series of integrable top equations associated with the projective geometry over Z_2 as a (2^n-1)-dimensional generalisation of the 3D Euler top equations. The general solution of the (2^n-1)D top is shown to be given by an integration over a Riemann surface with genus (2^{n-1}-1)^2.

John Ryan

Plemelj projection operators are introduced for spaces of square integrable functions defined over the boundaries of a class of compact real n-dimensional manifolds lying in C^n. These manifolds posses many properties similar to domains in R^n, and are consequently called domain manifolds. The key ingredients used here are techniques from both real and compl

B. van Geemen, E. Izadi

We complete the proof of the fact that the moduli space of rank two bundles with trivial determinant embeds into the linear system of divisors on $Pic^{g-1}C$ which are linearly equivalent to $2Θ$. The embedded tangent space at a semi-stable non-stable bundle $ξ\oplusξ^{-1}$, where $ξ$ is a degree zero line bundle, is shown to consist of those divisors in $|

Benoit Gerard

This thesis studies moduli spaces of singular connections on 3-manifolds and manifolds with cylindrical ends. A Chern-Simons functional is defined for singular connections on 3-manifolds which are singular along a knot. The critical points of that Chern-Simons functional are flat singular connections. The Hodge-de Rham theory of singular flat connections is

Takeshi Suzuki

The functors constructed by Arakawa and the author relate the representation theory of gl_n and that of the degenerate affine Hecke algebra H_l of GL_l. They transform the Verma modules over gl_n to the standard modules over H_l. They transform the simple modules to the simple modules. We also prove that they transform the Jantzen filtration on the Verma mod

M. Scheunert, R. B. Zhang

Using techniques developed in a recent article by the authors, it is proved that the 2-cohomology of the Lie superalgebra sl(m|1); m > 1, with coefficients in its enveloping algebra is trivial. The obstacles in solving the analogous problem for sl(3|2) are also discussed.

V. A. Groza, N. Z. Iorgov, A. U. Klimyk

Infinite dimensional representations of the real form U_q(u_{n,1}) of the Drinfeld--Jimbo algebra U_q(gl_{n+1}) are defined. The principal series of representations of U_q(u_{n,1}) is studied. Intertwining operators for pairs of the principal series representations are calculated in an explicit form. The structure of reducible representations of the principa

Mikhail Grinberg

Let X be a smooth, connected, closed subvariety of a complex vector space V. The asymptotic cone as(X) is naturally equipped with a nearby cycles sheaf P coming from the specialization of X to as(X). We show that if X is transverse to infinity in a suitable sense, then the Fourier transform of P is an intersection homology sheaf.

R. Kallosh, A. Rajaraman

We argue that supersymmetric higher-dimension operators in the effective actions of M-theory and IIB string theory do not affect the maximally supersymmetric vacua: $adS_4\times S^7$ and $adS_7\times S^4$ in M-theory and $adS_5\times S^5$ in IIB string theory. All these vacua are described in superspace by a fixed point with all components of supertorsion an

G. Fulop, D. M. Gitman, I. V. Tyutin

Reparametrization invariance being treated as a gauge symmetry shows some specific peculiarities. We study these peculiarities both from a general point of view and on concrete examples. We consider the canonical treatment of reparametrization invariant systems in which one fixes the gauge on the classical level by means of time-dependent gauge conditions. I

Efrain J. Ferrer, Vivian de la Incera

The magnetic response of the charged anyon fluid at temperatures larger than the fermion energy gap is investigated in the self-consistent field approximation. In this temperature region a new phase, characterized by an inhomogeneous magnetic penetration, is found. The inhomogeneity is linked to the existence of an imaginary magnetic mass which increases wit

Khosrow Chadan, N. N. Khuri, Andre Martin, Tai Tsun Wu

We prove that, in (2+1) dimensions, the S-wave phase shift, $ δ_0(k)$, k being the c.m. momentum, vanishes as either $δ_0 \to {c\over \ln (k/m)} or δ_0 \to O(k^2)$ as $k\to 0$. The constant $c$ is universal and $c=π/2$. This result is established first in the framework of the Schrödinger equation for a large class of potentials, second for a massive field th

Albert Schwarz

It was shown by Connes, Douglas, Schwarz[1] that one can compactify M(atrix) theory on noncommutative torus. We prove that compactifications on Morita equivalent tori are physically equivalent. This statement can be considered as a generalization of non-classical duality conjectured in [1] for two-dimensional tori.

Mark Trodden

A brief review of the fundamental ideas behind electroweak baryogenesis is presented. Since a successful implementation of these ideas requires an extension of the minimal standard model, I comment on the necessary physics and how experimental constraints make these scenarios testable at the LHC, and perhaps at existing colliders.

O. Schroeder, H. Reinhardt, H. Weigel

The three flavor version of the Nambu-Jona-Lasinio chiral soliton model for baryons is employed to calculate the twist-2 contribution to the polarized nucleon structure function $g_1(x)$. In particular the role of the strange quark degree of freedom as a collective excitation of the chiral soliton is investigated in the context of flavor symmetry breaking. T

A. Bartl, H. Eberl, S. Kraml, W. Majerotto

We discuss pair production of stops, sbottoms, staus and tau--sneutrinos at a $μ^+ μ^-$ collider. We present the formulae for the production cross sections and perform a detailed numerical analysis within the Minimal Supersymmetric Standard Model. In particular, we consider sfermion production near $\sqrt{s} = m_{H^0}$ and $\sqrt{s} = m_{A^0}$.

M. Nardi, H. Satz

We study the clustering of colour strings in the transverse plane of nucleus-nucleus collisions and argue that deconfinement sets in when the string density within a cluster reaches a critical value. We show that this implies a minimal cluster size at the onset of deconfinement, which in turn results in discontinuous behaviour for J/Psi suppression.

Michal Praszalowicz, Andrzej Rostworowski

The odderon equation is studied in terms of the variable suggested by the modular invariance of the 3 Reggeon system. Odderon charge is identified with the cross-product of three conformal spins. A complete set of commuting operators: h^2 and q is diagonalized and quantization conditions for eigenvalues of the odderon charge q are solved for arbitrary confor

S. Dawson, S. Dittmaier, M. Spira

Neutral Higgs-boson pair production provides the possibility of studying the trilinear Higgs couplings at future high-energy colliders. We present the QCD corrections to the gluon-initiated processes in the limit of a heavy top quark in the loops and the Drell-Yan-like pair production of scalar and pseudoscalar Higgs particles. The pp cross sections are disc

Alessandro De Angelis

Interactions between the products of the hadronic decays of different Ws in WW pair events can occur at several stages: from the colour rearrangement between the quarks coming from the primary branching, to the gluon exchange during the parton cascade, to the mixing of identical pions due to Bose-Einstein correlations. Besides the intrinsic interest of their

Valery Telnov

In this review we consider three important applications of lasers in high energy physics: gamma gamma, gamma electron colliders, laser cooling, positron production. These topics are actual now due to plans of construction linear e+e-, e-e-, gamma-gamma, gamma-e colliders with energies 0.3--1 TeV. High energy photons for gamma-gamma, gamma-e collisions can be

Richard A. Matzner, Mijan F. Huq, Deirdre Shoemaker

We present here an alternative approach to data setting for spacetimes with multiple moving black holes generalizing the Kerr-Schild form for rotating or non-rotating single black holes to multiple moving holes. Because this scheme preserves the Kerr-Schild form near the holes, it selects out the behaviour of null rays near the holes, may simplify horizon tr

G. Bimonte, R. Musto, A. Stern, P. Vitale

We find a one-parameter family of Lagrangian descriptions for classical general relativity in terms of tetrads which are not c-numbers. Rather, they obey exotic commutation relations. These noncommutative properties drop out in the metric sector of the theory, where the Christoffel symbols and the Riemann tensor are ordinary commuting objects and they are gi

Jean-Philippe Uzan, Nathalie Deruelle, Neil Turok

When working in synchronous gauges, pseudo-tensor conservation laws are often used to set the initial conditions for cosmological scalar perturbations, when those are generated by topological defects which suddenly appear in an up to then perfectly homogeneous and isotropic universe. However those conservation laws are restricted to spatially flat (K=0) Frie

J. M. Overduin, P. S. Wesson

We review higher-dimensional unified theories from the general relativity, rather than the particle physics side. Three distinct approaches to the subject are identified and contrasted: compactified, projective and noncompactified. We discuss the cosmological and astrophysical implications of extra dimensions, and conclude that none of the three approaches c

N. Lutke-Entrup, B. Placais, P. Mathieu, Y. Simon

We have measured the surface impedance of thick superconductors in the mixed state over a broad 2 kHz - 20 MHz frequency range. The depinning cross-over is observed; but it is much broader than expected from classical theories of pinning. A striking result is the existence of size effects which invalidate the common interpretation of the low-frequency surfac

N. Bernstein, M. J. Aziz, E. Kaxiras

The structural features of the interface between the cystalline and amorphous phases of Si solid are studied in simulations based on a combination of empirical interatomic potentials and a nonorthogonal tight-binding model. The tight-binding Hamiltonian was created and tested for the types of structures and distortions anticipated to occur at this interface.

Michael O. Ignatiev, Bulbul Chakraborty

We propose a simple dynamical model for a glass transition. The dynamics is described by a Langevin equation in a piecewise parabolic free energy landscape, modulated by a temperature dependent overall curvature. The zero-curvature point marks a transition to a phase with broken ergodicity which we identify as the glass transition. Our analysis shows a conne

Silvio Franz, Giorgio Parisi

In this paper we study the critical properties of a finite dimensional generalization of the p-spin model. We find evidence that in dimension three, contrary to its mean field limit, the glass transition is associated to a diverging susceptibility (and correlation length).

J. E. Berger, S. J. Smullin, W. L. Karlin, X. S. Ling

We report a crucial experimental test of the present models of the peak effect in weakly disordered type-II superconductors. Our results favor the scenario in which the peak effect arises from a crossover between the Larkin pinning length and a rapidly falling elastic length in a vortex phase populated with thermally excited topological defects. A thickness

Frederic Faure, Bernard Parisse

The semi-classical study of the integer Quantum Hall conductivity is investigated for electrons in a bi-periodic potential $V(x,y)$. The Hall conductivity is due to the tunnelling effect and we concentrate our study to potentials having three wells in a periodic cell. A non-zero topological conductivity requires special conditions for the positions, and shap

Maxim Mostovoy, Jasper Knoester

We use the optimal fluctuation method to find the density of electron states inside the pseudogap in disordered Peierls chains. The electrons are described by the one-dimensional Dirac Hamiltonian with randomly varying mass (the Fluctuating Gap Model). We establish a relation between the disorder average in this model and the quantum-mechanical average for a

Dario Alfe`, Michael J. Gillan

We demonstrate the practical feasibility of calculating transport coefficients such as the viscosity of liquids completely from first principles using the Green-Kubo relations. Results presented for liquid aluminum are shown to have a statistical error of only ca. 5%. The importance of such calculations is illustrated by results for a liquid iron-sulfur allo

Andrei Mudrov, Konstantin Varnashev

A new approach to summation of divergent field-theoretical series is suggested. It is based on the Borel transformation combined with a conformal mapping and does not imply the exact asymptotic parameters to be known. The method is tested on functions expanded in their asymptotic power series. It is applied to estimating the critical exponent values for an N

Ivan J. Griffin, Peter J. Klar, Daniel Wolverson, J. John Davies

Wide quantum dots were fabricated from multiple quantum well structures based on Zn_{1-x}Mn_xTe/ZnTe (x = 0.076) dilute magnetic semiconductors and were investigated via photoluminescence (PL) in a magnetic field. Calculations taking into account the strain in the two types of structure enabled the PL transitions to be identified and show that the dominant e

Frederic Mila

Starting from a modified version of the the S=1/2 Kagome antiferromagnet to emphasize the role of elementary triangles, an effective Hamiltonian involving spin and chirality variables is derived. A mean-field decoupling that retains the quantum nature of these variables is shown to yield a Hamiltonian that can be solved exactly, leading to the following pred

B. Groh, S. Dietrich

Based on density-functional theory we analyze the full phase diagram, the occurrence of long-ranged orientational order, and the structural properties of dipolar fluids. As a model system we consider the Stockmayer fluid that consists of spherical particles interacting via a Lennard-Jones potential plus dipolar forces. For sufficiently strong dipole moments

Jeong-Man Park, Michael W. Deem

We analyze the dynamics of the ion-dipole pairing reaction in the two-dimensional Coulomb gas in the presence of disorder. Sufficiently singular disorder forces the critical temperature of the Kosterlitz-Thouless-Berezinskii fixed point to be non-universal. This disorder leads to anomalous ion pairing kinetics with a continuously variable decay exponent. Suf

D. Helbing, P. Molnar, F. Schweitzer

A simulation model for the dynamic behaviour of pedestrian crowds is mathematically formulated in terms of a social force model, that means, pedestrians behave in a way as if they would be subject to an acceleration force and to repulsive forces describing the reaction to borders and other pedestrians. The computational simulations presented yield many reali

O. Baran, C. C. Wan, R. Harris

We show how to employ thermal lattice gas models to describe non-equilibrium phenomena. This is achieved by relaxing the restrictions of the usual micro-canonical ensemble for these models via the introduction of thermal ``demons'' in the style of Creutz. Within the Lattice Boltzmann approximation, we then derive general expressions for the usual tra

Marc Dymetman

This paper presents a model for linguistic description based on group theory. A grammar in this model, or "G-grammar", is a collection of lexical expressions which are products of logical forms, phonological forms, and their inverses. Phrasal descriptions are obtained by forming products of lexical expressions and by cancelling contiguous elements wh

L. M. Lubin, M. Postman, J. B. Oke

We present a dynamical study of the CL0023+0423 system at a redshift of z = 0.84. This system consists of two components separated in velocity space by 2900 km/s and on the plane of the sky by 0.23 h^{-1} Mpc. A kinematic analysis indicates that the two components are a poor cluster with a velocity dispersion of 415 km/s and a less massive group with a veloc

Leonid M. Ozernoy, Alexei M. Fridman, Peter L. Biermann

We discuss mechanisms for angular momentum transport in the clumpy medium of the circumnuclear disk at the Galactic center. The viscosity due to clump-clump collisions is found to be less than some critical viscosity; this meets the conditions at which a collective mode of nonaxisymmetric shear perturbations in the disk is able to grow until going into the s

J. Michael Owen, David H. Weinberg, Jens V. Villumsen

The growth of structure from scale-free initial conditions is one of the most important tests of cosmological simulation methods, providing a realistically complex problem in which numerical results can be compared to rigorous analytic scaling laws. Previous studies of this problem have incorporated gravitational dynamics and adiabatic gas dynamics, but radi

Tom MacFarland, H. M. P. Couchman, F. R. Pearce, Jakob Pichlmeier

We have developed a parallel Particle-Particle, Particle-Mesh (P3M) simulation code for the Cray T3E parallel supercomputer that is well suited to studying the time evolution of systems of particles interacting via gravity and gas forces in cosmological contexts. The parallel code is based upon the public-domain serial Adaptive P3M code of Couchman et al. Th

W. R. Hix, A. M. Khokhlov, J. C. Wheeler, F. -K. Thielemann

Examination of the process of silicon burning, the burning stage that leads to the production of the iron peak nuclei, reveals that the nuclear evolution is dominated by large groups of nuclei in mutual equilibrium. These quasi-equilibrium (QSE) groups form well in advance of the global Nuclear Statistical Equilibrium (NSE). We present an improved ``minimal&

Shude Mao, H. J. Mo

We suggest that the bulge-to-disc ratios of spiral galaxies are primarily determined by the angular momenta of their host haloes predicted in current hierarchical clustering models for structure formation. Gas with low specific angular momentum becomes self-gravitating and presumably forms stars before it can settle into a rotationally supported disc. We ass

Sandhya M. Rao, David A. Turnshek

The discovery of a z_abs = 0.0912 damped Lyman-alpha absorption-line system in the HST-FOS ultraviolet spectrum of the quasar OI 363 (0738+313) is reported. This is the lowest redshift quasar damped Lyman-alpha system known. Its neutral hydrogen column density is N(HI) = 1.5(+/- 0.2) E21 atoms/cm^2, which easily exceeds the classical criterion for damped Lym

Yuri Efremov, Bruce Elmegreen

The origin of a regular, 600 pc-long arc of young stars and clusters in the Constellation III region of the Large Magellanic Cloud is considered. The circular form of this arc suggests that the prestellar gas was uniformly swept up by a central source of pressure. In the center of the arc are six $\sim30$ My old A-type supergiant stars and a Cepheid variable

N. Audard, F. Kupka, P. Morel, J. Provost

Some of the rapidly oscillating (CP2) stars, have frequencies which are larger than the theoretical acoustic cut-off frequency. As the cut-off frequency depends on the T(tau) relation in the atmosphere, we have computed models and adiabatic frequencies for pulsating Ap stars with T(tau) laws based on Kurucz model atmospheres and on Hopf's purely radiativ

Istvan Szapudi

The first non-trivial cumulant correlator of the galaxy density field $Q_{21}$ is examined from the point of view of biasing. It is shown that to leading order it depends on two biasing parameters $b$, and $b_2$, and on $q_{21}$, the underlying cumulant correlator of the mass. As the skewness $Q_3$ has analogous properties, the slope of the correlation funct

Martin Kerscher

We use a measure of clustering derived from the nearest neighbour distribution and the void probability function to distinguish between regular and clustered structures. This measure offers a succinct way to incorporate additional information beyond the two-point correlation function. Application to a supercluster catalogue by Einasto et al. (1997) reveals n

Insu Yi, Jonathan E. Grindlay

We examine the spin-up of low luminosity, low mass X-ray binaries (LMXBs) to millisecond pulsars (MSPs). In the conventional spin-up model of the Ghosh & Lamb type, where the stellar magnetic field interacts with the Keplerian accretion disk, MSPs could be produced from LMXBs if their magnetic field B < 10^{8}({\dot M}/10^{16}g/s)^{1/2}G, where {\dot M} is t

Jeremy S. Heyl, Lars Hernquist

Recent observations of the compact source embedded within the supernova remnant RCW 103 rekindle interest in the origin of this object&#39;s emission. We contrast several models in which neutron-star cooling powers RCW 103. Specifically, either the presence of an accreted envelope or a sufficiently intense magnetic field can account for the X-ray emission fr

V. L. Khokhlova, D. V. Vasilchenko, V. V. Stepanov, V. V. Tsymbal

When using a recently developed method of Doppler-Zeeman mapping (Vasilchenko et al., 1996) for analysis of a real star and real observational data, we are confronted with limitations due to the model simplifications and unavoidable errors in observed spectra. We discuss the errors introduced by probable inaccurracies of the mathematical model: analytical fi

D. E. Mkrtichian, A. V. Kusakin, E. B. Janiashvili, J. G. Lominadze

The history and present status of informal asteroseismological network of Asian observatories of Ukraine, Russia, Kazakhstan, Georgia and Turkmenistan is given. We give briefly the description of facilities of CAN sites, the 1994-1997 activity of CAN in international multisite asteroseismological campaigns and further strategy of CAN. We call for close colla

I. Bigi, M. Shifman, N. Uraltsev, A. Vainshtein

The &#39;t Hooft model (two-dimensional QCD in the limit of large number of colors) is used as a laboratory for exploring various aspects of the heavy quark expansions in the nonleptonic and semileptonic decays of heavy flavors. We perform a complete operator analysis and construct the operator product expansion (OPE) up to terms O(1/m_Q^4), inclusively. The

D. J. Scalapino, Steven R. White

For the traditional low T_c superconductors, the superconducting condensation energy is proportional to the change in energy of the ionic lattice between the normal and superconducting state, providing a clear link between pairing and the electron-ion interaction. Here, for the t-J model, we discuss an analogous relationship between the superconducting conde

P. Vogel

It is shown that in N \simeq Z nuclei the effects of isovector pairing and the symmetry energy are intimately related. In particular, in the odd-odd N = Z nuclei these two effect are essentially equal in magnitude, causing near degeneracy of the lowest T = 1 and T = 0 states and appearance of the T = 1 ground state isospin in many such nuclei. Following the

Marco Mackaay

In this paper I define the notion of a non-degenerate finitely semi-simple semi-strict spherical 2-category of non-zero dimension. Given such a 2-category I define a state-sum for any triangulated compact closed oriented 4-manifold and show that this state-sum does not depend on the chosen triangulation by proving invariance under the 4D Pachner moves. This

B. T. Draine

If the Galaxy contains ~10^{11}M_sol in cold gas clouds of ~Jovian mass and ÃU size, these clouds will act as converging lenses for optical light, magnifying background stars at a detectable rate. The resulting light curves can resemble those due to gravitational lensing by a point mass, raising the possibility that some of the events attributed to gravitati

Christopher Beattie

How close are Galerkin eigenvectors to the best approximation available out of the trial subspace ? Under a variety of conditions the Galerkin method gives an approximate eigenvector that approaches asymptotically the projection of the exact eigenvector onto the trial subspace -- and this occurs more rapidly than the underlying rate of convergence of the app

Peter Constantin, Qing Nie, Norbert Schorghofer

The dynamics of large eddies in the atmosphere and oceans is described by the surface quasi geostrophic equation, which is reminiscent of the Euler equations. Thermal fronts build up rapidly. Two different numerical methods combined with analytical criteria are used to show there are no singularities in finite time.

T. M. Aliev, M. Savci

We investigate the radiative B_c -> rho^+ gamma and B_c -> K^{*+} gamma decays in the standard model. The transition form factors are calculated in the framework of the light cone QCD sum rules method. We estimate the branching ratios of the B_c -> rho^+ gamma and B_c -> K^{*+} gamma decays.

Aaron J. Romanowsky, Christopher S. Kochanek

We employ Schwarzschild&#39;s method of orbit modeling to constrain the mass profiles of the central lens galaxies in Q0957+561 and PG 1115+080. We combine the measured central projected stellar velocity dispersions of these galaxies with the self-similar radial profiles of the rms velocity and of the Gauss-Hermite moment h_4 observed in nearby galaxies for

Tim D. Cochran, Paul Melvin

A theory of finite type invariants for arbitrary compact oriented 3-manifolds is proposed, and illustrated through many examples arising from both classical and quantum topology. The theory is seen to be highly non-trivial even for manifolds with large first betti number, encompassing much of the complexity of Ohtsuki&#39;s theory for homology spheres. (For

R. Escribano, J. -M. Frere, A. Gevaert, D. Monderen

The presence of neutrinos from Boron decay in the flux observed on Earth is attested by the observation of their energy spectrum. Possible distortions of the spectrum investigated in current detectors are often interpreted in terms of evidence in favour or against various schemes of neutrino oscillations. We stress here that a distortion of the spectrum at h

P. M. Saffin, Anupam Mazumdar, E. J. Copeland

We look for instanton solutions in a class of two scalar field gravity models, which includes the low energy string action in four dimensions. In models where the matter field has a potential with a false vacuum, we find that non-singular instantons exist as long as the Dilaton field found in string theory has a potential with a minimum, and provide an examp

Nikolaos Irges

We present a dilaton dominated scenario for supersymmetry breaking in a recently constructed realistic superstring inspired model with an anomalous U(1) symmetry. Supersymmetry is broken via gaugino condensation due to a confining SU(Nc) gauge group in the hidden sector. In particular, we find that by imposing on the model the phenomenological constraint of

Sudipta Mukherji

We analyse various world-sheet properties of the $SL(2,Z)$ covariant type IIB string action by coupling it with $SL(2,Z)$ covariant source.

Hongying Jin

We discuss the rescattering effects in decays $B\to π+K$. The picture we take is very simple: first, B decay into $K*ρ$, then $K*$ and $ρ$ go to kaon and pion by exchanging a pion. We find a up to ten percent CP violation asymmetry rate. We also discuss its correction to the constraint of angle $γ$ proposed recently.

Glenn Barnich

In the context of algebraic renormalization, the extended antifield formalism is used to derive the general forms of the anomaly consistency condition and of the Callan-Symanzik equation for generic gauge theories. A local version of the latter is used to derive sufficient conditions for the vanishing of beta functions associated to terms whose integrands ar

D. A. Garanin, X. Martinez Hidalgo, E. M. Chudnovsky

The escape rate Γof the large-spin model described by the Hamiltonian H = -DS_z^2 - H_zS_z - H_xS_x is investigated with the help of the mapping onto a particle moving in a double-well potential U(x). The transition-state method yields $Γ$ in the moderate-damping case as a Boltzmann average of the quantum transition probabilities. We have shown that the tran