January 1996 arXiv papers — page 4

W. R. Magro, D. M. Ceperley, C. Pierleoni, B. Bernu

We present a path-integral Monte Carlo study of dissociation in dense hydrogen ($1.75 \leq r_s \leq 2.2$, with $r_s$ the Wigner sphere radius). As temperature is lowered from $10^5$ to 5000 K, a molecular hydrogen gas forms spontaneously from a neutral system of protons and electrons. At high density, $r_s < 2.0$, thermally activated dissociation is accompan

P. Fendley, H. Saleur

We compute exactly the non-equilibrium DC noise in a Luttinger liquid with an impurity and an applied voltage. By generalizing Landauer transport theory for Fermi liquids to interacting, integrable systems, we relate this noise to the density fluctuations of quasiparticles. We then show how to compute these fluctuations using the Bethe ansatz. The non-trivia

S. -R. Eric Yang, J. Rammer

The dependence of the localization length on the number of occupied subbands $N$ in low-dimensional semiconductors is investigated. The localization length is shown to be proportional to the number of occupied subbands in quasi-one-dimensional quantum wires while it grows exponentially with $N$ in quasi-two-dimensional systems. Also a weak localization theor

Raymond E. Goldstein, David J. Muraki, Dean M. Petrich

In the bistable regime of the FitzHugh-Nagumo model of reaction-diffusion systems, spatially homogeneous patterns may be nonlinearly unstable to the formation of compact ``localized states.&#34; The formation of space-filling patterns from instabilities of such structures is studied in the context of a nonlocal contour dynamics model for the evolution of bou

L. M. Pismen, B. Y. Rubinstein

Automated algorithms for derivation of amplitude equations in the vicinity of monotonic and Hopf bifurcation manifolds are presented. The implementation is based on Mathematica programming, and is illustrated by several examples

Carlo Graziani, Don Q. Lamb

We analyze the systematic errors in the positions of bursts in the BATSE 1B, 2B and 3B catalogs, using a likelihood approach. We use the BATSE data in conjunction with 196 single IPN arcs. We assume circular Gaussian errors, and that the total error is the sum in quadrature of the systematic error $\sigma_{\rm sys}$ and statistical error $\sigma_{\rm stat}$,

Eric G. Blackman, Insu Yi

A torus of reduced differential rotation can form in the inner $\siml 10$pc core of active galactic nuclei incurring a density enhancement that can account for obscuration of X-rays in Seyferts when the initial inner core to black hole mass ratio $\gsim 50$. The same density enhancement and reduction in differential rotation can also lead to dynamo growth of

Buell T. Jannuzi

The importance of HST for the study of quasar absorption lines and of the nature of the intergalactic medium is illustrated by reviewing selected results from past HST observations. Topics reviewed include the study of Ly-alpha absorbers at low redshift and the search for a diffuse IGM at high redshifts.

Todor Stanev, Robert Schaefer, Alan Watson

We examine the correlation between the arrival direction of ultra high energy cosmic ray showers and gamma ray bursts in the third BATSE catalog. We find no correlation between the two data sets. We also find no correlations between a pre-BATSE burst catalog and the Haverah Park Ultra High Energy shower set that cover approximately the same period of time.

Fred C. Adams, Marco Fatuzzo

We present models for the initial mass function (IMF) for stars forming within molecular clouds. These models use the idea that stars determine their own masses through the action of powerful stellar outflows. This concept allows us to calculate a semi-empirical mass formula (SEMF), which provides the transformation between initial conditions in molecular cl

Prasad Subramanian, Peter A. Becker, Menas Kafatos

We derive expressions for a ``hybrid&#39;&#39; viscosity arising from Coulomb collisions between ions in the presence of tangled magnetic fields. Such magnetic fields are expected to be embedded in accretion flows onto black holes and other compact objects. Ion viscosity in the absence of magnetic fields has been shown to appreciable in hot accretion disks,

John M. Blondin, P. Lundqvist, Roger A. Chevalier

Multiwavelength observations of Type II supernovae have shown evidence for the interaction of supernovae with the dense slow winds from the red supergiant progenitor stars. Observations of planetary nebulae and the nebula around SN 1987A show that the slow winds from extended stars frequently have an axisymme- tric structure with a high density in the equato

J. A. Peacock

These lectures cover the basics of inflationary models for the early universe, concentrating particularly on the generation of density fluctuations from scalar-field dynamics. The subsequent gravitational dynamics of these fluctuations in dark matter in a Friedmann model are described, leading to a review of the current situation in confronting inflationary

Georg B. Larsen, Jes Madsen

We calculate the linear power spectrum for a range of mixed dark matter (MDM) models assuming a massive (few eV) boson, $\phi$, instead of a neutrino as the hot component. We consider both the case where the hot dark matter (HDM) particle is a boson and the cold component is some other unknown particle, and the case where there is only one dark matter partic

Akihiko Tomita, Yoshio Tomita, Mamoru Saito

The star formation rate in spiral galaxies is considered to be decreasing continuously with time in a time scale of $10^{9}$ yr. The present star formation activity, on the other hand, shows various degrees among galaxies. We make a new data set of 1681 nearby spiral galaxies from available databases and study the statistics of the present star formation act

A. Mastichiadis

Shock waves associated with shell type supernova remnants are considered to be possible sites of cosmic ray acceleration. Since shocks are capable of accelerating electrons in addition to protons one anticipates both species to contribute to the high energy radiation expected from these objects. Adopting a simple model for particle acceleration we calculate

W. Bednarek, J. G. Kirk, A. Mastichiadis

The variable flux of TeV gamma-rays detected from Mkn 421 and Mkn 501 requires the presence of high energy electrons, which could in principle produce large numbers of electron/positron pairs, leading to an electromagnetic cascade. We point out that this scenario can be avoided if electrons are accelerated to high energy rectilinearly, rather than being inje

Yu Zhang, Avery Meiksin, Peter Anninos, Michael L. Norman

Soon after the first QSO was identified, Gunn & Peterson searched for the expected characteristic absorption trough on the blueward side of Lya in the spectrum of the QSO due to an Intergalactic Medium (IGM). They failed to find it, placing a constraint on the density of neutral hydrogen in the IGM that was less than 1 part in 10^5 of that residing in galaxi

Christopher W. Churchill, Steven S. Vogt

Studies of high resolution quasar absorption lines (QALs), arising from gas in local and z < 1.5 galaxies, provide direct probes of the kinematic, chemical, and ionization conditions and evolution of Milky Way-like galaxies. Inferences drawn from these studies provide a powerful analog for those based upon direct studies of the Halo. The observed gas kinemat

Gary Steigman

Big Bang Nucleosynthesis (BBN), along with the cosmic background radiation and the Hubble expansion, is one of the pillars ofthe standard, hot, big bang cosmology since the primordial synthesis of the light nuclides (D, $^3$He, $^4$He, $^7$Li) must have occurred during the early evolution of a universe described by this model. The overall consistency between

David M. Pierce

We construct a (1,2) heterotic string with gauge symmetry and determine its particle spectrum. This theory has a local N=1 worldsheet supersymmetry for left movers and a local N=2 worldsheet supersymmetry for right movers and describes particles in either two or three space-time dimensions. We show that fermionizing the bosons of the compactified N=1 space l

Serguei B. Isakov, Daniel P. Arovas, Jan Myrheim, Alexios P. Polychronakos

We discuss the thermodynamics of a gas of free particles obeying Haldane&#39;s exclusion statistics, deriving low temperature and low density expansions. For gases with a constant density of states, we derive an exact equation of state and find that temperature-dependent quantities are independent of the statistics parameter.

Patrick Dorey, Roberto Tateo, Kevin E. Thompson

The generally accepted phase diagrams for the discrete $Z_N$ spin models in two dimensions imply the existence of certain renormalisation group flows, both between conformal field theories and into a massive phase. Integral equations are proposed to describe these flows, and some properties of their solutions are discussed. The infrared behaviour in massless

R. M. Kashaev

The invariant of a link in three-sphere, associated with the cyclic quantum dilogarithm, depends on a natural number $N$. By the analysis of particular examples it is argued that for a hyperbolic knot (link) the absolute value of this invariant grows exponentially at large $N$, the hyperbolic volume of the knot (link) complement being the growth rate.

F. G. Markopoulou

We find a first--order partial differential equation whose solutions are all ultralocal scalar combinations of gravitational constraints with Abelian Poisson brackets between themselves. This is a generalisation of the Kuchař idea of finding alternative constraints for canonical gravity. The new scalars may be used in place of the hamiltonian constraint of g

M. Chertkov, G. Falkovich, V. Lebedev

We consider passive scalar convected by multi-scale random velocity field with short yet finite temporal correlations. Taking Kraichnan&#39;s limit of a white Gaussian velocity as a zero approximation we develop perturbation theory with respect to a small correlation time and small non-Gaussianity of the velocity. We derive the renormalization (due to tempor

Trygve Johnsen, Steven L. Kleiman

We introduce and study a likely condition that implies the following form of Clemens' conjecture in degrees $d$ between 10 and 24: given a general quintic threefold $F$ in complex $\IP^4$, the Hilbert scheme of rational, smooth and irreducible curves $C$ of degree $d$ on $F$ is finite, nonempty, and reduced; moreover, each $C$ is embedded in $F$ with balance

Erik A. Martinez

The features of the fundamental thermodynamical relation (expressing entropy as function of state variables) that arise from the self-gravitating character of a system are analyzed. The models studied include not only a spherically symmetric hot matter shell with constant particle number but also a black hole characterized by a general thermal equation of st

K. Martins

We present a microscopic calculation of the breakup cross sections of $J/ψ$ and $ψ&#39;$ on pions and nucleons as a function of the kinetic energy. These cross sections are used for the investigation of the $J/ψ$ to continuum and $ψ&#39;/J/ψ$ ratios in ultrarelativistic heavy ion collisions. The contribution of produced comoving pions to the $ψ&#39;/J/ψ$ sig

Hamish Cunningham, Robert J. Gaizauskas, Yorick Wilks

This report argues for the provision of a common software infrastructure for NLP systems. Current trends in Language Engineering research are reviewed as motivation for this infrastructure, and relevant recent work discussed. A freely-available system called GATE is described which builds on this work.

Hideki Kozima, Akira Ito

The paper proposes a computationally feasible method for measuring context-sensitive semantic distance between words. The distance is computed by adaptive scaling of a semantic space. In the semantic space, each word in the vocabulary V is represented by a multi-dimensional vector which is obtained from an English dictionary through a principal component ana

Hisakazu Minakata, Alexei Yu. Smirnov

Observation of the ultra-high energy neutrinos, in particular, detection of $\nu_{\tau}$ from cosmologically distant sources like active galactic nuclei (AGN) opens new possibilities to search for neutrino flavor conversion. We consider effects of violation of the equivalence principle (VEP) on propagation of these cosmic neutrinos. Two effects are studied:

Dileep P. Jatkar, Sudipta Mukherji, Sudhakar Panda

We study a class of rotating dyonic black holes in the heterotic string theory in four dimension which have left, right independent electric charges but have same magnitude for the left and right magnetic charges. In both left and right sector the electric and the magnetic vectors are orthogonal to each other. The gyromagnetic(electric) ratios are in general

H. C. Rosu

The bosonic strictly isospectral problem for Demkov-Ostrovsky (DO) effective potentials in the radially nodeless sector is first solved in the supersymmetric Darboux-Witten (DW) half line (or l-changing) procedure. As an application, for the κ=1 class, if one goes back to optics examples, it might be possible to think of a one-parameter family of Maxwell len

M. A. Pichowsky, T. -S. H. Lee

A Pomeron-exchange model of exclusive electroproduction of $ρ$-mesons is examined using a dressed-quark propagator. It is shown that by representing the photon-$ρ$-meson-Pomeron coupling by a nonperturbative, confined-quark loop, one obtains predictions for $ρ$-meson electroproduction that are in good agreement with experiment.

K. Maltman, H. B. O'Connell, A. G. Williams

The formalism underlying the analysis of e+e- -> pi+pi- in the rho-omega interference region is carefully revisited. We show that the standard neglect of the pure I=0 omega, omega_I, `direct'' coupling to pi-pi is not valid, and extract those combinations of the direct coupling and \rho-omega mixing allowed by experiment. The latter is shown to be only very

Cesar Miquel, Juan Pablo Paz, Roberto Perazzo

We describe an array of quantum gates implementing Shor&#39;s algorithm for prime factorization in a quantum computer. The array includes a circuit for modular exponentiation with several subcomponents (such as controlled multipliers, adders, etc) which are described in terms of elementary Toffoli gates. We present a simple analysis of the impact of losses a

Christopher A. Fuchs

This document focuses on translating various information-theoretic measures of distinguishability for probability distributions into measures of distin- guishability for quantum states. These measures should have important appli- cations in quantum cryptography and quantum computation theory. The results reported include the following. An exact expression fo

Timothy J. Hodges

The double quantum groups are the Hopf algebras underlying the complex quantum groups of which the simplest example is the quantum Lorentz group. They are non- standard quantizations of the double group $G \times G$. We construct a corresponding quantized universal enveloping algebra (QUE) and prove that the pairing between a quantum double group and its QUE

Aristophanes Dimakis, J. Madore

A method is proposed for defining an arbitrary number of differential calculi over a given noncommutative associative algebra. As an example the generalized quantum plane is studied. It is found that there is a strong correlation, but not a one-to-one correspondence, between the module structure of the 1-forms and the metric torsion-free connections on it. I

J. Caro, E. Ruiz Arriola, L. L. Salcedo

Dirac sea corrections for bulk properties of finite nuclei are computed within a self-consistent scheme in the $σ$-$ω$ model. The valence part is treated in the Hartree approximation whereas the sea contribution is evaluated semiclassically up to fourth order in $\hbar$. Numerically, we find a quick convergence of the semiclassical expansion; the fourth orde

Glenn Barnich, Marc Henneaux

One may introduce at least three different Lie algebras in any Lagrangian field theory : (i) the Lie algebra of local BRST cohomology classes equipped with the odd Batalin-Vilkovisky antibracket, which has attracted considerable interest recently~; (ii) the Lie algebra of local conserved currents equipped with the Dickey bracket~; and (iii) the Lie algebra o

A. Andraši, J. C. Taylor

We make some comments on the renormalization of Wilson operators (not just vacuum -expectation values of Wilson operators), and the features which arise in Minkowski space. If the Wilson loop contains a straight light-like segment, charge renormalization does not work in a simple graph-by-graph way; but does work when certain graphs are added together. We al

M. Temple-Raston

A tensor product generalisation of $B\wedge F$ theories is proposed to give a Bogomol&#39;nyi structure. Non-singular, stable, finite-energy particle-like solutions to the Bogomol&#39;nyi equations are studied. Unlike Yang-Mills(-Higgs) theory, the Bogomol&#39;nyi structure does not appear as a perfect square in the Lagrangian. Consequently, the Bogomol&#39;

J. Madore, J. Mourad, A. Sitarz

It has been suggested that quantum fluctuations of the gravitational field could give rise in the lowest approximation to an effective noncommutative version of Kaluza-Klein theory which has as extra hidden structure a noncommutative geometry. It would seem however from the Standard Model, at least as far as the weak interactions are concerned, that a double

M. Chaichian, R. Gonzalez Felipe, D. Louis Martinez

The Hamiltonian formulation of the motion of a spinning relativistic particle in an external electromagnetic field is considered. The approach is based on the introduction of new coordinates and their conjugated momenta to describe the spin degrees of freedom together with an appropriate set of constraints in the Dirac formulation. For particles with gyromag

L. Dolan

The role of Kac-Moody algebras in exploiting symmetries of particle physics and string theory is described.

Mikhail S. Plyushchay

Within a group-theoretical approach to the description of (2+1)-dimensional anyons, the minimal covariant set of linear differential equations is constructed for the fractional spin fields with the help of the deformed Heisenberg algebra (DHA), $[a^{-},a^{+}]=1+νK$, involving the Klein operator $K$, $\{K,a^{\pm}\}=0$, $K^{2}=1$. The connection of the minimal

P. Aurenche, G. A. Schuler, A. Bawa, E. Boudinov

This report is an overview of the gamma-gamma physics capabilities of LEP2, and covers the following topics: structure functions, equivalent photon approximation, tagging conditions etc, soft and semihard physics, large-$p_t$ processes, heavy-quark physics, and exclusive channels.

Robert D. Pisarski

Using constituent quarks coupled to a linear sigma model at nonzero temperature, I show that many anomalous mesonic amplitudes, such as $π^0 \rightarrow γγ$, vanish in a chirally symmetric phase. Processes which are allowed, such as $π^0 σ\rightarrow γγ$, are computed to leading order in a loop expansion.

M. Braun, V. Vechernin

In the framework of the recently proposed QCD based parton model for the cumulative phenomena in the interactions with nuclei two mechanisms for particle production, direct and spectator ones, are analysed. It is shown that due to final state interactions the leading terms of the direct mechanism contribution are cancelled and the spectator mechanism is the

Bodo Lampe

The theoretical background of the electroweak precision measurements at LEP1 is reviewed. The presentation is compact but specific enough to understand all details.

M. Hayakawa, T. Kinoshita, A. I. Sanda

The hadronic light-by-light scattering contribution to muon $g-2$ is examined based on the low energy effective theories of QCD, the Nambu-Jona-Lasinio model and hidden local symmetry approach, supplemented by a general information concerning the asymptotic behavior of QCD. Our result is $- 52 \times 10^{-11}$ with an uncertainty of $\pm 18 \times 10^{-11}$,

Christoph Best, Andreas Schaefer

We present a semiclassical nonlinear field equation for the confining field in 2+1--dimensional $U(1)$ lattice gauge theory (compact QED). The equation is derived directly from the underlying microscopic quantum Hamiltonian by means of truncation. Its nonlinearities express the dynamic creation of magnetic monopole currents leading to the confinement of the

Kenneth J. Dykema, Mikael Rordam

Examples of simple, separable, unital, purely infinite $C^*$--algebras are constructed, including: (1) some that are not approximately divisible; (2) those that arise as crossed products of any of a certain class of $C^*$--algebras by any of a certain class of non--unital endomorphisms; (3) those that arise as reduced free products of pairs of $C^*$--algebra

Kenneth J. Dykema

The von Neumann algebra free product of arbitary finite dimensional von Neumann algebras with respect to arbitrary faithful states, at least one of which is not a trace, is found to be a type~III factor possibly direct sum a finite dimensional algebra. The free product state on the type~III factor is what we call an extremal almost periodic state, and has ce

P. Exner, S. A. Vugalter

We consider the Dirichlet Laplacian for a strip in $\,\R^2$ with one straight boundary and a width $\,a(1+λf(x))\,$, where $\,f\,$ is a smooth function of a compact support with a length $\,2b\,$. We show that in the critical case, $\,\int_{-b}^b f(x)\, dx=0\,$, the operator has no bound states for small $\,|λ|\,$ if $\,b<(\sqrt{3}/4)a\,$. On the other hand,

Jimmy Petean

Indefinite Kaehler solutions of the Einstein equations are studied, and it is almost completely determined which compact complex surfaces admit such metrics.

Dimitris Stassinopoulos, Per Bak

The problem of learning in the absence of external intelligence is discussed in the context of a simple model. The model consists of a set of randomly connected, or layered integrate-and fire neurons. Inputs to and outputs from the environment are connected randomly to subsets of neurons. The connections between firing neurons are strengthened or weakened ac

N. E. Bonesteel, I. A. McDonald, C. Nayak

A symmetrically doped double layer electron system with total filling fraction $ν=1/m$ decouples into two even denominator ($ν=1/2 m$) composite fermion `metals&#39; when the layer spacing is large. Out-of-phase fluctuations of the statistical gauge fields in this system mediate a singular attractive pairing interaction between composite fermions in differen

David J. E. Callaway

Recent calculations have shown that the linear proportionality between black hole entropy and area can be explained by performing a density matrix calculation for a massless free field theory. By applying the same formalism to an empirical fluid ``field theory,&#39;&#39; entropic quantities such as surface tension can be calculated in a novel fashion. Good a

M. M. Fogler, A. A. Koulakov, B. I. Shklovskii

We study the ground state of a clean two-dimensional electron liquid in a weak magnetic field where $N \gg 1$ lower Landau levels are completely filled and the upper level is partially filled. It is shown that the electrons at the upper Landau level form domains with filling factor equal to one and zero. The domains alternate with a spatial period of the ord

A. -L. Barabási, G. Grinstein, M. A. Muñoz

The critical exponents for a class of one-dimensional models of interface depinning in disordered media can be calculated through a mapping onto directed percolation (DP). In higher dimensions these models give rise to directed surfaces, which do not belong to the directed percolation universality class. We formulate a scaling theory of directed surfaces, an

T. A. Costi, C. Kieffer

Wilson&#39;s momentum shell renormalization group method is used to solve for the dynamics of the dissipative two--state system. We utilize the mapping of the spin--boson model onto the anisotropic Kondo model (AKM) and solve for the dynamics of the latter. We find that the AKM captures the physics of the dissipative two--state system for dissipation strengt

P. B. Allen, H. Berger, O. Chauvet, L. Forro

SrRuO$_3$ is a metallic ferromagnet. Its electrical resistivity is reported for temperatures up to 1000K; its Hall coefficient for temperatures up to 300K; its specific heat for temperatures up to 230K. The energy bands have been calculated by self-consistent spin-density functional theory, which finds a ferromagnetic ordered moment of 1.45$μ_{\rm B}$ per Ru

Malte Henkel, Flavio Seno

The phase diagram of the collapse of a two-dimensional infinite branched polymer interacting with the solvent and with itself through contact interactions is studied from the $q\to 1$ limit of an extension of the $q-$ states Potts model. Exact solution on the Bethe lattice and Migdal-Kadanoff renormalization group calculations show that there is a line of $θ

Katharina Vollmayr, Walter Kob, Kurt Binder

Using molecular dynamics computer simulations we investigate how the glass transition and the properties of the resulting glass depend on the cooling rate with which the sample has been quenched. This is done by studying a two component Lennard-Jones system which is coupled to a heat bath whose temperature is decreased from a high temperature, where the syst

C. J. Pérez, A. Corral, A. Díaz-Guilera, K. Christensen

Lattice models of coupled dynamical systems lead to a variety of complex behaviors. Between the individual motion of independent units and the collective behavior of members of a population evolving synchronously, there exist more complicated attractors. In some cases, these states are identified with self-organized critical phenomena. In other situations, w

D. N. Aristov, S. V. Maleyev, A. G. Yashenkin

The RKKY interaction between rare-earth (RE) ions in high-$T_c$ superconductors is considered at $T\ll T_c$. It is shown that this interaction consists of two terms: conventional oscillating one and the positive term, which is proportional to the gap function and decreases in the $2D$ case inversely proportional to the distance. In the antiferromagnetic stat

James Badro, Jean-Louis Barrat, Philippe Gillet

The behavior of $α$-quartz under hydrostatic and non-hydrostatic high-pressure conditions has been investigated in Molecular Dynamics simulations of silica in order to clarify the role of non-hydrostatic stresses in the amorphization process. It is shown that the amorphization threshold is not modified if the stress along the {\bf c} direction is lowered, so

I. L. Aleiner, Penny Clarke, L. I. Glazman

We study the conduction of a {\sl N~-~Sm~-~S} junction, where {\sl Sm} is a strongly disordered semiconductor. The differential conductance $dI/dV$ of this {\sl N~-~Sm~-~S} structure is predicted to have a sharp peak at $V=0$. Unlike the case of a weakly disordered system, this feature persists even in the absence of an additional (Schottky) barrier on the b

G. M. Minkov, A. V. Germanenko, V. A. Larionova, O. E. Rut

The results of tunnelling studies of the energy spectrum of two-dimensional (2D) states in a surface quantum well in a semiconductor with inverted band structure are presented. The energy dependence of quasimomentum of the 2D states over a wide energy range is obtained from the analysis of tunnelling conductivity oscillations in a quantizing magnetic field.

Francis Bond, Kentaro Ogura, Tsukasa Kawaoka

This paper shows the necessity of distinguishing different referential uses of noun phrases in machine translation. We argue that differentiating between the generic, referential and ascriptive uses of noun phrases is the minimum necessary to generate articles and number correctly when translating from Japanese to English. Heuristics for determining these di

Francis Bond, Kentaro Ogura, Satoru Ikehara

Possessive pronouns are used as determiners in English when no equivalent would be used in a Japanese sentence with the same meaning. This paper proposes a heuristic method of generating such possessive pronouns even when there is no equivalent in the Japanese. The method uses information about the use of possessive pronouns in English treated as a lexical p

Hideki Kozima

This paper proposes a new indicator of text structure, called the lexical cohesion profile (LCP), which locates segment boundaries in a text. A text segment is a coherent scene; the words in a segment are linked together via lexical cohesion relations. LCP records mutual similarity of words in a sequence of text. The similarity of words, which represents the

Hideki Kozima, Teiji Furugori

This paper proposes a method for measuring semantic similarity between words as a new tool for text analysis. The similarity is measured on a semantic network constructed systematically from a subset of the English dictionary, LDOCE (Longman Dictionary of Contemporary English). Spreading activation on the network can directly compute the similarity between a

Daniel Laria, Raymond Kapral, Dario Estrin, Giovanni Ciccotti

Acid ionization in aprotic media is studied using Molecular Dynamics techniques. In particular, models for HCl ionization in acetonitrile and dimethylsulfoxide are investigated. The proton is treated quantum mechanically using Feynman path integral methods and the remaining molecules are treated classically. Quantum effects are shown to be essential for the

Yu. V. Ralchenko

In this report the current situation with availability and management of atomic data on the Internet is reviewed.

Jes Madsen

The possible identification of Her X-1 with a strange star (Li et al. 1995) is shown to be incorrect.

Armin Bartsch, Peter Schneider, Matthias Bartelmann

We develop a new statistical method to reanalyse angular correlations between background QSOs and foreground galaxies that are supposed to be a consequence of dark matter inhomogeneities acting as weak gravitational lenses. The method is based on a weighted average over the galaxy positions and is optimized to distinguish between a random distribution of gal

J. Greiner, R. Schwarz, G. Hasinger, M. Orio

Supersoft X-ray sources are commonly believed to be stably burning white dwarfs. However, the observations of some supersoft sources show dramatic variability of their X-ray flux on timescales ranging from days to years. Here, we present further observational data of the supersoft X-ray source RX J0527.8--6954 exhibiting a continuous decline over the past 5

Jes Madsen

Utilizing a recently derived extension of the Maxwell-Boltzmann distribution to low occupation numbers (Simons 1994) this investigation discusses the structure of stellar dynamical isothermal spheres. The resulting models, which resemble King models, constitute a new sequence of physically well-motivated spherical equilibrium configurations of finite mass, a

Philippe Jetzer, Eduard Masso

The most accurate way to get information on the mass of the MACHOs (Massive Astrophysical Compact Halo Objects) is to use the method of mass moments. For the microlensing events detected so far by the EROS and the MACHO collaborations in the Large Magellanic Cloud the average mass turns out to be 0.08$M_{\odot}$. Assuming a spherical standard halo model we f

F. W. Stecker, M. H. Salamon

We present the results of a new model calculation of the gamma-ray background produced by unresolved blazars, using the second EGRET catalogue and taking account of flaring. These results are compared to the preliminary gamma-ray background spectrum reported recently by the EGRET team. We find that blazars can account for the entire extragalactic gamma-ray b

Robert Treger

We construct a good compactification of the variety of irreducible projective plane curves of degree n with d nodes and no other singularities.

Wilberd van der Kallen, Peter Magyar

We consider compactifications of the space of triples of distinct points in projective $n$-space. One such space is a singular variety of configurations of points and lines; another is the smooth compactification of Fulton and MacPherson; and a third is the triangle space of Schubert and Semple. We compute the sections of line bundles on these spaces, and sh

S. Veseli, M. G. Olsson

We apply HQET to semi-leptonic $B$ meson decays into a variety of excited charm states. Using three realistic meson models with fermionic light degrees of freedom, we examine the extent that the sum of exclusive single charmed states account for the inclusive semi-leptonic $B$ decay rate. The consistency of form factors with the Bjorken and Voloshin sum rule

J. A. Oller, E. Oset

We use a nonpertubative approach which combines coupled channel Lippmann Schwinger equations with meson-meson potentials provided by the lowest order chiral Lagrangian. By means of one parameter, a cut off in the momentum of the loop integrals, which results of the order of 1 GeV, we obtain singularities in the S-wave amplitudes corresponding to the $σ$, f_0

B. de Wit, M. T. Grisaru, M. Rocek

In addition to the familiar contribution from a holomorphic function $\FF$, the K\"ahler potential of the scalars in the nonabelian $N=2$ vector multiplet receives contributions from a real function $\HH$. We determine the latter at the one-loop level, taking into account both supersymmetric matter and gauge loops. The function $\HH$ characterizes the four-p

Ernest Baver, Doron Gepner

The initial classification of fusion rules have shown that rational conformal field theory is very limited. In this paper we study the fusion rules of extend ed current algebras. Explicit formulas are given for the S matrix and the fusion rules, based on the full splitting of the fixed point fields. We find that in s ome cases sensible fusion rules are obtai

M. E. Simón, A. A. Aligia

We study the Cu-O valence instability (VI) and the related phase separation (PS) driven by Cu-O nearest-neighbor repulsion $U_{pd}$, using an effective extended one-band Hubbard model ($H_{eff}$) obtained from the extended three-bandHubbard model, through an appropriate low-energy reduction. $H_{eff}$ is solved by exact diagonalization of a square cluster wi

P. Chiappetta, J. Layssac, F. M. Renard, C. Verzegnassi

In order to explain possible departures from the Standard Model predictions for $b\bar b$ and $c\bar c$ production at $Z$ peak, we propose the existence of a $Z&#39;$ vector boson with enhanced couplings to quarks. We first show that this proposal is perfectly consistent with the full set of LEP1/SLC results. In particular, $Z-Z&#39;$ mixing effects naturall

Jordi Comellas, Yuri Kubyshin, Enrique Moreno

We give a review of the exact renormalization group (ERG) approach and illustrate its applications in scalar and fermionic theories. The derivative expansion and approximations based on the derivative expansion with further truncation in the number of fields (mixed approximation) are discussed. We analyse the mixed approximation for a three-dimensional scala

B. Jegerlehner, F. Neubig, G. Raffelt

We study the impact of neutrino oscillations on the interpretation of the supernova (SN) 1987A neutrino signal by means of a maximum-likelihood analysis. We focus on oscillations between $\overlineν_e$ with $\overlineν_μ$ or $\overlineν_τ$ with those mixing parameters that would solve the solar neutrino problem. For the small-angle MSW solution ($Δm^2\approx

Y. M. Hakobyan, D. B. Sahakyan, M. R. Daj

The boundary line between the ferromagnetic and the spin-glass phases was investigated. Finite size corrections to the free energy and magnetization were calculated. The situation coincides with the case in the information theory, when the transmission rate equals to the capacity of channel.

Greg Kuperberg

Jaeger [Geom. Dedicata 44 (1992), 23-52] discovered a remarkable checkerboard state model based on the Higman-Sims graph that yields a value of the Kauffman polynomial, which is a quantum invariant of links. We present a simple argument that the state model has the desired properties using the combinatorial $B_2$ spider [Comm. Math. Phys. 180 (1996), 109-151

Steven G. Krantz, Song-Ying Li

The authors study Hardy spaces, of arbitrary order, on a space of homogeneous type. This extends earlier work that treated only $H^p$ for $p$ near 1. Applications are given to the boundedness of certain singular integral operators, especially on domains in complex space.

Steven G. Krantz, Song-Ying Li

Elliptic estimates in Hardy classes are proved on domains with minimally smooth boundary. The methodology is different from the original methods of Chang/Krantz/Stein.

Luigi Fontana, Steven G. Krantz, Marco M. Peloso

The authors study the Hodge theory of the exterior differential operator $d$ acting on $q$-forms on a smoothly bounded domain in $\RR^{N+1}$, and on the half space $\rnp$. The novelty is that the topology used is not an $L^2$ topology but a Sobolev topology. This strikingly alters the problem as compared to the classical setup. It gives rise to a boundary-va

C. Acerbi, G. Mussardo, A. Valleriani

The magnetic deformation of the Ising Model, the thermal deformations of both the Tricritical Ising Model and the Tricritical Potts Model are governed by an algebraic structure based on the Dynkin diagram associated to the exceptional algebras $E_n$ (respectively for $n=8,7,6$). We make use of these underlying structures as well as of the discrete symmetries