June 1999 arXiv papers — page 6

M. Bojowald, H. A. Kastrup, F. Schramm, T. Strobl

The symplectic reduction of pure spherically symmetric (Schwarzschild) classical gravity in D space-time dimensions yields a 2-dimensional phase space of observables consisting of the Mass M (>0) and a canonically conjugate (Killing) time variable T. Imposing (mass-dependent) periodic boundary conditions in time on the associated quantum mechanical plane wav

H. A. Kastrup

Generalizing previous quantum gravity results for Schwarzschild black holes from 4 to D > 3 space-time dimensions yields an energy spectrum E_n = alpha n^{(D-3)/(D-2)} E_P, n=1,2,..., alpha = O(1), where E_P is the Planck energy in that space-time. This spectrum means that the quantized area A_{D-2}(n) of the D-2 dimensional horizon has universally the form

V. Barger, S. Geer, K. Whisnant

We examine the physics capabilities of known flavor neutrino beams from intense muon sources. We find that long-baseline neutrino experiments based on such beams can provide precise measurements of neutrino oscillation mass and mixing parameters. Furthermore, they can test whether the dominant atmospheric neutrino oscillations are ν_μ--> ν_τand/or ν_μ--> ν_s

E. Paspalakis, D. G. Angelakis, P. L. Knight

We study two distinct multi-level atomic models in which one transition is coupled to a Markovian reservoir, while another linked transition is coupled to a non-Markovian reservoir. We show that by choosing appropriately the density of modes of the non-Markovian reservoir the spontaneous emission to the Markovian reservoir is greatly altered. The existence o

Tanmoy Bhattacharya, Salman Habib, Kurt Jacobs

We formulate the conditions under which the dynamics of a continuously measured quantum system becomes indistinguishable from that of the corresponding classical system. In particular, we demonstrate that even in a classically chaotic system the quantum state vector conditioned by the measurement remains localized and, under these conditions, follows a traje

Pablo J. Marrero, Erick A. Roura, Dean Lee

We describe the generalization of spherical field theory to other modal expansion methods. The main approach remains the same, to reduce a d-dimensional field theory into a set of coupled one-dimensional systems. The method we discuss here uses an expansion with respect to periodic-box modes. We apply the method to phi^4 theory in two dimensions and compute

S. Shapira, E. H. Linfield, C. J. Lambert, R. Seviour

We observe a maximum in the conductance of Aluminum / n-GaAs junctions at temperatures 20 mK lower than the superconducting transition temperature. This is the first observation of a non- monotonic behavior of the conductance near the superconducting transition in superconducting normal junctions. To accommodate this effect we calculate the full temperature

Yujoung Bai

We study low-energy magnetic excitations of doped spin-ladders, based on an effective Hamiltonian describing interactions of mobile spin and background spins. The helicity modulus against fluctuations in the ladder plane as well as out-of-the-plane are calculated in terms of the doping concentration, the leg number and interaction strengths in the ladder. Th

Jean-Paul Blaizot, Edmond Iancu

By using the Boltzmann equation describing the relaxation of colour excitations in the QCD plasma, we obtain effective amplitudes for the ultrasoft colour fields carrying momenta of order $g^2 T$. These amplitudes are of the same order in $g$ as the hard thermal loops (HTL), which they generalize by including the effects of the collisions among the hard part

K. Ackerstaff, The HERMES Collaboration

Spin asymmetries of semi-inclusive cross sections for the production of positively and negatively charged hadrons have been measured in deep-inelastic scattering of polarized positrons on polarized hydrogen and 3He targets, in the kinematic range 0.023<x<0.6 and 1 GeV^2<Q^2<10 GeV^2. Polarized quark distributions are extracted as a function of x for up $(u+u

Z. Bajnok, D. Nogradi, D. Varga, F. Wagner

The reduced SL(2,R) WZW quantum mechanics is analysed in the framework of geometric quantization. The spectrum of the Hamiltonian is determined, and it is found, that contrary to the previous approaches, there is a unique, physically preferred quantisation of the system.

A. Di Giacomo, B. Lucini, L. Montesi, G. Paffuti

The dual superconductivity of the vacuum in SU(3) gauge theory is investigated by constructing a disorder parameter which signals monopole condensation in various abelian projections and by studying numerically on the lattice its behaviour at finite temperature. We find that the vacuum is a dual superconductor with respect to each U(1) of the residual gauge

A. Di Giacomo, B. Lucini, L. Montesi, G. Paffuti

We study dual superconductivity of the ground state of SU(2) gauge theory, in connection with confinement. We do that measuring on the lattice a disorder parameter describing condensation of monopoles. Confinement appears as a transition to dual superconductor, independent of the abelian projection defining monopoles. Some speculations are made on the existe

M. V. Indenbom, C. J. van der Beek, M. Konczykowski, F. Holtzberg

From magneto-optical imaging performed on heavy-ion irradiated YBaCuO single crystals, it is found that at fields and temperatures where strong single vortex pinning by individual irradiation-induced amorphous columnar defects is to be expected, vortex motion is limited by the nucleation of vortex kinks at the specimen surface rather than by half-loop nuclea

Tim Hoffmann, Johannes Kellendonk, Nadja Kutz, Nicolai Reshetikhin

It is shown that the factorization relation on simple Lie groups with standard Poisson Lie structure restricted to Coxeter symplectic leaves gives an integrable dynamical system. This system can be regarded as a discretization of the Toda flow. In case of $SL_n$ the integrals of the factorization dynamics are integrals of the relativistic Toda system. A subs

Peter Horak, Stephen M. Barnett, Helmut Ritsch

We study the mutual interaction of a Bose-Einstein condensed gas with a single mode of a high-finesse optical cavity. We show how the cavity transmission reflects condensate properties and calculate the self-consistent intra-cavity light field and condensate evolution. Solving the coupled condensate-cavity equations we find that while falling through the cav

Guillermo A. Mena Marugan, Manuel Montejo

Starting with the Hamiltonian formulation for spacetimes with two commuting spacelike Killing vectors, we construct a midisuperspace model for linearly polarized plane waves in vacuum gravity. This model has no constraints and its degrees of freedom can be interpreted as an infinite and continuous set of annihilation and creation like variables. We also cons

M. Copelli, C. Van den Broeck, M. Opper

We study a simple model of unsupervised learning where the single symmetry breaking vector has binary components $\pm 1$. We calculate exactly the Bayes-optimal performance of an estimator which is required to lie in the same discrete space. We also show that, except for very special cases, such an estimator cannot be obtained by minimization of a class of v

Bodo Geyer, Petr M. Lavrov, Pavel Yu. Moshin

We propose a modification of the gauge-fixing procedure in the Lagrangian method of superfield BRST quantization for general gauge theories which simultaneously provides a natural generalization of the well-known BV quantization scheme as far as gauge-fixing is concerned. A superfield form of BRST symmetry for the vacuum functional is found. The gauge-indepe

M. J. Pivovaroff, V. M. Kaspi, E. V. Gotthelf

We present X-ray observations of two young energetic radio pulsars, PSRs B1046-58 and B1610-50, and their surroundings, using archival data from the Advanced Satellite for Cosmology and Astrophysics (ASCA). The energetic pulsar PSR B1046-58 is detected in X-rays with a significance of 4.5 sigma. The unabsorbed flux, estimated assuming a power-law spectrum an

M. Toscano, M. C. Britton, R. N. Manchester, M. Bailes

We present the annual trigonometric parallax of PSR J1744-1134 derived from an analysis of pulse times of arrival. The measured parallax, pi = 2.8+/-0.3 mas ranks among the most precisely determined distances to any pulsar. The parallax distance of 357+/-39 pc is over twice that derived from the dispersion measure using the Taylor & Cordes model for the Gala

Michael A. Nowak, James Chiang

The bright Seyfert 1 galaxy \mcg shows large variability on a variety of time scales. We study the $\aproxlt 3$ day time scale variability using a set of simultaneous archival observations that were obtained from \rxte and the {\it Advanced Satellite for Cosmology and Astrophysics} (\asca). The \rxte\ observations span nearly $10^6$ sec and indicate that the

M. Beneke, A. Signer

We determine the bottom $\bar{\rm MS}$ quark mass $\bar{m}_b$ and the quark mass in the potential subtraction scheme from moments of the $b\bar{b}$ production cross section and from the mass of the Upsilon 1S state at next-to-next-to-leading order in a reorganized perturbative expansion that sums Coulomb exchange to all orders. We find $\bar{m}_b(\bar{m}_b)=

Michael P. McCooey

Recall that a pseudofree group action on a space is one whose singular set consists only of isolated points. In this paper, we classify all of the finite groups which admit pseudofree actions on S^2 x S^2. The groups turn out to be exactly the expected ones: those which admit orthogonal pseudofree actions on S^2 x S^2 as a subset of R^3 x R^3. They are expli

S. G. Schirmer, M. D. Girardeau, J. V. Leahy

In [1] Zhu and Rabitz presented a rapidly convergent iterative algorithm for optimal control of the expectation value of a positive definite observable in a pure-state quantum system. In this paper we generalize this algorithm to a quantum statistical mechanics setting and show that it is both efficient in the mixed-state case and effective in achieving the

J. Lesgourgues, D. Polarski, S. Prunet, A. A. Starobinsky

The appearance of peaks in various primordial fluctuation Fourier power spectra is a generic prediction of the inflationary scenario. We investigate whether future experiments, in particular the satellite experiment PLANCK, will be able to detect the possible appearance of these peaks in the B-mode polarization multipole power spectrum. This would yield a co

Lorenza Viola, Seth Lloyd, Emanuel Knill

It is shown that if one can perform a restricted set of fast manipulations on a quantum system, one can implement a large class of dynamical evolutions by effectively removing or introducing selected Hamiltonians. The procedure can be used to achieve universal noise-tolerant control based on purely unitary open-loop transformations of the dynamics. As a resu

Tomohiro Ogawa, Hiroshi Nagaoka

The hypothesis testing problem of two quantum states is treated. We show a new inequality between the error of the first kind and the second kind, which complements the result of Hiai and Petz to establish the quantum version of Stein&#39;s lemma. The inequality is also used to show a bound on the first kind error when the power exponent for the second kind

G. D&#39;Agostini

The choice of priors may become an insoluble problem if priors and Bayes&#39; rule are not seen and accepted in the framework of subjectivism. Therefore, the meaning and the role of subjectivity in science is considered and defended from the pragmatic point of view of an ``experienced scientist&#39;&#39;. The case for the use of subjective priors is then sup

Rajendra R. Zope

Positron binding to anions is investigated within the work formalism proposed by Harbola and Sahni for the halide anions and the systems Li^- through O^- excluding Be^- and N^-. The toal ground-state energies of the anion-positron bound systems are empirically found to be an upper bound to the Hartree-Fock energies. The computed expectation values as well as

Rajendra R. Zope, Manoj K. Harbola, Rajeev K. Pathak

The Impulse Compton Profiles (CP&#39;s) J(q) and the <p^n> - expectation values for some inert gas atoms (He-Kr) are computed and compared within the Harbola-Sahni (HS), Hartree-Fock(HF) theories and a Self Interaction Corrected (SIC) density functional model. The Compton profiles for excited states of Helium atom are also calculated. While the calculated CP

V. V. Flambaum

There are several factors which lead to a huge enhancement of parity and time invariance violating effects in the Ra atom: very close electronic levels of opposite parity, the large nuclear charge Z and the collective nature of T,P-odd nuclear moments. Experiments with Radium may be used to measure it&#39;s nuclear anapole, magnetic quadrupole and Schiff mom

Hiroyasu Yamada, Toshiyuki Nakagaki

Dispersion curves to a oscillatory reaction-diffusion system with the self-consistent flow have obtained by means of numerical calculations. The flow modulates the shape of dispersion curves and characteristics of traveling waves. The point of inflection which separates the dispersion curves into two branches corresponding to trigger and phase waves, moves a

Yu-Ming Zheng, C. M. Ko, Bao-An Li, Bin Zhang

The proton elliptic flow in collisions of Ca on Ca at energies from 30 to 100 MeV/nucleon is studied in an isospin-dependent transport model. With increasing incident energy, the elliptic flow shows a transition from positive to negative flow. Its magnitude depends on both the nuclear equation of state (EOS) and the nucleon-nucleon scattering cross section.

S. Jeon, V. Koch

In this letter we will argue that the event-by-event fluctuations of the ratio of positively over negatively charged pions provides a measurements of the number of rho and omega mesons right after hadronization. This finding can be utilized to put the hypothesis of chemical equilibration in relativistic heavy ion collisions to a test.

H. Müther

Correlations in the nuclear wave-function beyond the mean-field or Hartree-Fock approximation are very important to describe basic properties of nuclear structure. Attempts are made to explore details of these correlations in exclusive nucleon knock-out by electron scattering experiments. Basic results of $(e,e&#39;p)$ experiments are reviewed. The role of c

W. Cassing

The properties of $K^+$ and $K^-$ mesons are studied in nuclear reactions from SIS to RHIC energies within the covariant transport approach HSD in comparison to the experimental data whenever available. Whereas kaon abundancies and spectra indicate little repulsive or vanishing selfenergies in the medium, antikaons are found to experience strong attractive p

M. S. Fayache, L. Zamick, Y. Y. Sharon, Y. Durga Devi

We study the cross-correlation between the spin and orbital parts of magnetic dipole transitions M1 in both isoscalar and isovector channels. In particular, we closely examine certain cases where $\sum B(M1)$ is very close to $\sum B(M1)_σ + \sum B(M1)_l$, implying a cancellation of the summed interference terms. We gain some insight into this problem by con

F. Andreozzi, A. Porrino

A method for solving the shell-model eigenproblem in a severely truncated space, spanned by properly selected correlated states obtained by partitioning the full configuration space, is proposed. The method describes in a practically exact way the low energy spectroscopic properties of nuclei, as exemplified in schematic models. The applicability of the meth

C. P. Viazminsky, James P. Vary

We decompose the Hilbert space of wave functions into two subspaces, and assign to a given observable two effective representatives that act in the model space. The first serves to determine some of the eigenvalues of the full observable, while the second serves to determine its matrix elements, in any basis in one of the subspaces, in terms of quantities pe

John Etnyre, Robert Ghrist

We employ the relationship between contact structures and Beltrami fields derived in part I of this series to construct steady nonsingular solutions to the Euler equations on a Riemannian $S^3$ whose flowlines trace out closed curves of all possible knot and link types simultaneously. Using careful contact-topological controls, we can make such vector fields

Mikhail Khovanov

We show that induction and restriction functors for inclusions of nilCoxeter algebras provide a categorical realization of the algebra of polynomial differential operators in one variable.

L. Barbieri-Viale, V. Srinivas

We describe algebraically defined cohomological and homological Albanese and Picard 1-motives (or mixed motives) of any algebraic variety in characteristic zero, generalizing the classical Albanese and Picard varieties. We compute Hodge, l-adic and De Rham realizations proving Deligne&#39;s conjecture for the concerned mixed Hodge structures. We investigate

Alex Clark

Linear flows on inverse limits of tori are defined and it is shown that two linear flows on an inverse limit of tori are equivalent if and only if there is an automorphism of the inverse limit generating the equivalence.

Andrei Teleman

We prove generic regularity and Uhlenbeck-type compactification theorems for the moduli spaces of PU(2)-monopoles. Generic regularity is NOT obtained in the usual way (by applying Sard theorem to a smooth parameterized moduli space), since the parameterized moduli space can be a priori singular. We explain why, using the standard order 0-perturbations, one c

Alejandro Illanes, Sergio Macias, Sam B. Nadler,

An example is given of a compact absolute retract that is not a Hilbert cube manifold but whose second symmetric porduct is the Hilbert cube. A factor theorem is given for nth symmetric product of the cartesian product of any absolute neighborhood retract with the Hilbert cube. A short proof is included of the known fact that symmetric products preserve the

Andras Vasy

In this paper we describe the propagation of singularities of tempered distributional generalized eigenfunctions of many-body Hamiltonians under the assumption that no subsystem has a bound state and that the two-body interactions are real-valued polyhomogeneous symbols of order -1 (e.g. Coulomb-type with the singularity at the origin removed). Here the term

A. Caranti, M. F. Newman

We describe the isomorphism classes of infinite-dimensional graded Lie algebras of maximal class, generated by elements of weight one, over fields of odd characteristic.

Massimo Bianchi, Stefano Kovacs, Giancarlo Rossi, Yassen S. Stanev

We show that the logarithmic behaviour seen in perturbative and non perturbative contributions to Green functions of gauge-invariant composite operators in N=4 SYM with SU(N) gauge group can be consistently interpreted in terms of anomalous dimensions of unprotected operators in long multiplets of the superconformal group SU(2,2|4). In order to illustrate th

J. Cruz, A. Fabbri, D. J. Navarro, J. Navarro-Salas

We analyse an integrable model of two-dimensional gravity which can be reduced to a pair of Liouville fields in conformal gauge. Its general solution represents a pair of ``mirror&#39;&#39; black holes with the same temperature. The ground state is a degenerate constant dilaton configuration similar to the Nariai solution of the Schwarzschild-de Sitter case.

Z. Bajnok

We propose a new approach to the study of the correlation functions of W-algebras. The conformal blocks (chiral correlation functions), for fixed arguments, are defined to be those linear functionals on the product of the highest weight (h.w.) representation spaces which satisfy the Ward identities. First we investigate the dimension of the chiral correlatio

Christofer Cronstrom

The canonical structure of pure Yang-Mills theory is analysed in the case when Gauss&#39; law is satisfied identically by construction. It is shown that the theory has a canonical structure in this case, provided one uses a special gauge condition, which is a natural generalisation of the Coulomb gauge condition of electrodynamics. The emergence of a canonic

Herman Verlinde

Following a recent suggestion by Randall and Sundrum, we consider string compactification scenarios in which a compact slice of AdS-space arises as a subspace of the compactification manifold. A specific example is provided by the type II orientifold equivalent to type I theory on (orbifolds of) $T^6$, upon taking into account the gravitational backreaction

N. B. Narozhny, A. M. Fedotov, B. M. Karnakov, V. D. Mur

We have analyzed the Unruh problem in the frame of quantum field theory and have shown that the Unruh quantization scheme is valid in the double Rindler wedge rather than in Minkowski spacetime. The double Rindler wedge is composed of two disjoint regions ($R$- and $L$-wedges of Minkowski spacetime) which are causally separated from each other. Moreover the

Johannes Blümlein

The finite and infinite harmonic sums form the general basis for the Mellin transforms of all individual functions $f_i(x)$ describing inclusive quantities such as coefficient and splitting functions which emerge in massless field theories. We discuss the mathematical structure of these quantities.

Luca Girlanda, Jan Stern

The decays tau -> 3 pi + nu(tau) are analyzed at one loop order in the framework of Generalized Chiral Perturbation Theory, in order to test the sensitivity to the size of spontaneous chiral symmetry breaking parameters, contained in the S-wave. The latter, due to a kinematical suppression, at threshold, of the P-wave, is relatively large enough to be detect

W. Melnitchouk

Semi-inclusive electron scattering provides a powerful tool with which to study the spin and flavor distributions in the proton. Greater kinematic coverage at the proposed Electron-Polarized Ion Collider facility will enable the valence d/u ratio to be determined at large x through pion production. At small x, pion production can be used to extract the d-bar

Kyunsik Kang, Sin Kyu Kang, Utpal Sarkar

Recently a new general class of quark mass matrix ansatz has been proposed, which originates from some flavor symmetry. We extend that symmetry to the lepton sector and study the neutrino mass matrix and address the question of the baryon asymmetry of the universe in this model.

K. J. Eskola, V. J. Kolhinen, P. V. Ruuskanen, C. A. Salgado

Nuclear parton distributions $f_A(x,Q^2)$ are studied within a framework of the DGLAP evolution. Measurements of $F_2^A/F_2^D$ in deep inelastic $lA$ collisions, and Drell--Yan dilepton cross sections measured in $pA$ collisions are used as constraints. Also conservation of momentum and baryon number is required. It is shown that the calculated $Q^2$ evoluti

M. Werlen

High statistics fixed target and ISR inclusive photon production data are compared to next-to-leading order (NLO) QCD calculations. The dependence of the theoretical predictions on the structure functions, and on the theoretical scales is investigated. It is shown that the data cannot be simultaneously fitted with a single set of structure functions and scal

J. R. Cudell, I. Royen

We show that the ratio of the transverse to the longitudinal cross sections observed at HERA cannot be reproduced by models which assume that the meson can be described by an on-shell q qbar pair. We explain how a simple model allowing off-shell (anti)quarks can naturally lead to agreement with experiment.

N. Haba, N. Okamura

Recent neutrino experiments suggest the strong evidences of tiny neutrino masses and the lepton-flavor mixing. Neutrino-oscillation solutions for the atmospheric neutrino anomaly and the solar neutrino deficit can determine the texture of neutrino mass matrix according to the neutrino mass hierarchies as Type A: m_3 \gg m_2 \sim m_1, Type B: m_3 \ll m_2 \sim

I. Antoniadis, B. Pioline

Large extra dimensions, of size of order of TeV^{-1} ~= 10^{-16} cm, arise naturally in the context of supersymmetry breaking in string theory, while strings at a TeV scale offer a solution to the gauge hierarchy problem, as an alternative to softly broken supersymmetry or technicolor. In this short review, we present consistent perturbative realizations of

Jishnu Dey, Mira Dey, Ashik Iqubal

The $Ω^-$ magnetic moment was measured very accurately and experimentalists remarked that it differs from the theoretical estimates, thus posing a challenge to the latter. One such estimation uses QCDSR. We revisit this sumrule method, using condensate parameters which were obtained from fitting the differences ($μ_p - μ_n$), ($μ_{Σ^+}- μ_{Σ^-}$) and ($μ_{Ξ^

E. N. Bukina, V. M. Dubovik, V. S. Zamiralov

It is shown that upon considering an alternative form of a parity-violating part of the transition electromagnetic current it is possible to reformulate Hara theorem in a way that it does not forbid any more nonzero asymmetry in the hyperon weak radiative decays $Σ^{+} \to p+γ$ and $Ξ^{-} \to Σ^{-}+γ$ in the limit of exact $SU(3)_{f}$ symmetry thus resolving

M. Beneke, A. Signer, V. A. Smirnov

We use the threshold expansion and non-relativistic effective theory to determine the bottom quark mass from moments of the $b\bar{b}$ production cross section at next-to-next-to-leading order in the (resummed) perturbative expansion, and including a summation of logarithms. For the $\bar{\rm MS}$ mass $\bar{m}_b$, we find $\bar{m}_b(\bar{m}_b)=(4.26\pm 0.12

Bipin R. Desai, Alexander R. Vaucher

It is pointed out that Higgs bootstrap is inherent in the top-condensate models of Nambu and Bardeen et al in that the ladder sum of Higgs pole diagrams in one channel reproduces a Higgs pole in the crossed-channel. This result is exact whenever color flows simultaneously in both channel directions e.g. for N(sub c)=1. Bootstrap solutions for the Higgs boson

Bipin R. Desai, Alexander R. Vaucher

It is shown, using dispersion relations techniques for bound states, that the presence of a large top-Yukawa coupling lowers the Higgs mass from the condensate-model value of twice the top mass (~350 Gev) to 100-200 Gev consistent with the Z(super 0) width precision measurements. The coupling is found to be ~3.7 at the top-mass, much larger than the Standard

Takayuki Saeki

In 1998, the four experiments of LEP, i.e. ALEPH, DELPHI, L3 and OPAL, collected data of about 175 /pb per experiment at the center-of-mass energy of 189 GeV. Using these data, the mass of W boson was directly measured by reconstructing the decay products of two W bosons from the e+e- collisions. The W mass measurement was combined personally with the result

Ioannis Raptis

A scheme for an algebraic quantization of the causal sets of Sorkin et al. is presented. The suggested scenario is along the lines of a similar algebraization and quantum interpretation of finitary topological spaces due to Zapatrin and this author. To be able to apply the latter procedure to causal sets Sorkin&#39;s `semantic switch&#39; from `partially ord

Fumihiko Usui, Koji Uryu, Yoshiharu Eriguchi

We have developed a new numerical scheme to obtain quasiequilibrium structures of nonaxisymmetric compact stars such as binary neutron star systems as well as the spacetime around those systems in general relativity. Concerning quasiequilibrium states of binary systems in general relativity, several investigations have been already carried out by assuming co

Claus Kiefer

I give a review of the conceptual issues that arise in theories of quantum cosmology. I start by emphasising some features of ordinary quantum theory that also play a crucial role in understanding quantum cosmology. I then give motivations why spacetime cannot be treated classically at the most fundamental level. Two important issues in quantum cosmology --

Takashi Tamaki, Takashi Torii, Kei-ichi Maeda

We find a self-gravitating monopole and its black hole solution in Brans-Dicke theory. We mainly discuss the properties of these solutions in the Einstein frame and compare the solutions with those in general relativity.

J. Daude, L. Padro, G. Rigau

This paper explores the automatic construction of a multilingual Lexical Knowledge Base from pre-existing lexical resources. We present a new and robust approach for linking already existing lexical/semantic hierarchies. We used a constraint satisfaction algorithm (relaxation labeling) to select --among all the candidate translations proposed by a bilingual

R. K. P. Zia, L. B. Shaw, B. Schmittmann, R. J. Astalos

A century ago, the foundations of equilibrium statistical mechanics were laid. For a system in equilibrium with a thermal bath, much is understood through the Boltzmann factor, exp{-H[C]/kT}, for the probability of finding the system in any microscopic configuration C. In contrast, apart from some special cases, little is known about the corresponding probab

Douglas Davidson, Marcel den Nijs

Equilibrium crystal shapes (ECS) near facet ridge end points (FRE) are generically complex. We study the body-centered solid-on-solid model on a square lattice with an enhanced uniaxial interaction range to test the stability of the so-called stochastic FRE point where the model maps exactly onto one dimensional Kardar-Parisi-Zhang type growth and the local

G. Litak, J. F. Annett, B. L. Gyorffy

On the basis of a simple model we analyse the influence of disorder on critical temperature T_C in p-wave superconductors. The disorder is treated by means of the Coherent Potential Approximation (CPA) and we focus our attention on the effect of a van Hove singularity near Fermi energy E_F. For the appropriate values of its parameters our model reproduces th

Yuval Oreg, Alexander M. Finkel&#39;stein

The suppression of the mean field temperature of the superconducting transition, $T_c$, in homogeneous amorphous wires is studied. We develop a theory that gives $T_c$ in situations when the dynamically enhanced Coulomb repulsion competes with the contact attraction. The theory accurately describes recent experiments on $T_c$--suppression in superconducting

F. Bouis, M. N. Kiselev, F. Onufrieva, P. Pfeuty

We consider a 2D electron system on a square lattice with hopping beyond nearest neighbors. The existence of the quantum critical point associated with an electronic topological transition in the noninteracting system results in density wave (DW) and high temperature d-wave superconducting (dSC) instabilities in the presence of an exchange interaction J. We

Diego Porras, J. Fernandez-Rossier, C. Tejedor

In this work we present a theoretical description of the transient response of the Fermi Edge Singularity (FES). We study the linear and the nonlinear response of an n-doped QW to laser pulses in the Coherent Control (CC) and Four Wave Mixing (FWM) Configurations. By means of a bosonization formalism we calculate the FWM signal emitted by the sample when it

Alexander I. Olemskoi

An elementary system leading to the notions of fractional integrals and derivatives is considered. Various physical situations whose description is associated with fractional differential equations of motion are discussed.

Ronald Dickman, George Stell

We present a comprehensive study of the lattice restricted primitive model, i.e., a lattice gas consisting of an equal number of positively and negatively charged particles interacting via on-site exclusion and a 1/r potential. On the cubic lattice, Monte Carlo simulations show a line of Neel points separating a disordered, high-temperature phase from a phas

A. Diaz-Sanchez, L. A. Braunstein, R. C. Buceta

The roughening of interfaces moving in inhomogeneous media is investigated by numerical integration of the phenomenological stochastic differential equation proposed by Kardar, Parisi, and Zhang [Phys. Rev. Lett. 56, 889, (1986)] with quenched noise (QKPZ). We express the evolution equations for the mean height and the roughness into two contributions: the l

Oded Agam

A semiclassical diagrammatic approach is constructed for calculating correlation functions of observables in open chaotic systems with time reversal symmetry. The results are expressed in terms of classical correlation functions involving Wigner representations of the observables. The formalism is used to explain a recent microwave experiment on the 4-disk p

Christofer Cronstrom, Milan Noga

We have found a new mean field solution in the BCS theory of superconductivity. This unconventional solution indicates the existence of superconducting phase transitions of third order in thin films, or in bulk matter with a layered structure. The critical temperature increases with decreasing thickness of the layer, and does not exhibit the isotope effect.

Hagen Kleinert

We point out that the recently developed strong-coupling theory enables us to calculate the three main critical exponents nu, eta, omega, from the knowledge of only the two renormalization constants Z_phi of wave function and Z_m of mass. The renormalization constant of the coupling strength is superfluous, and with it also the beta-function, the crucial qua

Ren-Bao Liu, Bang-Fen Zhu

A novel DC and AC driving configuration is proposed for semiconductor superlattices, in which the THz AC driving is provided by an intense bichromatic cw laser. The two components of the laser, usually in the visible light range, are near but not exactly resonant with interband Wannier-Stark transitions, and their frequency difference equals the Wannier-Star

Katepalli R. Sreenivasan, Brindesh Dhruva, Inigo San Gil

The effects of removing large scales external to the inertial range on the properties of scales within the inertial range are studied in a high-Reynolds-number turbulent flow. Structure functions of both even and odd orders are strongly affected across the entire inertial range, but odd-order moments are affected to a greater degree. In particular, the skewn

R. van Zon, H. van Beijeren, J. R. Dorfman

It is generally believed that the dynamics of simple fluids can be considered to be chaotic, at least to the extent that they can be modeled as classical systems of particles interacting with short range, repulsive forces. Here we give a brief introduction to those parts of chaos theory that are relevant for understanding some features of non-equilibrium pro

K. Harada, T. Ikegami

Divergence in antigen response of the immune network is discussed, based on shape-space modelling. The present model extends the shape-space model by introducing the evolution of specificity of idiotypes. When the amount of external antigen increases, stability of the immune network changes and the network responds to the antigen. It is shown that specific a

Susan Kurien, Victor S. L&#39;vov, Itamar Procaccia, K. R. Sreenivasan

The statistical objects characterizing turbulence in real turbulent flows differ from those of the ideal homogeneous isotropic model.They containcontributions from various 2d and 3d aspects, and from the superposition ofinhomogeneous and anisotropic contributions. We employ the recently introduceddecomposition of statistical tensor objects into irreducible r

Mateusz Ruszkowski

The broad X-ray iron line, detected in many active galactic nuclei, is likely to be produced by fluorescence from the X-ray illuminated central parts of an accretion disc close to a supermassive black hole. The time-averaged shape of the line can be explained most naturally by a combination of special and general relativistic effects. Such line profiles cont

P. E. Freeman, D. Q. Lamb, J. C. L. Wang, I. Wasserman

We demonstrate that models of resonant cyclotron radiation transfer in a strong field (i.e. cyclotron scattering) can account for spectral lines seen at two epochs, denoted S1 and S2, in the Ginga data for GRB870303. Using a generalized version of the Monte Carlo code of Wang et al. (1988,1989b), we model line formation by injecting continuum photons into a

P. E. Freeman, C. Graziani, D. Q. Lamb, T. J. Loredo

The Ginga data for the gamma-ray burst GRB870303 exhibit low-energy dips in two temporally distinct spectra, denoted S1 and S2. S1, spanning 4 s, exhibits a single line candidate at ~ 20 keV, while S2, spanning 9 s, exhibits apparently harmonically spaced line candidates at ~ 20 and 40 keV. We evaluate the statistical evidence for these lines, using phenomen

Vahe&#39; Petrosian, Nicole M. Lloyd-Ronning, Andrew Lee

There have been several suggestions of the existence of cosmological redshift signatures in the temporal and spectral characteristics of gamma-ray bursts. However, recent discoveries of afterglows and redshift measurements indicate the presence of broad ``luminosity functions&#39;&#39; which may overwhelm such weaker cosmological signatures. The primary goal

A. L. Zezas, I. Georgantopoulos, M. J. Ward

We present results from the cross-correlation of the spectroscopic atlas of Ho etal (1995) with the ROSAT All-Sky Survey Bright Source Catalogue, in an attempt to understand the X-ray emission mechanisms in nearby galaxies. The resulting sample of 45 galaxies consists predominantly of AGN. However, there are several starforming galaxies spanning a wide range

Paolo Gondolo, Joseph Silk

If cold dark matter is present at the galactic center, as in current models of the dark halo, it is accreted by the central black hole into a dense spike. Particle dark matter then annihilates strongly inside the spike, making it a compact source of photons, electrons, positrons, protons, antiprotons, and neutrinos. The spike luminosity depends on the densit

Almudena Zurita, Maite Rozas, John E. Beckman

We use the catalogue of HII regions obtained from a high quality continuum-subtracted H$α$ image of the grand design spiral galaxy NGC 7479, to construct the luminosity function (LF) for the HII regions (over 1000) of the whole galaxy. Although its slope is within the published range for spirals of the same morphological type, the unusually strong star forma

Sergio Campana, Gabriele Ghisellini, Davide Lazzati, Francesco Haardt

If gamma-ray bursts originate in dense stellar forming regions, the interstellar material can imprint detectable absorption features on the observed X-ray spectrum. Such features can be detected by existing and planned X-ray satellites, as long as the X-ray afterglow is observed after a few minutes from the burst. Detection of these X-ray features will make

R. Atkins, W. Benbow, D. Berley, M. -L. Chen

Milagrito, a prototype for the Milagro detector, operated for 15 months in 1997-8 and collected 8.9 billion events. It was the first extensive air shower (EAS) array sensitive to showers intiated by primaries with energy below 1 TeV. The shadows of the sun and moon observed with cosmic rays can be used to study systematic pointing shifts and measure the angu