September 1997 arXiv papers — page 9

D0 Collaboration

We present the results of an upgrade to the D0 muon system. Scintillating counters have been added to the existing central D0 muon system to provide rejection for cosmic ray muons and out-of-time background, and to provide additional fast timing information for muons in an upgraded Tevatron. Performance and results from the 1994-1996 Tevatron run are present

Ted Jacobson

It is shown how the results of Deser and Levin on the response of accelerated detectors in anti-de Sitter space can be understood from the same general perspective as other thermality results in spacetimes with bifurcate Killing horizons.

John K. Beem, Andrzej Krolak

Cauchy horizons are shown to be differentiable at endpoints where only a single null generator leaves the horizon. A Cauchy horizon fails to have any null generator endpoints on a given open subset iff it is differentiable on the open subset and also iff the horizon is (at least) of class C^1 on the open subset. Given the null convergence condition, a compac

M. Bianchi, M. Brunetti, E. Coccia, F. Fucito

Gravitationally coupled scalar fields, originally introduced by Jordan, Brans and Dicke to account for a non constant gravitational coupling, are a prediction of many non-Einsteinian theories of gravity not excluding perturbative formulations of String Theory. In this paper, we compute the cross sections for scattering and absorption of scalar and tensor gra

D. S. Rokhsar

We consider the excitation spectrum and stability of quantized vortices in a weakly-interacting Bose gas trapped in a toroidal container, and discuss the driven rotation of such a condensate.

K. M. Rabe, P. H. Citrin

The fcc-based structure of Yb2.75C60 is unique among metal-doped fullerene compounds, exhibiting long-range-ordered vacancies, significantly off-centered divalent Yb cations, and distorted, crystallographically inequivalent, orientationally ordered C60 anions. A simple electrostatic-energy analysis, which models the constituents using point charges, is shown

Pascal Lederer, C. M. Chaves

The Ultra Quantum Crystal (UQC) phases observed in quasi-one-dimensional conductors of the Bechgaard salts family under magnetic field exhibit both Spin Density Wave order and a Quantized Hall Effect, which may exhibit sign reversals. We examine the case with no sign reversals. Collective modes in the UQC have been shown to have a rich spectrum, with local M

Alexander L. Fetter

The Bogoliubov approximation and the Gross-Pitaevskii equation characterize the effect of repulsive interactions on a dilute ideal Bose-Einstein gas in a spherical harmonic trap. For large $N$, the interactions expand the condensate relative to an ideal Bose gas; both the speed of sound and critical angular velocity $Ω_{c1}$ for creation of a quantized vorte

Kingshuk Majumdar, Selman Hershfield

We have studied the Junction Magnetoresistance (JMR) and the Differential junction magnetoresistance (DJMR) for double tunnel junctions with magnetic metals in the Coulomb Blockade regime. Spikes are seen in both the JMR and the DJMR vs. voltage curves. They occur at those places where the current increases by a step. In all cases the large bias limit can be

Richard P. Sear

The effect of adding nonadsorbing polymer to a lamellar phase of surfactant bilayers is studied theoretically. We find that the polymer produces coexistence between two lamellar phases of different layer spacings. The coexistence region is a closed loop, as in the experiments of Ficheux et al. [J. de Physique II 5 823 (1995)]. Within our model the coexistenc

M. Matsuda, K. Katsumata, T. Osafune, N. Motoyama

Neutron scattering measurements have been performed on the S=1/2 quasi-one-dimensional system Sr_{14-x}Y_{x}Cu_{24}O_{41}, which has both simple chains and two-leg ladders of copper ions. We observed that when a small amount of yttrium is substituted for strontium, which is expected to reduce the number of holes, the dimerized state and the structure in the

Ady Stern, Iddo Ussishkin

We consider Coulomb drag between two layers of two-dimensional electron gases subject to a strong magnetic field, with the Landau level filling factor in each layer being 1/2. We find $ρ_D$ to be very large, as compared to the zero magnetic field case. We attribute this enhancement to the slow decay of density fluctuations in a strong magnetic field. For a c

Jonathan Doye, David Wales

We have attempted to find the global minima of clusters containing between 20 and 80 atoms bound by the Morse potential as a function of the range of the interatomic force. The effect of decreasing the range is to destabilize strained structures, and hence the global minimum changes from icosahedral to decahedral to face-centred-cubic as the range is decreas

D. M. Carlucci, C. De Dominicis

The Replica Fourier Transform introduced previously is related to the standard definition of Fourier transforms over a group. Its use is illustrated by block-diagonalizing the eigenvalue equation of a four-replica Parisi matrix.

Xi Dai, Zhao-bin Su

In the present paper, we propose a mean field approach for spin ladders based upon the Jordan-Wigner transformation along an elaborately ordered path. We show on the mean field level that ladders with even number legs open a energy gap in their low energy excitation with a magnitude close to the corresponding experimental values, whereas the low energy excit

Di Bari Maria, Cipriani Piero

In this paper we discuss some general aspects of the so-called "geometrodynamical approach" (GDA) to Chaos and present some results obtained within this framework. In order to support the claim that the GDA isn't simply a mere re-transcription of the usual dynamics, but instead can give various hints on the understanding of the qualitative behavi

Cipriani Piero, Di Bari Maria

We here describe the possibility of a synthetic description of the onset of Chaos in many degrees of freedom dynamical systems within the framework of the geometric description of dynamics. We show how this approach to instability helps to single out the transition between different regimes of stochasticity in typical as well peculiar N-body systems. It is s

Barbara Drossel, Thomas Prellberg

We study the dynamics of a particle in a horizontally and periodically shaken box as a function of the box parameters and the coefficient of restitution. For certain parameter values, the particle becomes regularly chattered at one of the walls, thereby loosing all its kinetic energy relative to that wall. The number of container oscillations between two cha

Doug Geisler, Eduardo Bica, Horacio Dottori, Juan J. Clariá

We report the first results of a color-magnitude diagram survey of 25 candidate old LMC clusters. For almost all of the sample, it was possible to reach the turnoff region, and in many clusters we have several magnitudes of the main sequence. Age estimates based on the magnitude difference $δT_1$ between the giant branch clump and the turnoff revealed that n

Eli Waxman

The detection of delayed X-ray, optical and radio emission, ``afterglow,'' associated with gamma-ray bursts (GRBs) is consistent with models, where the bursts are produced by relativistic expanding blast waves, driven by expanding fireballs at cosmological distances. In particular, the time scales over which radiation is observed at different wave ba

L. R. Jones, C. Scharf, H. Ebeling, E. Perlman

X-ray selected surveys of clusters of galaxies can distinguish between hierarchical models of the growth of structure in the Universe. Here we present the first results from an X-ray selected, flux and surface brightness limited deep survey for high redshift clusters and groups of galaxies based on ROSAT PSPC pointed data. The log(N)-log(S) relation of all c

A. Mezzacappa, A. C. Calder, S. W. Bruenn, J. M. Blondin

We investigate neutrino-driven convection in core collapse supernovae and its ramifications for the explosion mechanism, for a 15 solar mass model. Our two-dimensional simulation begins at 12 ms after bounce and proceeds for 500 ms. We couple two-dimensional PPM hydrodynamics to precalculated one-dimensional MGFLD neutrino transport. (The accuracy of this ap

V. A. Kuzmin, V. A. Rubakov

We conjecture that the highest energy cosmic rays beyond the Greisen-Zatsepin-Kuzmin cut-off may provide a unique window into the very early epoch of the Universe, namely, that of reheating after inflation, provided these cosmic rays are due to decays of parent superheavy long-living X-particles. These particles may constitute a considerable fraction of cold

D. Montes, J. Sanz-Forcada, M. J. Fernandez-Figueroa, E. De Castro

The star EZ Peg, long ago classified as cataclysmic variable, has been shown to be a chromospherically active binary system of the RS CVn-type. In this paper we have analysed, using the spectral subtraction technique, simultaneous spectroscopic observations of the H_alpha, H_beta, Na I D_{1} and D_{2}, He I D_{3}, Mg I b triplet, Ca II H & K, and Ca II infra

A. Mezzacappa, A. C. Calder, S. W. Bruenn, J. M. Blondin

We couple two-dimensional hydrodynamics to realistic one-dimensional multigroup flux-limited diffusion neutrino transport to investigate protoneutron star convection in core collapse supernovae, and more specifically, the interplay between its development and neutrino transport, for both 15 and 25 solar mass models. In the presence of neutrino transport, pro

Jean-Pierre Chieze, Romain Teyssier, Jean-Michel Alimi

We simulate the formation of a large X-ray cluster using a fully 3D hydrodynamical code coupled to a Particle-Mesh scheme which models the dark matter component. We focus on a possible decoupling between electrons and ions temperatures. We then solve the energy transfer equations between electrons, ions and neutrals without assuming thermal equilibrium betwe

Y. K. Ng, G. Bertelli, G. Carraro, L. Portinari

New ages are computed for stars in the Solar Neighbourhood from the Edvardsson et al. (1993) data set. Distances derived from the Hipparcos parallaxes were adopted to obtain reliable ages (uncertainty less than 12%) for a subset of stars. There is no apparent age-metallicity relation for stars with an age less than 10 Gyr. Only if we consider older stars a s

Vicent Quilis, Diego Saez

The applicability of the potential approximation in the case of open universes is tested. Great Attractor-like structures are considered in the test. Previous estimates of the Cosmic Microwave background anisotropies produced by these structures are analyzed and interpreted. The anisotropies corresponding to inhomogeneous ellipsoidal models are also computed

Demosthenes Kazanas, Lev G. Titarchuk, Xin-Min Hua

Fenimore et al. (1995) have recently presented a very tight correlation between the spectral and the temporal structure in Gamma Ray Bursts (hereafter GRBs). In particular, they discovered that the durations of the constituent subpulses which make up the time profile of a given GRB have a well defined power-law dependence, of index $\simeq 0.45$, on the ener

I. V. Moskalenko, W. Collmar, V. Schoenfelder

We construct a model of Cyg X-1 which describes self-consistently its emission from soft X-rays to MeV gamma rays. Instead of a compact pair-dominated gamma-ray emitting region, we consider a hot optically thin and spatially extended proton-dominated cloud surrounding the whole accretion disc. The gamma-ray emission is due to the bremsstrahlung, Comptonizati

Jan Kuijpers

We propose a model for solar prominences based on converging flow observed in the chromosphere and photosphere. In contrast with existing models we do not apply a shearing motion along the neutral line. Instead we assume that bipolar loops approaching on different sides of the neutral line have a non-vanishing magnetic helicity of the SAME sign. In the conve

Sofia Randich

A population of cool dwarfs with extreme rotational velocities (v sini > 100 km/sec) is present in young open clusters. ROSAT observations have shown that these very fast rotators exhibit a level of X-ray activity a factor of 3-5 below the saturated level which is usually observed (both in X-rays and other magnetic activity indicators) for `normally' fas

Selma Junqueira, Duilia F. de Mello, Leopoldo Infante

We present photometric analysis of a local sample of 14 isolated pairs of galaxies. The photometric properties analyzed in the local pairs are: colors, morphology, tidal effects and activity. We verify that close pairs have an excess of early-type galaxies and many elliptical galaxies in this pairs are, in fact, lenticular galaxies. Many late-pairs in our sa

Hidenaga Yamagishi, Ismail Zahed

We find that QCD in covariant gauge yields zero for the topological susceptibility, even at the nonperturbative level. The result is derived in two ways, one using translational invariance, and the other using the BRST Hamiltonian. Comparison with the canonical formalism suggests that QCD is not uniquely defined at the nonperturbative level. Supporting evide

Ari Buchalter, David J. Helfand, Robert H. Becker, Richard L. White

In previous attempts to measure Omega_0 from the angular size-redshift (theta-z) relation of double-lobed radio sources, the observed data have been consistent with a static Euclidean universe, rather than with Friedmann models, and past authors have disagreed as to what effects are responsible. These results may be due to a variety of selection effects, dif

V. Delgado

In a previous paper [V. Delgado and J. G. Muga, Phys. Rev. A 56, 3425 (1997)] we introduced a self-adjoint operator $\hat {\cal T}(X)$ whose eigenstates can be used to define consistently a probability distribution of the time of arrival at a given spatial point. In the present work we show that the probability distribution previously proposed can be well un

R. Siebelink

We consider d=4 N=2 supergravity theories which serve as low-energy effective actions for heterotic strings on K_3 \times T^2. At the perturbative level we construct a new version of the heterotic effective action in which the axion has been traded for an antisymmetric tensor field. In the string frame the antisymmetric tensor doesn't transform under Poi

J. Maucourt, D. R. Grempel

We investigate the XY spin-glass model in two and three dimensions using the domain-wall renormalization-group method. The results for systems of linear sizes up to L=12 (2D) and L=8 (3D) strongly suggest that the lower critical dimension for spin-glass ordering may be $d_{c}\approx 3$ rather than four as is commonly believed. Our 3D data favor the scenario

M. A. Ivanov, J. G. Korner, V. E. Lyubovitskij, A. G. Rusetsky

Exclusive nonleptonic decays of bottom and charm baryons are studied within a relativistic three-quark model with a Gaussian shape for the momentum dependence of the baryon-three-quark vertex. We include factorizing as well as nonfactorizing contributions to the decay amplitudes. For heavy-to-light transitions Q -> q u d the total contribution of the nonfact

Victor G. Kac

Conformal algebra is an axiomatic description of the operator product expansion (or rather its Fourier transform) of chiral fields in a conformal field theory. This is a review of recent developments in the subject.

Igor F. Lyuksyutov, Thomas Nattermann, Valery Pokrovsky

A theory of the hysteresis loop in ferromagnets controlled by the domain wall motion is presented. Domain walls are considered as plane or linear interfaces moving in a random medium under the action of the external ac magnetic field $H=H_0\sinωt$. We introduce important characteristics of the hysteresis loop, such as dynamic threshold fields, reversal field

R. B. Laughlin

I argue that the conflict between the fermi-liquid and non-fermi-liquid metallic states viewed by Anderson as the central intellectual issue of cuprate superconductivity, and which motivates the recent criticism by Baskaran and Anderson [cond-mat/9706076] of the work of Zhang [cond-mat/9610140], is a fundamentally wrong concept. All experimental evidence poi

A. V. Belitsky, D. Mueller

Basing on the constraint equalities which arise from the algebra of the collinear conformal group and the conformal operator product expansion, we predict the solutions of the leading order evolution equations for the non-forward distributions, including transversity, in terms of the conformal moments; next-to-leading order flavour singlet coefficient functi

R. N. Faustov, A. P. Martynenko

The contribution of hadronic vacuum polarization to the hyperfine splitting of the muonic hydrogen ground state is calculated with the account of experimental data on the cross section of e^+e^-\to annihilation into hadrons and the dipole parameterization of electromagnetic proton form factors.

Riuji Mochizuki, Kenji Ikegami, Takayuki Suga

In this paper we study energy radiation from a moving mirror in 1+1 dimensional space-time. The mirror is assumed to have finite mass and accordingly to receive back reaction from scalar photon field. The mode expansion of the scalar field becomes different from that without back reaction though the trajectory of the mirror is not changed. Then energy densit

Taksu Cheon, T. Shigehara

It is shown that a potential consisting of three Dirac's delta functions on the line with disappearing distances can give rise to the discontinuity in wave functions with the proper renormalization of the delta function strength. This can be used as a building block, along with the usual Dirac's delta, to construct the most general three-parameter fa

F. Mancini, D. Villani, H. Matsumoto

A theoretical analysis of the thermodynamic response functions of the 2D single-band Hubbard model is realized by means of the composite operator method. It is shown that all the features of these quantities can be explained by looking at the dependence of the thermodynamic variables on their conjugate ones. It is found that the numerical data from quantum M

Oleg Y. Gnedin, Lars Hernquist, Jeremiah P. Ostriker

We derive expressions for the tidal field exerted by a spherically symmetric galaxy having an extended mass distribution, and use our analysis to calculate tidal perturbations and heating of stars in a globular cluster or a satellite galaxy orbiting in the external potential. We consider a Hernquist model and several power-law models for the primary. We inte

V. Barger, T. Han, J. Kelly

We explore the potential of electron-photon colliders to measure fundamental supersymmetry parameters via the processes $eγ\to \tilde e \tildeχ^0$ (selectron-neutralino) and $eγ\to \tildeν\tildeχ^-$ (sneutrino-chargino). Given the $\tildeχ^0$ and $\tildeχ^-$ masses from $e^+e^-$ and hadron collider studies, cross section ratios $σ(γ_-)/σ(γ_+)$ for opposite p

S. M. Sergeev

Local (or modified) Yang -- Baxter equation (LYBE) gives the functional map from the parameters of the weights in the left hand side to the parameters of the correspondent weights in the right hand side of LYBE. Such maps solve the functional tetrahedron equation. In this paper all the maps associated with LYBE of the ferro-electric type with single paramete

V. A. Kalatsky, E. Müller--Hartmann, V. L. Pokrovsky, G. S. Uhrig

It is shown that even for large spins $J$ the fundamental difference between integer and half-integer spins persists. In a quasi-classical description this difference enters via Berry's connection. This general phenomenon is derived and illustrated for large spins confined to a plane by crystalline electric fields. Physical realizations are rare-earth Ni

H. -D. Doebner, G. A. Goldin, P. Nattermann

Beginning with ordinary quantum mechanics for spinless particles, together with the hypothesis that all experimental measurements consist of positional measurements at different times, we characterize directly a class of nonlinear quantum theories physically equivalent to linear quantum mechanics through nonlinear gauge transformations. We show that under tw

K. Heinemann

I present some simple exactly solvable models of spin diffusion caused by synchrotron radiation noise in storage rings. I am able to use standard stochastic differential equation and Fokker-Planck methods and I thereby introduce, and exploit, the polarization density. This quantity obeys a linear evolution equation of the Bloch type, which is, like the Fokke

G. La Penna, S. Letardi, V. Minicozzi, S. Morante

In this talk I discuss the general question of the portability of Molecular Dynamics codes for diffusive systems on parallel computers of the APE family. The intrinsic single precision arithmetics of the today available APE platforms does not seem to affect the numerical accuracy of the simulations, while the absence of integer addressing from CPU to individ

J. L. Marín, J. C. Eilbeck, F. M. Russell

We show for the first time that highly localized in-plane breathers can propagate in specific directions with minimal lateral spreading in a model 2-D hexagonal non-linear lattice. The lattice is subject to an on-site potential in addition to longitudinal nonlinear inter-particle interactions. This study investigates the prediction that stable breather-like

Feng Pan, J. P. Draayer, W. E. Ormand

An exact, number-conserving solution to the generalized, orbit-dependent pairing problem is derived by introducing an infinite-dimensional algebra. A method for obtaining eigenvalues and eigenvectors of the corresponding Hamiltonian is also given. The relevance of the orbit-dependent pairing solution is demonstrated by comparing predictions of the model with

H. Kamada, J. Golak, K. Miyagawa, H. Witala

The pi-mesonic decay of the hypertriton is calculated based on a hypertriton wavefunction and 3N scattering states, which are rigorous solutions of 3-body Faddeev equations using realistic NN and hyperon-nucleon interactions. The total pi-mesonic decay rate is found to be 92% of the free Lambda decay rate, which is close to the experimental data. Together wi

P. Raychev, R. Roussev, N. Lo Iudice, P. Terziev

An analysis of the construction of a q-deformed version of the 3-dimensional harmonic oscillator, which is based on the application of q-deformed algebras, is presented. The results together with their applicability to the shell model are compared with the predictions of the modified harmonic oscillator.

P. G. Grinevich, A. Yu. Orlov

It is well-known that the algebra of vector fields on the circle acts on the space of Riemann surfaces with a marked point and a local parameter at this point. We show that this action has a natural realization in the soliton theory, indeed it coincides with the action of some non-isospectral Kadomtsev-Petviashvili symmetries on the finite-gap solutions. A t

Yuri Chekanov

The problem of classification of Legendrian knots (links) up to isotopy in the class of Legendrian embeddings (Legendrian isotopy) naturally leads to the following two subproblems. The first of them is: which combinations of the three classical invariants can be realized by a Legendrian knot? (It is well-known that each invariant by itself can be realized by

Rita Gitik

We show that the quasiconvex subgroups in doubles of certain negatively curved groups are closed in the profinite topology. This allows us to construct the first known large family of hyperbolic 3-manifolds such that any finitely generated subgroup of the fundamental group of any member of the family is closed in the profinite topology.

Vladimir Kadets, Roman Shvidkoy, Gleb Sirotkin, Dirk Werner

A Banach space $X$ is said to have the Daugavet property if every operator $T: X\to X$ of rank~$1$ satisfies $\|Id+T\| = 1+\|T\|$. We show that then every weakly compact operator satisfies this equation as well and that $X$ contains a copy of $\ell_{1}$. However, $X$ need not contain a copy of $L_{1}$. We also study pairs of spaces $X\subset Y$ and operators

Aharon Casher, Shmuel Nussinov

We present evidence that an interplay of the laws of microphysics and cosmology renders the Planck momentum unattainable by an elementary particle. Several categories of accelerators are analyzed and shown to fail.

Sabbir Rahman

We complete the set of string vertices of non-negative dimension by introducing in a consistent manner those moduli spaces which had previously been excluded. As a consequence we obtain a `geometrised' string action taking the simple form $S=f(\B)$ where `$\B$' is the sum of the string vertices. That the action satisfies the B-V master equation follo

I. N. Mishustin, L. M. Satarov, H. Stoecker, W. Greiner

We study the bremsstrahlung of virtual omega mesons due to the collective deceleration of nuclei at the initial stage of an ultrarelativistic heavy-ion collision. It is shown that electromagnetic decays of these mesons may give an important contribution to the observed yields of dileptons. Mass spectra of positron-electron and muon pairs produced in central

Yuri Shirman

We propose a simple class of nonrenormalizable models of gauge mediated dynamical supersymmetry breaking. The models do not have gauge singlet fields. The Standard Model gauge group is embedded in the global symmetry of the SUSY breaking sector. At the renormalizable level the models possess a set of classical flat directions. Only one of those flat directio

Boris Kayser

In the decay chain B(d) --> Psi + K --> Psi + (pi l nu), neutral K mixing follows on the heels of neutral B mixing. This "cascade mixing" leads to an interference which probes cos(2*beta), where beta is one of the three CP-violating phase angles which characterize CP violation in the Standard Model. Widely-discussed future B-system experiments will d

Michele Maris

A set of quantitative predictions for the day-night asymmetry in the Super - Kamiokande detector is presented. For these predictions, neutrino events are collected in ``samples'' defined by the trajectories in the Earth of the corresponding solar neutrinos. The more important samples considered here are: the full sample of neutrinos detected at night

Ramon Miquel

The analyses and results on WW physics obtained in the first year of running of LEP2 are summarized. The determination of the W mass, both through the measurement of the WW production cross section at a center-of-mass energy of 161 GeV and through the study of the invariant mass distribution of W decay products in the 172 GeV run are described first. Prelimi

Ramon Miquel

Searches for new physics in the first year of running of LEP2, at energies of 161 and 172 GeV, are summarized. After a short review of WW results and their implications on new physics, searches for the Higgs boson and SUSY particles, analyses of four-jet final states and constraints on possible explanations for the HERA high Q**2 anomaly are discussed in tur

P. A. Raczka

The problem of determination of $α_{s}$ and the condensates from the moments of invariant mass distribution in the semileptonic tau decays is considered. It is investigated how the extracted values of alpha_s(m^{2}_{tau}) and the condensates are affected by the the renormalization scheme dependence of the next-to-next-to-leading order perturbative correction

M. Beneke, M. Krämer, M. Vänttinen

The comparison of $J/ψ$ photoproduction data in the inelastic region with theoretical predictions based on the NRQCD approach has remained somewhat ambiguous and controversial, in particular at large values of the inelasticity variable $z$. We study the polar and azimuthal decay angular distribution of $J/ψ$ mesons as functions of $z$ and transverse momentum

A. B. Kobakhidze

It is shown, that the presently accepted value for b-quark mass can be obtained from the requirement of the exact b-$τ$ unification in the both non-SUSY and SUSY non-chiral extended GUTs.

Wojciech Krolikowski

An ansatz for mass matrix was recently proposed for charged leptons, predicting (in its diagonal approximation) $m_τ\simeq1776.80$ MeV from the experimental values of $m_e$ and $m_μ$, in agreement with $m_τ^{exp}= 1777.00^{+0.30}_{-0.27}$ MeV. Now it is applied to neutrinos. If the amplitude of neutrino oscillations $ν_μ\toν_τ$ is $\sim 1/2$ and $|m^2_{ν_τ}-

H. Navelet, R. Peschanski

We derive the full analytic expression for the QCD eikonal coupling of a quark-antiquark state to the exchanged gluon-gluon state in the BFKL formalism. The formula is valid for all conformal spin configurations of the quark-antiquark and gluon-gluon states. In particular, a new selection rule on conformal spins characterizes the non-dominant BFKL components

R. N. Faustov, A. P. Martynenko

In the framework of the quasipotential method we calculate the contributions of the kind α^6\lnα, alpha^6 of three-photon exchange diagrams to the energy spectrum of muonium $n^3S_1$ state in the leading order on $m_e/m_μ$. Analytical expression of obtained correction for arbitrary principal quantum number is equal to (Zα)^6(m_e/m_μ)m_e(6\ln(2)-35/48)/n^3.

G. Barenboim, F. J. Botella, G. C. Branco, O. Vives

We show that the study of CP asymmetries in neutral B-meson decays provides a very sensitive probe of flavour-changing neutral currents (FCNC). We introduce two new angles, $α_{SM}$ and $β_{SM}$, whose main feature is that they can be readily obtained from the measurement of the CP asymmetries $a_{J/ψK_s}$, $a_{π^+ π^-}$ and the ratio $R_u \equiv|V_{ud}V_{ub

Arttu Rajantie

I present a three-dimensional effective theory that describes the high-temperature equilibrium behavior of the SU(5) theory accurately, but is much easier to study using non-perturbative methods than the original four-dimensional one. The effective theory is obtained by perturbatively integrating out the super-heavy Matsubara modes as well as the heavy tempo

Eiichi Takasugi, Masaki Yoshimura

We examined the question that what is a general form of quark mass matrices which is achieved by the transformation that leaves the left-handed gauge interaction invariant. In particular, we analyzed in detail the Fritzsch-type and the Branco-Silva-Marcos-type parametrization. Both parametrizations contain ten parameters and can be expressed by the experimen

A. Agodi, G. Andronico, P. Cea, M. Consoli

We compute numerically the effective potential for the $(λΦ^4)_4$ theory on the lattice. Three different methods were used to determine the critical bare mass for the chosen bare coupling value. Two different methods for obtaining the effective potential were used as a control on the results. We compare our numerical results with three theoretical descriptio

P. Bialas, Z. Burda, D. A. Johnston

Four dimensional simplicial gravity has been studied by means of Monte Carlo simulations for some time, the main outcome of the studies being that the model undergoes a discontinuous phase transition between an elongated and a crumpled phase when one changes the curvature (Newton) coupling. In the crumpled phase there are singular vertices growing extensivel

Y. Iwasaki

The CP-PACS project is a five year plan, which formally started in April 1992 and has been completed in March 1997, to develop a massively parallel computer for carrying out research in computational physics with primary emphasis on lattice QCD. The initial version of the CP-PACS computer with a theoretical peak speed of 307 GFLOPS with 1024 processors was c

Alexander V. Karabegov

A unified approach to geometric, symbol and deformation quantizations on a generalized flag manifold endowed with an invariant pseudo-Kaehler structure is proposed. The Hilbert space of states is realized via the Bott-Borel-Weil theorem in the sheaf cohomology of the geometric quantization line bundle. The corresponding deformation quantization is a quantiza

Martin-D. Lacasse, Gary S. Grest, Alex J. Levine

A continuum-space bead-spring model is used to study the phase behavior of binary blends of homopolymers and the structure of the interface between the two immiscible phases. The structure of the interface is investigated as a function of immiscibility, chain length, and system size. Capillary waves are observed and their measurement allows us to determine t

W. Jaskolski, Garnett W. Bryant

Electron, hole, and exciton states of multishell CdS/HgS/CdS quantum-dot quantum well nanocrystals are determined by use of a multiband theory that includes valence-band mixing, modeled with a 6-band Luttinger-Kohn Hamiltonian, and nonparabolicity of the conduction band. The multiband theory correctly describes the recently observed dark-exciton ground state

Alessandro Vespignani, Stefano Zapperi

We present a unified mean-field theory, based on the single site approximation to the master-equation, for stochastic self-organized critical models. In particular, we analyze in detail the properties of sandpile and forest-fire (FF) models. In analogy with other non-equilibrium critical phenomena, we identify the order parameter with the density of ``active

Sukit Limpijumnong, Walter R. L. Lambrecht

The total energy differences between various SiC polytypes (3C, 6H, 4H, 2H, 15R and 9R) were calculated using the full-potential linear muffin-tin orbital method using the Perdew-Wang-(91) generalized gradient approximation to the exchange-correlation functional in the density functional method. Numerical convergence versus k-point sampling and basis set com

M. J. P. Gingras, M. Larkin, I. Mirebeau, W. D. Wu

We have performed an extensive muon spin relaxation study of the well known (Fe$_{1-x}$Mn$_{x}$)$_{75}$P$_{16}$B$_6$Al$_3$ reentrant spin glass. We find a strong increase of the dynamic as well as static muon depolarization rate at the paramagnetic to ferromagnetic transition temperature, $T_c$, and at $T_f$ ($T_f<T_c$) that corresponds to the onset of stron

Hiroaki Nakamura, Kazuaki Ikeda, Satarou Yamaguchi

Improvement of a superconducting magnet system makes induction of a strong magnetic field easier. This fact gives us a possibility of energy conversion by the Nernst effect. As the first step to study the Nernst element, we measured the conductivity, the Hall coefficient, the thermoelectric power and the Nernst coefficient of the InSb, which is one of candid

Manuel de Buenaga Rodriguez, Jose Maria Gomez Hidalgo, Belen Diaz Agudo

Automatic Text Categorization (TC) is a complex and useful task for many natural language applications, and is usually performed through the use of a set of manually classified documents, a training collection. We suggest the utilization of additional resources like lexical databases to increase the amount of information that TC systems make use of, and thus

Manuela Boros, Maria Aretoulaki, Florian Gallwitz, Elmar Noeth

One of the most important causes of failure in spoken dialogue systems is usually neglected: the problem of words that are not covered by the system&#39;s vocabulary (out-of-vocabulary or OOV words). In this paper a methodology is described for the detection, classification and processing of OOV words in an automatic train timetable information system. The v

Toni Tuells

This paper shows that previously reported generation algorithms run into problems when dealing with f-structure representations. A generation algorithm that is suitable for this type of representations is presented: the Semantic Kernel Generation (SKG) algorithm. The SKG method has the same processing strategy as the Semantic Head Driven generation (SHDG) al

Enrico Segre, Shigeo Kida

Two-dimensional decaying turbulent flow is known to approach apparently stable states after a long time evolution. A few theories and models have been so far proposed to account for this relaxation. In this paper, we compare results of numerical experiments with the predictions of these theories to assess their applicability. We study the long time decay of

H. -W. Chen, K. M. Lanzetta, J. K. Webb, X. Barcons

We present initial results of a program to obtain and analyze HST WFPC2 images of galaxies in fields of HST spectroscopic target QSOs. The goal of the program is to investigate how the properties of \lya absorption systems observed in the spectra of background QSOs vary with the properties of intervening galaxies. We found that \lya absorption equivalent wid

S. I. Blinnikov, K. A. Postnov

An energy deposition of \sim 10^{50} ergs into the exterior 10^{-3} M_\sun layers of a red giant is calculated to produce an optical phenomenon similar to afterglows of gamma-ray bursts (GRB) recently observed. This model can be realized if a GRB is generated by some mechanism in a close binary system. In contrast to a ``hypernova&#39;&#39; scenario for GRB

V. S. Dhillon, T. R. Marsh, D. H. P. Jones

We present spectrophotometry of the eclipsing nova-like variable SW Sex. The continuum is deeply eclipsed and shows asymmetries due to the presence of a bright spot. We derive a new ephemeris and, by measuring the eclipse width, we are able to constrain the inclination to i > 75^o and the disc radius to R_D > 0.6 L_1. In common with other members of its clas

G. M. Williger, A. Smette, C. Hazard, J. A. Baldwin

We present results from a survey of the Lyman alpha forest at 2.15<z<3.26 toward ten QSOs concentrated within a 1 degree field. We find correlations of the Lyman alpha absorption line wavelengths between different lines-of-sight over the whole redshift range. This indicates the existence of large-scale structures in the Lyman alpha forest extending at least

Paolo Ciliegi, Tommaso Maccacaro

Fifteen ROSAT PSPC observations available in the public archive are analyzed in order to study time and spectral variability of the 12 EMSS AGN detected by ROSAT with more than 2000 net counts. Time variability was investigated on 13 different time scales, ranging from 400 s to 1 year. Of the 12 sources analyzed, only two do not show a significant variabilit

Kenneth M. Lanzetta, John K. Webb, Xavier Barcons

We describe an analysis of the galaxy-absorber cross-correlation function as a function of velocity separation, impact parameter separation, and absorber Lyman alpha equivalent width on impact parameter scales that extend up to 1 Mpc.

X. Hernandez, Gerard Gilmore

We re-examine the Fall & Efstathiou (1980) scenario for galaxy formation, including the dark halo gravitational reaction to the formation of the baryon disk, as well as continuous variations in the intrinsic halo density profile. The recently published rotation curves of LSB and dwarf galaxies together with previously known scaling relations provide sufficie