July 1999 arXiv papers — page 23

Y. Levinson

We calculate the dephasing rate of an electron state in a pinched quantum dot, due to Coulomb interactions between the electron in the dot and electrons in a nearby voltage biased ballistic nanostructure. The dephasing is caused by nonequilibrium time fluctuations of the electron density in the nanostructure, which create random electric fields in the dot. A

T. Prikhna, W. Gawalek, V. Moshchil, R. Viznichenko

The effect of a short (10-30 min) thermobaric action (in the 1-5 GPa pressure and 700-1300$^\circ$C temperature range) on the structure, superconductive and mechanical properties of melt-textured-MBa$_2$Cu$_3$O$_{7-δ}$ (M=Y, Nd) or MT-MBCO have been studied. The existence has been established of pressure-temperature--time conditions (2 GPa, 800$^\circ$C for

A. A. Kordyuk, G. Krabbes, V. V. Nemoshkalenko, R. V. Viznichenko

The influence of surface treatment on AC loss in melt-processed quasi-single crystal HTS was investigated with resonance oscillations technique. We have found that amplitude dependencies of AC loss on magnetic field amplitude become rather complicated after surface polishing. The experimental data show well distinguished dynamic crossover from absence of bar

Giorgio Parisi

In these two lectures I review our theoretical understanding of spin glasses paying a particular attention to the basic physical ideas. We introduce the replica method and we describe its probabilistic consequences (we stress the recently discovered importance of stochastic stability). We show that the replica method is not restricted to systems with quenche

M. Maltoni, M. I. Vysotsky

Though LEP II direct searches still cannot exclude a chargino nearly degenerate with the lightest neutralino if their mass is only slightly above half of the Z boson mass, it can be excluded indirectly analyzing precision data. In this particular limit simple analytical formulas for oblique electroweak radiative corrections are presented.

Keiji Oguiso, De-Qi Zhang

In the present paper we describe the K3 surfaces admitting order 11 automorphisms and apply this to classify log Enriques surfaces of global index 11.

Anthony Aguirre, Zoltan Haiman

Recent observations of Type Ia SNe at redshifts 0 < z <1 reveal a progressive dimming which has been interpreted as evidence for a cosmological constant of Omega_Lambda ~ 0.7. An alternative explanation of the SN results is an open universe with Omega_Lambda=0 and the presence of > 0.1 micron dust grains with a mass density of Omega_dust ~ (few) * 10^{-5} in

Miroljub Dugic

We consider the CNOT quantum gate as a physical action, i.e. as unitary in time evolution of the two-qubit system. This points to the modeling of the interaction Hamiltonian of the two-qubit system which would correspond to the CNOT transformation; the analysis naturally generalizes to the Toffoli gate. Despite nonuniqueness of the model of the interaction H

T. F. Havel, S. S. Somaroo, C. -H. Tseng, D. G. Cory

This paper surveys our recent research on quantum information processing by nuclear magnetic resonance (NMR) spectroscopy. We begin with a geometric introduction to the NMR of an ensemble of indistinguishable spins, and then show how this geometric interpretation is contained within an algebra of multispin product operators. This algebra is used throughout t

Giulio Ruffini, Antonio Rius, Lidia Cucurull, Alex Flores

We have analyzed Zenith Wet Delay (ZWD) time series from an experiment over the Madrid (Spain) area obtained from 5 GPS receivers using two different techniques. In the first case a delay correlation analysis of the ZWD time-series has been carried out. We show that for this small network (with a spatial scale of less than 100 km) the correlation between the

M. Hasegawa, K. Kaneko

An extended pairing plus QQ force model, which has been shown to successfully explain the nuclear binding energy and related quantities such as the symmetry energy, is applied to study the alpha-like four-nucleon correlations in 1f_{7/2} shell nuclei. The double difference of binding energies, which displays a characteristic behavior at $N \approx Z$, is int

C. Grunspan

Cet article expose un isomorphisme entre l&#39;espace des phases du systeme de sinus-Gordon quantique sur reseaux et un espace homogene quantique pour $U_q(\hat{sl_2})$.

Leonid Frankfurt, Mark Strikman

The interaction of spatially small dipoles with nucleons, nuclei is calculated in the DGLAP approximation at the top of HERA energies and found to be close to the $S$-channel unitarity limit in the case of the color octet dipoles. The DGLAP analyses of the current diffractive data appear to support this conclusion as they indicate a $\sim 30-40%$ probability

E. Torrente-Lujan

The experimental measurement of $B(b \to sγ)$ imposes important constraints on the charged Higgs boson mass in the MSSM. We show that by adding bilinear R--Parity violation (BRpV) in the tau sector, these bounds are relaxed. The bound on $m_{H^{\pm}}$ in the MSSM--BRpV model is $\gsim 200-250$ GeV for the the heavy squark limit. For lighter squarks, light ch

Francesco Vissani

We introduce the representation on one unitarity triangle of the constraints resulting (1) from the interpretation of solar and atmospheric neutrino data in terms of oscillations, and (2) from the search for neutrinoless double beta decay. We show its use for the study of a nearly degenerate neutrino spectrum. The representation shows clearly the particular

M. N. Chernodub, Thomas C. Kraan, Pierre van Baal

We construct the fermion zero-mode for arbitrary charge one SU(n) calorons with non-trivial holonomy, both in the finite temperature context (anti-periodic boundary conditions in time) and in the Kaluza-Klein compactification context (periodic boundary conditions in time). The zero-mode is localised on one of the constituent monopoles and we discuss a relati

Akihiro Ishibashi, Akio Hosoya

To probe naked spacetime singularities with waves rather than with particles we study the well-posedness of initial value problems for test scalar fields with finite energy so that the natural function space of initial data is the Sobolev space. In the case of static and conformally static spacetimes we examine the essential self-adjointness of the time tran

S. Nojiri, O. Obregon, S. D. Odintsov

We review the anomaly induced effective action for dilaton coupled spinors and scalars in large N and s-wave approximation. It may be applied to study the following fundamental problems: construction of quantum corrected black holes (BHs), inducing of primordial wormholes in the early Universe (this effect is confirmed) and the solution of initial singularit

A. N. Lavrov, Yoichi Ando, Kouji Segawa, J. Takeya

We report on a contrasting behavior of the in-plane and out-of-plane magnetoresistance (MR) in heavily underdoped antiferromagnetic (AF) YBa_2Cu_3O_{6+x} (x<0.37). The out-of-plane MR (I//c) is positive over most of the temperature range and shows a sharp increase, by about two orders of magnitude, upon cooling through the Neel temperature T_N. A contributio

Seung-Pyo Hong, Kwangyl Park, Sung-Ho Suck Salk

Effects of nonmagnetic impurities on optical conductivity in the systems of antiferromagnetically correlated electrons are examined based on the Lanczos exact diagonalization scheme. As a result of resonant scattering a low-frequency peak in the optical conductivity is predicted to occur in the presence of the nonmagnetic impurities, which is consistent with

M. H. Montgomery, D. E. Winget

We consider the pulsational properties of white dwarf star models with temperatures appropriate for the ZZ Ceti instability strip and with masses large enough that they should be substantially crystallized. Our work is motivated by the existence of a potentially crystallized DAV, BPM 37093, and the expectation that digital surveys in progress will yield many

Ken D. Olum

Ori and Soen have proposed a spacetime which has closed causal curves on the boundary of a region of normal causality, all within a region where the weak energy condition (positive energy density) is satisfied. I analyze the causal structure of this spacetime in some simplified models, show that the Cauchy horizon is compactly generated, and argue that any a

Philip Nelson

It is well known that transcription can induce torsional stress in DNA, affecting the activity of nearby genes or even inducing structural transitions in the DNA duplex. It has long been assumed that the generation of significant torsional stress requires the DNA to be anchored, forming a limited topological domain, since otherwise it would spin almost freel

Adam G. Riess, Alexei V. Filippenko, Weidong Li, Brian P. Schmidt

We have compared the risetime for samples of nearby and high-redshift type Ia supernovae (SNe Ia). The fiducial risetime of the nearby SNe Ia is 2.5+/-0.4 days longer than the proemial risetime determined by Goldhaber (1998a,b) for high-redshift SNe Ia from the Supernova Cosmology Project. The statistical likelihood that the two samples have different fiduci

Adam G. Riess, Alexei V. Filippenko, Weidong Li, Richard R. Treffers

We present calibrated photometric measurements of the earliest detections of nearby type Ia supernovae (SNe Ia). The set of ~30 new, unfiltered CCD observations delineate the early rise behavior of SNe Ia > 18 to 10 days before maximum. Using simple empirical models, we demonstrate the strong correlation between the risetime (i.e., the time between explosion

Karl Martel, Eric Poisson

Inspiraling compact binaries have been identified as one of the most promising sources of gravitational waves for interferometric detectors. Most of these binaries are expected to have circularized by the time their gravitational waves enter the instrument&#39;s frequency band. However, the possibility that some of the binaries might still possess a signific

A. Suter, M. Mali, J. Roos, D. Brinkmann

We present a 17O nuclear magnetic resonance study in the stoichiometric superconductor YBa_2Cu_4O_8. A double irradiation method enables us to show that, below around 180 K, the spin-lattice relaxation rate of plane oxygen is not only driven by magnetic, but also significantly by quadrupolar fluctuations, i.e. low-frequency charge fluctuations. In the superc

H1 Collaboration, C. Adloff

A search for new bosons possessing couplings to lepton-quark pairs is performed in the H1 experiment at HERA using 1994 to 1997 data corresponding to an integrated luminosity of 37pb^-1. First generation leptoquarks (LQs) are searched in very high Q^2 neutral (NC) and charged (CC) current data samples. The measurements are compared to Standard Model (SM) exp

Neil. D. Lambert, David Tong

We show that there exist finite energy, non-singular instanton solutions for five-dimensional theories with broken gauge symmetry. The soliton is supported against collapse by a non-zero electric charge. The low-energy dynamics of these solutions is described by motion on the ADHM moduli space with potential.

Graeme Mitchison, Richard Jozsa

Suppose that we are given a quantum computer programmed ready to perform a computation if it is switched on. Counterfactual computation is a process by which the result of the computation may be learnt without actually running the computer. Such processes are possible within quantum physics and to achieve this effect, a computer embodying the possibility of

Reka Albert, Hawoong Jeong, Albert-Laszlo Barabasi

Despite its increasing role in communication, the world wide web remains the least controlled medium: any individual or institution can create websites with unrestricted number of documents and links. While great efforts are made to map and characterize the Internet&#39;s infrastructure, little is known about the topology of the web. Here we take a first ste

L. Didukh, Yu. Skorenkyy, Yu. Dovhopyaty, V. Hankevych

In the present paper we propose a doubly orbitally degenerate narrow-band model with correlated hopping. The peculiarity of the model is taking into account the matrix element of electron-electron interaction which describes intersite hoppings of electrons. In particular, this leads to the concentration dependence of the effective hopping integral. The cases

U. Lisenfeld, K. G. Isaak, R. Hills

We present new data taken at 850 $μ$m with SCUBA at the JCMT for a sample of 19 luminous infrared galaxies. Fourteen galaxies were detected. We have used these data, together with fluxes at 25, 60 and 100 $μ$m from IRAS, to model the dust emission. We find that the emission from most galaxies can be described by an optically thin, single temperature dust mod

V. Boerchers, S. Gieseke, G. Martens, J. Meyer

We present a new cascade-type microscopic simulation of Nucleus-Nucleus Collisions at RHIC energies. The basic elements are partons (quarks and gluons) moving in 8N-dimensional phase space according to Poincaré-covariant dynamics. The parton-parton scattering cross sections used in the model are computed within perturbative QCD in the tree-level approximatio

Jorma Louko, Carlo Rovelli

We investigate Refined Algebraic Quantization (RAQ) with group averaging in a constrained Hamiltonian system with unreduced phase space T^*R^4 and gauge group SL(2,R). The reduced phase space M is connected and contains four mutually disconnected `regular&#39; sectors with topology R x S^1, but these sectors are connected to each other through an exceptional

R. Manvelyan, R. Mkrtchyan

The SO(2,10) covariant extension of M-theory superalgebra is considered, with the aim to construct a correspondingly generalized M-theory, or 11d supergravity. For the orbit, corresponding to the $11d$ supergravity multiplet, the simplest unitary representations of the bosonic part of this algebra, with sixth-rank tensor excluded, are constructed on a langua

Mark Wardle, Mark Walker

We consider the thermal properties of cold, dense clouds of molecular hydrogen and atomic helium. For cloud masses below 10^-1.7 Msun, the internal pressure is sufficient to permit the existence of particles of solid or liquid hydrogen at temperatures above the microwave background temperature. Optically thin thermal continuum emission by these particles can

YuFen Liu, ZhongQi Ma, BoYuan Hou

Pure spinor formalism and non-integrable exponential factors are used for constructing the conformal-invariant wave equation and Lagrangian density for massive fermion. It is proved that canonical Dirac Lagrangian for massive fermion is invariant under induced projective conformal transformations.

A. Konechny, A. Schwarz

We give an explicit expression for classical 1/4-BPS fields in supersymmetric Yang-Mills theory on noncommutative tori. We use it to study quantum 1/4-BPS states. In particular we calculate the degeneracy of 1/4-BPS energy levels.

Robert Haslinger, Robert Joynt

Josephson tunneling between YBCO and Pb with the current flowing along the c-axis of the YBCO is persumed to come from an s-wave component of the superconductivity of the YBCO. Experiments on multi-twin samples are not entirely consistent with this hypothesis. The sign change of the s-wave order parameter across the N_T twin boundaries should give cancelatio

Hendry I. Elim

Two types of integrable coupled nonlinear Schrodinger (NLS) equations are derived by using Zakharov-Shabat (ZS) dressing method.The Lax pairs for the coupled NLS equations are also investigated using the ZS dressing method. These give new types of the integrable coupled NLS equations with certain additional terms. Then, the exact solutions of the new types a

M. J. Martins, X. W. Guan

We construct an extended Hubbard model with open boundaries from a $R$-matrix based on the $U_q[Osp(2|2)]$ superalgebra. We study the reflection equation and find two classes of diagonal solutions. The corresponding one-dimensional open Hamiltonians are diagonalized by means of the Bethe ansatz approach.

Carl Bender, Fred Cooper, Peter Meisinger, Van M. Savage

A variational calculation of the energy levels of a class of PT-invariant quantum mechanical models described by the non-Hermitian Hamiltonian H= p^2 - (ix)^N with N positive and x complex is presented. Excellent agreement is obtained for the ground state and low lying excited state energy levels and wave functions. We use an energy functional with a three p

André Stefanov, Nicolas Gisin, Olivier Guinnard, Laurent Guinnard

A physical random number generator based on the intrinsic randomness of quantum mechanics is described. The random events are realized by the choice of single photons between the two outputs of a beamsplitter. We present a simple device, which minimizes the impact of the photon counters&#39; noise, dead-time and after pulses.

Gao Shan

We show that the quantum superluminal communication based on the quantum nonlocal influence must exist if a basic principle of science is still valid, which states that if we have demonstrated the existence of something real, we can confirm its existence.

D. R. Bes, O. Civitarese, E. E. Maqueda, N. N. Scoccola

The long standing problem of proton-neutron pairing and, in particular, the limitations imposed on the solutions by the available symmetries, is revisited. We look for solutions with non-vanishing expectation values of the proton, the neutron and the isoscalar gaps. For an equal number of protons and neutrons we find two solutions where the absolute values o

W. M. Alberico, A. De Pace, G. Garbarino, R. Cenni

We present an evaluation of the non-mesonic decay widths for Lambda-hypernuclei (Lambda N --> NN, Lambda NN --> NNN) within the framework of the polarization propagator method. The full Lambda self-energy is evaluated microscopically in nuclear matter by using the functional approach, which supplies a theoretically well grounded approximation scheme for the

Hartmuth Arenhoevel

The formal properties of the recently derived set of linearly independent invariant amplitudes for the electromagnetic production of a pseudoscalar particle from a spin-one particle have been further exploited. The crossing properties are discussed in detail. Since not all of the amplitudes have simple crossing behaviour, we introduce an alternative set of b

M. M. Shakir&#39;yanov

The problem on the asymptotics for the solution of multidimensional nonlinear Boussinesq equation with respect to a small parameter $\ve$ is considered. The asymptotic expansion of the solution of this problem with respect to $\ve\to0$ for long times $t\sim {\cal O}(\ve^{-2})$ is constructed and justified. The leading terms of the asymptotic solution are def

M. J. Hopkins, J. H. Palmieri, J. H. Smith

We show that in a generalized Adams spectral sequence, the presence of a vanishing line of fixed slope (at some term of the spectral sequence, with some intercept) is a generic property.

H. R. Morton, M. Rampichini

This paper is concerned with detecting when a closed braid and its axis are &#39;mutually braided&#39; in the sense of Rudolph. It deals with closed braids which are fibred links, the simplest case being closed braids which present the unknot. The geometric condition for mutual braiding refers to the existence of a close control on the way in which the whole

V. K. Dobrev, H. -D. Doebner, U. Franz, R. Schott

Lévy processes on bialgebras are families of infinitely divisible representations. We classify the generators of Lévy processes on the compact forms of the quantum algebras $U_q(g)$, where $g$ is a simple Lie algebra. Then we show how the processes themselves can be reconstructed from their generators and study several classical stochastic processes that can

Y. Puri, T. Ward

The only recurrence sequence satisfying the Fibonacci recurrence and realizable as the number of periodic points of a map is (a multiple of) the Lucas sequence.

P. D&#39;Ambros, G. Everest, R. Miles, T. Ward

We exhibit a family of dynamical systems arising from rational points on elliptic curves in an attempt to mimic the familiar toral automorphisms. At the non-archimedean primes, a continuous map is constructed on the local elliptic curve whose topological entropy is given by the local canonical height. Also, a precise formula for the periodic points is given.

Gavril Farkas

We prove that the Kodaira dimension of the moduli space M_{23} of curves of genus 23 is at least 2. We also present some evidence for the hypothesis that the Kodaira dimension of the moduli space is actually equal to 2. Note that for g > 23 the moduli space is of general type, while for g\leq 22, Harris and Morrison conjectured that M_g is uniruled. The resu

F. Prosmans, J. -P. Schneiders

In this paper, we prove that any perfect complex of $D^{\infty}$-modules may be reconstructed from its holomorphic solution complex provided that we keep track of the natural topology of this last complex. This is to be compared with the reconstruction theorem for regular holonomic $D$-modules which follows from the well-known Riemann-Hilbert correspondence.

Boris Tsirelson

A relation between sigma-additivity and linearizability, conjectured by Jacob Feldman in 1971 for continuous products of probability spaces, is established by relating both notions to a recent idea of noise stability/sensitivity.

M. Einsiedler, T. Ward

We consider a class of algebraic dynamical systems introduced by Kitchens and Schmidt. Under a weak finiteness condition -- the Descending Chain Condition -- the dual modules have finite presentations. Using methods from commutative algebra we show how the dynamical properties of the system may be deduced from the Fitting ideals of a finite free resolution o

Hans Plesner Jakobsen

We set up a framework for discussing `$q$-analogues&#39; of the usual covariant differential operators for hermitian symmetric spaces. This turns out to be directly related to the deformation quantization associated to quadratic algebras satisfying certain conditions introduced by Procesi and De Concini.

Eduardo D. Sontag, Y. Wang

This paper deals with several related notions of output stability with respect to inputs. The inputs may be thought of as disturbances; when there are no inputs, one obtains generalizations of the classical concepts of partial stability. The main notion studied is called input to output stability (IOS), and it reduces to input to state stability (ISS) when t

G. K. Sankaran

We investigate the possibility of embedding minimal abelian surfaces in smooth toric 4-folds with Picard number 2. The existence of such an embedding imposes conditions on the 4-fold, which we partly describe. On the other hand, we exhibit such embeddings in a special case, using a simple description of morphisms into smooth toric varieties.

G. Veneziano

After discussing some old (and not-so-old) entropy bounds both for isolated systems and in cosmology, I will argue in favour of a &#34;Hubble entropy bound&#34; holding in the latter context. I will then apply this bound to recent developments in string cosmology, show that it is naturally saturated throughout pre-big bang inflation, and claim that its fulfi

Philippe Droz-Vincent

A constant homogeneous magnetic field is applied to a composite system made of two scalar particles with opposite charges. Motion is described by a pair of coupled Klein-Gordon equations that are written in closed form with help of a suitable representation. The relativistic symmetry associated with the magnetic field is carefully respected. Considering eige

Alec J. Schramm

The method of equivalent quanta is applied both to photon-photon and, by analogy, to double pomeron exchange in heavy-ion collisions. This Weizsäcker-Williams approach is used to calculate production cross sections for the glueball candidate $f_J(1710)$ meson via photon-photon and pomeron-pomeron fusion in peripheral heavy-ion collisions at both RHIC and LHC

S. T. Petcov

The interpretation of the existing experimental evidences for oscillations of neutrinos in schemes with three and four neutrino mixing is reviewed. Forms of the lepton mixing matrix allowed by the neutrino oscillation data are considered. The possible neutrino mass spectra compatible with the observations are analyzed. The possibility to obtain information a

L. Frankfurt, G. A. Miller, M. Strikman

A perturbative QCD treatment of the pion wave function is applied to computing the scattering amplitude for coherent high relative momentum di-jet production from a nucleon.

Pablo Laguna

A formulation of Einstein equations is presented that could yield advantages in the study of collisions of binary compact objects during regimes between linear-nonlinear transitions. The key idea behind this formulation is a separation of the dynamical variables into i) a fixed conformal 3-geometry, ii) a conformal factor possessing nonlinear dynamics and ii

Xian-ping Ge, David Eppstein, Padhraic Smyth

This paper analyzes the distribution of cycle lengths in turbo decoding and low-density parity check (LDPC) graphs. The properties of such cycles are of significant interest in the context of iterative decoding algorithms which are based on belief propagation or message passing. We estimate the probability that there exist no simple cycles of length less tha

David Eppstein

We introduce a class of "inverse parametric optimization" problems, in which one is given both a parametric optimization problem and a desired optimal solution; the task is to determine parameter values that lead to the given solution. We describe algorithms for solving such problems for minimum spanning trees, shortest paths, and other "optimal subgraph" pr

R. Schiller, W. Nolting

The electronic quasiparticle spectrum of a ferromagnetic film is investigated within the framework of the s-f model. Starting from the exact solvable case of a single electron in an otherwise empty conduction band being exchange coupled to a ferromagnetically saturated localized spin system we extend the theory to finite temperatures. Our approach is a momen

M. Reizer

We show that recently reported unusual hardening of optical phonons renormalized by the electron-phonon interaction is due to the neglect of screening effects. When the electron-ion interaction is properly screened optical phonons soften in three dimension. It is important that for short-wavelength optical phonons screening is static while for long-wavelengt

M. Reizer

We study the Coulomb interaction effects on the tunneling conductance of a contact constructed of two parallel quantum wires. The following contacts are considered: two clean identical quantum wires, two disordered identical quantum wires, and asymmetric contact of one clean and another disordered quantum wires. We show that the low-voltage anomaly of the tu

M. Reizer

The electron-electron relaxation in impure two-dimensional superconductors is studied. All channels of the electron-electron interaction classified in the Nambu representation are taken into account. It is shown that the recombination relaxation rate originates from quasipartical processes associated with fluctuations of the electron density and the phase of

Marion Linn, Alexander L. Fetter

We consider a cylindrically symmetric trap containing a small Bose-Einstein condensate with a singly quantized vortex on the axis of symmetry. A time-dependent variational Lagrangian analysis yields the small-amplitude dynamics of the vortex and the condensate, directly determining the equations of motion of the coupled normal modes. As found previously from

M. Reizer, A. Sergeev

The quantum transport equation (QTE) is extended to study weak localization (WL) effects on galvanomagnetic and thermomagnetic phenomena. QTE has many advantages over the linear response method (LRM): (i) particle-hole asymmetry which is necessary for the Hall effect is taken into account by the nonequilibrium distribution function, while LRM requires expans

W. Skrypnik

The reduced density matrices (RDMs) are calculated in the thermodynamic limit for the Chern-Simons non-relativistic particle system and Maxwell-Boltzmann (MB) statistics. It is established that they are zero outside of a diagonal and well-behaved after a renormalization, depending on an arbitrary real number, if the condition of neutrality holds.

E. Kanzieper, V. E. Kravtsov

Nonperturbative, in inverse Thouless conductance 1/g, corrections to distributions of level velocities and level curvatures in quasi-one-dimensional disordered conductors with a topology of a ring subject to a constant vector potential are studied within the framework of the instanton approximation of nonlinear sigma-model. It is demonstrated that a global c

Aaron A. Pesetski, Thomas R. Lemberger

Using a two-coil mutual inductance method, we have measured the complex resistivity, rho_v(T,Be), of pinned vortices in c-axis pulsed laser deposited YBa2Cu3O7-d films with magnetic field Be applied perpendicular to the film. At low frequencies, (<100 kHz), rho_v is inductive and is inversely proportional to the Labusch parameter, the average vortex pinning

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

We make a review of the two principal models that allows to explain the imbibition of fluid in porous media. These models, that belong to the directed percolation depinning (DPD) universality class, where introduced simultaneously by the Tang and Leschhorn [Phys. Rev A 45, R8309 (1992)] and Buldyrev et al. [Phys. Rev. A 45, R8313 (1992)] and reviewed by Brau

Takashi Hotta, Seiji Yunoki, Matthias Mayr, Elbio Dagotto

The effect of Jahn-Teller phonons on the magnetic and orbital structure of LaMnO$_3$ is investigated using a combination of relaxation and Monte Carlo techniques on three-dimensional clusters of MnO$_6$ octahedra. In the physically relevant region of parameter space for LaMnO$_3$, and after including small corrections due to tilting effects, the A-type antif

Stefan J. Turneaure, Thomas R. Lemberger, John M. Graybeal

High precision measurements of the complex sheet conductivity of superconducting Mo77Ge23 thin films have been made from 0.4 K through Tc. A sharp drop in the inverse sheet inductance, 1/L(T), is observed at a temperature, Tc, which lies below the mean-field transition temperature, Tco. Just below Tc, the suppression of 1/L(T) below its mean-field value indi

G. Jakob, F. Martin, S. Friedrich, W. Westerburg

By laser ablation we prepared thin films of the colossal magnetoresistive compound La_(1-x)Ca_xMnO_3 with doping levels 0.1<x<0.9 on MgO substrates. X-ray diffraction revealed epitaxial growth and a systematic decrease of the lattice constants with doping. The variation of the transport and magnetic properties in this doping series was investigated by SQUID

K. Doll, N. M. Harrison, V. R. Saunders

We report the bulk and surface properties of lithium computed within a full potential LCGTO formalism using both density functional theory and the Hartree-Fock approximation. We examine the convergence of computed properties with respect to numerical approximations and also explore the use of finite temperature density functional theory. We demonstrate that

G. Seibold, S. Varlamov

We study the pairing potential induced by fluctuations around a charge-density wave (CDW) with scattering vector Q by means of the Froehlich transformation. For general commensurability M, defined as |k+M*Q>=|k>, we find that the intraband pair scattering within the M subbands scales with M whereas the interband pair scattering becomes suppressed with increa

Michael Bulenda, Uwe C. T&#34;auber, Franz Schwabl

We investigate the static critical behaviour of a uniaxial magnetic layer, with finite thickness L in one direction, yet infinitely extended in the remaining d dimensions. The magnetic dipole-dipole interaction is taken into account. We apply a variant of Wilson&#39;s momentum shell renormalisation group approach to describe the crossover between the critica

J. Demsar, K. Zagar, V. V. Kabanov, D. Mihailovic

Time-resolved optical measurements give information on the quasiparticle relaxation dynamics in YBCO, from which the evolution of the gap with doping and temperature can be systematically deduced. In this paper these optical charge-channel `pseudogap&#39; data are compared with the `pseudogap&#39; obtained from the NMR Knight shift Ks, spin polarized neutron

H. Schomerus, E. G. Mishchenko, C. W. J. Beenakker

We investigate current fluctuations in non-degenerate semiconductors, on length scales intermediate between the elastic and inelastic mean free paths. The shot-noise power P is suppressed below the Poisson value P_{\rm Poisson}=2e\bar I (at mean current \bar I) by the Coulomb repulsion of the carriers. We consider a power-law dependence of the elastic scatte

A. Rebei, W. N. G. Hitchon

Correlated systems at both zero and nonzero temperature are treated here from a novel angle using a functional method. This functional method is an extension of the usual effective potential method. Here, however the effective action is made to depend explicitly on the correlation effects that are inherent in the physics involved. This will enable us to obta

P. Kalinay, P. Markos, L. Samaj, I. Travenec

The system under consideration is a two-dimensional one-component plasma in fluid regime, at density n and at arbitrary coupling Gamma=beta e^2 (e=unit charge, beta = inverse temperature). The Helmholtz free energy of the model, as the generating functional for the direct pair correlation c, is treated in terms of a convergent renormalized Mayer diagrammatic

J. J. Hope, G. M. Moy, M. J. Collett, C. M. Savage

We present a fully quantum mechanical treatment of a single-mode atomic cavity with a pumping mechanism and an output coupling to a continuum of external modes. This system is a schematic description of an atom laser. In the dilute limit where atom-atom interactions are negligible, we have been able to solve this model without making the Born and Markov appr

M. Machida, T. Koyama, M. Tachiki

We demonstrate that both microwave resonant absorptions and multiple-branch structures in the I-V characterisitcs observed in intrinsic Josephson junctions (IJJ&#39;s) are caused by dynamical breaking of charge neutrality (DBCN) inside the atomic-scale superconducting layer. The Lagranginan for the time-dependent Lawrence-Doniach model incorporating the effe

Kang Kim, Ryoichi Yamamoto

Molecular dynamics simulations are performed for a supercooled simple liquid with changing the system size from N=108 to $10^4$ to examine possible finite-size effects. Although almost no systematic deviation is detected in the static pair correlation functions, it is demonstrated that the structural $α$ relaxation in a small system becomes considerably slow

Edward C. Moran, Matthew D. Lehnert, David J. Helfand

The infrared-luminous galaxy NGC3256 is a classic example of a merger induced nuclear starburst system. We find here that it is the most X-ray luminous star-forming galaxy yet detected (~10^42 ergs/s). Long-slit optical spectroscopy and a deep, high-resolution ROSAT X-ray image show that the starburst is driving a &#34;superwind&#34; which accounts for ~20%

M. J. Hardcastle, D. M. Worrall

Over half the 3CRR sample of radio galaxies and quasars has been observed in X-rays with ROSAT pointed observations, and we present results from these observations, discussing many of the sources in detail. The improved spatial resolution of ROSAT over earlier missions allows a better separation of the nuclear and extended components of the X-ray emission. W

A. C. Fabian, A. Celotti, G. Pooley, K. Iwasawa

We report X-ray and radio variability of GB 1428+4217 which confirm its blazar nature. IR observations reveal a powerful optical-UV component, not obscured by dust, which is suggestive of the presence of a billion solar mass black hole, already formed by z ~ 5. A detailed comparison of the broad band spectral properties of GB 1428+4217 with those of nearby b

J. -P. Berger, K. Rousselet-Perraut, P. Kern, F. Malbet

We report first white-light interferograms obtained with an integrated optics beam combiner on a glass plate. These results demonstrate the feasability of single-mode interferometric beam combination with integrated optics technology presented and discussed in paper I. The demonstration is achieved in laboratory with off-the-shelves components coming from mi

F. Malbet, P. Kern, I. Schanen-Duport, J. -P. Berger

We propose a new instrumental concept for long-baseline optical single-mode interferometry using integrated optics which were developed for telecommunication. Visible and infrared multi-aperture interferometry requires many optical functions (spatial filtering, beam combination, photometric calibration, polarization control) to detect astronomical signals at

Remo Ruffini, Jay D. Salmonson, James R. Wilson, She-Sheng Xue

We study the relativistically expanding electron-positron pair plasma formed by the process of vacuum polarization around an electromagnetic black hole (EMBH). Such processes can occur for EMBH&#39;s with mass all the way up to $6\cdot 10^5M_\odot$. Beginning with a idealized model of a Reissner-Nordstrom EMBH with charge to mass ratio $ξ=0.1$, numerical hyd

Eline Tolstoy

The power of high quality imaging combined with the large collecting area of each VLT telescope is impressive, and there are clearly many exciting discoveries waiting to be made. The study of resolved stellar populations will certainly benefit greatly from this new observatory, as with Palomar before. We will now be able to probe a much large range of star f

D. Barrado y Navascues, J. R. Stauffer, B. M. Patten

We have identified a large number of possible very low mass members of the cluster IC2391 based primarily on their location in an I versus (R-I)_C CM diagram. We have obtained new photometry and low resolution ($Δλ= 2.7$ Å) spectroscopy of 19 of these objects (14.9 $\le$ I_C $\le$ 17.5) in order to confirm cluster membership. We identify 15 of our targets as