March 2000 arXiv papers — page 18

G. R. Meurer

The duration of starbursts is important for determining how they are regulated and the impact they have on their environment. Starbursts contain numerous prominent star clusters which typically comprise in total ~20% of the ultraviolet light, embedded in a diffuse glow of recently formed stars responsible for the dominant ~80%. Hubble Space Telescope images

Damien A. Easson

The purpose of this review is to discuss recent developments occurring at the interface of cosmology with string and M-theory. We begin with a short review of 1980s string cosmology and the Brandenberger-Vafa mechanism for explaining spacetime dimensionality. It is shown how this scenario has been modified to include the effects of p-brane gases in the early

F. A. Aharonian

One of remarkable features of the gamma ray blazar Markarian 501 is the reported shape of the TeV spectrum, which during strong flares of the source remains essentially stable despite dramatic variations of the absolute gamma-ray flux. I argue that this (to a large extent unexpected) behavior of the source could be explained assuming that the TeV gamma-ray e

Seungho Choe

We improve our previous QCD sum rule calculation on G(KNΛ) and G(KNΣ) coupling constants by including the contributions from higher dimensional condensates, <\bar{q} g_s σ\cdot G q> and <\bar{q}q> <(α_s /π) G^2>, in the OPE. It is found that the contribution of these condensates is non-negligible compared to that of the quark condensates. Using a best-fit an

Toshiyuki Morii, Teruya Yamanishi

Simple formulas on $Δ\bar d(x)-Δ\bar u(x)$ are proposed for extracting their values from polarized deep-inelastic semi-inclusive data. The present SMC and HERMES data suggest that $Δ\bar d(x)-Δ\bar u(x)$ is slightly negative, though the precision of the data is not enough for confirming it.

A. J. Williamson, A. Franceschetti, A. Zunger

We use a many-body, atomistic empirical pseudopotential approach to predict the multi-exciton emission spectrum of a lens shaped InAs/GaAs self-assembled quantum dot. We discuss the effects of (i) The direct Coulomb energies, including the differences of electron and hole wavefunctions, (ii) the exchange Coulomb energies and (iii) correlation energies given

X. X. Yi, C. Li, J. C. Su

We construct generally applicable small-loss rate expansions for the density operator of an open system. Successive terms of those expansions yield characteristic loss rates for dissipation processes. Three applications are presented in order to give further insight into the context of those expansions. The first application, of a two-level atom coupling to

K. K. Gudima, A. S. Parvan, M. Ploszajczak, V. D. Toneev

We apply the canonical quantum statistical model of nuclear multifragmentation generalized in the framework of recently proposed Tsallis non-extensive thermostatistics for the description of nuclear multifragmentation process. The test calculation in the system with A=197 nucleons show strong modification of the &#39;critical&#39; behaviour associated with t

Mohammad A. Asadi-Golmankhaneh, Peter J. Eccles

A self-transverse immersion of a smooth manifold M^{k+2} in R^{2k+2} has a double point self-intersection set which is the image of an immersion of a smooth surface, the double point self-intersection surface. We prove that this surface may have odd Euler characteristic if and only if k is congruent to 1 modulo 4 or k+1 is a power of 2. This corrects a previ

S. Moghimi-Araghi, S. Rouhani

We consider logarithmic conformal field theories near a boundary and derive the general form of one and two point functions. We obtain results for arbitrary and two dimensions. Application to two dimensional magnetohydrodynamics is discussed.

W. Bietenholz

If we construct a lattice fermion formulation, there are a number of goals to be considered: doubling should be avoided; even at finite lattice spacing, we want to represent chiral symmetry in a sound way; and we are seeking a good scaling behavior. Conceptually we have to require locality, and for practical purposes we even desire a high level of locality.

Lek-Heng Lim

We show that the Cao-Li cryptosystem proposed in \cite{CL1} is not secure. Its private key can be reconstructed from its public key using elementary means such as LU-decomposition and Euclidean algorithm.

F. Igloi, H. Rieger

We consider the non-stationary quantum relaxation of the Ising spin chain in a transverse field of strength h. Starting from a homogeneously magnetized initial state the system approaches a stationary state by a process possessing quasi long range correlations in time and space, independent of the value of $h$. In particular the system exhibits aging (or lac

B. I. Belevtsev, I. V. Volchok, N. V. Dalakova, V. I. Dotsenko

A bulk polycrystalline sample of YBa_(2)Cu_(3)O_(7-δ) (δ\approx 0.1) has been irradiated by γ-rays with ^{60}Co source. Non-monotonic behavior of T_{c} with increasing irradiation dose Φ(up to 220 MR) is observed: T_{c} decreases at low doses (Φ< 50 MR) from initial value (\approx 93 K) by about 2 K and then rises, forming a minimum. At higher doses (Φ> 120

C. Waidacher, J. Richter, K. W. Becker

We analyze the influence of the dimensionality on the Cu 2p_3/2 core level X-ray photoemission spectra of undoped cuprates. Both exchange splitting and delocalization properties are described within one framework using a multi-band Hubbard model. The spectral intensity is calculated by means of the Mori-Zwanzig projection technique for a CuO_4 plaquette (&#3

V. A. Vdovenkov

The mechanism of superconductivity caused by the electron-vibrational centres and their inherent oscillations in crystals and solid-state structures near room temperature and at higher temperatures - hyperconductivity is discussed and actualized. The experimental data about hiperconductivity in some materials are presented. Hyperconductivity arises and exist

Enrique Gaztanaga

Is gravitational growth responsible for the observed large scale structure in the universe? Do we need non-gaussian initial conditions or non-gravitational physics to explain the large scale features traced by galaxy surveys? I will briefly revise the basic ideas of non-linear perturbation theory (PT) as a tool to understand structure formation, in particula

N. M. McClure-Griffiths, John M. Dickey, B. M. Gaensler, A. J. Green

As part of a survey of HI 21-cm emission in the Southern Milky Way, we have detected two large shells in the interstellar neutral hydrogen near l=279 deg. The center velocities are +36 and +59 km/s, which puts the shells at kinematic distances of 7 and 10 kpc. The larger shell is about 610 pc in diameter and very empty, with density contrast of at least 15 b

S. V. Bogovalov, F. A. Aharonian

We show that the relativistic wind in the Crab pulsar, which is commonly thought to be invisible in the region upstream of the termination shock at R < 0.1 pc, in fact could be directly observed through its inverse Compton gamm-ray emission. The search for such specific component of radiation in the gamma-ray spectrum of the Crab can provide unique informati

Piercarlo Bonifacio, Pierluigi Selvelli, Elisabetta Caffau

We report on photometric observations of V 1493 Aql during the early decline and highlight some uncommon aspects of the light curve. V 1493 Aql was hotter at maximum light than in the following phases, and was characterized by the presence of a long lasting secondary maximum, that, unlike in other novae, was quite red in color. The mean of three distance est

Dennis Zaritsky, Jason Harris, Eva K. Grebel, Ian B. Thompson

We compare the distribution of stars of different spectral types, and hence mean age, within the central SMC and find that the asymmetric structures are almost exclusively composed of young main sequence stars. Because of the relative lack of older stars in these features, and the extremely regular distribution of red giant and clump stars in the SMC central

F. Gelis

In this talk, I review recent progress made in two areas of thermal field theory. In particular, I discuss various approaches for the calculation of the quark gluon plasma thermodynamical properties, and the problem of its photon production rate.

Manuel Peimbert, Antonio Peimbert, Maria Teresa Ruiz

Spectrophotometry in the 3400-7400 range is presented for 13 areas of the brightest H II region in the SMC: NGC 346. The observations were obtained at CTIO with the 4-m telescope. Based on these observations its chemical composition is derived. The helium and oxygen abundances by mass are given by: Y(SMC)=0.2405+-0.0018 and O(SMC)=0.00171+-0.00025. From mode

Matthias Vojta, Ying Zhang, Subir Sachdev

We use a number of large-N limits to explore the competition between ground states of square lattice doped antiferromagnets which break electromagnetic U(1), time-reversal, or square lattice space group symmetries. Among the states we find are d-, (s+id)-, and (d+id)-wave superconductors, Wigner crystals, Wigner crystals of hole pairs, orbital antiferromagne

Stanley J. Brodsky, Dae Sung Hwang, Bo-Qiang Ma, Ivan Schmidt

The matrix elements of local operators such as the electromagnetic current, the energy momentum tensor, angular momentum, and the moments of structure functions have exact representations in terms of light-cone Fock state wavefunctions of bound states such as hadrons. We illustrate all of these properties by giving explicit light-cone wavefunctions for the t

George A. Baker,

The Schwarzchild solution insertion in an expanding universe, the so-called &#34;Swiss cheese model,&#34; is shown to possess a very unphysical property. Specifically, in this model some trajectories are discontinuous functions of their initial conditions. An alternate metric is proposed as a remedy. It goes smoothly between the Schwarzchild exterior solutio

Mikhail S. Volkov, Andreas Wipf

We present an exact one-loop calculation of the tunneling process in Euclidean quantum gravity describing creation of black hole pairs in a de Sitter universe. Such processes are mediated by $S^2\times S^2$ gravitational instantons giving an imaginary contribution to the partition function. The required energy is provided by the expansion of the universe. We

R. Fusco-Femiano, D. Dal Fiume, S. De Grandi, L. Feretti

After the positive detection by BeppoSAX of hard X-ray radiation up to ~80 keV in the Coma cluster spectrum, we present evidence for nonthermal emission from A2256 in excess of thermal emission at a 4.6sigma confidence level. In addition to this power law component, a second nonthermal component already detected by ASCA could be present in the X-ray spectrum

Weinan E, Eric Vanden Eijnden

The study of passive scalar transport in a turbulent velocity field leads naturally to the notion of generalized flows which are families of probability distributions on the space of solutions to the associated ODEs, which no longer satisfy the uniqueness theorem for ODEs. Two most natural regularizations of this problem, namely the regularization via adding

Ludwik Turko, Jan Rafelski

We consider the dynamics governing the evolution of a many body system constrained by an nonabelian local symmetry. We obtain explicit forms of the global macroscopic condition assuring that at the microscopic level the evolution respects the overall symmetry constraint. We demonstrate the constraint mechanisms for the case of SU(2) system comprising particl

N. N. Achasov, A. A. Kozhevnikov

The decays rho(770) to 4 pi and omega(782) to 5pi are considered in detail in the approach based on the Weinberg Lagrangian obtained upon the nonlinear realization of chiral symmetry, added with the term induced by the anomalous Lagrangian of Wess and Zumino. The partial widths and excitation curves of the decays rho^0 to 2 pi^+ 2 pi^-, pi^+ pi^- 2 pi^0, rho

Md. A. I. Khan, J. C. Vassilicos

In planar turbulence modelled as an isotropic and homogeneous collection of 2-D non-interacting compact vortices, the structure functions S_p(r) of a statistically stationary passive scalar field have the following scaling behaviour in the limit where the Péclet number Pe -> \infty S_p(r) ~ constant+\ln({\frac{r}{LPe^{-1/3}}}) for LPe^{-1/3} << L, S_p(r) ~ (

Michael Annan Lisa, Ulrich Heinz, Urs Achim Wiedemann

Intensity interferometry in noncentral heavy ion collisions provides access to novel information on the geometry of the effective pion-emitting source. We demonstrate analytically that, even for vanishing pair momentum, the cross terms $R_{ol}^2$ and $R_{sl}^2$ of the HBT correlation function in general show a strong first harmonic in their azimuthal depende

Th. Feldmann, P. Kroll

We argue that charmonium decays into meson pairs fall into two distinct classes: one that is under control of perturbative QCD and another one that is governed by a soft mechanism. We concentrate on a systematic analysis of J/Psi (Psi&#39;) decays into a light pseudoscalar and a light vector meson and eta(c) decays into a pair of light vector mesons. These p

Angel Sanchez, A. R. Bishop, Esteban Moro

We present a comparative numerical study of the ordered and the random two-dimensional sine-Gordon models on a lattice. We analytically compute the main features of the expected high temperature phase of both models, described by the Edwards-Wilkinson equation. We then use those results to locate the transition temperatures of both models in our Langevin dyn

H. Qin, F. Simmel, R. H. Blick, J. P. Kotthaus

A small quantum dot containing approximately 20 electrons is realized in a two-dimensional electron system of an AlGaAs/GaAs heterostructure. Conventional transport and microwave spectroscopy reveal the dot&#39;s electronic structure. By applying a coherently coupled two-source technique, we are able to determine the complex microwave induced tunnel current.

A. I. Smirnov, S. S. Sosin, R. Calemczuk, V. Villar

The specific heat, magnetic susceptibility and ESR signals of a Na-deficient vanadate Na_xV_2O_5 (x=1.00 - 0.90) were studied in the temperature range 0.07 - 10 K, well below the transition point to a spin-gap state. The contribution of defects provided by sodium vacancies to the specific heat was observed. It has a low temperature part which does not tend t

E. G. Nikolaev, H. B. Brom, A. A. Zakharov

In crystals of La2CuO4.02 oxygen diffusion can be limited to such small length scales, that the resulting phase separation is invisible for neutrons. Decomposition of the 139La NQR spectra shows the existence of three different regions, of which one orders antiferromagnetically below 17K concomitantly with the onset of a weak superconductivity in the crystal

H. C. Spruit

In this lecture the basic theory of accretion disks is introduced, with emphasis on aspects relevant for X-ray binaries and Cataclysmic Variables.

Partha Ghose

An experiment is suggested that is capable of distinguishing between the de Broglie-Bohm theory and standard quantum mechanics.

Satish D. Joglekar

In this work, we suggest a view-point that leads to an intrinsic mass scale in Quantum Field Theories. This view-point is fairly independent of dynamical details of a QFT and does not rely on any particular framework to go beyond the standard Model. We use the setting of the nonlocal quantum field theories NLQFT with a finite scale parameter Lambda, which ar

Rafael D. Sorkin

Within the context of a recently proposed family of stochastic dynamical laws for causal sets, one can ask whether the universe might have emerged from the quantum-gravity era with a large enough size and with sufficient homogeneity to explain its present-day large-scale structure. In general, such a scenario would be expected to require the introduction of

Masafumi Seriu

We derive the evolution equations for the spectra of the Universe. Here &#34;spectra&#34; means the eigenvalues of the Laplacian defined on a space, which contain the geometrical information on the space. These equations are expected to be useful to analyze the evolution of the geometrical structures of the Universe. As an application, we investigate the tim

G. C. McLaughlin, J. N. Ng

Theories which include neutrinos in large extra dimensions can be constrained by nuclear beta decay experiments. We examine universality of beta decay strengths of Fermi transitions. From this we find that the extra dimensional Yukawa coupling for a higher dimensional scale of 10 TeV, and two extra dimensions can be constrained to y < 1. Kinematic implicatio

B. G. Sidharth

Two recent findings necessitate a closer look at the existing standard models of Particle Physics and Cosmology. These are the discovery of Neutrino oscillation, and hence a non zero mass on the one hand and, on the other, observations of distant supernovae which indicate that contrary to popular belief, the universe would continue to expand for ever, possib

David A. Brown

We investigate what conditions allow us to extract the relative distribution of freeze-out space and time points in an arbitrary reference frame using tomography and source imaging. The source function may be extracted from the two-particle correlation function measured in heavy-ion collisions using imaging techniques. This imaged source function is related

T. Odeh, ALADIN collaboration

Kinetic energies of light fragments A <= 10 from the decay of target spectators in 197Au 197Au collisions at 1000 MeV per nucleon have been measured with high-resolution telescopes at backward angles. Except for protons and apart from the observed evaporation components, the kinetic-energy spectra exhibit slope temperatures of about 17 MeV, independent of th

S. Derkachov, D. Karakhanyan, R. Kirschner

We find solutions of the Yang-Baxter equation acting on tensor product of arbitrary representations of the superalgebra sl(2|1). Based on these solutions we construct the local Hamiltonians for integrable homogeneous periodic chains and open chains.

JS Shiner, Matt Davison, PT Landsberg

We respond to the comment by Crutchfield, Feldman and Shalizi and that by Binder and Perry, pointing out that there may be many maximum entropies, and therefore ``disorders&#39;&#39; and ``simple complexities&#39;&#39;. Which ones are appropriate depend on the questions being addressed. ``Disorder&#39;&#39; is not restricted to be the ratio of a nonequilibri

Giovanni Gallavotti

This note reviews some physical aspects of the chaotic hypothesis in nonequilibrium statistical mechanics and attempts at the physical interpretation of the fluctuation theorem as a quantitative intermittency property

I. G. Korepanov

One of the generalizations of the pentagon equation to higher dimensions is the so-called &#34;six-term equation&#34;. Geometrically, it corresponds to one of the &#34;Alexander moves&#34;, that is elementary rebuildings of simplicial complexes, namely, replacing a &#34;cluster&#34; of three 4-simplices by another &#34;cluster&#34;, also of three 4-simplices

J. S. Hersch, M. R. Haggerty, E. J. Heller

In this paper, we demonstrate the existence and significance of diffractive orbits in an open microwave billiard, both experimentally and theoretically. Orbits that diffract off of a sharp edge of the system are found to have a strong influence on the transmission spectrum of the system, especially in the regime where there are no stable classical orbits. On

S. P. Novikov, I. A. Dynnikov

Euler-Darboux-Backlund and Laplace transformations are considered for the one- and two-dimensional Schrodinger operators. Their discrete analogs are constructed and generalized for the multidimensional lattices and two-manifolds with special &#34;black-white&#34; triangulations. Nonstandard generalizations of the connections and curvature are constructed for

S. P. Novikov, A. P. Veselov

Different cases of sequences of the Laplace Transformations for the 2D Schrodinger operator in the periodic magnetic field and electric potential are considered. They lead to the exactly solvable operators with nonstandard spectral properties including the double-periodic operators with algebraic Fermi surface known from the periodic soliton theory. Two appe

Charles Rezk

We show that any closed model category of simplicial algebras over an algebraic theory is Quillen equivalent to a proper closed model category. By ``simplicial algebra&#39;&#39; we mean any category of algebras over a simplicial algebraic theory, which is allowed to be multi-sorted. The results have applications to the construction of localization model cate

Kazuyoshi MORI

In 1994, Sule presented the necessary and sufficient conditions of the feedback stabilizability of systems over unique factorization domains in terms of elementary factors and in terms of reduced minors. Recently, Mori and Abe have generalized his theory over commutative rings. They have introduced the notion of the generalized elementary factor, which is a~

Brendan Hassett, Yuri Tschinkel

We study the distribution of integral points on log varieties.

Guyan Robertson

Let $\G$ be a group of type rotating automorphisms of an affine building $\cB$ of type $\wt A_2$. If $\G$ acts freely on the vertices of $\cB$ with finitely many orbits, and if $Ω$ is the (maximal) boundary of $\cB$, then $C(\Om)\rtimes \G$ is a p.i.s.u.n. $C^*$-algebra. This algebra has a structure theory analogous to that of a simple Cuntz-Krieger algebra

Shihoko Ishii

This paper gives the all possible global indices of log Calabi-Yau 3-folds with standard coefficients on the boundaries and having lc, non-klt singularities. This follows easily from the discussion in the paper: The indices of log canonical singularities by Fujino (AG/9909035).

S. P. Gavrilov, D. M. Gitman, A. E. Goncalves

The article is a natural continuation of our paper {\em Quantum scalar field in FRW Universe with constant electromagnetic background}, Int. J. Mod. Phys. {\bf A12}, 4837 (1997). We generalize the latter consideration to the case of massive spinor field, which is placed in FRW Universe of special type with a constant electromagnetic field. To this end specia

H. Garcia-Compean, O. Obregon, C. Ramirez

We overview some attempts to find S-duality analogues of non-supersymmetric Yang-Mills theory, in the context of gravity theories. The case of MacDowell-Mansouri gauge theory of gravity is discussed. Three-dimensional dimensional reductions from the topological gravitational sector in four dimensions, enable to recuperate the 2+1 Chern-Simons gravity and the

Bodo Geyer, Markus Lazar

A group theoretical procedure, introduced earlier (hep-th/9901090), to decompose bilocal light-ray operators into (harmonic) operators of definite twist is applied to the case of arbitrary 2nd rank tensors. As a generic example the bilocal gluon operator is considered which gets contributions of twist-2 up to twist-6 from four different symmetry classes char

J. -P. Derendinger, R. Sauser

In the low-energy limit, M-theory compactified on S1/Z2 is formulated in terms of Bianchi identities with sources localized at orbifold singularities and anomaly-cancelling counterterms to the Wilson effective Lagrangian. Compactifying to four dimensions on a Calabi-Yau space leads to N=1 local supersymmetry. We derive a formulation of the effective supergra

Hyunji Cho, David Kastor, Jennie Traschen

We study the formation and stability of regular black holes by employing a thin shell approximation to the dynamics of collapsing magnetic monopoles. The core deSitter region of the monopole is matched across the shell to a Reissner-Nordstrom exterior. We find static configurations which are nonsingular black holes and also oscillatory trajectories about the

Bogdan Mihaila, Tara Athan, Fred Cooper, John Dawson

We study a quantum dynamical system of N, O(N) symmetric, nonlinear oscillators as a toy model to investigate the systematics of a 1/N expansion. The closed time path (CTP) formalism melded with an expansion in 1/N is used to derive time evolution equations valid to order 1/N (next-to-leading order). The effective potential is also obtained to this order and

A. Mondragon, E. Rodriguez-Jauregui

The phase equivalence of the theoretical quark mixing matrix ${\bf V}^{th}$ derived from the breaking of the flavour permutational symmetry and the phenomenological parametrizations ${\bf V}^{PDG}$ and ${\bf V}^{KM}$ is explicitly exhibited. From here, we derive exact explicit expressions for the three mixing angles and the CP violating phase of the two phen

S. F. King

I motivate and discuss non-minimal and non-universal models of supersymmetry and supergravity consistent with string unification at $10^{16}$ GeV.

Hans Peter Nilles

Anomalous U(1) gauge symmetries appear frequently both in heterotic and type I/type II string theory. In the heterotic case we find at most a single anomalous U(1), while in open string theories several such symmetries can appear. We review the properties of the anomalous gauge bosons, the appearance of Fayet-Iliopoulos terms and the concept of heterotic-typ

S. M. Barr

Talk given at Orbis Scientiae Conference, Coral Gables, FLA, Dec. 16-19, 1999. Talk surveys some recent three-neutrino models of neutrino masses and mixings.

Johannes Blümlein

The analytic continuation of the Mellin transforms to complex values of N for the basic functions $g_i(x)$ of the momentum fraction x emerging in the quantities of massless QED and QCD up to two-loop order, as the unpolarized and polarized splitting functions, coefficient functions, and hard scattering cross sections for space- and time-like momentum transfe

T. I. Rashba, V. B. Semikoz

We suggest to use a polarized electron target for improving the sensitivity of the search for the neutrino magnetic moment to the level $\sim 3\cdot10^{-13}μ_B$ in the processes of neutrino (antineutrino) -- electron scattering. It is shown that in this case the weak interaction term in the total cross section is significantly suppressed comparing with unpol

M. B. Gay Ducati, V. P. Gonçalves

We discuss the distinct approaches for high density QCD (hdQCD) in the asymptotic regime of large values of parton density. We derive the AGL equation for running coupling constant and obtain the asymptotic solution, demonstrating that the property of partial saturation of the solution of the AGL equation is not modified by the running of the coupling consta

P. Kroll

The b - u skewed parton distributions (SPDs) are discussed. The SPDs allow an unambigous superposition of overlap and resonsance contributions and their zeroth order moments represent the B - pi transition form factors. The values of the form factors at maximum recoil are found to be F+(0)=F0(0)=0.22 with an error of 0.05 in agreement with measurements of th

N. H. Brook, I. O. Skillicorn

The evolution with energy scale of the partonic logarithmic scaled energy spectra is investigated in the framework of the modified leading logarithmic approximation (MLLA). The behaviour of the higher order moments is compared to a number of analytic predictions and $\rm e^+e^-$ data.

E. A. Kuraev, J. Manjavidze, A. Sissakian

The idea that the hard channels may dominate in the very high multiplicity processes is investigated. Quantitative realization of the `hard Pomeron&#39;, deep inelastic scattering and large-angle annihilation mechanism combinations are considered in the pQCD frame for this purpose.

Amarjit Soni

Lattice matrix elements are briefly reviewed. In the quenched approximation $f_B$, $B_B$ and $B_K$ are now under good control. Experimental hints for $f^{\rm expt}_{D_S}> f^{\rm QQCD}_{D_S}$ are noted; precise determination of $f_{D_S}$ from experiment as well as from the lattice is strongly advocated. Lattice calculations of the form factor for $B\toπ\ellν$

B. Grzadkowski, J. F. Gunion, J. Pliszka

We study the use of polarization asymmetries at a muon collider to determine the CP-even and CP-odd couplings of a Higgs boson to $μ^+mu^-$. We determine achievable accuracy as a function of beam polarization and luminosity. The appropriate techniques for dealing with the polarization precession are outlined. Strategies especially appropriate for a two-Higgs

The OPAL collaboration, G. Abbiendi

The magnitude of the Cabibbo-Kobayashi-Maskawa matrix element Vcb has been measured using B0 to D*l nu decays recorded on the Z0 peak using the OPAL detector at LEP. The D* to D0 pi+ decays were reconstructed both in the particular decay modes D0 to K- pi+ and D0 to K- pi+ pi- and via an inclusive technique. The product of |Vcb| and the decay form factor of

A. Beesham, S. G. Ghosh

We study the occurrence of naked singularities in the spherically symmetric collapse of a charged null fluid in an expanding deSitter background - a piece of charged Vaidya-deSitter spacetime. The necessary conditions for the formation of a naked singularity are found. The results for the uncharged solutions can be recovered from our analysis.

Renata Wassermann

In an earlier work, we have presented operations of belief change which only affect the relevant part of a belief base. In this paper, we propose the application of the same strategy to the problem of model-based diangosis. We first isolate the subset of the system description which is relevant for a given observation and then solve the diagnosis problem for

Alberto Artosi, Guido Governatori

In this paper we present a theorem proving methodology for a restricted but significant fragment of the conditional language made up of (boolean combinations of) conditional statements with unnested antecedents. The method is based on the possible world semantics for conditional logics. The KEM label formalism, designed to account for the semantics of normal

Antonis Kakas

ACLP is a system which combines abductive reasoning and constraint solving by integrating the frameworks of Abductive Logic Programming (ALP) and Constraint Logic Programming (CLP). It forms a general high-level knowledge representation environment for abductive problems in Artificial Intelligence and other areas. In ACLP, the task of abduction is supported

Igor I. Smolyaninov

Recent calculations by Vorobev and Malyshenko (JETP Letters, 71, 39, 2000) show that molecular hydrogen may stay liquid and superfluid in strong electric fields of the order of $4\times 10^7 V/cm$. I demonstrate that strong local electric fields of similar magnitude exist beneath a two-dimensional layer of electrons localized in the image potential above the

P. Ao, S. T. Chui

Two stages of quantum spinodal decomposition is proposed and analyzed for this highly non-equilibrium process. Both time and spatial scales for the process are found. Qualitative agreement with existing data is found. Some cases the agreements are quantitative. Further experimental verifications are indicated.

Ute Ebert, Wim van Saarloos

The derivation of a Moving Boundary Approximation or of the response of a coherent structure like a front, vortex or pulse to external forces and noise, is generally valid under two conditions: the existence of a separation of time scales of the dynamics on the inner and outer scale and the existence and convergence of solvability type integrals. We point ou

K. H. Kim, M. Uehara, C. Hess, P. A. Sharma

We measured thermal conductivity, k, thermoelectric power, S, and dc electric conductivity, sigma, of La_{5/8-x}Pr_{x}Ca_{3/8}MnO_{3}, showing an intricate interplay between metallic ferromagnetism (FM) and charge ordering (CO) instability. The change of k, S and sigma with temperature (T) and x agrees well with the effective medium theories for binary metal

O. Bengone, M. Alouani, P. Bloechl, J. Hugel

The so-called local density approximation plus the multi-orbital mean-field Hubbard model (LDA+U) has been implemented within the all-electron projector augmented-wave method (PAW), and then used to compute the insulating antiferromagnetic ground state of NiO and its optical properties. The electronic and optical properties have been investigated as a functi

Ute Ebert, Wim van Saarloos

Fronts that start from a local perturbation and propagate into a linearly unstable state come in two classes: pulled and pushed. ``Pulled&#39;&#39; fronts are ``pulled along&#39;&#39; by the spreading of linear perturbations about the unstable state, so their asymptotic speed $v^*$ equals the spreading speed of linear perturbations of the unstable state. The

Marc Lätzel, Stefan Luding, Hans J. Herrmann

One of the essential questions in the area of granular matter is, how to obtain macroscopic tensorial quantities like stress and strain from ``microscopic&#39;&#39; quantities like the contact forces in a granular assembly. Different averaging strategies are introduced, tested, and used to obtain volume fractions, coordination numbers, and fabric properties.

E. Burgos, Horacio Ceva

A minority game whose strategies are given by probabilities p, is replaced by a &#39;simplified&#39; version that makes no use of memories at all. Numerical results show that the corresponding distribution functions are indistinguishable. A related approach, using a random walk formulation, allows us to identify the origin of correlations and self organizati

Dimitar I. Pushkarov

In this comment I show that the experimental data on quantum diffusion of 3-He impurities in solid 4-He can be explained using the adopted quasiparticle theory. The contention by E.G. Kisvarsanyi and N.S. Sullivan (KS) in Phys.Rev.B v. 48, 16557 (1993) as well as in their Reply (ibid. v. 55, 3989 (1997)) to the Grigor&#39;ev&#39;s Comment (Phys.Rev. B v. 55,

Tadeusz Kosztolowicz, Stanislaw Mrowczynski

Using a microscopic phase-space model of the membrane system, the boundary condition at a membrane is derived. According to the condition, the substance flow across the membrane is proportional to the difference of the substance concentrations at the opposite membrane surfaces. The Green&#39;s function of the diffusion equation is found for the derived bound

Markus Keil, Herbert Schoeller

We investigate the one-dimensional polaron problem and calculate the ground state energy and the effective mass. We use a real-time renormalization group method and compare our results with first and second order perturbation theory, with Feynman&#39;s variational principle and with the method of Lee, Low and Pines.

N. S. Skantzos, A. C. C. Coolen

We solve a class of attractor neural network models with a mixture of 1D nearest-neighbour and infinite-range interactions, which are of a Hebbian-type form. Our solution is based on a combination of mean-field methods, transfer matrices and 1D random-field techniques, and is obtained for Boltzmann-type equilibrium (following sequential Glauber dynamics) and

Damian H. Zanette

We consider an ensemble of globally coupled phase oscillators whose interaction is transmitted at finite speed. This introduces time delays, which make the spatial coordinates relevant in spite of the infinite range of the interaction. We show that one-dimensional arrays synchronize in an asymptotic state where all the oscillators have the same frequency, wh

H. Feldmann, E. P. Nakhmedov, R. Oppermann

A real space diagrammatic method, which is an extension of the Berezinskii technique to problems with periodic boundary condition, is formulated to study the density of states (DOS) ρ(ε,ϕ) and its moments for a one-channel weakly disordered ring threaded by an external magnetic flux ϕ. The exact result obtained for the average value of the DOS shows that ρ(ε

Stefan Luding, Maxime Nicolas, Olivier Pouliquen

Based on experiments of the compaction of granular materials under periodic shear of a packing of glass beads, a minimal model for the dynamics of the packing density as a function of time is proposed. First, a random ``energy landscape&#39;&#39; is created by a random walk (RW) in energy. Second, an ensemble of RWs is performed for various temperatures in d

G. M. Minkov, A. V. Germanenko, O. E. Rut, O. I. Khrykin

The weak localization correction to the conductivity in coupled double layer structures is studied both experimentally and theoretically. Statistics of closed paths has been obtained from the analysis of magnetic field and temperature dependencies of negative magnetoresistance for magnetic field perpendicular and parallel to the structure plane. The comparis

Mario Castro, Rodolfo Cuerno, Angel Sanchez, Francisco Dominguez-Adame

We present a complete study of the Multiparticle Biased Diffusion-Limited Aggregation (MBDLA) model supplemented with surface difussion (SD), focusing on the relevance and effects of the latter transport mechanism. By comparing different algorithms, we show that MBDLA+SD is a very good qualitative model for electrodeposition in practically all the range of c

Carlo Pierleoni, Jean-Paul Ryckaert

The effect of excluded volume interactions on the structure of a polymer in shear flow is investigated by Brownian Dynamics simulations for chains with size $30\leq N\leq 300$. The main results concern the structure factor $S({\bf q})$ of chains of N=300 Kuhn segments, observed at a reduced shear rate $β=\dotγτ=3.2$, where $\dotγ$ is the bare shear rate and