December 1998 arXiv papers — page 7

U. Ellwanger, C. Hugonie

We study the possible signals of the (M+1)SSM with a singlino LSP at LEP2. First we identify regions of the parameter space which are ruled out by negative results of sparticle searches in the context of the MSSM. In the remaining kinematically accessible regions we present total event rates for topologies which require further studies, i.e. estimations of t

Rie Tatsumi, George Chikenji

We examined what determines the designability of 2-letter codes (H and P) lattice proteins from three points of view. First, whether the native structure is searched within all possible structures or within maximally compact structures. Second, whether the structure of the used lattice is bipartite or not. Third, the effect of the length of the chain, namely

Klaus Behrndt

The 3-d BTZ black hole represents an orbifold of $AdS_3$ gravity. The UV as well as the IR region of the CFT is governed by a gauged SL(2, R) WZW model. In the UV it corresponds to a light-cone gauging (Liouville model) whereas in the IR it is a space-like gauging (2-d black hole).

N. V. Mikheev, A. Ya. Parkhomenko, L. A. Vassilevskaya

The axion decay $a \to e^+ e^-$ is investigated in the presence of a plasma and an external magnetic field. The results demonstrate a strong catalyzing influence of medium. The axion lifetime in the magnetic field of order $10^{15}$ G and at the temperature of order 10 MeV is reduced to $10^4$ s.

Daniel Schaerer, Thierry Contini, Maximilien Pindao

We present a new compilation of Wolf-Rayet (WR) galaxies and extra-galactic HII regions showing BROAD HeII emission drawn from the literature. Relevant information on the presence of other broad emission lines (NIII 4640, CIV 5808 and others) from WR stars of WN and WC subtypes, and other existing broad nebular lines is provided. In total we include 139 know

V. E. Vekslerchik

In this paper I continue studies of the functional representation of the Ablowitz-Ladik hierarchy (ALH). Using formal series solutions of the zero-curvature condition I rederive the functional equations for the tau-functions of the ALH and obtain some new equations which provide more straightforward description of the ALH and which were absent in the previou

A. C. Petkou, M. B. Silva Neto

We study the O(N) vector model and the U(N) Gross-Neveu model with fixed total fermion number, in three dimensions. Using non-trivial polylogarithmic identities, we calculate the large-N renormalized free-energy density of these models, at their conformal points in a ``slab'' geometry with one finite dimension of length L. We comment on the possible

A. R. King, H. Ritter

We consider the unusual evolutionary state of the secondary star in Cygnus X-2. Spectroscopic data give a low mass ($M_2 \simeq 0.5 - 0.7\msun$) and yet a large radius ($R_2 \simeq 7\rsun$) and high luminosity ($L_2 \simeq 150\lsun$). We show that this star closely resembles a remnant of early massive Case B evolution, during which the neutron star ejected m

S. Nojiri, O. Obregon, S. D. Odintsov, K. E. Osetrin

Using one-loop effective action in large N and s-wave approximation we discuss the possibility to induce primordial wormholes at the early Universe. An analytical solution is found for self-consistent primordial wormhole with constant radius. Numerical study gives the wormhole solution with increasing throat radius and increasing red-shift function. There is

Zurab Kakushadze

Recently we proposed a TeV-scale Supersymmetric Standard Model in which the gauge coupling unification is as precise (at one loop) as in the MSSM, and occurs in the TeV range. One of the key ingredients of this model is the presence of new states neutral under $SU(3)_c\otimes SU(2)_w$ but charged under $U(1)_Y$ whose mass scale is around that of the electrow

I. Bars, C. Deliduman, D. Minic

We construct an Sp(2,R) gauge invariant particle action which possesses manifest space-time SO(d,2) symmetry, global supersymmetry and kappa supersymmetry. The global and local supersymmetries are non-abelian generalizations of Poincare type supersymmetries and are consistent with the presence of two timelike dimensions. In particular, this action provides a

Richard L. Hall

We suppose that the ground-state eigenvalue E = F(v) of the Schroedinger Hamiltonian H = -Δ+ vf(x) in one dimension is known for all values of the coupling v > 0. The potential shape f(x) is assumed to be symmetric, bounded below, and monotone increasing for x > 0. A fast algorithm is devised which allows the potential shape f(x) to be reconstructed from the

E. Farhi, J. Goldstone, S. Gutmann, M. Sipser

We consider the problem of inserting a new item into an ordered list of N-1 items. The length of an algorithm is measured by the number of comparisons it makes between the new item and items already on the list. Classically, determining the insertion point requires log N comparisons. We show that, for N large, no quantum algorithm can reduce the number of co

Stephen Fenner, Frederic Green, Steven Homer, Randall Pruim

It is shown that determining whether a quantum computation has a non-zero probability of accepting is at least as hard as the polynomial time hierarchy. This hardness result also applies to determining in general whether a given quantum basis state appears with nonzero amplitude in a superposition, or whether a given quantum bit has positive expectation valu

Christophe Coste, Fernando Lund

Previous results on the scattering of surface waves by vertical vorticity on shallow water are generalized to the case of dispersive water waves. Dispersion effects are treated perturbatively around the shallow water limit, to first order in the ratio of depth to wavelength. The dislocation of the incident wavefront, analogous to the Aharonov-Bohm effect, is

Christophe Coste, Makoto Umeki, Fernando Lund

When a surface wave interacts with a vertical vortex in shallow water the latter induces a dislocation in the incident wavefronts that is analogous to what happens in the Aharonov-Bohm effect for the scattering of electrons by a confined magnetic field. In addition to this global similarity between these two physical systems there is scattering. This paper r

G. Ribordy, J. -D. Gautier, N. Gisin, O. Guinnard

An improved "plug & play" interferometric system for quantum key distribution is presented. Self-alignment and compensation of birefringence remain, while limitations due to reflections are overcome. Original electronics implementing the BB84 protocol makes adjustment simple. Key creation with 0.1 photon per pulse at a rate of 325 Hz with a 2.9 perce

Jim McElwaine

This paper describes an algorithm for selecting a consistent set within the consistent histories approach to quantum mechanics and investigates its properties. The algorithm select from among the consistent sets formed by projections defined by the Schmidt decomposition by making projections at the earliest possible time. The algorithm unconditionally predic

T. Hotta, M. Fujiwara, T. Kinashi, Y. Kuno

We evaluate the performances of a 100 um-thick silicon strip detector (SSD) with a 300 MeV proton beam and a 90Sr beta-ray source. Signals from the SSD have been read out using a VLSI chip. Common-mode noise, signal separation efficiency and energy resolution are compared with those for the SSD's with a thickness of 300 um and 500 um. Energy resolution f

Th. Gallay, G. Raugel

We consider the damped hyperbolic equation (1) εu_{tt} + u_t = u_{xx} + F(u), x \in R, t \ge 0, where εis a positive, not necessarily small parameter. We assume that F(0) = F(1) = 0 and that F is concave on the interval [0,1]. Under these hypotheses, Eq.(1) has a family of monotone travelling wave solutions (or propagating fronts) connecting the equilibria u

H. Frauenkron

We integrate the one-dimensional nonlinear Schrödinger equation numerically for solitons moving in external potentials. In particular, we study the scattering off an interface separating two regions of constant potential modeled by a linear ramp. Transmission coefficients and inelasticities are computed as functions of the potential difference and the slope

J. L. Friar, J. Martorell, D. W. L. Sprung

Recent improvements in the determination of the running of the fine-structure constant also allow an update of the hadronic vacuum-polarization contribution to the Lamb shift. We find a shift of -3.40(7) kHz to the 1S level of hydrogen. We also comment on the contribution of this effect to the determination by elastic electron scattering of the r.m.s. radii

J. A. Sheikh, K. Hara

The projected shell model analysis is carried out using the triaxial Nilsson+BCS basis. It is demonstrated that, for an accurate description of the moments of inertia in the transitional region, it is necessary to take the triaxiality into account and perform the three-dimensional angular-momentum projection from the triaxial Nilsson+BCS intrinsic wavefuncti

A. Hombach, W. Cassing, S. Teis, U. Mosel

We study flow phenomena in relativistic heavy-ion collisions, both in transverse and radial direction, in comparison to experimental data. The collective dynamics of the nucleus-nucleus collision is described within a transport model of the coupled channel BUU type (CBUU). This recently developed version includes all nucleonic resonances up to 1.95 GeV in ma

Abhijit Bhattacharya, Sanjay K. Ghosh, S. C. Phatak

Masses of hadrons (baryons as well as mesons) are modified in the nuclear medium because of their interactions. In this paper we investigate the effect of in-medium meson masses on the properties of the nuclear matter. The calculations are performed in the Walecka model. We find that with the inclusion of meson mass modification, the computed equation of sta

John H. Conway, Charles Radin, Lorenzo Sadun

We consider the rational linear relations between real numbers whose squared trigonometric functions have rational values, angles we call ``geodetic''. We construct a convenient basis for the vector space over Q generated by these angles. Geodetic angles and rational linear combinations of geodetic angles appear naturally in Euclidean geometry; for i

Sergio Albeverio, Yuri Kondratiev, Yuri Kozitsky

Models of quantum and classical particles on the d-dimensional cubic lattice with pair interparticle interactions are considered. The classical model is obtained from the corresponding quantum one when the reduced physical mass of the particle tends to infinity. For these models, it is proposed to define the convergence of the Euclidean Gibbs states, when th

Christian Maes

Common ground to recent studies exploiting relations between dynamical systems and non-equilibrium statistical mechanics is, so we argue, the standard Gibbs formalism applied on the level of space-time histories. The assumptions (chaoticity principle) underlying the Gallavotti-Cohen fluctuation theorem make it possible, using symbolic dynamics, to employ the

Rafe Mazzeo, Richard B. Melrose

Let $X$ be a compact manifold with boundary. Suppose that the boundary is fibred, $ϕ:\pa X\longrightarrow Y,$ and let $x\in\CI(X)$ be a boundary defining function. This data fixes the space of `fibred cusp' vector fields, consisting of those vector fields $V$ on $X$ satisfying $Vx=O(x^2)$ and which are tangent to the fibres of $ϕ;$ it is a Lie algebra an

Blake Mellor

We define a notion of finite type invariants for links with a fixed linking matrix. We show that Milnor's triple link homotopy invariant is a finite type invariant, of type 1, in this sense. We also generalize the approach to Milnor's higher order homotopy invariants and show that they are also, in a sense, of finite type. Finally, we compare our app

Pavel Etingof, Shlomo Gelaki

In a previous paper we prove that any semisimple triangular Hopf algebra A over an algebraically closed field of characteristic 0 (say the field of complex numbers C) is obtained from a finite group after twisting the ordinary comultiplication of its group algebra in the sense of Drinfeld; that is A=C[G]^J for some finite group G and a twist J\in C[G]\ot C[G

Bernd Ammann

We study the behavior of the spectrum of the Dirac operator on collapsing S^1-bundles. Convergent eigenvalues will exist if and only if the spin structure is projectable.

Uri Abraham, Saharon Shelah

A forcing poset of size 2^{2^{aleph_1}} which adds no new reals is described and shown to provide a Delta^2_2 definable well-order of the reals (in fact, any given relation of the reals may be so encoded in some generic extension). The encoding of this well-order is obtained by playing with products of Aronszajn trees: Some products are special while other a

Andras Hajnal, Istvan Juhasz, Saharon Shelah

The relations M(kappa,lambda,mu)->B [resp. B(sigma)] meaning that if A subset [kappa]^lambda with |A|=kappa is mu-almost disjoint then A has property B [resp. has a sigma-transversal] had been introduced and studied under GCH by Erdos and Hajnal in 1961. Our two main results here say the following: Assume GCH and rho be any regular cardinal with a supercompa

R. Laubenbacher, I. Swanson

The principal result is a primary decomposition of ideals generated by the (2x2)-subpermanents of a generic matrix. These permanental ideals almost always have embedded components and their minimal primes are of three distinct heights. Thus the permanental ideals are almost never Cohen-Macaulay, in contrast with determinantal ideals.

Yuri Kozitsky, Lech B. Wolowski

A scale of the Frechet spaces of exponential type entire functions of one complex variable is considered. Certain special properties of subsets of these spaces consisting of Laguerre entire functions, which are obtained as uniform limits on compact subsets of the complex plane of polynomials with real nonpositive zeros only, are described. A class of infinit

Elena Rubei

The subject of this paper is a Jacobian, introduced by F. Lazzeri, (unpublished), associated to every compact oriented riemannian manifold of dimension twice an odd number. We start the investigation of Torelli type problems and Schottky type problem for Lazzeri's Jacobian; in particular we examine the case of tori with flat metrics. Besides we study Laz

Ph. Ellia, D. Franco

We show, among other things, that in most cases the gonality of a subcanonical curve in projective-three space is computable by multisecants.

H. Ahmedov, I. H. Duru

Green function (which can be called the q-analogous of the Hankel function) on the quantum plane E_q^2= E_q(2)/U(1) is constructed.

A. Sevostyanov

We suggest new realizations of quantum groups corresponding to complex simple Lie algebras, and of affine quantum groups. These new realizations are labeled by Coxeter elements of the corresponding Weyl group and have the following key feature: The natural counterparts of the subalgebras U(n), where n is a maximal nilpotent subalgebra in g, possess non--sing

B. Shklyar

For linear evolution control system described by $\dot{x}=Ax(t)+Bu(t),x(0)=x_{0}$ ($A$ generates a strongly continuous semigroup ${S(t)}_{t\ge 0}$ in a Banach space $X$; $B$ is a linear unbounded operator), the attainable set $K(t)$ is studied. Conditions of the independence of $t$ for its closure $\bar{K(t)}$ are established. Controllability conditions for

M. Asorey

We introduce two maximal non-abelian gauge fixing conditions on the space of gauge orbits M for gauge theories over spaces with dimensions d < 3. The gauge fixings are complete in the sense that describe an open dense set M_0 of the space of gauge orbits M and select one and only one gauge field per gauge orbit in M_0. There are not Gribov copies or ambiguit

M. Asorey, F. Falceto, G. Luzon

The relation between connections on 2-dimensional manifolds and holomorphic bundles provides a new perspective on the role of classical gauge fields in quantum field theory in two, three and four dimensions. In particular we show that there is a close relation between unstable bundles and monopoles, sphalerons and instantons. Some of these classical configur

K. A. Milton, I. L. Solovtsov

We study a possible symmetrical behavior of the effective charges defined in the Euclidean and Minkowskian regions and prove that such symmetry is inconsistent with the causality principle.

G. Dall&#39;Agata, K. Lechner, M. Tonin

We review the construction of a manifestly covariant, supersymmetric and SL(2R) invariant action for IIB supergravity in D=10.

Magnus Holm

We will show that gauge theory can be described by an almost product structure, which is a certain type of endomorphism of the tangent bundle. We will recover the gauge field strength as the Nijenhuis tensor of this endomorphism. We discuss a generalization to the case of a general Kaluza-Klein theory. Furthermore, we will look at the classification of these

M. Pawlowski, V. N. Pervushin, V. I. Smirichinski

We discuss the application of the method of the gaugeless Hamiltonian reduction to general relativity. This method is based on explicit resolving the global part of the energy constraint and on identification of one of the metric components with the evolution parameter of the equivalent unconstrained (reduced) system. The Hamiltonian reduction reveals a poss

Konstadinos Sfetsos

Multicenter supergravity solutions corresponding to Higgs phases of supersymmetric Yang-Mills theories are considered. For NS5 branes we identify three cases where there is a description in terms of exact conformal field theories. Other supergravity solutions, such as D3-branes with angular momentum, are understood as special limits of multicenter ones. With

Giampiero Esposito, Alexander Yu. Kamenshchik, Klaus Kirsten

Since the Maxwell theory of electromagnetic phenomena is a gauge theory, it is quite important to evaluate the zero-point energy of the quantized electromagnetic field by a careful assignment of boundary conditions on the potential and on the ghost fields. Recent work by the authors has shown that, for a perfectly conducting spherical shell, it is precisely

Volker Braun, Chien-Hao Liu

M-theory compactification leads one to consider 7-manifolds obtained by rolling Calabi-Yau threefolds in the web of Calabi-Yau moduli spaces. The resulting 7-space in general has singularities governed by the extremal transition undergone. After providing some background in Sec. 1, the simplest case of conifold transitions is studied in Sec. 2. In Sec. 3 we

Michael Nauenberg

A quantum wave packet treatment of neutrino and neutral K and B meson oscillations is presented which incorporates the recoil particle in the production process, and includes the effect of the localization and lifetime of the source assumed to be a resonance or unstable particle. This approach removes the ambiguities in the conventional single particle treat

Carl E. Carlson, Christopher D. Carone, Jose L. Goity, Richard F. Lebed

We consider in detail the mass operator analysis for the nonstrange L=1 excited baryons in large N_c QCD. We present a straightforward procedure for constructing the large N_c baryon wavefunctions, and provide complete analytic expressions for the matrix elements of all the independent isosinglet mass operators. We discuss the relationship between the old-fa

Dan-Di Wu

I suggest two new unitarity tests for the quark charged current coupling constants which are $(sin γ/sin α) = ζ$, and $(sin 2γ)/(sin 2α) = - ((1-ζcos β))/(cos β-ζ)$ where $ζ$ is a CKM parameter defined in the text. These unitarity identities do not suffer some of the multi-value ambiguities. Related problems are discussed. The sign of $Δm_{_{B_d}}$ should sa

T. P. Cheng, N. I. Kochelev, V. Vento

The recent suggestion of a vanishing flavor-singlet axial charge of nucleon due to a nontrivial vacuum structure is further amplified. A perturbative QCD discussion, applicable for the heavy quark contributions, relates it to the physics of the decoupling theorem. It is also shown that $g_{A}^{0}\simeq 0$ leads to a negative $η&#39;$-meson-quark coupling, wh

A. Ali

We address a number of theoretical and phenomenological issues in two-body charmless non-leptonic B decays in the context of a factorization model. A classification of the exclusive decays involving tree and penguin amplitudes is reviewed. The role of QCD anomaly in exclusive decays involving an $η$ or $η&#39;$ is elucidated and comparison is made with the e

A. Ali, G. Hiller

Leading order (in $α_s$) perturbative QCD and power ($1/m_b^2)$ corrections to the hadronic invariant mass and hadron energy spectra in the decay $B \to X_s \ell^+ \ell^-$ are reviewed in the standard model using the heavy quark expansion technique (HQET). In particular, the first two hadronic moments $<S_H^n>$ and $<E_H^n>$, $n=1,2$, are presented working o

J. R. Cudell, V. V. Ezhela, K. Kang, S. B. Lugovsky

We present a preliminary report on the determination of the intercepts and couplings of the soft pomeron and of the rho/omega and f/a trajectories from the largest data set available for all total cross sections and real parts of the hadronic amplitudes. Factorization is reasonably satisfied by the pomeron couplings, which allows us to make predictions on ga

T. P. Cheng, Ling-Fong Li

Chiral quark model with a broken-U(3) flavor symmetry can be interpreted as the effective theory of the instanton-dominated non-perturbative QCD. This naturally suggests the possibility of a negative singlet/octet coupling ratio, which has been found, in a previous publication, to be compatible with the phenomenological description of the nucleon spin-flavor

C. Wetterich

The naturalness of maximal mixing between myon- and tau-neutrinos is investigated. A spontaneously broken nonabelian generation symmetry can explain a small parameter which governs the deviation from maximal mixing. In many cases all three neutrino masses are almost degenerate. Maximal ny_my-ny_tau-mixing would indicate that the leading contribution to the l

L. R. Babukhadia, M. D. Scadron

We consider techniques (based on an ultraviolet cutoff) used to prove that the pure boson ($ϕ^4)_4$ field theory is trivial and apply them instead to the dynamically generated quark-level linear sigma model. This cutoff approach leads to the conclusion that the latter field theory is in fact nontrivial.

Yong Liu, Jing-Ling Chen, Wu-Sheng Dai

Taking use of the relation between weak CP phase and the other three mixing angles in Cabibbo-Kobayashi-Maskawa matrix postulated by us before, the uncertainty coming from the weak interaction can be reduced, furthermore, by means of the relation between the calculation result about mixing parameter epsilon from the box diagrams and the related experimental

W. Bietenholz, H. Dilger

We construct and test a quasi-perfect lattice action for staggered fermions. The construction starts from free fermions, where we suggest a new blocking scheme, which leads to excellent locality of the perfect action. An adequate truncation preserves a high quality of the free action. An Abelian gauge field is inserted in d=2 by effectively tuning the coupli

J. Ambjorn, P. Bialas, J. Jurkiewicz

We discuss the concept of connected, reparameterization invariant matter correlators in quantum gravity. We analyze the effect of discretization in two solvable cases: branched polymers and two-dimensional simplicial gravity. In both cases the naively defined connected correlators for a fixed volume display an anomalous behavior, which could be interpreted a

C. Adloff

The triple-differential dijet cross-section, d^3 sigma_{ep}/dQ2 dE_t2 dxgjets, is measured with the H1 detector at HERA as a function of the photon virtuality Q^2, the fraction of the photon&#39;s momentum carried by the parton entering the hard scattering, xgjets, and the square of the mean transverse energy, E_t2, of the two highest E_t jets. Jets are foun

C. Adloff

With the H1 detector at the ep collider HERA, D* meson production cross sections have been measured in deep inelastic scattering with four-momentum transfers Q^2>2 GeV2 and in photoproduction at energies around W(gamma p)~ 88 GeV and 194 GeV. Next-to-Leading Order QCD calculations are found to describe the differential cross sections within theoretical and e

G. Iovane

OPERA(Oscillation Project with Emulsion-tRacking Apparatus) is a new detector concept, iron(lead)-emulsion for a long-baseline neutrino oscillation experiment. This experiment would perform an appearance search for nu_mu-nu_tau oscillation in the parameter region indicated by the atmospheric neutrino anomaly. OPERA can run at the Gran Sasso Laboratory in the

Ruth Lazkoz

I present here a new algorithm to generate families of inhomogeneous massless scalar field cosmologies. New spacetimes, having a single isometry, are generated by breaking the homogeneity of massless scalar field $G_2$ models along one direction. As an illustration of the technique I construct cosmological models which in their late time limit represent pert

Willy Kley, Gerhard Schaefer

Treating problems in full general relativity is highly complex and frequently approximate methods are employed to simplify the solution. We present comparative solutions of a infinitesimally thin relativistic, stationary, rigidly rotating disk obtained using the full equations and the approximate approach suggested by Wilson & Mathews. We find that the Wilso

Robert J Low

Some standard results on the initial value problem of general relativity in matter are reviewed. These results are applied first to show that in a well defined sense, finite perturbations in the gravitational field travel no faster than light, and second to show that it is impossible to construct a warp drive as considered by Alcubierre (1994) in the absence

L. C. Garcia de Andrade

Chern-Simons electrodynamics in 2+1-spacetimes with torsion is investigated. We start from the usual Chern-Simons (CS) electrodynamics Lagrangian and Cartan torsion is introduced in the covariant derivative and by a direct coupling of torsion vector to the CS field. Variation of the Lagrangian with respect to torsion shows that Chern-Simons field is proporti

Abhay Ashtekar, Christopher Beetle, Stephen Fairhurst

A set of boundary conditions defining a non-rotating isolated horizon are given in Einstein-Maxwell theory. A space-time representing a black hole which itself is in equilibrium but whose exterior contains radiation admits such a horizon . Physically motivated, (quasi-)local definitions of the mass and surface gravity of an isolated horizon are introduced. A

A. K. Kolezhuk, H. -J. Mikeska, K. Maisinger, U. Schollwock

We propose an effective theory for the critical phase of a quantum ferrimagnetic chain with alternating spins 1 and 1/2 in an external magnetic field. With the help of the matrix product variational approach, the system is mapped to a spin-1/2 XXZ chain in an (effective) magnetic field; as a byproduct, we obtain an excellent description of the optical magnon

J. M. Eroles, C. D. Batista, A. A. Aligia

Using a mapping from the three-band extended Hubbard model for cuprate superconductors into a generalized t-J model, and exact diagonalization of the latter in a 4x4 cluster, we determine the quasiparticle weight for destruction of a Cu or an O electrons with definite wave vector k. We also derive an approximate but accurate analytical expression which relat

E. Marinari, G. Parisi, J. J. Ruiz-Lorenzo, F. Zuliani

In a recent letter Moore et al. claim to exhibit evidence for a non-mean-field behavior of the $3d$ Ising spin glass. We show that their claim is insubstantial, and by analyzing in detail the behavior of the Migdal-Kadanoff approximation (MKA) as compared to the behavior of the Edwards-Anderson (EA) spin glass we find further evidence of a mean-field like be

Le Anh Thu, L I Komarov

The operator method is used to construct the solutions of the problem of the polaron in the strong coupling limit and of the helium atom on the basis of the Hartree-Fock equation. $E_0=-0.1085128052α^2$ is obtained for the polaron ground-state energy. Energies for 2s- and 3s-states are also calculated. The other excited states are briefly discussed.

E. Akkermans, R. Narevich

We present topological features of the magnetic response (orbital and spin) of a two-dimensional degenerate and non interacting electron gas due to inhomogeneous applied magnetic fields. These issues are analysed from the point of view of the Index theory with a special emphasis on the non perturbative aspects of this response. The limiting case of a Aharono

M. Lisowski, E. Zipper, M. Stebelski

A microscopic Hamiltonian of the magnetostatic interaction is discussed. This long-range interaction can play an important role in mesoscopic systems leading to an ordered ground state. The self-consistent mean field approximation of the magnetostatic interaction is performed to give an effective Hamiltonian from which the spontaneous, self-sustaining curren

Oded Agam

The tunneling spectra of small metallic grains shows an unusual structure of the differential conductance peaks. Namely, resonance peaks appear in clusters, or develop substructure as the the gate voltage is changed. These features are manifestations of a nonequilibrium behavior which appears when the applied source-drain voltage is sufficiently large. Elect

Ingo Morgenstern, Werner Fettes, Thomas Husslein, Dennis M. Newns

In this paper we revisit the glass model describing the macroscopic behavior of the High-Temperature superconductors. We link the glass model at the microscopic level to the striped phase phenomenon, recently discussed widely. The size of the striped phase domains is consistent with earlier predictions of the glass model when it was introduced for High-Tempe

D. Zanchi, H. J. Schulz

We formulate the exact Wilsonian renormalization group for a system of interacting fermions on a lattice. The flow equations for all vertices of the Wilson effective action are expressed in form of the Polchinski equation. We apply this method to the Hubbard model on a square lattice using both zero- and finite- temperature methods. Truncating the effective

R. F. Sawyer

Certain perturbation graphs in the calculation of the effects of the medium on neutrino scattering in supernova matter have a nonintegrable singularity in a physical region. A number of papers have addressed the apparent pathology through an ansatz that invokes higher order (rescattering) effects. Taking the Gamow-Teller terms as an example, we display an ex

U. Fritze-v. Alvensleben, U. Lindner, C. S. Möller

Comparison of our chemically consistent models for spiral galaxies with observed DLA abundances shows that at high redshift DLA galaxies may well be the progenitors of normal spiral disks of all types from Sa through Sd. Towards lower redshifts z </= 1.5 however, early type spirals drop out of DLA samples due to low gas or/and high dust content. We use the s

Gerhardt R. Meurer, Timothy M. Heckman, Daniela Calzetti

We detail a technique for estimating the UV extinction and luminosity of UV selected galaxies using UV quantities alone. The technique is based on a tight correlation between the ratios of far infrared (FIR) to UV flux ratios and UV color for a sample of local starbursts. A simple empirical fit to this correlation can be used to estimate UV extinction as a f

D. D. Dixon

Image processing is an increasingly important aspect for analysis of data from X and $γ$-ray astrophysics missions. In this paper, I review a method proposed by Kebede (L. W. Kebede 1994, ApJ, 423, 878), and point out an error in the derivation of this method. It turns out that this error is not debilitating -- the method still ``works&#39;&#39; in some sens

P. C. Schmidtke, A. L. Ponder, A. P. Cowley

The luminous X-ray binary and black-hole candidate LMC X-1 has been observed with the Rossi X-ray Timing Explorer (RXTE) to search for quasi-periodic oscillations (QPO), previously reported in its high state. The source was observed monthly in a series of nine observations. Analysis of the temporal variations shows no evidence for QPO or other periodic chang

N. R. Tanvir

Thanks to HST, there are now many galaxies with Cepheid distances and these provide the main platform for the calibration of the secondary distance indicators. I review recent progress in our understanding of the standard candle properties of Cepheids with particular emphasis on the techniques used in the HST studies. The PL relation defined by Cepheids in t

G. A. Luppino, I. M. Gioia, F. Hammer, O. Le Fevre

We present the results of a CCD imaging survey for gravitational lensing in a sample of 38 X-ray-selected clusters of galaxies. Our sample consists of the most X-ray luminous (Lx>= 2x10^{44} erg s^{-1}) clusters selected from the Einstein Observatory Extended Medium Sensitivity Survey (EMSS) that are observable from Mauna Kea (dec > -40deg). The sample spans

N. Vlahakis, K. Tsinganos

By a systematic method we construct general classes of exact and selfconsistent axisymmetric MHD solutions describing flows which originate at the near environment of a central gravitating astrophysical object. The unifying scheme contains two large groups of exact MHD outflow models, (I) meridionally self-similar ones with spherical critical surfaces and (I

R. Falomo, C. Megan Urry, Riccardo Scarpa, Joseph E. Pesce

Snapshot images of about 100 BL Lac objects were obtained with WFPC2 on HST. Sources from various samples, in the redshift range 0.05 to 1.2, were observed and 61 resolved (51 with known z). The high resolution and homogeneity of the images allow us to address the properties of the immediate environments of BL Lacs with unprecedented capability. Host galaxie

Jesper Sommer-Larsen

The structure, kinematics and dynamics of the Galactic stellar halo are reviewed including evidence of substructure in the spatial distribution and kinematics of halo stars. Implications for galaxy formation theory are subsequently discussed; in particular it is argued that the observed kinematics of stars in the outer Galactic halo can be used as an importa

M. R. Goad, A. P. Koratkar, D. J. Axon, K. T. Korista

During the 1996 HST/FOS monitoring campaign of the Seyfert 1 galaxy NGC 3516, the UV continuum showed a factor of 5 variation; correspondingly the strongest broad UV emission lines (e.g. Ly-alpha, CIV) displayed somewhat weaker, though still significant variations (a factor of 2). In contrast, no variation was detected in the strong broad MgII+UV FeII emissi

K. M. Gorski, E. Hivon, B. D. Wandelt

Multi-frequency, high resolution, full sky measurements of the anisotropy in both temperature and polarisation of the cosmic microwave background radiation are the goals of the satellite missions MAP (NASA) and Planck (ESA). The ultimate data products of these missions - multiple microwave sky maps, each of which will have to comprise more than 10^6 pixels i

L. Sidoli, S. Mereghetti

We are performing a survey of the Galactic Center region with the BeppoSAX satellite. Several known point sources are visible (including one at the position of SgrA*), as well as newly discovered sources and diffuse emission. Here we report the preliminary results of the on-going analysis of both the point sources and the diffuse X-ray emission.

A. Udalski, I. Soszynski, M. Szymanski, M. Kubiak

We present the catalog of 1459 eclipsing binary stars detected in the central 2.4 square degree area of the Small Magellanic Cloud during the OGLE-II microlensing search. The sample includes objects brighter than I=20 mag with periods ranging from about 0.3 to 250 days. The average completeness of the catalog is about 80%. Statistics of the entire sample and

K. Mattila, K. Lehtinen, D. Lemke

The spectrum of the unidentified infrared (UIR) emission bands between 5.9 and 11.7 [micro]m has been observed for the first time in the disk of an external galaxy. We have used the low-resolution spectrometer of the ISOPHOT instrument aboard ISO. The UIR bands at 6.2, 7.7 and 11.3 [micro]m have absolute intensities which are similar to the values observed f

Daniel Schaerer

We review the observations of nebular HeII 4686 emission in Local Group objects and extra-galactic HII regions. Different ionization mechanisms proposed to explain the unusually high excitation are summarized. The models of Schaerer (1996) and Schaerer & Vacca (1998) predict nebular HeII emission due to hot WN and WC/WO stars, in good agreement with observat

M. Bellazzini, F. R. Ferraro, R. Buonanno

We present first results of a large photometric survey devoted to study the star formation history of the Sagittarius dwarf spheroidal galaxy (Sgr dSph). Three wide strips (9 X 35 arcmin^2) located at l~5 and b=-16, -14, -12 have been observed. Each strip is roughly EW oriented, nearly along the major axis of the galaxy. A control field (~9 X 24 arcmin^2), l

G. Stasinska

After briefly reviewing the impact of various parameters on photoionization models, we illustrate the importance of the nebular geometry by two examples: we first compare the results from models with thin shell and full shell geometry, and we study the influence of a diffuse ionized medium in the integrated spectra of galaxies at large redshift. Finally, we

HEGRA Collaboration, M. Hess et al

The time profiles of Cherenkov images of cosmic-ray showers and of gamma-ray showers are investigated, using data gathered with the HEGRA system of imaging atmospheric Cherenkov telescopes during the 1997 outbursts of Mrk 501. Photon arrival times are shown to vary across the shower images. The dominant feature is a time gradient along the major axis of the

Alfredo Santillan, Jose Franco, Marco Martos, Jongsoo Kim

We present two-dimensional MHD numerical simulations for the interaction of high-velocity clouds with both magnetic and non-magnetic Galactic thick gaseous disks. For the magnetic models, the initial magnetic field is oriented parallel to the disk, and we consider two different field topologies (with and without tension effects): parallel and perpendicular t