November 1997 arXiv papers — page 17

Andrzej J. Buras

We review the present status of the CKM matrix and we offer some visions of its future. After a brief presentation of the theoretical framework for weak decays we discuss the following topics: i) CKM matrix from tree level decays, ii) Standard analysis of the unitarity triangle, iii) CKM matrix from rare and CP violating K- and B-decays, iv) CKM matrix from

Ilja Schmelzer

We define realism using a slightly modified version of the EPR criterion of reality. This version is strong enough to show that relativity is incomplete. We show that this definition of realism is nonetheless compatible with the general principles of causality and canonical quantum theory as well as with experimental evidence in the (special and general) rel

Maximo Banados

Black holes of constant curvature are constructed by identifying points in anti-de Sitter space. In n dimensions the resulting topology is R^{n-1} * S_1, as opposed to the usual R^2 * S_{n-2} Schwarzschild black hole.

Nigel Hitchin

This paper considers the natural geometric structure on the moduli space of deformations of a compact special Lagrangian submanifold $L^n$ of a Calabi-Yau manifold. From the work of McLean this is a smooth manifold with a natural $L^2$ metric. It is shown that the metric is induced from a local Lagrangian immersion into the product of cohomology groups $H^1(

H. Gillet, C. Soulé

Let $E$ be a holomorphic vector bundle on a compact Kähler manifold $X$. If we fix a metric $h$ on $E$, we get a Laplace operator $Δ$ acting upon smooth sections of $E$ over $X$. Using the zeta function of $Δ$, one defines its regularized determinant $det'(Δ)$. We conjectured elsewhere that, when $h$ varies, this determinant $det'(Δ)$ remains bounded

Gene F. Mazenko

A consistent perturbation theory expansion is presented for phase ordering kinetics in the case of a nonconserved scalar order parameter. At lowest order in this formal expansion one obtains the theory due to Ohta, Jasnow and Kawasaki (OJK). At next order, worked out explicitly in d dimensions, one has small corrections to the OJK result for the nonequilibri

N. Schopohl, O. V. Dolgov

Based on the third law of thermodynamics it is shown, that the first derivative of the magnetic penetration depth with respect to temperature should vanish irrespective of the symmetry of Cooper pairs.

A. Moser, U. Krey, A. Paintner, B. Zellermann

In a self-consistent semi-empirical numerical approach based on ab-initio-calculations for small samples, we evaluate the GMR effect for disordered (001)-(3--Fe/3--V)$_\infty$ multilayers by means of a Kubo formalism. We consider four different types of disorder arrangements: In case (i) and (ii), the disorder consists in the random interchange of some Fe an

R. Baviera, M. Pasquini, M. Serva

We introduce a hierarchical class of approximations of the random Ising spin glass in $d$ dimensions. The attention is focused on finite clusters of spins where the action of the rest of the system is properly taken into account. At the lower level (cluster of a single spin) our approximation coincides with the SK model while at the highest level it coincide

Igor A. Luk'yanchuk

The upper critical temperature Tc2 for the phase transition between the Cholesteric phase (N*) and the Twist Grain Boundary C phase with the layer inclination tilted to the pitch axis (TGBct) in thermotropic liquid crystals is determined by the mean field Chen-Lubensky approach. We show that the N*-TGBct phase transition is split in two with the appearance o

I. M. Jánosi, G. Vattay, A. Harnos

We compare the spectral properties of long meteorological temperature records with laboratory measurements in small convection cells. Surprisingly, the atmospheric boundary layer sampled on a daily scale shares the statistical properties of temperature fluctuations in small-scale experiments. This fact can be explained by the hydrodynamical similarity betwee

Beat Ammon, Hans Gerd Evertz, Naoki Kawashima, Matthias Troyer

We propose a generalization of the Quantum Monte Carlo loop algorithm to the t-J model by a mapping to three coupled six-vertex models. The autocorrelation times are reduced by orders of magnitude compared to the conventional local algorithms. The method is completely ergodic and can be formulated directly in continuous time. We introduce improved estimators

A. Fledderjohann, K. -H. Mütter, M. -S. Yang, M. Karbach

We study the first derivative of the staggered magnetization squared $dm^†(θ)^2/dθ$ and the second derivative $d^2e_0(θ)/dθ^2$ of the ground state energy per site. The parameter $θ$ controls the anisotropy between horizontal and vertical couplings in a two-dimensional (2D) spin-1/2 antiferromagnetic Heisenberg model. It is shown, that both derivatives diverg

Rosario Fazio, Roberto Raimondi

We study resonant Andreev tunneling through a strongly interacting quantum dot connected to a normal and to a superconducting lead. We obtain a formula for the Andreev current and apply it to discuss the linear and non-linear transport in the nonperturbative regime, where the effects of the Kondo resonance on the two particle tunneling arise. In particular w

Harald Kallabis, Dietrich E. Wolf

During epitaxial crystal growth a pattern that has initially been imprinted on a surface approximately reproduces itself after the deposition of an integer number of monolayers. Computer simulations of the one-dimensional case show that the quality of reproduction decays exponentially with a characteristic time which is linear in the activation energy of sur

P. Sen, G. Aggarwal, U. Tiwari

We report 4-probe resistivity measurements of cold-rolled Ni and Fe during 100 MeV oxygen ion irradiation, at 300K. The resistivity shows increase and saturation, marked by jumps. Employing 200 MeV silver ion irradiation of Fe and Si(100) and topographically identifying strain at an artificial interface in the latter, we assign the resistivity behavior to at

P. Schmelcher, F. K. Diakonos

We present a method to detect the unstable periodic orbits of a multidimensional chaotic dynamical system. Our approach allows us to locate in an efficient way the unstable cycles of, in principle, arbitrary length with a high accuracy. Based on a universal set of linear transformations the originally unstable periodic orbits are transformed into stable ones

Michael A. K. Gross, Rachel S. Somerville, Joel R. Primack, Stefano Borgani

The combination of measurements of the local abundance of rich clusters of galaxies and its evolution to higher redshift offers the possibility of a direct measurement of $Ω_0$ with little contribution from other cosmological parameters. We investigate the significance of recent claims that this evolution indicates that $Ω_0$ must be small. The most recent c

Claus Beisbart, Thomas Buchert

The morphology of galaxy clusters is quantified using Minkowski functionals, especially the vector-valued ones, which contain directional information and are related to curvature centroids. The asymmetry of clusters and the amount of their substructure can be characterized in a unique way using these measures. -- We briefly introduce vector-valued Minkowski

G. Burbidge

Arguments and evidence against the hot big bang model are summarized. The observations which point to an explosive cosmogony and the quasi-steady state cosmology are outlined.

M. Boettcher, W. Collmar

We present model calculations to the observed spectral variability in the gamma-ray spectrum of the ultraluminous blazar-type quasar PKS 0528+134. We argue that the observed appearance of a spectral break between the COMPTEL and the EGRET energy range can plausibly be explained by a variation of the Doppler beaming factor in the framework of a relativistic j

Thomas Buchert

I report on a systematic derivation of the phenomenological ``adhesion approximation'' from gravitational instability together with a brief evaluation of the related status of analytical modeling of large-scale structure.

P. A. Caraveo, M. G. Lattanzi, G. Massone, R. P. Mignani

Accuracy in the absolute position in the sky is one of the limiting factors for pulsar timing, and timing parameters have a direct impact on the understanding of the physics of Isolated Neutron Stars (INS). We report here on a high-accuracy measurement of the optical position of Geminga (V=25.5), the only known radio-quiet INS. The procedure combines the Hip

E. Poretti, S. Campana, O. Citterio, P. Conconi

The Joint European Telesscope (JET-X) is one of the core scientific instruments of the SPECTRUM-X-Gamma mission. JET-X was designed to study X-ray emissions in the band 0.3-10 KeV. Its angular resolution is better than 20 arcsec; the values of the effective areas are 161 cm2 at 1.5 KeV and 69 cm2 at 8 Kev (for one telescope). The value of the HEW circle in f

Masaaki Morita, Kouji Nakamura, Masumi Kasai

We compare relativistic approximation methods, which describe gravitational instability in the expanding universe, in a spherically symmetric model. Linear perturbation theory, second-order perturbation theory, relativistic Zel'dovich approximation, and relativistic post-Zel'dovich approximation are considered and compared with the Lema\^ıtre-Tolman-

Nami Mowlavi, Stephane Goriely, Marcel Arnould

The now extinct 205Pb is a pure s-process radionuclide (t_{1/2} = 1.5x10^7 y) of possible substantial cosmochemical interest. As a necessary complement to the detailed theoretical study of the nuclear physics and astrophysics aspects of the 205Pb - 205Tl pair carried out by Yokoi et al. (1985), and to the recent calculation of the 205Pb production in Wolf-Ra

Ennio Poretti

The recent results (Pardo & Poretti 1997, A&A 324, 121; Poretti & Pardo 1997, A&A 324, 133) obtained on the frequency content of Double-Mode Cepheids light curves and the properties of their Fourier parameters are reviewed. Some points briefly discussed in previous papers (no third periodicity, methodological aspects on the true peaks detection, the action o

Nami Mowlavi

An overview of the main phases of the evolution of low- and intermediate-mass stars is presented, and the different types of nucleosynthesis operating from the pre-main sequence up to and including the asymptotic giant branch phase described. The surface abundance modifications brought by each nucleosynthesis process is also briefly discussed.

Takuji Tsujimoto, Masanori Miyamoto, Yuzuru Yoshii

The present determination of the absolute magnitude $M_V(RR)$ of RR Lyrae stars is twofold, relying upon Hipparcos proper motions and trigonometric parallaxes separately. First, applying the statistical parallax method to the proper motions, we find $<M_V(RR)>=0.69\pm0.10$ for 99 halo RR Lyraes with $<$[Fe/H]$>$ =--1.58. Second, applying the Lutz-Kelker corr

W. J. Couch, A. J. Barger, I. Smail, R. S. Ellis

We present new results of a program to study the detailed morphologies of galaxies in intermediate redshift clusters and hence understand the physical origin of the enhanced star formation in these environments at earlier epochs. Deep, high resolution imagery has been obtained of 3 rich clusters, AC103,AC118 & AC114 at z=0.31, using the WFPC2 on HST. For AC1

Bernhard Sendhoff, Martin Kreutz, Werner von Seelen

The appropriate choice of the genotype-phenotype mapping in combination with the mutation operator is important for a successful evolutionary search process. We suggest a measure to quantify the quality of this combination by addressing the question whether the relation among distances is carried over from one space to the other. Search processes which do no

Anvar R. Mavlyutov

We show that through a point of an affine variety there always exists a smooth plane curve inside the ambient affine space, which has the multiplicity of intersection with the variety at least 3. This result has an application to the study of affine schemes.

M. A. Bransford, P. N. Appleton, C. A. Heisler, R. P. Norris

This is the first of two papers in which a study is made of a sample of 12 southern radio-luminous Seyfert galaxies. Our aim is to investigate possible correlations between radio morphology and nuclear/circumnuclear emission-line properties. In this paper we present radio images at 13, 6, and 3 cm taken with the Australia Telescope Compact Array (ATCA), glob

C. L. Brogan, T. H. Troland, D. A. Roberts, R. M. Crutcher

We have carried out VLA Zeeman observations of HI absorption lines toward the HII region in the M17 giant molecular cloud complex. The HI absorption lines toward M17 show between 5 and 8 distinct velocity components which vary spatially in a complex manner across the source. We explore possible physical connections between these components and the M17 region

Kingman Cheung, Duane A. Dicus, B. Dutta, S. Nandi

In the framework of gauge-mediated supersymmetry breaking models pair production of the lightest neutralinos, scalar leptons, or charginos at LEPII gives rise to interesting signals involving multilepton final states and missing energy. In the parameter space where the scalar tau, $\tildeτ_1$, is the next-to-lightest supersymmetric particle, we identify thre

N. C. Leung, C. Vafa

We show that toric geometry can be used rather effectively to translate a brane configuration to geometry. Roughly speaking the skeletons of toric space are identified with the brane configurations. The cases where the local geometry involves hypersurfaces in toric varieties (such as P^2 blown up at more than 3 points) presents a challenge for the brane pict

Yosef Nir, Mihir P. Worah

We study the implications of various supersymmetric models on the rare $K^+ \to π^+ ν\barν$ and $K_L \to π^0 ν\barν$ decays. Although large effects are possible in generic supersymmetric models, most of the known supersymmetric flavor models lead to negligible effects. Thus, it is likely that one can get information about CKM matrix elements from these decay

Francesco M. Russo

We investigate the connection between the well known Sherrington-Kirkpatrick Ising Spin Glass and the corresponding Lattice Gas model by analyzing the relation between their thermodynamical functions. We present results of replica approach in the Replica Symmetric approximation and discuss its stability as a function of temperature and external source. Next

Paolo Cea, Luigi Tedesco

We investigate the effects of thermal fluctuations on the spontaneous magnetic condensate in three dimensional QED coupled with P-odd Dirac fermions. Our results show that the phenomenon of the spontaneous generation of the constant background magnetic field survives to the thermal corrections even at infinite temperature. We also study the thermal correctio

A. Brandhuber, N. Itzhaki, J. Sonnenschein, S. Yankielowicz

We generalize the Gibbons-Wiltshire solution of four dimensional Kaluza-Klein black holes in order to describe Type IIA solutions of bound states of D6 and D0-branes. We probe the solutions with a D6-brane and a D0-brane. We also probe a system of D2+D0-branes and of a D2-brane bound to a F1-string with a D2-brane. A precise agreement between the SYM and the

Hanno Hammer

We derive the fully extended supersymmetry algebra carried by D-branes in a massless type IIA superspace vacuum. We find that the extended algebra contains not only topological charges that probe the presence of compact spacetime dimensions but also pieces that measure non-trivial configurations of the gauge field on the worldvolume of the brane. Furthermore

Sean Carroll, Miguel Ortiz, Washington Taylor

We analyze the Ising model on a random surface with a boundary magnetic field using matrix model techniques. We are able to exactly calculate the disk amplitude, boundary magnetization and bulk magnetization in the presence of a boundary field. The results of these calculations can be interpreted in terms of renormalization group flow induced by the boundary

Igor Bandos, Alexey Maznytsia, Dmitri Sorokin

We propose doubly supersymmetric actions in terms of n=2(D-2) worldline superfields for N=2 superparticles in D=3,4 and Type IIA D=6 superspaces. These actions are obtained by dimensional reduction of superfield actions for N=1 superparticles in D=4,6 and 10, respectively. We show that in all these models geometrodynamical constraints on target superspace co

Giancarlo D&#39;Ambrosio, Jorge Portoles

We study the long-distance dominated K_L -> pi^+ pi^- gamma decay at O(p^6) in Chiral Perturbation Theory. The complete calculation of the O(p^6) loop magnetic amplitude is carried out. At this chiral order the model dependent part of the vector meson exchange contribution to the magnetic amplitude is evaluated in the two models : FM (Factorization Model) an

Daniel Arnaudon

We construct two quantum spin chains Hamiltonians with quantum sl(2|1) invariance. These spin chains define variants of the Hubbard model and describe electron models with pair hoppings. A cubic algebra that admits the Birman-Wenzl-Murakami algebra as a quotient allows exact solvability of the periodic chain. The two Hamiltonians, respectively built using th

Fu-Guang Cao, Yuan-Ben Dai, Chao-Shang Huang

Non-leading contribution to the pion electromagnetic form factor which comes from the pion twist-3 wave function is analyzed in the modified hard scattering approach (MHSA) proposed by Li and Sterman. This contribution is enhanced significantly due to bound state effect (the twist-3 wave function is independent of the fractional momentum carried by the parto

Andrei Mudrov

The universal ${\cal R}$--matrix for a quantized Poincar{é} algebra ${\cal P}(3+1)$ introduced by Ballesteros et al is evaluated. The solution is obtained as a specific case of a formulated multidimensional generalization to the non-standard (Jordanian) quantization of $sl(2)$.

R. Beutler, B. G. Konopelchenko

Surfaces of revolution in three-dimensional Euclidean space are considered. Several new examples of surfaces of revolution associated with well-known solvable cases of the Schoedinger equation (infinite well, harmonic oscillator, Coulomb potential, Bargmann potential, etc.) are analyzed and visualized. The properties of such surfaces are discussed. Two types

Margit Rösler, Michael Voit

Dunkl operators are differential-difference operators on $\b R^N$ which generalize partial derivatives. They lead to generalizations of Laplace operators, Fourier transforms, heat semigroups, Hermite polynomials, and so on. In this paper we introduce two systems of biorthogonal polynomials with respect to Dunkl&#39;s Gaussian distributions in a quite canonic

A. Ballesteros, F. J. Herranz, P. Parashar

Two quantum Hopf structures for the Schrödinger algebra as well as their corresponding differential-difference realizations are presented. For each case a (space or time) discretization of the Schrödinger equation is deduced and the quantum Schrödinger generators are shown to be symmetry operators.

R. B. Zhang

The method of vector coherent states is generalized to study representations of the affine Lie algebra $\hat{sl}(2)$. A large class of highest weight irreps is explicitly constructed, which contains the integrable highest weight irreps as special cases.

S. A. Boldyrev

Magnetosonic waves are intensively studied due to their importance in space plasmas and also in fusion plasmas where they are used in particle acceleration and heating experiments. In the present paper we investigate the magnetosonic waves propagating in a multi-ion-species plasma perpendicular to an external magnetic field. Due to the presence of several io

J. Pan, S. Das Gupta

In this paper we continue the investigation of the lattice gas model. The main improvement is that we use two strengths for bonds: one between like particles and another between unlike particle to implement the isospin-dependence of nuclear force. The main effect is the elimination of unphysical clusters, like the dineutron or diproton. It is therefore a bet

Steve Seif, Zeljko Sokolovic, Csaba Szabo

Complexity problems associated with finite rings and finite semigroups, particularly semigroups of matrices over a field and the Rees matrix semigroups, are examined. Let M_nF be the ring of n x n matrices over the finite field F and let T_nF be the multiplicative semigroup of n x n matrices over the finite field F. It is proved that for any finite field F a

Carel F. Faber

Looijenga recently proved that the tautological ring of M_g vanishes in degree d>g-2 and is at most one-dimensional in degree g-2, generated by the class of the hyperelliptic locus. Here we show that K_{g-2} is non-zero on M_g. The proof uses the Witten conjecture, proven by Kontsevich. With similar methods, we expect to be able to prove some (possibly all)

Carel F. Faber

The purpose of this paper is to formulate a number of conjectures giving a rather complete description of the tautological ring of M_g and to discuss the evidence for these conjectures.

J. X. Lu

In the absence of a complete M-theory, we gather certain quantum aspects of this theory, namely, M-2 and M-5 brane duality and their tension quantization rule $2κ^2 T_2 T_5 = 2 πn$, the M-2 brane tension quantization $T_2 =\bigg({(2π)^2/2κ^2 m}\bigg)^{1/3}$, supersymmetry, perturbative gauge and gravitational anomaly cancellations, and the half-integral quan

F. Lizzi, N. E. Mavromatos, R. J. Szabo

We describe a dynamical worldsheet origin for the Lagrangian describing the low-energy dynamics of a system of parallel D-branes. We show how matrix-valued collective coordinate fields for the D-branes naturally arise as couplings of a worldsheet sigma-model, and that the quantum dynamics require that these couplings be mutually noncommutative. We show that

G. Amelino-Camelia, N. E. Mavromatos

Recent work on the action of T duality on Dirichlet-branes is generalized to the case in which the open string satisfies boundary conditions that are neither Neumann nor Dirichlet. This is achieved by implementing T duality as a canonical transformation of the $σ$-model path integral. A class of boundary interactions that violate conformal symmetry is found

N. Kim, Soo-Jong Rey

M(atrix) theory compactified on an orbifold ${\bf T}_9/{\bf Z}_2$ is studied. Via zero-brane parton scattering we find that each of the $2^9 = 512$ orbifold fixed points carry $-1/32$ units of zero-brane charge. The anomalous flux is cancelled by introducing a twisted sector consisting of 32 zero-branes that are spacetime supersymmetry singlets. These twiste

Juan Garcia-Bellido, Jaume Garriga, Xavier Montes

We show that a large class of two-field models of single-bubble open inflation do not lead to infinite open universes, as it was previously thought, but to an ensemble of very large but finite inflating `islands&#39;. The reason is that the quantum tunneling responsible for the nucleation of the bubble does not occur simultaneously along both field direction

R. Baier, M. Dirks, K. Redlich

The electromagnetic emissivity from QCD media away from equilibrium is studied in the framework of closed time path thermal field theory. For the dilepton rate a nonequilibrium mesonic medium is considered applying finite temperature perturbation theory for $π-ρ$ interactions. The dilepton rate is derived up to the order $g_ρ^2$. For hard photon production a

Jari Häkkinen, Markus Ringner

We study effects on the W mass measurements at LEP2 from non-perturbative interference effects in the fully hadronic decay channel. Based on a model for Bose-Einstein interference, which is in agreement with LEP1 data, we argue that there are no Bose-Einstein correlations between bosons coming from the different W&#39;s. For small reconnection probabilities

Giancarlo D&#39;Ambrosio, Jorge Portoles

We use the Vector formulation to evaluate vector and axial-vector exchange contributions to the O(p^4) weak Chiral Lagrangian. We recover in this framework the bulk of the contributions found previously by Ecker et al. in the antisymmetric formulation of vectors and axial-vectors, but new interesting features arise: i) most of our results are independent of

Dongsheng Du, Hongying Jin, Yadong Yang

With help of the recent developments in the heavy quarkonium physics, we reexamine the long distance(LD) effects in \Bsee dominantly from the charmonium resonances $J/Ψ$ and $Ψ^{\prime}$ through the decay chains $B\ra X_s J/Ψ(Ψ^{\prime}) \ra X_s e^+ e^-$. We find that the resonance to nonresonance interference are reduced substantially.

W. Buchmuller, M. Plumacher

Baryogenesis appears to require lepton number violation. This is naturally realized in extensions of the standard model containing right-handed neutrinos. We discuss the generation of a baryon asymmetry by the out-of-equilibrium decay of heavy Majorana neutrinos in these models, without and with supersymmetry. All relevant lepton number violating scattering

F. Cardarelli, S. Simula

The space-like elastic form factors of baryons containing a heavy quark are investigated within a light-front constituent quark model in the limit of infinite heavy-quark mass, adopting a gaussian-like ansatz for the three-quark wave function. The results obtained for the Isgur-Wise form factors corresponding both to a spin-0 and a spin-1 light spectator pai

Esteban Roulet

We study the effects of strong magnetic fields ($B> 10^{13}$~G) in the cross section for $ν_e n\to p e$ scattering in the presence of a degenerate electron background. This can be relevant for the $ν_e$ propagation in the proto-neutron star stage after supernovae collapse. We find that for field strengths $B> 10^{16}$~G$(E_ν/10$ MeV$)^2$ the $ν_e$ opacity is

M. Lüscher

The past few years have seen many interesting theoretical developments in lattice QCD. This talk (which is intended for non-experts) focuses on the problem of non-perturbative renormalization and the question of how precisely the continuum limit is reached. Progress in these areas is crucial in order to be able to compute quantities of phenomenological inter

Hoang Ngoc Long

A scalar sector of the 3 3 1 model with three Higgs triplets is considered. The mass spectrum, eigenstates and interactions of the Higgs and the SM gauge bosons are derived. We show that one of the neutral scalars can be identified with the standard model Higgs boson, and in the considered potential there is no mixing between scalars having VEV and ones with

Tamas S. Biro, Markus Feurstein, Harald Markum

We analyze the leading Lyapunov exponents of SU(2) Yang-Mills field configurations on the lattice which are initialized by quantum Monte Carlo simulations. We find that configurations in the strong coupling phase at finite temperature are substantially more chaotic than in deconfinement.

Marcelo E. Araujo, Patricio S. Letelier, Samuel R. Oliveira

We present a semi-analytical approach to the interaction of two (originally) Kerr black holes through a head-on collision process. An expression for the rate of emission of gravitational radiation is derived from an exact solution to the Einstein&#39;s field equations. The total amount of gravitational radiation emitted in the process is calculated and compa

Pierre Savaria

Solutions to the field equations of the Nonsymmetric Gravitational Theory with $g_[i0] = 0$ are obtained for the homogeneous, plane-symmetric, time-dependent case, both in vacuum and in the presence of a perfect fluid. Cosmological consequences include a dependence of the speed of light on its polarisation, as in a birefringent crystal.

H. Burton, R. B. Mann

We consider a Palatini variation on a generalized Einstein-Hilbert action. We find that the Hilbert constraint, that the connection equals the Christoffel symbol, arises only as a special case of this general action, while for particular values of the coefficients of this generalized action, the connection is completely unconstrained. We discuss the relation

L. Herrera, A. Di Prisco, J. L. Hernandez-Pastora, N. O. Santos

We obtain an expression for the active gravitational mass of a collapsing fluid distribution, which brings out the role of density inhomogeneity and local anisotropy in the fate of spherical collapse.

U. von der Goenna, D. Kramer

The well-known treatment of asymptotically flat vacuum fields is adapted to pure radiation fields. In this approach we find a natural normalization of the radiation null vector. The energy balance at null infinity shows that the mass loss results from a linear superposition of the pure and the gravitational radiation parts. By transformation to Bondi-Sachs c

Cristian F. Moukarzel, Nestor Parga

The complex-field zeros of the Random Energy Model are analytically determined. For T<T_c they are distributed in the whole complex plane with a density that decays very fast with the real component of H. For T>T_c a region is found which is free of zeros and is associated to the paramagnetic phase of the system. This region is separated from the former by a

Richard P. Sear

The phase behaviour of a single large semiflexible polymer immersed in a suspension of spherical particles is studied. All interactions are simple excluded volume interactions and the diameter of the spherical particles is an order of magnitude larger than the diameter of the polymer. The spherical particles induce a quite long ranged depletion attraction be

C. M. Newman, D. L. Stein

We present a combination of heuristic and rigorous arguments indicating that both the pure state structure and the overlap structure of realistic spin glasses should be relatively simple: in a large finite volume with coupling-independent boundary conditions, such as periodic, at most a pair of flip-related (or the appropriate number of symmetry-related in t

J. Zaanen

It will be attempted to present a coherent view on the current ideas regarding the origin of the stripe instability. Special emphasis will be put on the problem of how to combine the microscopic pictures, leaning on spin-charge topological aspects, with the notion of frustrated phase separation.

J. Rotyis, G. Vattay

Scaling properties of the BUX index are similar to those observed in other parts of the world. The main difference is that the traditional quantities like volatility, growth and autocorrelation of returns follows more closely the assumptions of the traditional stock market theory developed by Bachelier and by Black and Scholes.

Carlo Presilla, Ubaldo Tanbini

During a continuous measurement, quantum systems can be described by a stochastic Schrödinger equation which, in the appropriate limit, reproduces the von Neumann wave-function collapse. The average behavior on the ensemble of all measurement results is described by a master equation obtained from a general model of measurement apparatus consisting of an inf

V. V. Kuznetsov, A. K. Savchenko, D. R. Mace, E. H. Linfield

We study effects of Coulomb interactions between localised states in a potential barrier by measuring resonant-tunneling spectra with a small bias applied along the barrier. In the ohmic regime the conductance of 0.2um--gate lateral GaAs microstructures shows distinct peaks associated with individual localised states. However, when an electric field is appli

L. Biferale, G. Boffetta, A. Celani, A. Crisanti

An efficient method for the construction of a multiaffine process, with prescribed scaling exponents, is presented. At variance with the previous proposals, this method is sequential and therefore it is the natural candidate in numerical computations involving synthetic turbulence. The application to the realization of a realistic turbulent-like signal is di

F. Borgonovi, I. Guarneri, F. M. Izrailev, G. Casati

A quantum dynamical model of two interacting spins, with chaotic and regular components, is investigated using a finite two-particles symmetrized basis. Chaotic eigenstates give rise to an equilibrium occupation number distribution in close agreement with the Bose-Einstein distribution despite the small number of particles ($n=2$). However, the corresponding

M. Ipsen, F. Hynne, P. G. Soerensen

The paper discusses the use of amplitude equations to describe the spatio-temporal dynamics of a chemical reaction-diffusion system based on an Oregonator model of the Belousov-Zhabotinsky reaction. Sufficiently close to a supercritical Hopf bifurcation the reaction-diffusion equation can be approximated by a complex Ginzburg-Landau equation with parameters

G. F. Lewis, M. J. Irwin, P. C. Hewett, C. B. Foltz

We present both photometry and spectra of the individual images of the quadruple gravitational lens system Q2237+0305. Comparison of spectra obtained at two epochs, separated by $\sim~3\,$years, shows evidence for significant changes in the emission line to continuum ratio of the strong ultraviolet CIV~$λ$1549, CIII]~$λ$1909 and MgII~$λ$2798 lines. The short

Geraint F. Lewis, Kunegunda E. Belle

The physical nature of the material responsible for the high--velocity, broad-absorption line features seen in a small fraction of quasar spectra has been the subject of debate since their discovery. This has been especially compounded by the lack of observational probes of the absorbing region. In this paper we examine the role of ``microlenses&#39;&#39; in

S. Maddox

Spectroscopic observations for a new survey of 250 000 galaxy redshifts are underway, using the 2dF instrument at the AAT. The input galaxy catalogue and commissioning data are described. The first result from the preliminary data is a new estimate of the galaxy luminosity function at <z>=0.1.

Rosanne Di Stefano, Richard A. Scalzo

We propose and evaluate the feasibility of a new strategy to search for planets via microlensing observations. This new strategy is designed to detect planets in &#34;wide&#34; orbits, i.e., with orbital separation, a, greater than ~1.5 R_E. Planets in wide orbits may provide the dominant channel for the discovery of planets via microlensing, particularly lo

N. M. McClure-Griffiths, Simon Johnston, Daniel R. Stinebring, Luciano Nicastro

PSR B1259-63 is in a highly eccentric 3.4 yr orbit around the Be-star SS2883. The system is located in the direction of the Sagittarius-Carina spiral arm at a distance of $\sim$1.5 kpc. We have made scintillation observations of the pulsar far from periastron at 4.8 GHz and 8.4 GHz, determining the diffractive bandwidth, $Δν_{\rm d}$, and timescale, $Δt_{\rm

R. I. Hynes, P. F. L. Maxted

Multiple sets of synthetic spectra of OB-binary stars are used to test the suitability of disentangling for deriving accurate spectroscopic orbits. Given a set of spectra with broad phase coverage and sufficient total integration time (almost independent of the number of spectra), it appears that disentangling yields accurate and reliable semi-amplitudes of

P. N. Best, M. S. Longair, H. J. A. R&#34;ottgering

We present evidence that the 3CR radio galaxies at redshift one are already very massive, highly dynamically evolved galaxies, which lie at the heart of (proto--)cluster environments. Since nearby 3CR double radio sources are generally found in more isolated surroundings, the galactic environments of these galaxies must change dramatically with redshift. The

E. M. Puchnarewicz, K. O. Mason, A. Siemiginowska

We present UV spectroscopy of RE1034+396, taken with the Faint Object Spectrograph on the Hubble Space Telescope. With a spectral resolution of ~1-2A FWHM and a typical S/N of ~15 per diode, this is one of the first detailed UV spectra of an object in the narrow-line Seyfert 1 (NLS1) class. The spectrum probes the physics and kinematics of the high-ionizatio

Paolo Padoan, John Bally, Youssef Billawala, Mika Juvela

We compare the statistical properties of J=1-0 13CO spectra observed in the Perseus Molecular Cloud with synthetic J=1-0 13CO spectra from a 5 pc model cloud. The synthetic spectra are computed solving the non-LTE radiative transfer problem for a model cloud obtained as solutions of the 3-D magneto-hydrodynamic (MHD) equations in both the highly supersonic a

Bohdan Paczynski

The first micro-lensing event discovered towards the Small Magellanic Cloud by the MACHO collaboration (Alcock et al. 1997b) had a very long time scale, t_0 = 123 days. The EROS collaboration (Palanque-Delabrouille et al. 1997) discovered a 2.5% brightness variation with a period P = 5.1 days. The OGLE collaboration (Udalski et al. 1997) established that the

F. Combes

HI observations have revealed large gaseous extensions in interacting and merging systems. The interstellar gas is obviously dragged out in tidal tails during an encounter, and the percentage of HI in the tails increases with the merging stage. However, the opposite is true for the molecular gas, which is observed highly concentrated towards the nuclei of in

R. Fux

A new picture accounting for the dominant features in the observed l-V distribution of the Milky Way gas within the central few kpcs is proposed, based on symmetry-free and high resolution 3D N-body and SPH simulations.

Ivan R. King, Jay Anderson, Adrienne M. Cool, Giampaolo Piotto

Second-epoch HST observations of NGC 6397 have led to the measurement of proper motions accurate enough to separate the faintest cluster stars from the field, thus extending the luminosity function of this globular cluster far enough to approach the limit of hydrogen burning on the main sequence. We isolate a sample of 1385 main-sequence stars, from just bel

William Pardon, Mark Stern

Let $V$ be a complex projective variety with isolated singularities. Let the smooth part be given the metric induced by a projective imbedding. Then we develop the $L_2$ harmonic theory and construct a pure Hodge structure on the $L_2$-cohomology of $V$. If the dimension of $V$ is two, we put a cohomological Hodge structure on its complex of sheaves of $L_2$