December 1999 arXiv papers — page 13

Dennis Dieks

Modal interpretations of quantum mechanics assign definite properties to physical systems and specify single-time joint probabilities of these properties. We show that a natural extension, applying to properties at several times, can be given if a decoherence condition is satisfied. This extension defines "consistent histories" of modal properties. W

Toshiki Shimbori

The one-dimensional parabolic potential barrier dealt with in an earlier paper is re-examined from the point of view of operator methods, for the purpose of getting generalized Fock spaces.

Nguyen Tuan Anh

The basic assumptions and the general results of our bag model for nuclei are presented in detail. Nuclei are considered in a unified integration of the mean field theory and the MIT bag model

Nguyen Tuan Anh

We pursue research leading towards the nature of causality in the universe. We establish the equation of the universe's evolution from the universe-state function and its series expansion, in which causes and effects connect together to construct a linked chain of causality. And the equation of causality [1] is rederived. Therefrom, our theory informs th

Kestutis Staliunas

Noise power spectra in spatially extended dynamical systems are investigated, using as a model the Complex Ginzburg-Landau equation with a stochastic term. Analytical and numerical investigations show that the temporal noise spectra are of 1/f^a form, where a=2-D/2 with D the spatial dimension of the system. This suggests that nonequilibrium order-disorder p

Ilona Bednarek, Ryszard Manka

In this paper the equation of state of hot neutron matter is calculated. Involving the Oppenheimer-Volkov-Tolman equation global parameters of a neutron star at the finite temperature are obtained. The objective of our work was to study the influence of the temperature on the main parameters of a neutron star.

J. B. Elliott, A. S. Hirsch

Both simple and sophisticated models are frequently used in an attempt to understand how real nuclei breakup when subjected to large excitation energies, a process known as nuclear multifragmentation. Many of these models assume equilibriumthermodynamics and produce results often interpreted as evidence of a phase transition. This work examines one class of

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

A quantum statistical model of nuclear multifragmentation is proposed. The recurrence equation method used within the canonical ensemble makes the model solvable and transparent to physical assumptions and allows to get results without involving the Monte Carlo technique. The model exhibits the first order phase transition. Quantum statistics effects are cle

M. M. Pavan, R. A. Arndt, I. I Strakovsky, R. L. Workman

A new result for the nucleon sigma term from an updated pion-nucleon partial-wave and dispersion relation analysis of the Virginia Polytechnic Institute (now George Washington University) group is discussed. Using a method similar to that of Gasser, Leutwyler, Locher, and Sainio, we obtain Sigma=90 +/- 8 MeV (preliminary), in disagreement with the canonical

Palle E. T. Jorgensen

This paper is devoted to an approximation problem for operators in Hilbert space, that appears when one tries to study geometrically the cascade algorithm in wavelet theory. Let $ H $ be a Hilbert space, and let $ π$ be a representation of $ L^\infty(T) $ on $ H $. Let $ R $ be a positive operator in $ L^\infty(T) $ such that $ R(1)=1 $, where $ 1 $ denotes

Sergey Fomin

This is an exposition of some recent developments related to the object in the title, particularly the combinatorial computation of the (genus 0) Gromov-Witten invariants of the flag manifold and the quadratic algebra approach. The notes are largely based on my joint papers with S.Gelfand, A.N.Kirillov, and A.Postnikov. This is by no means an exhaustive surv

Ola Bratteli, David E. Evans, Palle E. T. Jorgensen

We study the harmonic analysis of the quadrature mirror filters coming from multiresolution wavelet analysis of compactly supported wavelets. It is known that those of these wavelets that come from third order polynomials are parametrized by the circle, and we compute that the corresponding filters generate irreducible mutually disjoint representations of of

Sergey Fomin, Andrei Zelevinsky

An introduction to total positivity (TP), with the emphasis on efficient TP criteria and parametrizations of TP matrices. Intended for general mathematical audience.

Palle E. T. Jorgensen, Steen Pedersen

We show that certain iteration systems lead to fractal measures admitting exact orthogonal harmonic analysis.

Thomas Britz, Sergey Fomin

A survey on the Greene-Kleitman correspondence, with complete proofs, many of which are new.

Sergey Fomin, Michael Shapiro

By a theorem of A.Björner, for every interval $[u,v]$ in the Bruhat order of a Coxeter group $W$, there exists a stratified space whose strata are labeled by the elements of $[u,v]$, adjacency is described by the Bruhat order, and each closed stratum (resp., the boundary of each stratum) has the homology of a ball (resp., of a sphere). Answering a question p

Alexei Borodin, Grigori Olshanski

We construct examples of nonnegative harmonic functions on certain graded graphs: the Young lattice and its generalizations. Such functions first emerged in harmonic analysis on the infinite symmetric group. Our method relies on multivariate interpolation polynomials associated with Schur's S and P functions and with Jack symmetric functions. As a by-pro

Zhongmin Shen, Jyh-Yang Wu

Two main theorems are proved in this paper. Theorem 1: There is a constant C(n, D) depending only on n and D such that for a closed Riemannian n-manifold satisfying Ric > -(n-1) and Diam < D, the ith bounded Betti number is bounded by C(n, D). Here the ith bounded Betti number is defined as the dimension of the image of the ith bounded cohomology in the ith

Siqi Fu, Emil J. Straube

This paper surveys the theory of compactness of the d-bar-Neumann problem. It also contains several results which improve upon what was previously known.

Hideo Mitsuhashi

We construct a subalgebra of the Hecke algebra of type A. This is a generalization of the group algebra of the alternating groups. All the equivalent classes of irreducible representations of the subalgebra and the q-analogue of the branching rule between symmetric groups and alternating groups is obtained.

Vadim E. Levit, Eugen Mandrescu

A square (0,1)-matrix X of order n > 0 is called fully indecomposable if there exists no integer k with 0 < k < n, such that X has a k by n-k zero submatrix. A stable set of a graph G is a subset of pairwise nonadjacent vertices. The stability number of G, denoted by $α(G)$, is the cardinality of a maximum stable set in G. A graph is called $α$-stable if its

S. Chanillo, D. Grieser, K. Kurata

This is a continuation of the paper &#39;Symmetry breaking and other phenomena in the optimization of eigenvalues for composite membranes&#39; by S. Chanillo, D. Grieser, M. Imai, K. Kurata, and I. Ohnishi. Again, we consider the following eigenvalue optimization problem: Given a bounded domain $Ω\subset\R^n$ and numbers $α\geq 0$, $A\in [0,|Ω|]$, find a sub

Volker Buchholz

This text is dedicated to the real Killing equation on 3-dimensional Weyl manifolds. Any manifold admitting a real Killing spinor of weight 0 satisfies the conditions of a Gauduchon-Tod geometry. Conversely, any simply connected Gauduchon-Tod geometry has a 2-dimensional space of solutions of the real Killing equation on the spinor bundle of weight 0.

Giovanna Carnovale

I continue the investigation of a q-analogue of the convolution on the line started in a joint work with Koornwinder and based on a formal definition due to Kempf and Majid. Two different ways of approximating functions by means of the convolution and convolution of delta functions are introduced. A new family of functions that forms an increasing chain of a

Thomas Friedrich

The aim of the present paper is the investigation of $Spin(9)$-structures on 16-dimensional manifolds from the point of view of topology as well as holonomy theory. First we construct several examples. Then we study the necessary topological conditions resulting from the existence of a $Spin(9)$-reduction of the frame bundle of a 16-dimensional compact manif

Roberto Emparan, Gary T. Horowitz, Robert C. Myers

We extend our recent discussion of four-dimensional black holes bound to a two-brane to include a negative cosmological constant on the brane. We find that for large masses, the solutions are precisely BTZ black holes on the brane, and BTZ `black strings&#39; in the bulk. For smaller masses, there are localized black holes which look like BTZ with correction

A. Peterman

The freedom in choosing finite renormalizations in quantum field theories (QFT) is characterized by a set of parameters $\{c_i \}, i = 1 ..., n >...$, which specify the renormalization prescriptions used for the calculation of physical quantities. For the sake of simplicity, the case of a single $c$ is selected and chosen mass-independent if masslessness is

G. Landi, F. Lizzi, R. J. Szabo

We describe how and to what extent the noncommutative two-torus can be approximated by a tower of finite-dimensional matrix geometries. The approximation is carried out for both irrational and rational deformation parameters by embedding the algebra of the noncommutative torus into an approximately finite algebra. The construction is a rigorous derivation of

Chiang-Mei Chen, Dmitri V. Gal&#39;tsov, Sergei A. Sharakin

A correspondence between the three-block truncated 11D supergravity and the 8D pure Einstein gravity with two commuting Killing symmetries is discussed. The Kaluza-Klein two-forms of the 6D theory obtained after dimensional reduction along the Killing orbits generate the four-form field of supergravity via an inverse dualization. Thus any solution to the vac

Gerhard Buchalla

We summarize both the study of CP violation with $K$ and $B$ mesons, as well as rare decays of kaons, emphasizing recent developments. The topics discussed include the unitarity triangle, $ε&#39;/ε$, $K\toπν\barν$ and other rare $K$ decays, T-odd asymmetries in kaon physics, theoretical aspects of CP violation in B decays, $B\to J/ΨK_S$, $B\toππ$, $B\toπK$ a

Maria Krawczyk, Andrzej Zembrzuski

The discussion on the production of prompt photons with pT of a few GeV in the tagged process ep -> e gamma X with small Q^2 (DIC process) at the HERA collider is presented. Photons produced in the forward (proton) direction are mainly originating from subprocesses involving interactions of the gluonic content of the exchanged photon. The large enhancement o

Yuri V. Kovchegov, Eugene Levin, Larry McLerran

We discuss particle production mechanisms for heavy ion collisions. We present an argument demonstrating how the fluctuations of the number of produced particles in a series of classical emissions can account for KNO scaling. We predict rapidity correlations in the particle production in the event by event analysis of heavy ion collisions on the rapidity sca

Gregory W. Anderson, Tomas Blazek

In an effort to develop tools for grand unified model building for the Lie group $E_6$, in this paper we present the computation of the Clebsch-Gordan coefficients for the product (100000) $\otimes$ (000010), where (100000) is the fundamental 27-dimensional representation of $E_6$ and (000010) is its charged conjugate. The results are presented in terms of t

M. Diehl, Th. Feldmann, P. Kroll, C. Vogt

We consider pion pair production in two-photon collisions, gamma* gamma -> pi+ pi-, at large photon virtuality Q^2 and center-of-mass energy \sqrt{s} in the hard-scattering picture. In the limit where s is large but s << Q^2 we derive an expression for the two-pion light-cone distribution in terms of the conventional pion distribution amplitudes. Our result

A. Kaidalov

A short summary of main results of theoretical talks presented at XXIX International Symposium on Multiparticle Dynamics is given.

D. Ebert, R. N. Faustov, V. O. Galkin

Exclusive semileptonic B decays to radially excited charmed mesons are investigated at the first order of the heavy quark expansion. The arising leading and subleading Isgur-Wise functions are calculated in the framework of the relativistic quark model. It is found that the 1/m_Q corrections play an important role and substantially modify results. An interes

S. Moch, J. A. M. Vermaseren

We present the analytic calculation of the Mellin moments of the structure functions F_2, F_3 and F_L in perturbative QCD up to second order corrections and in leading twist approximation. We calculate the 2-loop contributions to the anomalous dimensions of the singlet and non-singlet operator matrix elements and the 2-loop coefficient functions of F_2, F_3

Laurent Lellouch

The current status of lattice and dispersive bound calculations for exclusive semileptonic B decays is reviewed. Emphasis is placed on decays relevant for the measurement of the sides of the unitarity triangle determined by |V_{ub}| and |V_{cb}|.

D. Dutta, A. K. Mohanty, K. Kumar, R. K. Choudhury

The effect of baryon density on parton production processes of $gg\rightleftharpoons ggg$ and $gg\rightleftharpoons q{\bar q}$ is studied using full phase space distribution function and also with inclusion of quantum statistics i.e. Pauli blocking and Bose enhancement factors, in the case of both saturated and unsaturated quark gluon plasma. The rate for th

Eric Laenen

I present a short overview of the NLO QCD calculations available for deep-inelastic production of heavy quarks.

Fabio Benatti, Roberto Floreanini

Direct CP-violating effects in the neutral kaon system result in violations of certain Bell-like inequalities. The new experimental results on the determination of the phenomenological parameter epsilon&#39; allow to dismiss a large class of ``hidden variable&#39;&#39; alternatives to quantum mechanics.

Y. Koma, H. Suganuma, K. Amemiya, M. Fukushima

We study abelian dominance and monopole condensation for the quark confinement physics using the lattice QCD simulations in the MA gauge. These phenomena are closely related to the dual superconductor picture of the QCD vacuum, and enable us to construct the dual Ginzburg-Landau (DGL) theory as an useful effective theory of nonperturbative QCD. We then apply

A. Rusetsky

The talks delivered by M. Knecht, H. Neufeld, V.E. Lyubovitskij, A. Rusetsky and J. Soto during the session of the working group of electromagnetic corrections to hadronic processes at the Eight International Symposium MENU99, cover a wide range of problems. In particular, those include: construction of the effective Lagrangians that then are used for the ev

Jihn E. Kim, Bumseok Kyae, Hyun Min Lee

The effective gravitational interaction below the Planck scale in the Randall-Sundrum world is shown to be the Gauss-Bonnet term. In this theory we find that there exists another static solution with a positive bulk cosmological constant. Also, there exist solutions for positive visible sector cosmological constant, which are needed for a later Friedman-Robe

Wolfgang Bock, Maarten Golterman, Ka Chun Leung, Yigal Shamir

After an introduction in which we review the fundamental difficulty in constructing lattice chiral gauge theories, we summarize the analytic and numerical evidence that abelian lattice chiral gauge theories can be nonperturbatively constructed through the gauge-fixing approach. In addition, we indicate how we believe that the method may be extended to nonabe

M. N. Chernodub, E. -M. Ilgenfritz, A. Schiller

We study properties of Z-vortices in the crossover region of the 3D SU(2) Higgs model. Correlators of the vortex currents with gauge field energy and Higgs field squared (&#34;quantum vortex profile&#34;) reveal a structure that can be compared with a classical vortex. We define a core size and a penetration depth from the vortex profile. Z-vortices are foun

Werner Kerler

Normality of the Dirac operator is shown to be necessary for chiral properties. From the global chiral Ward identity, which in the continuum limit gives the index theorem, a sum rule results which constrains the spectrum. The Ginsparg-Wilson relation is to be restricted to its simple form and is a member of a set of spectral constraints. A family of alternat

Karl M. Ecklund

I report results in semileptonic decays of B mesons from the CLEO collaboration, with a focus on recent results. Results for exclusive reconstruction of B -> D* l nu, B -> D l nu and B -> rho l nu are given including the q^2 dependence of the form factors. These results are used to measure |V_cb| and |V_ub|. Two preliminary analyses using inclusive technique

Draza Markovic, Stuart Shapiro

We consider the effect of a positive cosmological constant on spherical gravitational collapse to a black hole for a few simple, analytic cases. We construct the complete Oppenheimer-Snyder-deSitter (OSdS) spacetime, the generalization of the Oppenheimer-Snyder solution for collapse from rest of a homogeneous dust ball in an exterior vacuum. In OSdS collapse

Benjamin J. Owen

Since the last Amaldi meeting in 1997 we have learned that the r-modes of rapidly rotating neutron stars are unstable to gravitational radiation reaction in astrophysically realistic conditions. Newborn neutron stars rotating more rapidly than about 100Hz may spin down to that frequency during up to one year after the supernova that gives them birth, emittin

P. Hajicek

This paper is an extended version of a talk at the conference Constrained Dynamics and Quantum Gravity QG99. It reviews some work on the quantum collapse of the spherically symmetric gravitating thin shell of zero rest mass. Recent results on Kuchař decomposition are applied. The constructed version of quantum mechanics is unitary, although the shell falls u

T. P. Singh, Cenalo Vaz

A sufficiently massive collapsing star will end its life as a spacetime singularity. The nature of the Hawking radiation emitted during collapse depends critically on whether the star&#39;s boundary conditions are such as would lead to the eventual formation of a black hole or, alternatively, to the formation of a naked singularity. This latter possibility i

X. Jaen, A. Balfagon

We are presenting an algorithm capable of simplifying tensor polynomials with indices when the building tensors have index symmetry properties. These properties include simple symmetry, cyclicity and those due to the presence of covariant derivatives. The algorithm is part of a Mathematica package called Tools of Tensor Calculus (TTC) [web address: http://ba

J. -F. Pascual-Sánchez

In this work, I develop an alternative explanation for the acceleration of the cosmic expansion, which seems to be a result of recent high redshift Supernova data. In the current interpretation, this cosmic acceleration is explained by including a positive cosmological constant term (or vacuum energy), in the standard Friedmann models. Instead, I will consid

X. Jaen, A. Balfagon

We use computational algorithms recently developed by us to study completely four index divergence free quadratic in Riemann tensor polynomials in GR. Some results are new and some other reproduce and/or correct known ones. The algorithms are part of a Mathematica package called Tools of Tensor Calculus (TTC)[web address: http://baldufa.upc.es/ttc]

Manfred Requardt

In the following we undertake to describe how macroscopic space-time (or rather, a microscopic protoform of it) is supposed to emerge as a superstructure of a web of lumps in a stochastic discrete network structure. As in preceding work (mentioned below), our analysis is based on the working philosophy that both physics and the corresponding mathematics have

Chia-Chen Chang, James M. Nester, Chiang-Mei Chen

Traditional approaches to energy-momentum localization led to reference frame dependent pseudotensors. The more modern idea is quasilocal energy-momentum. We take a Hamiltonian approach. The Hamiltonian boundary term gives not only the quasilocal values but also boundary conditions via the Hamiltonian variation boundary principle. Selecting a Hamiltonian bou

Michael Hess

A system is described that uses a mixed-level representation of (part of) meaning of natural language documents (based on standard Horn Clause Logic) and a variable-depth search strategy that distinguishes between the different levels of abstraction in the knowledge representation to locate specific passages in the documents. Mixed-level representations as w

T. Olson, A. P. Young

We present results of Monte Carlo simulations of the gauge glass model in three dimensions using exchange Monte Carlo. We show for the first time clear evidence of the vortex glass ordered phase at finite temperature. Using finite size scaling we obtain estimates for the correlation length exponent, nu = 1.39 +/- 0.20, the correlation function exponent, eta

S. V. Borisenko, M. S. Golden, S. Legner, T. Pichler

On the basis of angle-scanned photoemission data recorded using unpolarised radiation, with high (E,k) resolution, and an extremely dense sampling of k-space, we resolve the current controversy regarding the normal state Fermi surface (FS) in Bi_2Sr_2CaCu_2O_8 (Bi2212). The true picture is simple, self-consistent and robust: the FS is hole-like, with the for

Gianaurelio Cuniberti, Andrea Fechner, Maura Sassetti, Bernhard Kramer

We investigate the nonlinear ac transport through a quantum wire with an impurity in the presence of finite range electron-electron interactions. We discuss the influence of the spatial shape of the ac electric field onto transport properties of the system and find that the scaling behavior of the occupation probability of the sidebands depends on the range

G. Cristofano, G. Maiella, V. Marotta

We construct an effective conformal field theory by using a procedure which induces twisted boundary conditions for the fundamental scalar fields. That allows to describe a quantum Hall fluid at Jain hierarchical filling, nu=m/(2pm+1), in terms of one charged scalar field and m-1 neutral ones. Then the resulting algebra of the chiral primary fields is U(1)xW

B. Schmittmann, H. K. Janssen, U. C. Taeuber, R. K. P. Zia

It has recently been suggested that the driven lattice gas should be described by a novel field theory in the limit of infinite drive. We review the original and the new field theory, invoking several well-documented key features of the microscopics. Since the new field theory fails to reproduce these characteristics, we argue that it cannot serve as a viabl

M. Konczykowski, C. J. van der Beek, M. V. Indenbom, E. Zeldov

The angular dependence of the first-order phase transition (FOT) in the vortex lattice in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ crystals was investigated by a low frequency AC shielding technique (with the AC field $\parallel c$), in which the static-field component parallel to $c$- ($H_{\perp}$) was varied with the in-plane field $H_{\parallel}$ held constant.

M. Konczykowski, C. J. van der Beek, S. Colson, M. V. Indenbom

We identify a new regime of decay of the irreversible magnetization in clean Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ crystals, at induction values close to the ``second peak field&#39;&#39; at which the bulk critical current density steeply increases. A time window is identified during which the decay of the induction is controlled by the slow propagation of the p

I. V. Stasyuk, O. V. Velychko

The four-state model is proposed for description of phase transition in ferroelectric crystals of DMAGaS and DMAAlS type. Thermodynamical functions of the model are obtained in the mean field approximation. The phase transition between paraelectric and ferroelectric phases is investigated. It is established that order of the phase transitions depends on rela

C. J. van der Beek, S. Colson, M. Konczykowski, M. V. Indenbom

Time resolved magneto-optical images show hysteresis associated with the transition at the so-called ``second magnetization peak&#39;&#39; at B_sp in single-crystalline Bi_2Sr_2CaCu_2O_8+d. By rapid quenching of the high-field phase, it can be made to persist metastably in the sample down to fields that are nearly half B_sp.

J. Bergenholtz, M. Fuchs, Th. Voigtmann

Within the framework of the mode coupling theory (MCT) of structural relaxation, mechanisms and properties of non-ergodicity transitions in rather dilute suspensions of colloidal particles characterized by strong short-ranged attractions are studied. Results building on the virial expansion for particles with hard cores and interacting via an attractive squa

A. Erbe, G. Corso, H. Krommer, A. Kraus

Nanomechanical resonators, machined out of Silicon-on-Insulator wafers, are operated in the nonlinear regime to investigate higher-order mechanical mixing at radio frequencies, relevant to signal processing and nonlinear dynamics on nanometer scales. Driven by two neighboring frequencies the resonators generate rich power spectra exhibiting a multitude of sa

F. Schautz, H. -J. Flad

In our previous publication we have mistakenly claimed that the applicability of the Hellmann-Feynman theorem in fixed-node quantum Monte Carlo calculations is not subject to the manner how the nodal boundary depends on an external parameter. This statement is not correct in general, except where the Hellmann-Feynman force is calculated for a nodal boundary

C. J. van der Beek, S. Colson, M. V. Indenbom, M. Konczykowski

Time-resolved local induction measurements near to the vortex lattice order-disorder transition in optimally doped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+δ}$ single crystals shows that the high-field, disordered phase can be quenched to fields as low as half the transition field. Over an important range of fields, the electrodynamical behavior of the vortex system

N. Destainville, M. Widom, R. Mosseri, F. Bailly

Two-dimensional random tilings of rhombi can be seen as projections of two-dimensional membranes embedded in hypercubic lattices of higher dimensional spaces. Here, we consider tilings projected from a $D$-dimensional space. We study the limiting case, when the quantity $D$, and therefore the number of different species of tiles, become large. We had previou

Kestutis Staliunas

A technique for vortex creation in trapped Bose-Einstein condensates is suggested: Vortices can be excited at the edge of a condensate and guided to the center by a laser beam moving along a spiral trajectory. Numerical simulations demonstrate the suggested technique. Parameter ranges for the method are given. Computer animations illustrate the dynamics of t

Beat Ammon, Masatoshi Imada

We investigate doping of a two-orbital chain with mobile $S=1/2$ fermions as a valid model for $\rm Y_{2-x}Ca_xBaNiO_5$. The S=1 spins are stabilized by strong, ferromagnetic (fm) Hund&#39;s rule couplings. We calculate correlation functions and thermodynamic quantities by DMRG methods and find a new hierarchy of energy scales in the spin sector upon doping.

Takashi Yamamoto, Yasuhiro Saiga, Mitsuhiro Arikawa, Yoshio Kuramoto

The dynamical structure factor $S(q,ω)$ of the SU(K) (K=2,3,4) Haldane-Shastry model is derived exactly at zero temperature for arbitrary size of the system. The result is interpreted in terms of free quasi-particles which are generalization of spinons in the SU(2) case; the excited states relevant to $S(q,ω)$ consist of K quasi-particles each of which is ch

Chetan Nayak

We show that slave particles are always confined in U(1) gauge theories of interacting electron systems. Consequently, the low-lying degrees of freedom are different from the slave particles. This is done by constructing a dual formulation of the slave-particle representation in which the no-double occupany constraint becomes linear and, hence, soluble. Spin

B. Barbiellini, M. Hakala, R. M. Nieminen, M. J. Puska

We present first-principles approaches based on density functional theory for calculating positron states and annihilation characteristics in condensed matter. The treatment of the electron-positron correlation effects (the enhancement of the electron density at the positron with respect to mean-field density) is shown to play a crucial role when calculating

D. Pazo, I. P. Marino, V. Perez-Munuzuri, V. Perez-Villar

Phase synchronization is shown to occur between opposite cells of a ring consisting of chaotic Lorenz oscillators coupled unidirectionally through driving. As the coupling strength is diminished, full phase synchronization cannot be achieved due to random generation of phase jumps. The brownian dynamics underlying this process is studied in terms of a stocha

P. D. Ditlevsen, P. Giuliani

In a helical flow there is a subrange of the inertial range in which there is a cascade of both energy and helicity. In this range the scaling exponents associated with the cascade of helicity can be defined. These scaling exponents are calculated from a simulation of the GOY shell model. The scaling exponents for even moments are associated with the scaling

Holger Schanz, Uzy Smilansky

We present the first quantum system where Anderson localization is completely described within periodic-orbit theory. The model is a quantum graph analogous to an a-periodic Kronig-Penney model in one dimension. The exact expression for the probability to return of an initially localized state is computed in terms of classical trajectories. It saturates to a

O. V. Verkhodanov, S. A. Trushkin, H. Andernach

The authors describe the largest existing publicly accessible radio source database CATS (``astrophysical CATalogues Supporting system&#39;&#39;; http://cats.sao.ru). CATS contains more than 300 catalogues of objects detected in different (but mostly radio) wavelength ranges. These include catalogues from the largest existing surveys, like NVSS, FIRST, WENSS

O. V. Verkhodanov, H. Andernach, N. V. Verkhodanova

We describe a method to construct continuum spectra for radio sources on the basis of entries from various source catalogues in comparatively large error boxes around a given sky position. Sources from the UTR-2 catalogue (Braude et al. 1978--1994), observed at decametric wavelengths (10--25 MHz) with an antenna beam of about 40$&#39;$, were cross-identified

Dipak Munshi, Bhuvnesh Jain

Weak lensing surveys are expected to provide direct measurements of the statistics of the projected dark matter distribution. Most analytical studies of weak lensing statistics have been limited to quasilinear scales as they relied on perturbative calculations. On the other hand, observational surveys are likely to probe angular scales less than 10 arcminute

Martin Kerscher

Methods for the statistical characterization of the large-scale structure in the Universe will be the main topic of the present text. The focus is on geometrical methods, mainly Minkowski functionals and the J-function. Their relations to standard methods used in cosmology and spatial statistics and their application to cosmological datasets will be discusse

Thibaut Lery, Adam Frank

MHD jet equilibria that depend on source properties are obtained using a simplified model for stationary, axisymmetric and rotating magnetized outflows. The present rotation laws are more complex than previously considered and include a Keplerian disc. The ensuing jets have a dense, current-carrying central core surrounded by an outer collar with a return cu

Peter W. Gorham, William M. Folkner, Gary H. Blackwood

We present the enabling concept and technology for a dual spacecraft formation-flying optical interferometer, to be launched into a deep space orbit as Space Technology 3. The combiner spacecraft makes use of a nested cat&#39;s eye delay line configuration that minimizes wavefront distortion and stores 20 m of optical pathlength in a package of \sim 1.5 m le

J. Greiner

Microquasars are binary systems in our Galaxy which sporadically eject matter at relativistic speeds along bipolar jets. While phenomenologically similar to quasars, their vicinity allows much more in-depth studies. I review the observational aspects of microquasars, in particular the new developments on the interplay between accretion disk instabilities and

J. Darling, R. Giovanelli

We report the discovery of 11 OH megamasers and one OH absorber, along with upper limits on the OH luminosity of 53 other luminous infrared galaxies at z > 0.1. The new megamasers show a wide range of spectral properties, but are consistent with the extant set of 55 previously reported objects, 8 of which have z > 0.1. The new OH detections are the prelimina

Letizia Stanghellini

Planetary Nebulae (PNe) have been used satisfactory to test the effects of stellar evolution on the Galactic chemical environment. Moreover, a link exists between nebular morphology and stellar populations and evolution. We present the latest results on Galactic PN morphology, and an extension to a distance unbiased and homogeneous sample of Large Magellanic

James S. Graber

Gamma-ray bursts (GRBs) are still an enigma. In particular the central engine, the total energy, and the very narrow distribution of peak energies challenge model builders. Motivated by recent theoretical developments (string theory, quantum gravity, critical collapse), which suggest that complete gravitational collapse can occur without singularities or eve

Mateusz Ruszkowski, Andrew C. Fabian

The fluorescent iron K$α$ emission line profile provides an excellent probe of the innermost regions of active galactic nuclei. Fe XXV and Fe XXVI in diffuse plasma above the accretion disc can affect the X-ray spectrum by iron K$α$ resonant absorption. This in turn can influence the interpretation of the data and the estimation of the accretion disc and bla

Richard C. Henry

I have derived the Kretschmann scalar for a general black hole of mass m, angular momentum per unit mass a, and electric charge Q. The Kretschmann scalar gives the amount of curvature of spacetime, as a function of position near (and within) a black hole. This allows one to display the &#34;appearance&#34; of the black hole itself, whether the black hole is

Takashi Hamana, Toshifumi Futamase

The gravitational lensing magnification or demagnification due to large-scale structures induces a scatter in peak magnitudes of high redshift type Ia supernovae (SNe Ia). The amplitude of the lensing dispersion strongly depends on that of density fluctuations characterized by the $σ_8$ parameter. Therefore the value of $σ_8$ is constrained by measuring the

G. Fabbiano

Galaxies are key objects for the study of cosmology, the life cycle of matter, and stellar evolution. X-ray observations have given us a new key window into these building blocks of the Universe, that allows us to investigate their hot gaseous component. While significant advances in our knowledge are expected from Chandra and XMM, there is a number of funda

James S. Graber

Gamma-ray bursts are still a puzzle. In particular, the central engine, the total energy and the very narrow distribution of peak energies challenge model builders. We consider here an extreme model of gamma-ray bursts based on highly red- and blue-shifted positron annihilation radiation. The burst emerges from inside the red hole created by the complete gra

Robin H. D. Corbet, Andrew G. Peele

We present the results of Rossi X-ray Timing Explorer observations of the Be star X-ray binary system RX J0812.4-3114. A light curve obtained with the RXTE All-Sky Monitor shows that the source is currently in an active state with outbursts occurring at approximately 80 day intervals. The source underwent a transition from an inactive state to this regular o

David Marsden, Richard Lingenfelter, Richard Rothschild, James Higdon

Soft gamma-ray repeaters (SGRs) and anomalous x-ray pulsars (AXPs) are young (<100 kyr), radio-quiet, x-ray pulsars which have been rapidly spun-down to slow spin periods clustered at 5-12 s. Nearly all of these unusual pulsars also appear to be associated with supernova shell remnants (SNRs) with typical ages <20 kyr. If the unusual properties of SGRs and A

B. E. J. Pagel, G. Tautvaisiene

We try to understand the s- and r-process elements vs Ti/Fe plots derived by Jehin et al. (1999) for mildly metal-poor stars within the framework of the analytical semi-empirical models for these elements by Pagel & Tautvaisiene (1995, 1997). Jehin et al. distinguished two Pop II subgroups: IIa with alpha/Fe and s-elements/Fe increasing together, which they

Sergei Y. Sazonov, Rashid A. Sunyaev

Compton scattering of low-frequency radiation by an isotropic distribution of (i) mildly and (ii) ultra relativistic electrons is considered. It is shown that the ensemble-averaged differential cross-section in this case is noticeably different from the Rayleigh phase function. The scattering by an ensemble of ultra-relativistic electrons obeys the law p=1-c

W. Collmar, V. Schoenfelder, A. W. Strong, H. Bloemen

We use all COMPTEL data from the beginning of the CGRO mission (April &#39;91) up to the end of CGRO Cycle 6 (November &#39;97) to carry out all-sky point source analyses in the four standard COMPTEL energy bands for different time periods. We apply our standard maximum-likelihood method to generate all-sky significance and flux maps for point sources by sub