March 1999 arXiv papers — page 12

G. Nelemans, S. F. Portegies Zwart, F. Verbunt

Double white dwarfs could be important sources for space based gravitational wave detectors like OMEGA and LISA. We use population synthesis to predict the current population of double white dwarfs in the Galaxy and the gravitational waves produced by this population. We simulate a detailed power spectrum for an observation with an integration time of 10^6 s

Niraj Upadhyay, Patrick Das Gupta, R. P. Saxena

Incorporating a realistic model for accretion of ultra-relativistic particles by primordial blackholes (PBHs), we study the evolution of an Einstein-de Sitter universe consisting of PBHs embedded in a thermal bath from the epoch $\sim 10^{-33}$ sec to $\sim 5\times 10^{-9}$ sec. In this paper we use Barrow et al's ansatz to model blackhole evaporation in

Somnath Bharadwaj, A. K. Gupta, T. R. Seshadri

We have carried out a multi-fractal analysis of the distribution of galaxies in the three Northern slices of the Las Campanas Redshift Survey. Our method takes into account the selection effects and the complicated geometry of the survey. In this analysis we have studied the scaling properties of the distribution of galaxies on length scales from $20 h^{-1}

Aiichi Iwazaki

We indicate a possible mechanism of generating gamma ray bursts. They are generated by a collision between an axionic boson star and a neutron star. The axionic boson star can dissipates its whole energy $10^{50}$ erg in the magnetized conducting medium of the neutron star. This dissipation arises only around envelope of the neutron star so that a fire ball

C. C. Dudley

New moderate-resolution mid-infrared spectroscopy at 10 micron of 27 infrared galaxies is presented. The galaxies have been chosen from three 60 micron selected and one 12 micron selected complete flux-limited catalogs of galaxies; 17 of these sources have L_IR(8--1000 micron) >= 5 times 10^11 L_sun. A high-resolution spectrum of the source Arp 299B1 is also

A. T. Lee, P. Ade, A. Balbi, J. Bock

We describe the MAXIMA experiment, a balloon-borne measurement designed to map temperature anisotropy in the Cosmic Microwave Background (CMB) over a wide range of angular scales (multipole range 80 < l < 800). The experiment consists of a 1.3 m diameter off-axis Gregorian telescope and a receiver with a 16 element array of bolometers cooled to 100 mK. The f

Andrew H. Jaffe, Eric Gawiser, Douglas Finkbeiner, Joanne C. Baker

The Wavelength-Oriented Microwave Background Analysis Team (WOMBAT) is constructing microwave maps which will be more realistic than previous simulations. Our foreground models represent a considerable improvement: where spatial templates are available for a given foreground, we predict the flux and spectral index of that component at each place on the sky a

R. Shvidkoy

Let X be a closed subspace of a Banach space Y and J be the inclusion map. We say that the pair (X,Y) has the Daugavet property if for every rank one bounded linear operator T from X to Y the following equality \|J+T\|=1+\|T\| holds. A new characterization of the Daugavet property in terms of weak open sets is given. It is shown that the operators not fixing

T. V. Shahbazyan, M. E. Raikh, Z. V. Vardeny

We study theoretically the cooperative light emission from a system of $N\gg 1$ classical oscillators confined within a volume with spatial scale, $L$, much smaller than the radiation wavelength, $λ_0=2πc/ω_0$. We assume that the oscillators frequencies are randomly distributed around a central frequency, $ω_0$, with some characteristic width, $Ω\llω_0$. In

C. Mueller, E. Perkins

It is well known that, starting with finite mass, the super-Brownian motion dies out in finite time. The goal of this article is to show that with some additional work, one can prove finite time die-out for two types of systems of stochastic differential equations on the lattice Z^d. Our first system involves the heat equation on the lattice Z^d, with a nonl

I. Jack, D. R. T. Jones

We explore a more general class of soft supersymmetry-breaking masses and interactions than that usually considered, both in general and in the MSSM context, where our results for the one-loop $β$-functions correct some errors in the literature. We identify a new class of one-loop finite supersymmetric theories.

Ashkan Alavi-Harati

We present a branching ratio measurement for the beta decay of neutral Cascade hyperon to a positive Sigma, electron and neutrino. Data were collected during 1997 with the KTeV detector at Fermilab. We used the principal decay mode, Cascade to a Lambda and a neutral pion, as the flux normalization mode. The status of the measurement of the ratio of the axial

C. de Calan, F. S. Nogueira

We consider the scaling behavior in the critical domain of superconductors at zero external magnetic field. The first part of the paper is concerned with the Ginzburg-Landau model in the zero magnetic field Meissner phase. We discuss the scaling behavior of the superfluid density and we give an alternative proof of Josephson&#39;s relation for a charged supe

D. Becirevic, Ph. Boucaud, J. P. Leroy, J. Micheli

We study the flavorless gluon propagator in the Landau gauge from high statistics lattice calculations. Hypercubic artifacts are efficiently eliminated by taking the $\sum p_μ^4 \to 0$ limit. The propagator is fitted to the three-loops perturbative formula in an energy window ranging form $\sim$ 2.5 GeV up to $\sim$ 5.5 GeV. $α_s$ is extracted from the best

V. V. Gafiychuk, I. A. Lubashevsky, Yu. L. Klimontovich

We propose a model for a market which structure is of the tree form. Each branch of the tree is composed by identical firms, its root (the branch of the first level) is formed by the firms producing raw material, and the branches of the last level are the retail outlets. The branching points (tree nodes) are micromarkets for firms forming branches connected

P. Wagner, J. Richert, V. A. Karnaukhov, H. Oeschler

We use a binary sequential decay model in order to describe the fragmentation of a nucleus induced by the high energy collisions of protons with Au nuclei. Overall agreement between measured and calculated physical observables is obtained. We evaluate and analyse the decay times obtained with two different parametrisations of the decay rates and discuss the

G. W. Semenoff, K. Zarembo

We examine the possibility that gauge field configurations on stacks of parallel Dp branes support topological solitons. We give an exhaustive list of possible soliton charges for p<7. We also discuss how configurations carrying the soliton charges can be constructed from intersecting branes.

Xiao-Guang Wang, Hong-Chen Fu

We introduce excited binomial states and excited negative binomial states of the radiation field by repeated application of the photon creation operator on binomial states and negative binomial states. They reduce to Fock states and excited coherent states in certain limits and can be viewed as intermediate states between Fock states and coherent states. We

Frithjof Karsch

We discuss the critical behaviour of strongly interacting matter close to the QCD phase transition. Emphasis is put on a presentation of results from lattice calculations that illustrate deconfining as well as chiral symmetry restoring features of the phase transition. We show that both transitions coincide in QCD while they fall apart in an SU(3) gauge theo

J. Engels, O. Kaczmarek, F. Karsch, E. Laermann

We discuss the thermodynamics of gluons in the background of static quark sources. In order to do so we formulate the quenched limit of QCD at non-zero baryon number. A first numerical analysis of this system shows that it undergoes a smooth deconfining transition. We find evidence for a region of coexisting phases that becomes broader with increasing baryon

I. V. Bargatin, B. A. Grishanin, V. N. Zadkov

Effectiveness of using laser field to produce entanglement between two dipole-interacting identical two-level atoms is considered in detail. The entanglement is achieved by driving the system with a carefully designed laser pulse transferring the system&#39;s population to one of the maximally entangled Dicke states in a way analogous to population inversion

Bom Soo Kim, Hyuk-jae Lee, Jae Hyung Yee

We have constructed nonrelativistic fermion and scalar field theories coupled to a Maxwell-Chern-Simons gauge field which admit static multi-vortex solutions. This is achieved by introducing a magnetic coupling term in addition to the usual minimal coupling.

Masaru Onoda, Ikuo Ichinose, Tetsuo Matsui

We calculate the spin-gap effect on dc resistivity in the t-J model of high-$T_{\rm c}$ cuprates by using the Ginzburg-Landau theory coupled with a gauge field as its effective field theory to get $ρ(T) \propto T \{1-c\:(T^* -T)^d \}$, where $T^*$ is the spin-gap onset temperature. By taking the compactness of massive gauge field into account, the exponent $

H. Ahmedov, O. F. Dayi

A group theoretical understanding of the two dimensional fractional supersymmetry is given in terms of the quantum Poincare group at roots of unity. The fractional supersymmetry algebra and the quantum group dual to it are presented and the pseudo-unitary, irreducible representations of them are obtained. The matrix elements of these representations are expl

G. Bimonte, D. Iniguez, A. Tarancon, C. L. Ullod

We present here a new MC study of ISB at finite temperature in a $Z_2\times Z_2$ $λϕ^4$ model in four dimensions. The results of our simulations, even if not conclusive, are favourable to ISB. Detection of the effect required measuring some critical couplings with six-digits precision, a level of accuracy that could be achieved only by a careful use of FSS t

M. Pudlak, V. A. Osipov

The vortex-like solutions are studied in the framework of the gauge model of disclinations in elastic continuum. A complete set of model equations with disclination driven dislocations taken into account is considered. Within the linear approximation an exact solution for a low-angle wedge disclination is found to be independent from the coupling constants o

E. Gozzi, M. Regini

In this paper we continue the study of the path-integral formulation of classical mechanics and in particular we better clarify, with respect to previous papers, the geometrical meaning of the variables entering this formulation. With respect to the first paper with the same title, we {\it correct} here the set of transformations for the auxiliary variables

R. Nolty

A preliminary analysis is presented of low-energy ($\bar{E_\nu} \sim 4 GeV$) neutrino interactions observed by the MACRO detector. These include neutrino interactions in the detector, as well as upgoing neutrino-induced muons that stop in the detector. At these energies, essentially all observed interactions can be attributed to atmospheric neutrinos. A larg

Osamu Abe

We analytically and numerically investigate the &#39;t Hooft-Bergknoff-Eller equations, the lowest order mesonic Light-Front Tamm-Dancoff equations for U(N_C) and SU(N_C) gauge theories. We find the wavefunction can be well approximated by new basis functions and obtain an analytic formula for the mass of the lightest bound state. Its value is consistent wit

866 Collaboration

Charged kaon production has been measured in Si+Al and Si+Au collisions at 14.6 A GeV/c, and Au+Au collisions at 11.1 A GeV/c by Experiments 859 and 866 (the E--802 Collaboration) at the BNL AGS. Invariant transverse mass spectra and rapidity distributions for both K+ and K- are presented. The centrality dependence of rapidity-integrated kaon yields is studi

Antonio Masiero, Hitoshi Murayama

The possible supersymmetric contribution to ε&#39;/εhas been generally regarded small in the literature. We point out, however, that this is a result based on specific assumptions, such as universal scalar mass, and in general needs not to be true. Based on a general situation, (1) hierarchical quark Yukawa matrices protected by flavor symmetry, (2) generic

SDSS Collaboration, X. Fan

We present photometric and spectroscopic observations of 15 high-redshift quasars (z > 3.6) discovered from ~140 deg^2 of five-color (u&#39;g&#39;r&#39;i&#39;z&#39;) imaging data taken by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. The quasars are selected by their distinctive colors in SDSS multicolor space. Four of the quasars have

Mirjam Cvetic, Steven S. Gubser

We determine the thermodynamic stability conditions for near-extreme rotating D3, M5, and M2-branes with multiple angular momenta. Critical exponents near the boundary of stability are discussed and compared with a naive field theory model. From a partially numerical computation we conclude that outside the boundary of stability, the angular momentum density

Gary Felder, Lev Kofman, Andrei Linde

We study inflationary models in which the effective potential of the inflaton field does not have a minimum, but rather gradually decreases at large $ϕ$. In such models the inflaton field does not oscillate after inflation, and its effective mass becomes vanishingly small, so the standard theory of reheating based on the decay of the oscillating inflaton fie

Seth Lloyd

Entanglement of quantum variables is usually thought to be a prerequisite for obtaining quantum speed-ups of information processing tasks such as searching databases. This paper presents methods for quantum search that give a speed-up over classical methods, but that do not require entanglement. These methods rely instead on interference to provide a speed-u

Ron A. Nemirovsky, Amit Ben-Kish, Moshe Shuker, Amiram Ron

We study the effect of neutral atoms on the dynamics of a capillary discharge Z-pinch, in a regime for which a large soft-x-ray amplification has been demonstrated. We extended the commonly used one-fluid magneto-hydrodynamics (MHD) model by separating out the neutral atoms as a second fluid. Numerical calculations using this extended model yield new predict

Tom Ostoma, Mike Trushyk

We use ElectroMagnetic Quantum Gravity (EMQG) to provide a simple physical model of the Lense-Thirring effect on the earth. The Lense-Thirring effect is a tiny perturbation of the motion of a free-falling particle near a massive rotating object, first calculated by the physicists J. Lense and H. Thirring in 1918 using general relativity. The Lense-Thirring e

Claus O. Wilke, Thomas Martinetz

The idea of adaptive walks on fitness landscapes as a means of studying evolutionary processes on large time scales is extended to fitness landscapes that are slowly changing over time. The influence of ruggedness and of the amount of static fitness contributions are investigated for model landscapes derived from Kauffman&#39;s $NK$ landscapes. Depending on

Igor P. Omelyan

A new approach is developed to integrate numerically the equations of motion for systems of interacting rigid polyatomic molecules. With the aid of a leapfrog framework, we directly involve principal angular velocities into the integration, whereas orientational positions are expressed in terms of either principal axes or quaternions. As a result, the rigidn

J. J. Garcia-Ripoll, V. M. Perez-Garcia, P. Torres

We study an example of exact parametric resonance in a extended system ruled by nonlinear partial differential equations of nonlinear Schrödinger type. It is also conjectured how related models not exactly solvable should behave in the same way. The results have applicability in recent experiments in Bose-Einstein condensation and to classical problems in No

R. Alzetta, G. Liberti, G. Preparata

We present a few simple observations on the occurrence of $π$-condensation in Nuclei, aimed at clarifying the nature of the $π$-condensation implied by the coherent nuclear $π$-N-$Δ$ interaction, proposed in 1990 to explain the puzzling emergence of the Shell-Model. We show that such condensation is totally unrelated to the one proposed by A. B. Migdal at th

S. De Bievre, J. V. Pule

We study the quantum mechanical motion of a charged particle moving in a half plane (x>0) subject to a uniform constant magnetic field B directed along the z-axis and to an arbitrary impurity potential W_B, assumed to be weak in the sense that ||W_B||_\infty < δB, for some δsmall enough. We show rigorously a phenomenon pointed out by Halperin in his work on

C. P. Boyer, J. C. Hurtubise, R. J. Milgram

Let X be a smooth algebraic variety on which a solvable Lie group acts freely on a dense open orbit. Such varieties include generalized flag varieties, toric varieties, Bott-Samelson varieties, and many spherical varieties, as well as equivariant blow-ups of these. We prove that the space of based holomorphic maps from the Riemann sphere to X approximates in

Franz-Viktor Kuhlmann

We prove that every place of an algebraic function field F|K of arbitrary characteristic admits local uniformization in a finite extension F&#39; of F. We show that F&#39;|F can be chosen to be normal. If K is perfect and P is of rank 1, then alternatively, F&#39; can be obtained from F by at most two Galois extensions; if in addition P is zero-dimensional,

Feng Xu

Some mathematical questions relating to Coset Conformal Field Theories (CFT) are considered in the framework of Algebraic Quantum Field Theory as developed previously by us. We consider the issue of fixed point resolution in the diagonal coset of type A, and show how to decompose reducible representations into irreducibles. We show the corresponding coset CF

I. P. Goulden, D. M. Jackson

We consider the determination of the number $c_k(α)$ of ordered factorisations of an arbitrary permutation on n symbols, with cycle distribution $α$, into k-cycles such that the factorisations have minimal length and such that the group generated by the factors acts transitively on the n symbols. The case k=2 corresponds to the celebrated result of Hurwitz o

David P. Robbins

There is a theory of continued fractions for Laurent series in x^{-1} with coefficients in a field F. This theory bears a close analogy with classical continued fractions for real numbers with Laurent series playing the role of real numbers and the sum of the terms of non-negative degree in x playing the role of the integral part. In this paper we survey the

K. R. Goodearl

This paper is partly a report on current knowledge concerning the structure of (generic) quantized coordinate rings and their prime spectra, and partly propaganda in support of the conjecture that since these algebras share many common properties, there must be a common basis on which to treat them. The first part of the paper is expository. We survey a numb

H. Ahmedov, I. H. Duru

q-Neumann function of integer order N_n(x,q) is obtained and some of its properties are given. q-Psi function which is used in deriving N_n(x,q) is also introduced and some of its properties are presented.

Dimitrios I. Dais, Christian Haase, G&#34;unter M. Ziegler

It is known that the underlying spaces of all abelian quotient singularities which are embeddable as complete intersections of hypersurfaces in an affine space can be overall resolved by means of projective torus-equivariant crepant birational morphisms in all dimensions. In the present paper we extend this result to the entire class of toric l.c.i.-singular

Claudio A. Scrucca, Marco Serone

We derive the general form of the anomaly for chiral spinors and self-dual antisymmetric tensors living on D-brane and O-plane interesections, using both path-integral and index theorem methods. We then show that the anomalous couplings to RR forms of D-branes and O-planes in a general background are precisely those required to cancel these anomalies through

Andre Lukas, Burt A. Ovrut, Daniel Waldram

We construct vacua of heterotic M-theory with general gauge bundles and five-branes. Some aspects of the resulting low-energy effective theories are discussed.

W. A. Sabra

Electrically charged solutions breaking half of the supersymmetry in Anti-De Sitter four dimensional N=2 supergravity coupled to vector supermultiplets are constructed. These static black holes live in an asymptotic $AdS_4$ space-time. The Killing spinor, i. e., the spinor for supersymmetry variation is explicitly constructed for these solutions.

Andreas Recknagel, Volker Schomerus

D-branes in curved backgrounds can be treated with techniques of boundary conformal field theory. We discuss the influence of scalar condensates on such branes, i.e. perturbations of boundary conditions by marginal boundary operators. A general criterion is presented that guarantees a boundary perturbation to be truly marginal in all orders of perturbation t

N. J. MacKay

We investigate the integrability of the SO(N) principal chiral model on a half-line, and find that mixed Dirichlet/Neumann boundary conditions (as well as pure Dirichlet or Neumann) lead to infinitely many conserved charges classically in involution. We use an anomaly-counting method to show that at least one non-trivial example survives quantization, compar

Shinichi Deguchi

A universal Lagrangian that defines various four-dimensional massive Yang-Mills theories without Higgs bosons is presented. Each of the theories is characterized by a constant k contained in the Lagrangian. For k=0, the Lagrangian reduces to one defining the topologically massive Yang-Mills theory, and for k=1, the Lagrangian reduces to one defining the Free

Changrim Ahn, Chanju Kim, Chaiho Rim

In this paper we compute the scaling functions of the effective central charges for various quantum integrable models in a deep ultraviolet region $R\to 0$ using two independent methods. One is based on the ``reflection amplitudes&#39;&#39; of the (super-)Liouville field theory where the scaling functions are given by the conjugate momentum to the zero-modes

Greg Anderson, Howard Baer, Chih-hao Chen, Xerxes Tata

We explore the reach of luminosity upgrades of the Fermilab Tevatron collider for SU(5) supergravity models in which non-universal GUT-scale gaugino masses arise via a vacuum expectation value for the auxiliary component of a superfield that transforms as a 24, 75 or 200 dimensional representation of SU(5). This results in a different pattern of sparticle ma

Jeff Gronberg

The CLEO collaboration reported the observation of the ``wrong sign&#39;&#39; decay D0 -> K+ pi- in 1993. Recent upgrades to the CLEO detector, including the installation of a silicon vertex detector, have increased the sensitivity of the detector to D0 -> K+ pi-. Using 5.6 fb-1 of data we report a preliminary measurement of the rate of the wrong sign decay

H. -W. Hammer, M. J. Ramsey-Musolf

We analyse the isoscalar vector current form factors of the nucleon using dispersion relations. In addition to the usual vector meson poles, we account for the K\bar{K}-continuum contribution by drawing upon a recent analytic continuation of KN scattering amplitudes. For the Pauli form factor all strength in the ϕregion is already given by the continuum cont

Alexey A. Petrov

We review some recent developments in the studies of direct CP violation and final state interactions in weak decays of heavy quarks.

Yu. F. Pirogov, O. V. Zenin

The standard model extended with the pairs of the vector-like families is studied. The model independent analysis for an arbitrary case and an explicit realization for the case with one pair of the heavy vector-like families are considered. The mixing matrices of the light quarks for the left- and right-handed charged currents, as well as those for the flavo

Ken Kiers, Amarjit Soni, Guo-Hong Wu

In the absence of natural flavor conservation, multi-Higgs doublet models generally contain new sources of CP violation and anomalous charged Higgs Yukawa couplings. We present a charged-Higgs CP violation study of one such two-Higgs doublet model (2HDM) which treats the top quark differently from the other quarks. The phenomenological implications for the K

I. Montvay

Multi-bosonic fermion simulation algorithms are reviewed, with particular emphasis on a recent application in SU(2) Yang-Mills theory with light gluinos.

E. Bittner, A. Hauke, H. Markum, J. Riedler

We consider two versions of quantum Regge calculus. The Standard Regge Calculus where the quadratic link lengths of the simplicial manifold vary continuously and the Z_2-Regge Model where they are restricted to two possible values. The goal is to determine whether the computationally more easily accessible Z_2 model still retains the universal characteristic

T. Yoshie

I present recent developments in the lattice QCD calculations of the light hadron spectrum. Emphasis is placed on the limitation of the quenched approximation in reproducing the observed spectrum and indications that the discrepancy is reduced by introducing two flavors of light dynamical quarks.

John Richardson, representing the ATLAS Pixel Project

The ATLAS experiment, at the Large Hadron Collider, will incorporate discrete, high-resolution tracking sub-systems in the form of segmented silicon detectors with 40MHz radiation-hard readout electronics. In the region closest to the pp interaction point, the thin silicon tiles will be segmented into a pixel geometry providing two-dimensional space-point in

Michael B Smy

The discrepancy of the measured solar neutrino flux compared to the predictions of the standard solar model may be explained by the neutrino flavor oscillation hypothesis. A more direct and less model-dependent test of this hypothesis is a measurement of the distortion of the shape of the solar neutrino energy spectrum. Super-Kamiokande studies the energy sp

Erik Gottschalk

BTeV is a collider experiment at Fermilab designed for precision studies of CP violation and mixing. Unlike most collider experiments, the BTeV detector has a forward geometry that is optimized for the measurement of B and charm decays in a high-rate environment. While the rate of B production gives BTeV an advantage of almost four orders of magnitude over e

Thomas R. Junk

A selection of recent heavy-flavor results from OPAL using the LEP1 data sample are presented. The average polarization of b baryons in hadronic Z^0 decay has been measured to be -0.56^{+0.20}_{-0.13} (stat.) +- 0.09(syst.) using semileptonic decays of Lambda_b baryons. A search has been conducted for the radially excited D*&#39; and has produced a 95% CL up

Brett Viren

Evidence for Nucleon Decay has yet to be observed. Current results from the observation of a 45 kton-year exposure of Super-Kamiokande and lifetime limits for nucleons to decay via lepton + pion, lepton + eta and lepton + kaon modes are presented.

Kristin Schleich, Donald M. Witt

Recent arguments have indicated that the sum over histories formulation of quantum amplitudes for gravity should include sums over conifolds, a set of histories with more general topology than that of manifolds. This paper addresses the consequences of conifold histories in gravitational functional integrals that also include scalar fields. This study will b

John C. Baez, John W. Barrett

Recent work on state sum models of quantum gravity in 3 and 4 dimensions has led to interest in the `quantum tetrahedron&#39;. Starting with a classical phase space whose points correspond to geometries of the tetrahedron in R^3, we use geometric quantization to obtain a Hilbert space of states. This Hilbert space has a basis of states labeled by the areas o

Anatoly D. Plotnikov

The objective of this article is to formalize the definition of NP problems. We construct a mathematical model of discrete problems as independence systems with weighted elements. We introduce two auxiliary sets that characterize the solution of the problem: the adjoint set, which contains the elements from the original set none of which can be adjoined to t

T. Timusk

The infrared spectra of the non-traditional superconductors share certain common features. The lack of a gap signature at $2Δ$ and the residual conductivity are the consequence of a d-wave order parameter. The high $T_c$ materials, the organic conductors and the heavy Fermion materials have a strong mid-infrared absorption band which can be interpreted as st

S. P. Hastings, W. C. Troy

We study a boundary value problem associated with a system of two second order differential equations with cubic nonlinearity which model a film of superconductor material subjected to a tangential magnetic field. We show that for an appropriate range of parameters there are {\it asymmetric} solutions, and only trivial {\it symmetric} solutions. We then show

Alexander Shnirman, Inanc Adagideli, Paul M. Goldbart, Ali Yazdani

We examine the role of order-parameter suppression in the development of low-energy peaks (i.e., resonances) in the tunneling density of states near a non-magnetic impurity in a d-wave superconductor. Without order-parameter suppression, the zero-energy resonance appears only in the unitary (i.e., strong impurity) limit. However, suppression makes the resona

J. P. Rodriguez

The low-energy charge excitations of a doped antiferromagnetic ladder are modeled by a system of interacting spinless fermions that live on the same ladder. A relatively large spin gap is assumed to ``freeze out&#39;&#39; all spin fluctuations. We find that the formation of rung hole pairs coincides with the opening of a single-particle gap for charge excita

Leticia F. Cugliandolo

We describe some interesting effects observed during the evolution of nonequilibrium systems, using domain growth and glassy systems as examples. We breafly discuss the analytical tools that have been recently used to study the dynamics of these systems. We mainly concentrate on one of the results obtained from this study, the violation of the fluctuation-di

A. Foussats, A. Greco, O. S. Zandron

By using the supersymmetric version of the Faddeev-Jackiw symplectic formalism, a family of first-order constrained Lagrangians for the t-J model is found. In this approach the Hubbard ${\hat X}$-operators are used as field variables. In this framework, we first study the spinless fermion model which satisfies the graded algebra spl(1,1). Later on, in order

K. Mallick, S. Mallick, N. Rajewsky

We present an exact solution for an asymmetric exclusion process on a ring with three classes of particles and vacancies. Using a matrix product Ansatz, we find explicit expressions for the weights of the configurations in the stationary state. The solution involves tensor products of quadratic algebras.

P. T. Coleridge, P. Zawadzki

The temperature dependence of an integer Quantum Hall effect transition is studied in a sample where the disorder is dominated by short-ranged potential scattering. At low temperatures the results are consistent with a $(T/T_0)^κ$ scaling behaviour and at higher temperatures by a linear dependence similar to that reported in other material systems. It is sho

M. J. Graf, R. J. Keizer, A. de Visser, J. J. M. Franse

We report measurements of the specific heat and resistivity (T < 1 K) for high quality polycrystals of U(Pt1-xPdx)3 with x < 0.006. The Tc-x phase diagram can be constructed, and superconductivity is destroyed for x = 0.006; this is approximately the same concentration above which the onset of large-moment antiferromagnetism is observed to occur. The splitti

Jesper Lykke Jacobsen, Jean Vannimenus

A relation between the average length of loops and their free energy is obtained for a variety of O(n)-type models on two-dimensional lattices, by extending to finite temperatures a calculation due to Kast. We show that the (number) averaged loop length L stays finite for all non-zero fugacities n, and in particular it does not diverge upon entering the crit

Eugene H. Kim, J. Solyom

We study the opening of the Haldane gap in two-leg and four-leg anisotropic spin ladders using bosonization and renormalization group methods, and we determine the phase diagram as a function of the interchain coupling and the relative anisotropy. It is found that the opening of the Haldane gap is qualitatively different for the two cases considered. For the

A. Yu. Cherny, A. A. Shanenko

The well-known results concerning a dilute Bose gas with the short-range repulsive interaction should be reconsidered due to a thermodynamic inconsistency of the method being basic to much of the present understanding of this subject. The aim of our paper is to propose a new way of treating the dilute Bose gas with an arbitrary strong interaction. Using the

Sh. Ashkenazi, V. Steinberg

$SF_6$ in the vicinity of its critical point was used to study turbulent convection up to exceptionally high Rayleigh numbers, $Ra$, (up to $5\cdot 10^{14}$) and to verify for the first time the generalized scaling laws for the heat transport and the large scale circulation velocity as a function of $Ra$ and the Prandtl number, $Pr$, in very wide range of th

M. S. Briggs, D. L. Band, R. M. Kippen, R. D. Preece

GRB 990123 was the first burst from which simultaneous optical, X-ray and gamma-ray emission was detected; its afterglow has been followed by an extensive set of radio, optical and X-ray observations. We have studied the gamma-ray burst itself as observed by the CGRO detectors. We find that gamma-ray fluxes are not correlated with the simultaneous optical ob

Q. Daniel Wang

Based on an ultra deep (230 ks) ROSAT HRI imaging of M101, we have detected 5 X-ray sources that coincide spatially with optical emission line features previously classified as supernova remnants in this nearby galaxy. Two of these coincidences (SNR MF83 and NGC5471B) most likely represent the true physical association of X-ray emission with shock-heated int

J. B. Hutchings, B. Cavanagh, L. Bianchi

We present F336W (U), F439W (B), F555W (V), and F675W (R) Wide Field Planetary Camera 2 (WFPC2) photometry of two outer regions of the Local Group dwarf irregular galaxy NGC6822. The NE region is ~13 arcmin from the galaxy centre, while the W region lies 10 arcmin out, and within the wispy low surface brightness outer regions of the galaxy. The fields are no

Michael Catanese

In the last ten years, the field of Cherenkov astronomy has become an important contributor to high energy astrophysics with the detection of eight objects at energies above 300 GeV. These observations have advanced our understanding of active galactic nuclei, supernova remnants, the extragalactic background light and cosmic-ray acceleration and production.

H. W. Hartmann, J. Heise, P. Kahabka, C. Motch

The Super Soft Source RX J0925.7--4758 was observed by BeppoSAX LECS and MECS on January 25--26 1997. The source was clearly detected by the LECS but only marginally detected by the MECS. We apply detailed Non-Local Thermodynamic Equilibrium (Non-LTE) models including metal line opacities to the observed LECS spectrum. We test whether the X-ray spectrum of R

Faustin Munyaneza, David Tsiklauri, Raoul D. Viollier

It has been recently shown (Munyaneza, Tsiklauri and Viollier 1998) that the analysis of the orbits of the fast moving stars close to Sgr A$^{*}$ (Eckart and Genzel 1997) provides a valuable tool to probe the gravitational potential near the Galactic center. As an example, we present here the results on a calculation of possible orbits of the star S0-1 in bo

S. Van Eck, A. Jorissen

This paper is the first one in a series investigating the properties of the S stars belonging to the Henize sample (205 S stars with delta<-25 deg. and R<10.5) in order to derive the respective properties (like galactic distribution and relative frequencies) of intrinsic (i.e. genuine asymptotic giant branch) S stars and extrinsic (i.e. post mass-transfer bi

R. Hoogerwerf, L. A. Aguilar

A new method to identify coherent structures in velocity space --- moving groups --- in astrometric catalogues is presented: the Spaghetti method. It relies on positions, parallaxes, and proper motions and is ideally suited to search for moving groups in the Hipparcos Catalogue. No radial velocity information is required. The method has been tested extensive

Jos H. J. de Bruijne

The Hipparcos data allow a major step forward in the research of `moving groups&#39; in the Solar neighbourhood, as the common motion of group members causes converging proper motions. Previous knowledge on these coherent structures in velocity space has always been limited by the availability, reliability, and accuracy of ground-based proper motion measurem

Junichiro Makino

In this paper, we study the thermal relaxation in the one-dimensional self-gravitating system, or the so-called sheet model. According to the standard argument, the thermal relaxation time of the system is around $Nt_c$, where $N$ is the number of sheets and $t_c$ is the crossing time. It has been claimed that the system does not reach the thermal equilibriu

A. S. Fruchter, E. Pian, R. Gibbons, S. E. Thorsett

We report on observations of the field of GRB~970508 made in early August 1998, 454 days after outburst, with the STIS CCD camera onboard the Hubble Space Telescope. The images, taken in open filter (50CCD) mode, clearly reveal the presence of a galaxy which was obscured in earlier (June 1997) HST images by emission from the optical transient (OT). The galax

A. Lazarian, B. T. Draine

We identify a new mechanism of internal dissipation of rotational kinetic energy in spinning dust grains, arising from the reorientation of nuclear angular momentum, e.g., spins of protons. Grain rotation induces magnetization of the nuclear spin system, with net alignment of nuclear spins parallel to the grain angular velocity. When the grain does not rotat

S. I. Kuznetsov, M. R. Gilfanov, E. M. Churazov, R. A. Sunyaev

The results of GRANAT/SIGMA hard X-ray observations of GRS 1758-258 in 1990-1998 are presented. The source lies at ~5\arcdeg from the Galactic Center and was within the SIGMA field of view during the GRANAT surveys of this region. The total exposure time of the Galactic Center was 11x10^6 s. The regular SIGMA observations revealed strong variability of the s