September 1999 arXiv papers — page 20

Ikuo Ichinose, Keiichi Nagao

We investigate the chiral properties of overlap lattice fermion by using two dimensional Gross-Neveu model coupled with a gauge field. Chiral properties of this model are similar to those of QCD$_4$, that is, the chiral symmetry is spontaneously broken in the presence of small but finite fermion mass and also there appears the chiral anomaly because of the c

Jorge Pullin

Research Briefs: Does the GSL imply an entropy bound?, by Warren G. Anderson A lightweight review of middleweight black holes, by Ben Bromley The physics of isolated horizons, by Daniel Sudarsky LIGO project update, by Stan Whitcomb Meeting reports: Worskhop on initial value for binary black holes, by Carlos Lousto ITP Conference on strong gravitational fiel

Kriten Joshi, Frederic Rasio, Simon Portegies Zwart

We present a new parallel supercomputer implementation of the Monte-Carlo method for simulating the dynamical evolution of globular star clusters. Our method is based on a modified version of Henon's Monte-Carlo algorithm for solving the Fokker-Planck equation. Our code allows us to follow the evolution of a cluster containing up to 5x10^5 stars to core

Pavel Fileviez Perez, Alejandro Cabo Montes de Oca, Carlos Rodriguez Castellanos

The wave propagation of edge modes in a superlattice of 2D electron Gases in quantum Hall regime is investigated. After introducing surfaces charge and current densities at the edge, the Maxwell equations are solved for waves running along the boundary. The constitutive relations expressing the edge charge and current densities in terms of the fields at the

G. Feverati, F. Ravanini, G. Takacs

We describe an extension of the nonlinear integral equation (NLIE) method to Virasoro minimal models perturbed by the relevant operator $Φ_{(1,3)$. Along the way, we also complete our previous studies of the finite volume spectrum of sine-Gordon theory by considering the attractive regime and more specifically, breather states. For the minimal models, we exa

Jerome Benoit, Rossen Dandoloff, Avadh Saxena

Classical Heisenberg spins in the continuum limit (i.e. the nonlinear sigma-model) are studied on an elastic cylinder section with homogeneous boundary conditions. The latter may serve as a physical realization of magnetically coated microtubules and cylindrical membranes. The corresponding rigid cylinder model exhibits topological soliton configurations wit

D. K. Demskoy, A. G. Meshkov

The symmetry classification method is applied to the string-like scalar fields in two-dimensional space-time. When the configurational space is three-dimensional and reducible we present the complete list of the systems admiting higher polynomial symmetries of the 3rd, 4th and 5th-order.

Andrey Tsiganov

The motion on the sphere $S^2$ with the potential $V= (x_1x_2x_3)^{-2/3}$ is considered. The Lax representation and the linearisation procedure for this two-dimensional integrable system are discussed.

M. Turek, P. Rozmej, R. Arvieu

We discuss an extension of the theory of {\em spin-orbit pendulum} phenomenon given in [1] to relativistic approach. It is done within the so called Dirac Oscillator. Our first results, focusing on circular wave packet motion have been published recently [2]. The scope of this paper is motion of a linear wave packet. In relativistic approach we found {\em Zi

R. Arvieu, P. Rozmej

A family of angular momentum coherent states on the sphere is constructed using previous work by Aragone et al [1]. These states depend on a complex parameter which allows an arbitrary squeezing of the angular momentum uncertainties. The time evolution of these states is analyzed assuming a rigid body hamiltonian. The rich scenario of fractional revivals is

Ashwin Nayak

Consider the finite regular language L_n = {w0 : w \in {0,1}^*, |w| \le n}. It was shown by Ambainis, Nayak, Ta-Shma and Vazirani that while this language is accepted by a deterministic finite automaton of size O(n), any one-way quantum finite automaton (QFA) for it has size 2^{Omega(n/log n)}. This was based on the fact that the evolution of a QFA is requir

J. C. Bronski, R. M. McLaughlin

In previous work Majda and McLaughlin computed explicit expressions for the $2N$th moments of a passive scalar advected by a linear shear flow in the form of an integral over ${\bf R}^N$. In this paper we first compute the asymptotics of these moments for large moment number. We are able to use this information about the large N behavior of the moments, alon

M. Bezzi, A. Ciliberto, A. Mengoni

We present a simple model based on a reaction-diffusion equation to explain pattern formation in a multicellular bacterium (Streptomyces). We assume competition for resources as the basic mechanism that leads to pattern formation; in particular we are able to reproduce the spatial pattern formed by bacterial aerial mycelium in case of growth in minimal (low

B. G. Sidharth

In this paper, we demonstrate how space-time is, rather than a differentiable manifold, a Random Heap, and how this ties up with fractal dimension 2 of a Quantum Mechanical path. In this light, we can see that there is a harmonious convergence between the stochastic approach of Nelson and the de Broglie-Bohm approach. These considerations are shown to lead t

S. S. Stepanov

The principle which allows to construct new physical theories on the basis of classical mechanics by reduction of the number of its axiom without engaging new postulates is formulated. The arising incompleteness of theory manifests itself in terms of theoretically undefinable fundamental physical constants $\hbar$ and c. As an example we built up a parametri

Thomas Schaefer

We summarize some recent results on the structure of QCD at very high baryon density.

Alexander Sakharuk, P. Gregers Hansen, Vladimir Zelevinsky

Single-particle removal reactions are becoming an important tool for studying radioactive nuclei. The nuclei far from stability may reveal new regions of large deformation. We discuss the influence of the projectile deformation on the stripping cross sections and longitudinal momentum distributions of the core. The Glauber formalism for describing such react

Ulf-G. Meißner

I discuss the dynamics of the two-nucleon system as obtained from a chiral nucleon-nucleon potential. This potential is based on a modified Weinberg power counting and contains chiral one- and two-pion exchange as well as four-nucleon contact interactions. The description of the S-waves is very precise. Higher partial waves are also well reproduced. We also

S. V. Akkelin, Yu. M. Sinyukov

The decay of fireballs containing the disoriented chiral condensate (DCC) in A+A collisions has been analyzed. We found that the high phase-space density and probably the large final fireball volume are the favorable factors to extract a DCC signal from the thermal background. Both of these factors are expected to take place at RHIC and LHC energies. A coher

Denis Lacroix, Philippe Chomaz

The nuclear collective response is investigated in the framework of a doorway picture in which the spreading width of the collective motion is described as a coupling to more and more complex configurations. It is shown that this coupling induces fluctuations of the observed strength. In the case of a hierarchy of overlapping decay channels, we observe Erics

A. V. Razumov, M. V. Saveliev, A. B. Zuevsky

The grading operators for all nonequivalent Z-gradations of classical Lie algebras are represented in the explicit block matrix form. The explicit form of the corresponding nonabelian Toda equations is given.

David P. Blecher, Krzysztof Jarosz

For a function algebra A we investigate relations between the following three topics: isomorphisms of singly generated A-modules, Morita equivalence bimodules, and `real harmonic functions' with respect to A. We also consider certain groups which are naturally associated with A. We illustrate the notions considered with several examples.

Yi-Zhi Huang, Antun Milas

This is Part I of a series of papers constructing intertwining operator superalgebras and vertex tensor categories associated to the superconformal minimal models and other related models. In this paper, we construct the intertwining operator superalgebras and vertex tensor categories in the N=1 case.

Markus Fulmek, Christian Krattenthaler

We compute the number of rhombus tilings of a hexagon with side lengths N,M,N,N,M,N, with N and M having the same parity, which contain a particular rhombus next to the center of the hexagon. The special case N=M of one of our results solves a problem posed by Propp. In the proofs, Hankel determinants featuring Bernoulli numbers play an important role.

Marc Lackenby

The aim of this paper is to demonstrate that very many Dehn fillings on a cusped hyperbolic 3-manifold yield a 3-manifold which is irreducible, atoroidal and not Seifert fibred, and which has infinite, word hyperbolic fundamental group. We establish an extension of the Thurston-Gromov $2π$ theorem by showing that if each filling slope has length more than si

Hirosi Ooguri

Talk presented at Strings '99 in Potsdam, Germany (July 19 - 24, 1999).

R. Banerjee, H. J. Rothe, K. D. Rothe

We obtain, for a subclass of structure functions characterizing a first class Hamiltonian system, recursive relations from which the general form of the local symmetry transformations can be constructed in terms of the independent gauge parameters. We apply this to a non-trivial Hamiltonian system involving two primary constraints, as well as two secondary c

J. Witters

A model for the fundamental structure of nature is presented. It is based on two fundamental fermions moving with the velocity of light and differing from each other by the projection of the spin on the momentum vector. The energy of both fermions is proportional to the momentum, which is scaled inversely with the size of a length quantum. All the known forc

B. Kleihaus, Jutta Kunz

As shown by Taubes, in the Bogomol'nyi-Prasad-Sommerfield limit the SU(2) Yang-Mills-Higgs model possesses smooth finite energy solutions, which do not satisfy the first order Bogomol'nyi equations. We construct numerically such a non-Bogomol'nyi solution, corresponding to a monopole-antimonopole pair, and extend the construction to finite Higgs

Milan Petras

It is argued that a low energy string may be an Aristotelian top, i.e. a rigid body which however cannot be rotationally excited, but in an external electromagnetic field exhibits a sort of precession with a Larmor type angular velocity. On the basis of this observation a proposal is made for a new two steps derivation of the electroweak standard model from

Dongsu Bak, Kimyeong Lee

We rederive the nonrelativistic Lagrangian for the low energy dynamics of 1/4 BPS dyons by considering the time dependent fluctuations around classical 1/4 BPS configurations. The relevant fluctuations are the zero modes of the underlying 1/2 BPS monopoles.

Cihan Saclioglu

We present unique solutions of the Seiberg-Witten Monopole Equations in which the U(1) curvature is covariantly constant, the monopole Weyl spinor consists of a single constant component, and the 4-manifold is a product of two Riemann surfaces of genuses p_1 and p_2. There are p_1 -1 magnetic vortices on one surface and p_2 - 1 electric ones on the other, wi

Victor M. Villanueva, Jan Govaerts, Jose-Luis Lucio-Martinez

The quantisation of gauge invariant systems usually proceeds through some gauge fixing procedure of one type or another. Typically for most cases, such gauge fixings are plagued by Gribov ambiguities, while it is only for an admissible gauge fixing that the correct dynamical description of the system is represented, especially with regards to non perturbativ

Stuart Raby

New data on neutrino masses is very exciting. It is the first evidence for physics beyond the standard model. In this talk we discuss this data and how it may (or may not) be used to constrain theories of charged fermion masses. The talk is divided into two parts. In part I, we briefly discuss the theoretical framework for fermion masses and mixing angles as

L. Giusti

We introduce a new parameterization of four-fermion matrix elements which does not involve quark masses and thus allows a reduction of systematic uncertainties in physical amplitudes. As a result the apparent quadratic dependence of e'/e on m_s is removed. To simplify the matching between lattice and continuum renormalization schemes, we express our resu

L. Lavoura

I present a simple three-Higgs-doublet extension of the standard model in which real CP violation takes place. The strong CP problem is attenuated by this model.

Victor Elias, Kevin Sprague, Ying Xue

We address anticipated fermion-antifermion and dimension-4 gauge-field vacuum-condensate contributions to the magnetic portion of the fermion-photon vertex function in the presence of a vacuum with nonperturbative content, such as that of QCD. We discuss how inclusion of such condensate contributions may lead to a vanishing anomalous magnetic moment, in whic

Dubravko Klabucar, Dalibor Kekez

We present a recent treatment of the $π^0γ^\starγ$ transition form factor in the coupled Schwinger-Dyson and Bethe-Salpeter approach to stress the desirability of measuring it at CEBAF.

S. M. Darbinian, N. L. Ter-Isaakian

The radiation emission spectra of polarized photons emitted from charge particle in single crystal are obtained in semiclassical theory in Baer-Katkov-Strakhovenko approximation for planar crystal orientation. The range of applicability of this approximation is estimated by comparing the results with calculations in exact semiclassical theory. Optimal crysta

Anna Kulesza, W. J. Stirling

The perturbation series for electroweak vector boson production at small transverse momentum is dominated by large double logarithms at each order in perturbation theory. An accurate theoretical prediction therefore requires a resummation of these logarithms. This can be performed either directly in transverse momentum space or in impact parameter (Fourier t

C. F. Berger, W. Schweiger

We consider the reaction $γp \to M p$, with M being either a $Φ$ or a $J/Ψ$ meson, within perturbative QCD treating the proton as a quark-diquark system. The phenomenological couplings of gauge bosons to (spatially extended) diquarks and the quark-diquark distribution amplitude of the proton are adopted from previous investigations of baryon form factors and

S. Moch, J. A. M. Vermaseren

We perform the analytic calculation of the Mellin moments of the structure functions F_2 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 and F_L. O

B. Stech

The mass matrices of quarks have a simple structure if expressed in powers of the small parameter σ=(m_c/m_t)^{1/2}. If there is a close relation between quarks and leptons, one would expect similar structures for the lepton matrices which involve the same parameter. To have a specific proposal, the see-saw mechanism is employed together with the stringent r

Manuel Drees, Monoranjan Guchait, D. P. Roy

We study the signature of $H^\pm$ decay into $h^0W$ at the LHC in SUSY models. It has only marginal viability in the MSSM. But in the singlet extensions like the NMSSM one can have a spectacular signature for $H^\pm$ decay into $(h^0,A^0)W$ over a significant domain of parameter space.

PACS Collaboration, A. Ali Khan, S. Aoki, R. Burkhalter

We present results for the mass of the flavor singlet meson calculated on two-flavor full QCD configurations generated by the CP-PACS full QCD project. We also investigate topological charge fluctuations and their dependence on the sea quark mass.

Ivan Horvath

I propose a large class of stochastic Markov processes associated with probability distributions analogous to that of lattice gauge theory with dynamical fermions. The construction incorporates the idea of approximate spectral split of the determinant through local loop action, and the idea of treating the infrared part of the split through explicit diagonal

H. Neuberger

I present several tricks to help implement the overlap Dirac operator numerically.

H. Neuberger

Chiral fermions resisted being put on the lattice for twenty years. This raised the suspicion that asymptotically free chiral gauge theories were not renormalizable outside perturbation theory and therefore could not be mathematically extended to infinite energies. During the last several years the situation has reversed itself. Today we believe that all the

A. Donini, V. Gimenez, L. Giusti, G. Martinelli

We introduce a new parameterization of four-fermion matrix elements which does not involve quark masses and thus allows a reduction of systematic uncertainties in physical amplitudes. As a result the apparent quadratic dependence of e'/e on m_s is removed. To simplify the matching between lattice and continuum renormalization schemes, we express our resu

G. Aarts, J. Smit

In approximate dynamical equations, inhomogenous classical (mean) gauge and Higgs fields are coupled to quantized fermions. The equations are solved numerically on a spacetime lattice. The fermions appear to equilibrate according to the Fermi-Dirac distribution with time-dependent temperature and chemical potential.

D. Becirevic, V. Lubicz, G. Martinelli, M. Testa

We have computed the light and strange quark masses and the renormalization constants of the quark bilinear operators, by studying the large-p^2 behaviour of the lattice quark propagator and 3-point functions. The calculation is non-perturbatively improved, at O(a), in the chiral limit. The method used to compute the quark masses has never been applied so fa

T. Manke

We study in detail the spectrum of heavy quarkonia with different orbital angular momentum along with their radial and gluonic excitations. Using an anisotropic formulation of Lattice QCD we achieved an unprecedented control over statistical errors and were able to study systematic errors such as lattice spacing artefacts, finite volume effects and relativis

I. Wetzorke, F. Karsch, E. Laermann

We present preliminary results for the mass of the 6q flavor-singlet state ($J^P=0^+$, $S=-2$) called H-dibaryon, calculated in quenched QCD on $16^3$x30 and $24^3$x30 lattices with improved gauge and fermion actions (Symanzik improvement, Clover action). For both lattice sizes we applied the fuzzing technique to enhance the overlap with the ground state. We

C. Michael, M. S. Foster, C. McNeile

We measure correlations appropriate for favour-singlet mesons using dynamical quark configurations from UKQCD. Improved methods of evaluating the disconnected quark diagrams are presented. The scalar and pseudoscalar meson channels are explored, with special reference to the mixing of scalar mesons with scalar glueballs.

M. Giorgini

This paper describes an experimental search for GUT magnetic monopoles in the MACRO experiment using the nuclear track subdetector CR39. After discussing the working principle, the charge resolution and the calibration of the detector, the experimental procedure for searching for magnetic monopoles is described. Since no candidates were found, the upper flux

Saul A. Teukolsky

The iterated Crank-Nicholson method has become a popular algorithm in numerical relativity. We show that one should carry out exactly two iterations and no more. While the limit of an infinite number of iterations is the standard Crank-Nicholson method, it can in fact be worse to do more than two iterations, and it never helps. We explain how this paradoxica

Luca Lusanna, Roberto de Pietri

A discussion of asymptotic weak and strong Poincare' charges in metric gravity is given to identify the proper Hamiltonian boundary conditions. The asymptotic part of the lapse and shift functions is put equal to their analogues on Minkowski hyperplanes. By adding Dirac's ten extra variables at spatial infinity, metric gravity is extended to incorpor

Valery Koryukin

The detection and the research of the neutrinos background of Universe are the attractive problems. This problems do not seem the unpromising one in the case of the high neutrinos density of Universe. It is offered to use the low energy neutrinos background of Universe for the explanation of the gravitational phenomena with the quantum position attracting th

Jorge Pullin

This is the writeup of the talk I gave at the Yukawa International Symposium at Kyoto, Japan on June 29, 1999. The talk summarizes the present status of the close limit approximation for colliding black holes.

L. C. Garcia de Andrade

An exact 2-dimensional conical Riemannian defect solution of 3-dimensional Euclidean Einstein equations of stresses and defects representing a shear-free Heisenberg ferromagnet is given.The system is equivalent to the Einstein equations in vacuum.Geodesics of magnetic monopoles around the ferromagnet are also investigated.

J. A. Anta, A. A. Louis

We use the Quantum Hypernetted Chain Approximation (QHNC) to calculate the ion-ion and electron-ion correlations for liquid metallic Li, Be, Na, Mg, Al, K, Ca, and Ga. We discuss trends in electron-ion structure factors and radial distribution functions, and also calculate the free-atom and metallic-atom form-factors, focusing on how bonding effects affect t

V. J. Goldman

Comment on M. Kataoka et al., Phys. Rev. Lett. 83, 160 (1999).

M. O. Dzero, L. P. Gor'kov, V. Z. Kresin

Fermi liquid characteristics for ferromagnetic ~manganites, A$_{1-x}$B$_x$MnO$_3$, are evaluated in the tight-binding approximation and compared with experimental data for the best studied region $x\simeq0.3$. The bandwidths change only slightly for different compositions. The Sommerfeld coefficient, $γ$, the $T^2$-term in resistivity and main scales in opti

V. N. Narozhnyi, D. Eckert, G. Fuchs, K. Nenkov

Magnetic properties were studied for the high quality Al-free orthorhombic Gd_{1-x}Pr_xBa_2Cu_3O_{7-y} single crystals (0<=x<=1.0) grown by the flux method. An indication on the interaction between the Pr and Cu(2) magnetic sublattices was found for Pr123. Different signs of magnetic anisotropy were established for the Pr and Gd ions at low temperatures. It

C. Raman, M. Kohl, R. Onofrio, D. S. Durfee

We have studied dissipation in a Bose--Einstein condensed gas by moving a blue detuned laser beam through the condensate at different velocities. Strong heating was observed only above a critical velocity.

Igor S. Aranson, Len M. Pismen

We consider interaction of vortices in the vector complex Ginzburg--Landau equation (CVGLE). In the limit of small field coupling, it is found analytically that the interaction between well-separated defects in two different fields is long-range, in contrast to interaction between defects in the same field which falls off exponentially. In a certain region o

V. N. Narozhnyi, D. Eckert, K. A. Nenkov, G. Fuchs

In PrBa_2Cu_3O_{7-y} (Pr123) single crystals grown by the flux method the kink in the magnetic susceptibility chi_{ab}(T), connected with AFM ordering of Pr, disappears after field cooling (FC) in a field H||ab-plane whereas the kink in chi_c(T) remains unchanged after FC in H||c-axis. This seems to be connected with the coupling between the Pr and Cu(2) sub

J. Zaanen

A limiting case of a dynamical stripe state which is of potential significance to cuprate superconductors is considered: a gas of elastic quantum strings in 2+1 dimensions, interacting merely via a hard-core condition. It is demonstrated that this gas solidifies always, by a mechanism which is the quantum analogue of the entropic interactions known from soft

M. Barth, U. Kuhl, H. -J. Stoeckmann

The spectra of Sinai microwave billiards and rectangular billiards with statistically distributed circular scatterers have been taken as a function of the position of one wall, and of one of the scatterers, respectively. Whereas in the first case the velocity distribution and correlations obey the universal behaviour predicted by Simons and Altshuler, in the

A. Jagannathan

Energy level spacing statistics are discussed for a two dimensional quasiperiodic tiling. The property of self-similarity under inflation is used to write a recursion relation for the level spacing distributions defined on square approximants to the perfect quasiperiodic structure. New distribution functions are defined and determined by a combination of num

T. S. Evans, D. A. Steer

We perform a well defined derivative expansion to obtain the time dependent effective theory for a BCS superconductor at finite temperature, using an arbitrary curve in the complex time plane. Our expansion is unique, being free of any problems related to the order in which analytical continuation and the derivative expansion are made, or equivalently to the

M. Amoruso, I. Meccoli, A. Minguzzi, M. P. Tosi

We discuss the ground state and the small-amplitude excitations of a degenerate vapour of fermionic atoms placed in two hyperfine states inside a spherical harmonic trap. An equations-of-motion approach is set up to discuss the hydrodynamic dissipation processes from the interactions between the two components of the fluid beyond mean-field theory and to emp

Ralf Bulla, Matthew T Glossop, David E Logan, Thomas Pruschke

The symmetric Anderson impurity model, with a soft-gap hybridization vanishing at the Fermi level with power law r > 0, is studied via the numerical renormalization group (NRG). Detailed comparison is made with predictions arising from the local moment approach (LMA), a recently developed many-body theory which is found to provide a remarkably successful des

Joaquim Casulleras, Jordi Boronat

The application of the diffusion Monte Carlo method to a strongly interacting Fermi system as normal liquid $^3$He is explored. We show that the fixed-node method together with the released-node technique and a systematic method to analytically improve the nodal surface constitute an efficient strategy to improve the calculation up to a desired accuracy. Thi

Y. Avishai, A. Golub

Josephson current for a system consisting of an Anderson impurity weakly coupled to two unconventional superconductors is studied and shown to be driven by a surface zero energy (mid-gap) bound-state. The repulsive Coulomb interaction in the dot can turn a $π$ junction into a 0-junction. This effect is more pronounced in p-wave superconductors while in high-

Kouichi Okunishi, Tomotoshi Nishino

We investigate the Kramers-Wannier approximation for the three-dimensional (3D) Ising model. The variational state is represented by an effective 2D Ising model, which contains two variational parameters. We numerically calculate the variational partition function using the corner transfer matrix renormalization group (CTMRG) method, and find its maximum wit

Ingve Simonsen, Alex Hansen

We consider a string with fixed endpoints where the mass density and/or the elastic coefficient vary in a self-affine way as function of position. It is demonstrated how the eigenvalues in the asymptotic limit are distributed. Scaling laws for the Weyl term of the asymptotic integrated density of states is established and confirmed numerically.

Ross H. McKenzie

A simple consistency check is proposed for the Fermi liquid description of the low-temperature properties of quasi-two-dimensional metals. In a quasi-two-dimensional Fermi liquid the Zeeman splitting of magnetic oscillations can be used to determine g^*, the gyro-magnetic ratio which is renormalised by many-body effects. It is shown that g^*/g is equal to Wi

Uzy Smilansky

The compatibility of the semiclassical quantization of area-preserving maps with some exact identities which follow from the unitarity of the quantum evolution operator is discussed. The quantum identities involve relations between traces of powers of the evolution operator. For classically {\it integrable} maps, the semiclassical approximation is shown to b

Laura Ferrarese, Brad Gibson, Daniel Kelson, Shoko Sakai

The final efforts of the HST Key Project on the Extragalactic Distance Scale are presented. Four distance indicators, the Surface Brightness Fluctuation method, the Fundamental Plane for early-type galaxies, the Tully-Fisher relation and the Type Ia Supernovae, are calibrated using Cepheid distances to galaxies within 25 Mpc. The calibration is then applied

J. Garrett Jernigan, Richard I. Klein, Jonathan Arons

We report the discovery of kHz fluctuations, including quasi-periodic oscillations (QPO) at ~330 Hz and ~760 Hz and a broadband kHz continuum in the power density spectrum of the high mass X-ray binary pulsar Centaurus X-3. These observations of Cen X-3 were carried out with the Rossi X-ray Timing Explorer (RXTE). The fluctuation spectrum is flat from mHz to

David H. Hughes

Using the submm array camera SCUBA on the 15-m JCMT it is now possible to conduct unbiased submm surveys and quantify the level of star-formation activity in the young Universe by observing the rest-frame FIR thermal emission from dust in high-redshift galaxies. However an accurate interpretation of these existing submm cosmological surveys is prevented by u

K. O&#39;Neil, G. D. Bothun, J. Schombert

[Abridged] Using the refurbished 305m Arecibo Gregorian Telescope, we detected 43 low surface brightness (LSB) galaxies from the catalog of O&#39;Neil, Bothun, & Cornell (1997a). The detected galaxies range from 22.0 mag/arcsec^2 < mu_B(0) < 25.0 mag/arcsec^2, with colors ranging from the blue through the first detection of a very red LSB galaxies (B-V = -0.

Alexandra N. Cha, Kenneth R. Sembach

We present high resolution (R~75,000), high signal-to-noise (S/N~100) Ca II $λ$3933.663 and Na I $λλ$5889.951, 5895.924 spectra of 68 stars in the direction of the Vela supernova remnant. The spectra comprise the most complete high resolution, high S/N, optical survey of early type stars in this region of the sky. A subset of the sight lines has been observe

J. E. Gizis, D. G. Monet, I. N. Reid, J. D. Kirkpatrick

We report the discovery of two binary M dwarf systems in the immediate solar neighborhood using 2MASS. The first is an M6.5 companion to the nearby G star HD 86728 (Gl 376). The known properties of HD 86728 indicate that the M dwarf (Gl 376B) is old, metal-rich and only 14.9 parsecs away. The M dwarf is highly active with both H alpha and X-ray emission. Thu

D. Horns, D. Schmele

Data taken with the HEGRA Scintillator Array have been used to search for spatial anisotropies in the arrival directions of cosmic rays above 20 TeV. In this paper results on the search for TeV gamma-ray emission from the Galactic plane and the Gould belt are presented. Furthermore, a search for TeV gamma-ray emission correlated with the arrival directions o

Atsushi Taruya

Distribution of galaxies may be a biased tracer of the dark matter distribution and the relation between the galaxies and the total mass may be stochastic, non-linear and time-dependent. Since many observations of galaxy clustering will be done at high redshift, the time evolution of non-linear stochastic biasing would play a crucial role for the data analys

K. O&#39;Neil, G. Bothun

Using the catalog of O&#39;Neil, Bothun, & Schombert (1999), we examine the central surface brightness distribution (phi(mu_B(0))) of galaxies in the 22.0 < mu_B(0) < 25.0 mag arcsec^{-2} range. Taking advantage of having a catalog in which each galaxy has a known central surface brightness, scale length, and redshift, we apply a bi-variate volume correction

Daisuke Kawata

In order to understand the formation process of elliptical galaxies which are not rotationally supported, we have carried out numerical simulations of the galaxy formation from the density perturbation with a rotation corresponding to a small spin parameter. The three-dimensional TREE N-Body/SPH simulation code used in this paper includes the dark matter and

J. P. Leahy, Nectaria A. B. Gizani

We analyze ROSAT data for cluster gas surrounding powerful radio galaxies, which is well fitted by a ``beta-model&#39;&#39; gas distribution, after allowing for a compact central source. The cluster thermal pressure at the distance of the radio lobes is typically an order of magnitude larger than the lobe minimum pressure. Since radio lobes are sharply-bound

S. Boissier, N. Prantzos

We study the chemical and spectro-photometric evolution of galactic disks with detailed models calibrated on the Milky Way and using simple scaling relations, based on currently popular semi-analytic models of galaxy formation. We compare our results to a large body of observational data on present day galactic disks, including: disk sizes and central surfac

Matthias Bartelmann

Given its extraordinary spatial resolution and sensitivity, the projected Next Generation Space Telescope (NGST) is likely to detect a large number of high-redshift QSOs lensed by spiral galaxies. Using realistic models for the QSO and spiral populations, we calculate the expected number density of detectable QSOs multiply imaged by spirals, and investigate

Sang Min Lee, Seung Soo Hong

A linear stability analysis has been performed onto a self-gravitating magnetized gas disk bounded by external pressure. The resulting dispersion relation is fully explained by three kinds of instability: a Parker-type instability driven by self-gravity, usual Jeans gravitational instability and convection. In the direction parallel to the magnetic fields, t

Tom Richtler, Georg Drenkhahn

Type Ia supernovae (SNe) are the best standard candles available today in spite of an appreciable intrinsic variation of their luminosities at maximum phase, and of probably non-uniform progenitors. For an unbiased use of type Ia SNe as distance indicators it is important to know accurately how the decline rate and colour at maximum phase correlate with the

Atsushi Kawai, Toshiyuki Fukushige, Junichiro Makino, Makoto Taiji

We have developed a special-purpose computer for gravitational many-body simulations, GRAPE-5. GRAPE-5 is the successor of GRAPE-3. Both consist of eight custom pipeline chips (G5 chip and GRAPE chip). The difference between GRAPE-5 and GRAPE-3 are: (1) The G5 chip contains two pipelines operating at 80 MHz, while the GRAPE chip had one at 20 MHz. Thus, the

D. B. Sanders, J. A. Surace, C. M. Ishida

At luminosities above ~10^{11} L_sun, infrared galaxies become the dominant population of extragalactic objects in the local Universe (z < 0.5), being more numerous than optically selected starburst and Seyfert galaxies, and QSOs at comparable bolometric luminosity. At the highest luminosities, ultraluminous infrared galaxies (ULIGs: L_ir > 10^{12} L_sun), o

H. Che

If Gamma-ray Bursts (GRBs) are generally associated with supernovae like 1998bw, a relatively wide intrinsic luminosity function is implied, which indicates the existence of a large amount of undetected dim bursts, and a much higher event-rate than is often assumed. If it is assumed that the intrinsic luminosity function of GRBs is a power-law: ${ϕ(L)} \prop

G. Felder, J. Fröhlich, J. Fuchs, C. Schweigert

The structures in target space geometry that correspond to conformally invariant boundary conditions in WZW theories are determined both by studying the scattering of closed string states and by investigating the algebra of open string vertex operators. In the limit of large level, we find branes whose world volume is a regular conjugacy class or, in the cas

Christopher Thompson, Piero Madau

We consider the effects of rapid pair creation by an intense pulse of gamma-rays propagating ahead of a relativistic shock. Side-scattered photons colliding with the main gamma-ray beam amplify the density of scattering charges. The acceleration rate of the pair-loaded medium is calculated, and its limiting bulk Lorentz factor related to the spectrum and com

J. Zhu, H. L. Stormer, L. N. Pfeiffer, K. W. Baldwin

We observe sharp peaks and strong hysteresis in the electronic transport of a two-dimensional electron gas (2DEG) in the region of the integral quantum Hall effect. The peaks decay on time scales ranging from several minutes to more than an hour. Momentary grounding of some of the contacts can vastly modify the strength of the peaks. All these features disap