October 2000 arXiv papers — page 5

Guillermo Abramson

We analyze the asymptotic states in the partially ordered phase of a system of globally coupled logistic maps. We confirm that, regardless of initial conditions, these states consist of a few clusters, and they properly belong in the ordered phase of these systems. The transient times necessary to reach the asymptotic states can be very long, especially very

Irene Sendiña-Nadal, Vicente Pérez-Muñuzuri, Víctor M. Eguíluz, Emilio Hernández-García

We investigate the impact of the domain shape on wave propagation in excitable media. Channelled domains with sinusoidal boundaries are considered. Trains of fronts generated periodically at an extreme of the channel are found to adopt a quasiperiodic spatial configuration stroboscopically frozen in time. The phenomenon is studied in a model for the photo-se

Pavel Exner

We investigate an infinite array of point interactions of the same strength in R^d, d=2,3, situated at vertices of a polygonal curve with a fixed edge length. We demonstrate that if the curve is not a line, but it is asymptotically straight in a suitable sense, the corresponding Hamiltonian has bound states. Example is given in which the number of these boun

Dennis Gaitsgory

Let $G$ be a reductive group, let $Gr=G((t))/G[[t]]$ be the corresponding affine Grassmannian and let $Fl=G((t))/I$ be the affine flag variety. We construct, following an idea of Belinson, a 1-parametric deformation of the product $Gr\times G/B$ to $Fl$. We use this construction to produce perverse sheaves on $Fl$ which are central with respect to the convol

Oliver T. Dasbach, Xiao-Song Lin

A famous result of Bennequin states that for any braid representative of the unknot the Bennequin number is negative. We will extend this result to all n-trivial closed n-braids. This is a class of infinitely many knots closed under taking mirror images. Our proof relies on a non-standard parametrization of the Homfly polynomial.

Francois Lalonde, Dusa McDuff

This survey presents some recent results by the authors and Polterovich on the topological properties of ruled symplectic manifolds. The bundle M \to P \to B that is associated with a ruled manifold has the group of Hamiltonian symplectomorphisms of M as structure group if the base is simply connected. Thus information about Hamiltonian bundles gives stabili

Igor Burban, Hans-Georg Freiermuth

In this survey article we want to discuss a way of constructing arithmetically Gorenstein varieties of high codimension. Consider kernel sheaves B_G of general, generically surjective morphisms G between decomposable bundles on P^n. The top-dimensional part of the zero-locus of a regular section of B_G is Gorenstein if B_G has odd rank. We show how to implem

David Borthwick

We develop the scattering theory of general conformally compact metrics. For low frequencies, the domain of the scattering matrix is shown to be frequency dependent. In particular, generalized eigenfunctions exhibit L^2 decay in directions where the asymptotic curvature is sufficiently negative. The scattering matrix is shown to be a pseudodifferential opera

M. A. Lledó

We study properties of a family of algebraic star products defined on coadjoint orbits of semisimple Lie groups. We connect this description with the point of view of differentiable deformations and geometric quantization.

Lorenz Halbeisen, Saharon Shelah

If we assume the axiom of choice, then every two cardinal numbers are comparable. In the absence of the axiom of choice, this is no longer so. For a few cardinalities related to an arbitrary infinite set, we will give all the possible relationships between them, where possible means that the relationship is consistent with the axioms of set theory. Further w

Mustafa Korkmaz

S. Bigelow proved that the braid groups are linear. That is, there is a faithful representation of the braid group into the general linear group of some field. Using this, we deduce from previously known results that the mapping class group of a sphere with punctures and hyperelliptic mapping class groups are linear. In particular, the mapping class group of

F. J. Castro-Jiménez, J. M. Ucha-Enriquez

We prove a duality formula for two ${\cal D}$-modules arising from logarithmic derivations w.r.t. a plane curve. As an application we give a differential proof of a logarithmic comparison theorem of Calderón-Mond-Narváez-Castro.

Alan Forrest, John Hunton, Johannes Kellendonk

We analyze and compare different dynamical systems and groupoids which can be obtained from projection point patterns. We define the cohomology of a point pattern as the cocycle cohomology of the pattern groupoid. We describe this cohomology qualitatively and calculate it for canonical projection method tilings with codimension smaller or equal than 3.

Paul C. Eklof, Saharon Shelah

We give a new proof that there are arbitrarily large indecomposable abelian groups; moreover, the groups constructed are absolutely indecomposable, that is, they remain indecomposable in any generic extension. However, any absolutely rigid family of groups has cardinality less than the partition cardinal kappa(omega).

Chi-Keung Ng

By giving an interesting characterisation of amenable multiplicative unitaries in term of one dimensional representations, we show in a simple way that bicrossproducts of amenable locally compact groups is both amenable and coamenable.

Vsevolod Shevchishin

The deformation problem for pseudoholomorphic curves and related geometrical properties of the total moduli space of pseudoholomorphic curves are studied. A sufficient condition for the saddle point property of the total moduli space is established. The local symplectic isotopy problem is formulated and solved for the case of imbedded pseudoholomorphic curve

Ranee Brylinski

Lecomte and Ovsienko constructed $SL_{n+1}(R)$-equivariant quantization maps $Q_λ$ for symbols of differential operators on $λ$-densities on $\RP^n$. We derive some formulas for the associated graded equivariant star products $star_λ$ on the symbol algebra $Pol(T*\RP^n)$. These give some measure of the failure of locality. Our main result expresses (for $n$

Ranee Brylinski

Let $\XR$ be a (generalized) flag manifold of a non-compact real semisimple Lie group $\GR$, where $\XR$ and $\GR$ have complexifications X and G. We investigate the problem of constructing a graded star product on $Pol(T^*\XR)$ which corresponds to a $\GR$-equivariant quantization of symbols into smooth differential operators acting on half-densities on $\X

Otto Rutwig Campoamor, Jose Maria Ancochea

We introduce the concept of weight graph for the weight system $P\frak{g}(T)$ of a finite dimensional nilpotent Lie algebra $\frak{g}$ and analyze the necessary conditions for a $(p,q)$-graph to be a weight graph for some $\frak{g}$.

Mariano Cadoni, Paolo Carta

We use the correspondence between string states and local operators on the world-sheet boundary defined by vertex operators in open string theory to put in correspondence, holographically, the bosonic open string with the large N limit of a mechanical system living on the world-sheet boundary. We give a natural interpretation of this system in terms of a one

O. A. Castro-Alvaredo, A. Fring

We provide a systematic construction for all n-particle form factors of the SU(N)_2/U(1)^{N-1}-homogeneous Sine-Gordon model in terms of general determinant formulae for a huge class of local operators. The ultraviolet limit is carried out and the corresponding Virasoro central charge together with the conformal dimensions of various operators are identified

ST Tsou

The origin of fermion generations is one of the great mysteries in particle physics. We consider here a possible solution within the Standard Model framework based on a nonabelian generalization of electric-magnetic duality. First, nonabelian duality says that dual to the colour (electric) symmetry SU(3), there is a ``colour magnetic symmetry'' $\wid

J. F. Gomes, E. P. Gueuvoghlanian, G. M. Sotkov, A. H. Zimerman

A class of non abelian affine Toda models is constructed in terms of the axial and vector gauged WZW model. It is shown that the multivacua structure of the potential together with non abelian nature of the zero grade subalgebra allows soliton solutions with non trivial electric and topological charges. Their zero curvature representation and the classical $

Noboru Kawamoto, Takuya Tsukioka, Hiroshi Umetsu

We extend previously proposed generalized gauge theory formulation of Chern-Simons type and topological Yang-Mills type actions into Yang-Mills type actions. We formulate gauge fields and Dirac-Kähler matter fermions by all degrees of differential forms. The simplest version of the model which includes only zero and one form gauge fields accommodated with th

Hiromi Kase, Katsusada Morita, Yoshitaka Okumura

Connes' gauge theory on $M_4\times Z_2$ is reformulated in the Lagrangian level. It is pointed out that the field strength in Connes' gauge theory is not unique. We explicitly construct a field strength different from Connes' one and prove that our definition leads to the generation-number independent Higgs potential. It is also shown that the no

G. I. Gakh, M. I. Konchatnij, N. P. Merenkov

Deep-inelastic events for the scattering of the longitudinally polarized electron by polarized proton with tagged collinear photon radiated from initial-state electron are considered. The corresponding cross-section is derived in the Born approximation. The model-independent radiative corrections to the Born cross-section are also calculated. Obtained result

K. J. Eskola, K. Tuominen

We compute in next-to-leading order (NLO) perturbative QCD the amount of transverse energy produced into a rapidity region $ΔY$ of a nuclear collision from partons created in the few-GeV subcollisions. The NLO formulation assumes collinear factorization and is based on the subtraction method. We first study the results as a function of the minimum transverse

Edmond Iancu

The high energy limit of QCD is controlled by the small-$x$ part of a hadron wavefunction. I argue that this part is universal to all hadrons and is composed of a new form of matter: a Colored Glass Condensate. This matter is weakly interacting at very small $x$, but is non-perturbative because of the highly occupied boson states which compose the condensate

P V Landshoff

Key issues in pomeron physics include whether the hard and soft pomerons are distinct objects, and whether the hard pomeron is already present in amplitudes at $Q^2=0$. It is urgent to learn how to combine perturbative and nonperturbative concepts, and to construct a sound theory of perturbative evolution at small $x$. Other questions are whether screening c

Cetin Savkli

In nuclear and particle physics one is often faced with problems where perturbation theory is not applicable. An example of this is the description of bound states. Therefore, an exact solution of field theory to all orders is an unavoidable and interesting problem. Path integrals provide a framework for exact solutions in field theory. In this talk I will p

Travis R. Miller, Michael C. Ogilvie

After a rapid increase in temperature across the deconfinement temperature T_d to temperatures T >> T_d, pure gauge theories exhibit unstable long wavelength fluctuations in the approach to equilibrium. This phenomenon is analogous to spinodal decomposition observed in condensed matter physics, and also seen in models of disordered chiral condensate formatio

M. Salle, J. Smit, J. C. Vink

We study a Hartree ensemble approximation for real-time dynamics in the toy model of 1+1 dimensional scalar field theory. Damping behavior seen in numerical simulations is compared with analytical predictions based on perturbation theory in the original (non-Hartree-approximated) model.

F. Farchioni, A. Feo, T. Galla, C. Gebert

The SUSY Ward identities (WIs) for the N=1 SU(2) SUSY Yang Mills theory discretized on the lattice with Wilson fermions (gluinos) are considered. The study is performed in the framework of a Monte Carlo simulation of the model with light dynamical gluinos. The renormalization and mixing constants of the lattice SUSY current $Z_S$ and $Z_T$ and the additively

Adrian Patrascioiu, Erhard Seiler

We investigate the percolation properties of equatorial strips in the two-dimensional O(3) nonlinear $σ$ model. We find convincing evidence that such strips do not percolate at low temperatures, provided they are sufficiently narrow. Rigorous arguments show that this implies the vanishing of the mass gap at low temperature and the absence of asymptotic freed

Natalia Kuznetsova

Using a sample of 3.7 x 10^6$ Upsilon(4S) -> B Bbar events collected with the BaBar detector at the PEP-II storage ring, we search for the electroweak penguin decays B+ -> K+ e+ e-, B+ -> K+ mu+ mu-, B0 -> K*0 e+ e-, and B0 -> K*0 mu+ mu-. We observe no significant signals for these modes and set preliminary 90% C.L. upper limits of Br(B+ -> K+ e+ e-) < 12.5

Gabriel Cl

In this paper, we study by a functional method the vacuum instability of a charged scalar field, when it is quantized in the background of the Reissner-Nordtrom black hole; we also show that the first stage of the evaporation process of the black hole can be driven by a Schwinger-like effect.

N. Andersson, K. D. Kokkotas

In this review we summarize the current understanding of the gravitational-wave driven instability associated with the so-called r-modes in rotating neutron stars. We discuss the nature of the r-modes, the detailed mechanics of the instability and its potential astrophysical significance. In particular we discuss results regarding the spin-evolution of nasce

Christoph Durr, Huong LeThanh, Miklos Santha

In this paper we introduce a new quantum computation model, the linear quantum cellular automaton. Well-formedness is an essential property for any quantum computing device since it enables us to define the probability of a configuration in an observation as the squared magnitude of its amplitude. We give an efficient algorithm which decides if a linear quan

Rakesh M. Verma

An equational logic program is a set of directed equations or rules, which are used to compute in the obvious way (by replacing equals with ``simpler&#39;&#39; equals). We present static analysis techniques for efficient equational logic programming, some of which have been implemented in $LR^2$, a laboratory for developing and evaluating fast, efficient, an

Daniel C. Hong, Paul V. Quinn, Stefan Luding

In the Brazil nut problem (BNP), hard spheres with larger diameters rise to the top. There are various explanations (percolation, reorganization, convection), but a broad understanding or control of this effect is by no means acheived. A theory is presented for the crossover from the BNP to the reverse Brazil nut problem (RBNP) based on a competition between

M. D. Girardeau, E. M. Wright

A recent paper of Tanatar and Erkan [Phys. Rev. A 62, 053601 (2000)] discusses a density functional approach to the impenetrable point Bose gas in one dimension and an equation for the order parameter of the system, due originally to Kolomeisky et al. [Phys. Rev. Lett. 85, 1146 (2000)], is derived. We comment on the regime of validity of such a model and on

F. Leonard, J. Tersoff

Carbon nanotube junctions are predicted to exhibit negative differential resistance, with very high peak-to-valley current ratios even at room temperature. We treat both nanotube p-n junctions and undoped metal-nanotube-metal junctions, calculating quantum transport through the self-consistent potential within a tight-binding approximation. The undoped junct

David Sherrington, Juan P. Garrahan, Esteban Moro

Recent results and interpretations are presented for the thermal minority game, concentrating on deriving and justifying the fundamental stochastic differential equation for the microdynamics.

G. De Smedt, C. Godreche, J. M. Luck

We revisit the work of Dhar and Majumdar [Phys. Rev. E 59, 6413 (1999)] on the limiting distribution of the temporal mean $M_{t}=t^{-1}\int_{0}^{t}du \sign y_{u}$, for a Gaussian Markovian process $y_{t}$ depending on a parameter $α$, which can be interpreted as Brownian motion in the scale of time $t^{\prime}=t^{2α}$. This quantity, for short the mean `magn

Ivan Markov

The effect of surfactants on the thermodynamics and kinetics of semiconductor heteroepitaxy is briefly discussed. It is argued that the way the surfactants suppress the thermodynamic driving force for 3D islanding depends on the mechanism of exchange of overlayer and surfactant atoms. If the overlayer atoms occupy bulk-like positions provided by the outgoing

M. Filoche, B. Sapoval

A process based on particle evaporation, diffusion and redeposition is applied iteratively to a two-dimensional object of arbitrary shape. The evolution spontaneously transforms the object morphology, converging to branched structures. Independently of initial geometry, the structures found after long time present fractal geometry with a fractal dimension ar

C. Riva, F. M. Peeters, K. Varga

A variational calculation of the ground-state energy of neutral excitons and of positively and negatively charged excitons (trions) confined in a single-quantum well is presented. We study the dependence of the correlation energy and of the binding energy on the well width and on the hole mass. The conditional probability distribution for positively and nega

Toru Sakai, Yoshinori Takahashi

The pseudogap phenomena observed on cuprate high temperature superconductors are investigated based on the exact diagonalization method on the finite cluster t-J model. The results show the presence of the gap-like behavior in the temperature dependence of various magnetic properties; the NMR relaxation rate, the neutron scattering intensity and the static s

Yu. E. Kuzovlev, Yu. V. Medvedev, A. M. Grishin

It is shown, with citing tunnel junction as an example, that mutual interplay of electron quantum transfers in a conducting system can be the fast mechanism for generation fundamental low-frequency flicker conductance fluctuations (1/f noise) without composing Lorentzians. This effect is lost in a theory which neglects the actual discreteness of electron ene

Toru Sakai, Shoji Yamamoto

Magnetization process of ferrimagnetic Heisenberg chains of alternating spins are theoretically studied. The size scaling analysis with the exact diagonalization of finite systems for ($S$,$s$)=(3/2,1) and (2,1) indicates a multi-plateau structure in the ground-state magnetization curve for $S$ and $s$ $>1/2$. The first plateau at the spontaneous magnetizati

C. Ciuhu, A. Lodder

The proximity-effect theory developed by Takahashi and Tachiki for infinite multilayers is applied to multilayer systems with a finite number of layers in the growth direction. The purpose is to investigate why previous applications to infinite multilayers fail to describe the measured data satisfactorily. Surface superconductivity may appear, depending on t

J. M. Pitarke, A. G. Eguiluz

We report extensive self-consistent calculations of jellium surface energies, by going beyond the local-density approximation. The density-response function of a bounded free-electron gas is evaluated within the random-phase approximation, with use of self-consistent electron density profiles. The exchange-correlation energy is then obtained from an exact ad

Munetaka Sasaki, Koji Nemoto

Magnetizations are introduced to the Generalized Random Energy Model (GREM) and numerical simulations on ac susceptibility is made for direct comparison with experiments in glassy materials. Prominent dynamical natures of spin glasses, {\it i.e.}, {\em memory} effect and {\em reinitialization}, are reproduced well in the GREM. The existence of many layers ca

K. E. Nagaev

The shot noise in long diffusive SNS contacts is calculated using the semiclassical approach. At low frequencies and for purely elastic scattering, the voltage dependence of the noise is of the form S_I = (4Δ+ 2eV)/3R. The electron-electron scattering suppresses the noise at small voltages resulting in vanishing noise yet infinite dS_I/dV at V = 0. The distr

J. A. Folk, C. M. Marcus, R. Berkovits, I. L. Kurland

We investigate experimentally and theoretically the behavior of Coulomb blockade (CB) peaks in a magnetic field that couples principally to the ground-state spin (rather than the orbital moment) of a chaotic quantum dot. In the first part, we discuss numerically observed features in the magnetic field dependence of CB peak and spacings that unambiguously ide

R. Weinkamer, H. Gupta, P. Fratzl, J. L. Lebowitz

We investigate, via three-dimensional atomistic computer simulations, phase separation in an alloy under external load. A regular two-dimensional array of cylindrical precipitates, forming a mesoscopic precipitate lattice, evolves in the case of applied tensile stress by the movement of mesoscopic lattice defects. A striking similarity to ordinary crystals i

Arkadiusz Wojs, John J. Quinn

The photoluminescence (PL) spectrum of a two-dimensional electron gas (2DEG) in the fractional quantum Hall regime is studied. The response of the 2DEG to an optically injected valence hole depends on the separation d between the electron and hole layers. At d smaller than the magnetic length lambda, the PL spectrum shows recombination of neutral (X) and cha

Toshimasa Fujisawa, Yasuhiro Tokura, Yoshiro Hirayama

Transient current spectroscopy is proposed and demonstrated in order to investigate the energy relaxation inside a quantum dot in the Coulomb blockade regime. We employ a fast pulse signal to excite an AlGaAs/GaAs quantum dot to an excited state, and analyze the non-equilibrium transient current as a function of the pulse length. The amplitude and time-const

M. Franz, Z. Tesanovic

The idea of spin-charge separation in cuprate superconductors has been recently energized by Senthil and Fisher who formulated a Z_2 gauge theory and, within its context, proposed a ``vison detection&#39;&#39; experiment as a test for topological order in a sample with multiply connected geometry. Here we show that the same experiment can be performed to tes

J. Corson, J. Orenstein, Seongshik Oh, J. O&#39;Donnel

We report measurements of the phase of the conductivity, $ϕ_σ\equiv arg(σ)$, in the normal state of a $Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}$ (BSCCO) thin film from 0.2-1.0 THz. From $ϕ_σ$ we obtain the time delay of the current response, $τ_σ\equivϕ_σ/ω$. After discovering a systematic error in the data analysis, the extracted $τ_σ$ has changed from that reported ear

M. Franz, Z. Tesanovic

We analyze the recent vortex core spectroscopy experiments in cuprate superconductor and discuss what can be learned from them about the nature of the ground state in these compounds. We argue that the data are inconsistent with the assumption of a simple metallic ground state and exhibit characteristics of a doped Mott insulator. A theory for a vortex core

Bruce G. Elmegreen

Observations and theories of the stellar initial mass function are reviewed. The universality and large total mass range of the power law portion of the IMF suggest a connection between stellar mass and cloud structure. The fractal patterns and formation times of young clusters suggest a further connection to turbulence. There is also a similarity between th

Paul A. Crowther

We review the various techniques through which wind properties of massive stars - O stars, AB supergiants, Luminous Blue Variables (LBVs), Wolf-Rayet (WR) stars and cool supergiants - are derived. The wind momentum-luminosity relation (e.g. Kudritzki et al. 1999) provides a method of predicting mass-loss rates of O stars and blue supergiants which is superio

A. Mezzacappa

In this paper, we discuss the current status of core collapse supernova models and the future developments needed to achieve significant advances in understanding the supernova mechanism and supernova phenomenology, i.e., in developing a supernova standard model.

A. Mezzacappa

In this paper, we present results from a simulation of stellar core collapse, bounce, and postbounce evolution with Boltzmann neutrino transport. We motivate the development of our Boltzmann solver in light of the sensitivity of the neutrino-heating core collapse supernova paradigm to details in the neutrino transport, particularly near the neutrinospheres,

Bruce G. Elmegreen, Sungeun Kim, Lister Staveley-Smith

A composite map of HI in the LMC using the ATCA interferometer and the Parkes multibeam telescope was analyzed in several ways in an attempt to characterize the structure of the neutral gas and to find an origin for it. Fourier transform power spectra in 1D, 2D, and in the azimuthal direction were found to be approximate power laws over 2 decades in length.

A. Mezzacappa

A new facility to measure neutrino mass differences and mixing angles and neutrino-nucleus cross sections, such as the proposed ORLaND facility at Oak Ridge, would contribute to the experimental determination of vacuum mixing parameters and would provide an experimental foundation for the many neutrino-nucleus weak interaction rates needed in supernova model

J. Goodman, R. R. Rafikov

We revisit the idea that density-wave wakes of planets drive accretion in protostellar disks. The effects of many small planets can be represented as a viscosity if the wakes damp locally, but the viscosity is proportional to the damping length. Damping occurs mainly by shocks even for earth-mass planets. The excitation of the wake follows from standard line

Thomas H. Reiprich, Hans Boehringer

It is shown that galaxy cluster surveys selecting clusters by their X-ray luminosity effectively select by cluster mass. It is shown that a selection based solely on Abell galaxy richness is less efficient in terms of mass. Furthermore the empirical X-ray luminosity - gravitational mass relation and its scatter is quantified and the relation is compared to p

Joan M. Centrella, Kimberly C. B. New, Lisa L. Lowe, J. David Brown

Dynamical instability is shown to occur in differentially rotating polytropes with N = 3.33 and $T/|W| \gtrsim 0.14$. This instability has a strong m=1 mode, although the m=2, 3, and 4 modes also appear. Such instability may allow a centrifugally-hung core to begin collapsing to neutron star densities on a dynamical timescale. The gravitational radiation emi

D. A. Turnshek, S. Rao, D. Nestor, W. Lane

New optical and infrared observations along the sight-line toward the quasar OI 363 (0738+313) are presented and discussed. Excluding systems which lack confirming UV spectroscopic observations of the actual Lyman alpha line, this sight-line presently contains the two lowest-redshift classical damped Lyman alpha (DLA) quasar absorption line systems known (i.

F. Combes

Active Galactic Nuclei are fueled from material (gas or stars) that are in general far away from the gravitational influence of the central black hole, the engine thought to be responsible for their activity. The required material has a lot of angular momentum, that is a priori quite difficult to evacuate. The various dynamical mechanisms that may play a rol

H. Hoekstra, T. S. van Albada, R. Sancisi

We have studied a mass model for spiral galaxies in which the dark matter surface density is a scaled version of the observed HI surface density. Applying this mass model to a sample of 24 spiral galaxies with reliable rotation curves one obtains good fits for most galaxies. The scaling factors cluster around 7, after correction for the presence of primordia

M. Szymczak, R. Szczerba, P. S. Chen

A sample of J-type carbon stars was searched for OH maser emission. The new detection of three OH lines towards two silicate carbon stars is reported. In V778 Cyg, previously known as the main-lines (1665 and 1667 MHz) maser source, the satellite 1612 MHz emission was discovered while in NSV 2814 the main OH lines were detected. The presence of OH maser line

I. Appenzeller, F. -J. Zickgraf, J. Krautter, W. Voges

In order to derive statistical properties of a complete X-ray selected sample of AGN we used the classification spectra of the RASS Selected Areas-North survey to study the luminosities, redshifts, X-ray/visual flux ratios, line widths, and various correlations between observed parameters of all Seyfert galaxies and QSOs in this sample. On the basis of these

P. O. Pleuss, C. H. Heller, K. J. Fricke

Two continuum subtracted H-alpha HST frames of M101 are used to determine the positions, angular sizes and absolute fluxes of 237 HII regions using a semi-automated technique. From these we have constructed the luminosity and diameter distribution functions. We repeat this process on the images after artificially reducing the linear resolution to that typica

Charles D. Dermer

Statistical arguments show that the volume- and time-averaged kinetic power of GRBs and fireball transients (FTs) into an L* galaxy like the Milky Way is at the level of 10^40 ergs/s. This number, though with wide uncertainties related to the internal or external shock efficiency, is sufficient to power hadronic cosmic rays observed locally. The release of e

Glenn D. Starkman, Dejan B. Stojkovic

Recently Pen and Spergel (1997) have shown that a universe whose energy density is dominated by a frustrated network of non-Abelian TeV-scale cosmic strings could account for a broad class of cosmological observations. In this paper we consider the effects of such a string network on the massive black holes widely believed to inhabit the centers of many gala

S. Cristiani, A. Grazian, A. Omizzolo, C. Corbally

We present progress results of a new survey for bright QSOs (V<14.5, R<15.4, B_J<15.2) covering the whole sky at high galactic latitudes, |b|>30. The surface density of QSOs brighter than B_J=14.8 turns out to be 2.9 +- 0.8 10^{-3} deg^{-2}. The optical Luminosity Function at 0.04 < z < 0.3 shows significant departures from the standard pure luminosity evolu

Nobuhiro Maekawa

In this talk, we discuss the possibility that the vacuum is dynamically determined in the history of the universe. The point is that some of the bubbles with a certain vacuum shrink by the evolution of the universe via gravity and may become black holes. It is interesting that in many cases false vacua are favored in the context of cosmology. By using this a

A. Moneti, S. Stolovy, J. A. D. L. Blommaert, D. F. Figer

In an attempt to determine the nature of the enigmatic cocoon stars in the Quintuplet Cluster, we have obtained mid-infrared imaging and spectrophotometry of the cluster, using the CAM and SWS instruments on ISO, using SpectroCam-10 on the Palomar 5m telescope, and NICMOS on HST. The spectra show smooth continua with various dust and ice absorption features.

M. Valdez-Gutierrez, M. Rosado, L. Georgiev, J. Borissova

We present Halpha and [SII] observations for the Local Group irregular galaxy IC 1613 using the PUMA scanning Fabry-Perot interferometer. Our goal is to analyze the kinematics of the ionized gas in the complex sample of superbubbles located in the whole extension of our field (10 arcmin), which includes most of the optical emission of this galaxy, and to stu

A. M. Chandler, R. E. Rutledge

We searched for coherent X-ray pulsations from Aql X-1 in a series of RXTE observations taken shortly after a recent outburst. During the course of these observations, Aql X-1 passes through an apparent ``propeller&#39;&#39; phase as its luminosity fades to its quiescent value. No pulsations were detected, and we place upper limits (ranging from 0.52% to 9.0

D. B. Kieda, S. P. Swordy, S. P. Wakely

The accurate determination of the elemental composition of cosmic rays at high energies is expected to provide crucial clues on the origin of these particles. Previous direct measurements of composition have been limited by experiment collecting power, resulting in marginal statistics above $10^{14}$ eV, precisely the region where the ``knee&#39;&#39; of the

Janna Levin

A typical stellar mass black hole with a lighter companion is shown to succumb to a chaotic precession of the orbital plane. As a result, the optimal candidates for the direct detection of gravitational waves by Earth based interferometers can show irregular modulation of the waveform during the last orbits before plunge. The precession and the subsequent mo

G. L. Kane, S. F. King, Lian-Tao Wang

We examine what can be deduced from the discovery of a Higgs boson, focusing on a possible discovery at LEP. The analysis begins with the most general situation where no further constraints can be deduced, and then specializes to include various assumptions. Assuming naturalness, the relatively large mass suggests that one or more of larger $\tan β$, large p

Koji Hashimoto

We show that the fluxon solution of the non-commutative gauge theory and its variations are obtained by the soliton generation method recently given by J. A. Harvey, P. Kraus and F. Larsen [hep-th/0010060]. Although this method generally produces non-BPS solutions of equations of motion, the solutions we obtained are BPS. We give the brane interpretation of

Roger Haydock

In periodic, two-dimensional potentials a classical particle might be expected to escape from any finite region if it has enough energy to escape from a single cell. However, for a class of sinusoidal potentials in which the barriers between neighboring cells can be varied, numerical tridiagonalization of Liouville&#39;s equation for the evolution of functio

Satabhisa Dasgupta, Tathagata Dasgupta

Renormalization group analysis of boundary conformal field theory on bosonic D25-brane is used to study tachyon condensation. Placing the lump on a finite circle and triggering only the first three tachyon modes, the theory flows to nearby IR fixed point representing lumps that are extended object with definite profile. The boundary entropy corresponding to

M. P. Nightingale, Vilen Melik-Alaverdian

A quantum Monte Carlo method is introduced to optimize excited state trial wavefunctions. The method is applied in a correlation function Monte Carlo calculation to compute ground and excited state energies of bosonic van der Waals clusters of upto seven particles. The calculations are performed using trial wavefunctions with general three-body correlations.

Angelica de Oliveira-Costa, Max Tegmark, Douglas P. Finkbeiner, R. D. Davies

We present a new puzzle involving Galactic microwave emission and attempt to resolve it. On one hand, a cross-correlation analysis of the WHAM H-alpha map with the Tenerife 10 and 15 GHz maps shows that the well-known DIRBE correlated microwave emission cannot be dominated by free-free emission. On the other hand, recent high resolution observations in the 8

V. Gimenez, J. Reyes

We present recent results for the prediction of the Bs lifetime difference from lattice Heavy Quark Effective Theory simulations. In order to get a next-to-leading order result we have calculated the matching between QCD and HQET and the two-loop anomalous dimensions in the HQET for all the ΔB=2 operators, in particular for the operators which enter the widt

Andre de Gouvea, J. W. F. Valle

We consider the simplest model which solves the solar and atmospheric neutrino puzzles, in the sense that it contains the smallest amount of beyond the Standard Model ingredients. The solar neutrino data is accounted for by Planck-mass effects while the atmospheric neutrino anomaly is due to the existence of a single right-handed neutrino at an intermediate

David Martinez-Delgado, Antonio Aparicio, Maria Angeles Gomez Flechoso, Ricardo Carrera

Standard cosmology predicts that dwarfs were the first galaxies to be formed in the Universe and that many of them merge afterwards to form bigger galaxies such as the Milky Way. This process would have left behind traces such as tidal debris or star streams in the outer halo. We report here the detection of a very low density stellar system at 50+/- 10 kpc

V. K. Magas, L. P. Csernai, D. D. Strottman

A model for energy, pressure and flow velocity distributions at the beginning of ultra-relativistic heavy ion collisions is presented, which can be used as an initial condition for hydrodynamic calculations. Our model takes into account baryon recoil for both target and projectile, arising from the acceleration of partons in an effective field, produced in t

K. G. Selivanov, A. V. Smilga

Flat connections for unitary gauge groups on a 3--torus with twisted boundary conditions as well as recently discovered periodic nontrivial flat connections with ``nondiagonalizable&#39;&#39; triples of holonomies for higher orthogonal and exceptional groups are constructed explicitly in terms of Jacobi theta functions with rational characteristics. The (fra

Luis Benet, Thomas Rupp, Hans A. Weidenmueller

We consider $m$ spinless Fermions in $l > m$ degenerate single-particle levels interacting via a $k$-body random interaction with Gaussian probability distribution and $k <= m$ in the limit $l$ to infinity (the embedded $k$-body random ensembles). We address the cases of orthogonal and unitary symmetry. We derive a novel eigenvalue expansion for the second m

C. G. S. Costa

We review the calculation of the prompt lepton flux, produced in the atmosphere by the semileptonic decay of charmed particles. We describe side by side the intermediary ingredients used by different authors, which include not only the charm production model, but also other atmospheric particle showering parameters. After evaluating separately the relevance

Jiangfeng Du, Hui Li, Xiaodong Xu, Xianyi Zhou

We investigate a multi-player and multi-choice quantum game. We start from two-player and two-choice game and the result is better than its classical version. Then we extend it to N-player and N-choice cases. In the quantum domain, we provide a strategy with which players can always avoid the worst outcome. Also, by changing the value of the parameter of the

J. Charles, L. Oliver

We review briefly the problem of the discrete ambiguities in the determination of the CKM angles, by classifying them into different categories. We then focus on cos(2beta) and the extraction of alpha using QCD factorization.