October 1998 arXiv papers — page 11

S. P. Klevansky

This series of three lectures covers (a) a basic introduction to symmetry breaking in general and chiral symmetry breaking in QCD, (b) an overview of the present status of lattice data and the knowlegde that we have at finite temperature from chiral perturbation theory. (c) Results obtained from the Nambu--Jona-Lasinio model describing static mesonic propert

Harald Fritzsch

In analogy to the mixing pattern of the pseudoscalar mesons in QCD we discuss the mixing of massive neutrinos. Unlike the quarks flavor mixing angles the leptonic mixing angles are large, nearly maximal. The three massive neutrinos are nearly degenerate.

J. F. Gunion

I review selected topics in supersymmetry, including: effects of non-universality, high $\tanb$ and phases on SUSY signals; a heavy gluino as the LSP; gauge-mediated SUSY signals involving delayed decays; R-parity violation and the very worst case for SUSY discovery; some topics regarding Higgs bosons in supersymmetry; and doubly-charged Higgs and higgsinos

F. Borzumati, C. Greub

The next--to--leading order predictions for the branching ratio BR(B -> X_s gamma) are given in a generalized class of two Higgs doublets models. Included are the recently calculated leading QED corrections. It is shown that the high accuracy of the Standard Model calculation is in general not shared by these models. Updated lower limits on the mass of the c

Jeffrey E. Mandula

We address the question of why global gauge fixing, specifically to the lattice Landau gauge, becomes an extremely lengthy process for large lattices. We construct an artificial "gauge-fixing" problem which has the essential features encountered in actuality. In the limit in which the size of the system to be gauge fixed becomes infinite, the problem

Larry Nodulman

Four lectures on experimental test of the standard model presented at the Advanced Summer Institute on Techniques and Concepts of High Energy Physics.

VES collaboration, D. V. Amelin, E. B. Berdnikov, S. I. Bityukov

The production of eta pi - system at low mass by the pi- beam in the Coulomb field of Be nuclei was studied. The cross section of the reaction pi- Be --> eta pi- Be was compared to the experimental data on the decay eta --> pi+ pi- gamma and to the theoretical predictions.

Ioannis Giannakis, K. Kleidis, K. Kuiroukidis, D. Papadopoulos

We study string propagation in an anisotropic, cosmological background. We solve the equations of motion and the constraints by performing a perturbative expansion of the string coordinates in powers of c^2, the world-sheet speed of light. To zeroth order the string is approximated by a tensionless string (since c is proportional to the string tension T). We

Stephen L. Adler

We give a systematic, abstract formulation of the image normalization method as applied to a general group of image transformations, and then illustrate the abstract analysis by applying it to the hierarchy of viewing transformations of a planar object.

Jorge Alfaro, Oscar Cubero, Luis F. Urrutia

The quantum mechanical version of a classical model for studying the orientational degrees of freedom corresponding to a nematic liquid composed of biaxial molecules is presented. The effective degrees of freedom are described by operators carrying an SU(3) representation, which allows the explicit calculation of the partition function in the mean field appr

Michele Pasquini, Maurizio Serva

We perform a scaling analysis on NYSE daily returns. We show that volatility correlations are power-laws on a time range from one day to one year and, more important, that they exhibit a multiscale behaviour.

Nicolas Sourlas

We study numerically the zero temperature Random Field Ising Model on cubic lattices of various linear sizes $ 6 \le L \le 90 $ in three dimensions with the purpose of verifying the validity of universality for disordered systems. For each random field configuration we vary the ferromagnetic coupling strength J and compute the ground state exactly. We examin

K. Reuter, F. J. Garcia-Vidal, P. L. de Andres, F. Flores

Applying a Keldysh Green`s function method it is shown that hot electrons injected from a STM-tip into a CoSi${}_2$/Si(111) system form a highly focused beam due to the silicide band structure. This explains the atomic resolution obtained in recent Ballistic Electron Emission Microscopy (BEEM) experiments. Localized surface states in the $(2 \times 1)$-recon

N. Mason, A. Kapitulnik

Results on the superconductor to insulator transition in two-dimensional films are analyzed in terms of coupling of the system to a dissipative bath. Upon lowering the temperature the parameter that controls this coupling becomes relevant and a wide range of metallic phase is recovered.

T. J. Newman, Michael R. Swift

We reply to the recent comment cond-mat/9809184 on our original paper `Non-universal exponents in interface growth', Phys. Rev. Lett, 79, 2261 (1997).

Kevin Ingersent, Qimiao Si

The variant of the single-impurity Kondo problem in which the conduction-band density of states has a power-law pseudogap at the Fermi energy is known to exhibit a zero-temperature phase transition at a finite exchange coupling. The critical properties of this transition are studied both for N=2 and for N>>1, where N is the spin degeneracy. The critical expo

M. Bocquet

We study spectral properties of a one-dimensional Dirac equation with various disorder. We use replicas to calculate the exact density of state and typical localization length of a Dirac particle in several cases. We show that they can be calculated in any type of disorder obeying a Gaussian white noise distribution. In particular, we study the random electr

S. S. Murzin, I. Claus, A. G. M. Jansen, N. T. Moshegov

It is shown that the observed Quantum Hall Effect in epitaxial layers of heavily doped n-type GaAs with thickness (50-140 nm) larger the mean free path of the conduction electrons (15-30 nm) and, therefore, with a three-dimensional single-particle spectrum is induced by the electron-electron interaction. The Hall resistance R_xy of the thinnest sample reveal

Beom Jun Kim, Gun Sang Jeon, M. -S. Choi, M. Y. Choi

We study the zero-temperature phase transitions of two-dimensional superconducting arrays with both the self- and the junction capacitances in the presence of external magnetic fields. We consider two kinds of excitations from the Mott insulating phase: charge-dipole excitations and single-charge excitations, and apply the second-order perturbation theory to

Miki Matsuo, Shin-ichi Sasa

We propose an energetic interpretation ofstochastic processes described by Langevin equations with non-uniform temperature. In order to avoid Itô-Stratonovich dilemma, we start with a Kramers equation, and derive a Fokker-Plank equation by the renormalization group method. We give a proper definition of heat for the system. Based on our formulations,we analy

Pierre Le Doussal, Thierry Giamarchi

We discuss the question of the generation of topological defects (dislocations) by quenched disorder in two dimensional periodic systems. In a previous study [Phys. Rev. B {\bf 52} 1242 (1995)] we found that, contrarily to $d=3$, unpaired dislocations appear in $d=2$ above a length scale $ξ_D$, which we estimated. We extend this description to include effect

Anders Johansen, Olivier Ledoit, Didier Sornette

We study a rational expectation model of bubbles and crashes. The model has two components : (1) our key assumption is that a crash may be caused by local self-reinforcing imitation between noise traders. If the tendency for noise traders to imitate their nearest neighbors increases up to a certain point called the ``critical'' point, all noise trade

H. Alt, C. I. Barbosa, H. -D. Graef, T. Guhr

Two superconducting microwave billiards have been electromagnetically coupled in a variable way. The spectrum of the entire system has been measured and the spectral statistics analyzed as a function of the coupling strength. It is shown that the results can be understood in terms of a random matrix model of quantum mechanical symmetry breaking -- as e.g. th

Rosendo Vilchez-Gomez

I present here a review of the observed characteristics of the optical diffuse light in clusters, the possible sources of this light and some of the theories that try to explain the existence of big envelopes around the brightest cluster galaxies.

Adam G. Riess, Robert P. Kirshner, Brian P. Schmidt, Saurabh Jha

We present 1210 Johnson/Cousins B,V,R, and I photometric observations of 22 recent type Ia supernovae (SNe Ia): SN 1993ac, SN 1993ae, SN 1994M, SN 1994S, SN 1994T, SN 1994Q, SN 1994ae, SN 1995D, SN 1995E, SN 1995al, SN 1995ac, SN 1995ak, SN 1995bd, SN 1996C, SN 1996X, SN 1996Z, SN 1996ab, SN 1996ai, SN 1996bk, SN 1996bl, SN 1996bo, and SN 1996bv. Most of the

Norman K. Glendenning, Jurgen Schaffner-Bielich

First order Bose condensation in asymmetric nuclear matter and in neutron stars is studied, with particular reference to kaon condensation. We demonstrate explicitly why the Maxwell construction fails to assure equilibrium in multicomponent substances. Gibbs conditions and conservation laws require that for phase equilibrium, the charge density must have opp

R. Schild

We analyze the Q0957+561 A,B brightness record with 3 types of wavelets to define properties that are independent of the nature of the analyzing wavelet. The wavelet analysis picks out features having arbitrary shape, and localizes them in time and fits amplitudes. We find that independently of the analyzing wavelet, the mean wavelet amplitude is zero, meani

R. E. Rutledge, L. Bildsten, E. F. Brown, G. G. Pavlov

We re-analyze the available X-ray spectral data of the type I bursting neutron star transients Aql X-1, Cen X-4, and 4U 1608-522 using realistic hydrogen atmosphere models. Previous spectral fits assumed a blackbody spectrum; because the free-free dominated photospheric opacity decreases with increasing frequency, blackbody spectral fits overestimate the eff

D. H. McIntosh, M. J. Rieke, H. -W. Rix, C. B. Foltz

We have obtained H-band spectra of 32 luminous quasars at 2.0<z<2.5 with the Multiple Mirror Telescope. The sample contains 15 radio-loud quasars (RLQs) and 17 radio-quiet quasars (RQQs). We have measured emission line properties from the rest-frame wavelength range of approximately 4500-5500 Angstroms, by fitting the data with composite model spectra. Our a

P. Sikivie

The late infall of cold dark matter onto an isolated galaxy produces flows with definite local velocity vectors throughout the galactic halo. It also produces caustic rings, which are places in the halo where the dark matter density is very large. The self-similar model of halo formation predicts that the caustic ring radii $a_n$ follow the approximate law $

Rodger I. Thompson, Lisa J. Storrie-Lombardi, Ray J. Weymann, Marcia J. Rieke

This paper contains a catlog of sources observed in a portion of the Hubble Deep Field by the NICMOS instrument. Methods of observation and data analysis are discussed. The catalog has two parts. The first is a listing of all sources with signal to noise ratios greater than or equal to 2.5. The second part contains sources with signal to noise ratios less th

Norman K. Glendenning, Jeurgen Schaffner-Bielich

We discuss the nature of the kaon condensation phase transition. We find several features which, if kaons condense in neutron stars, are not only remarkable, but must surely effect such properties as superfluidity and transport properties, which in turn are relevant to the glitch phenomenon and cooling rates of neutron stars. The mixed phase, because of the

J. A. de Freitas Pacheco, S. Stoica, F. Thevenin, J. E. Horvath

The apparent discrepancy between abundances of light nuclides predicted by the standard Big-Bang and observational data is explained, by assuming the presence of metastable H dibaryons at the nucleosynthesis era. These dibaryons could be formed out of a small fraction of strange quarks at the moment of the confinement transition. For a primordial deuterium a

I. Kreykenbohm, P. Kretschmar, J. Wilms, R. Staubert

We present results from four observations of the accreting X-ray pulsar Vela X-1 with RXTE in 1996 February. The light curves show strong pulse to pulse variations, while the average pulse profiles are quite stable, similar to previous results. Below 5keV the pulse profiles display a complex, 5-peaked structure with a transition to a simple, double peak abov

Ian Smail, Rob Ivison, Andrew Blain, Jean-Paul Kneib

We review published deep surveys in the submillimeter (sub-mm) regime from the new Sub-millimetre Common User Bolometer Array (SCUBA) on the 15-m James Clerk Maxwell Telescope (JCMT), Mauna Kea, Hawaii. Summarising the number counts of faint sub-mm sources determined from the different surveys we show that the deepest counts from our completed SCUBA Lens Sur

A. C. S. Friaca, L. C. Jafelice

Large masses of absorbing material are inferred to exist in cooling flows in clusters of galaxies from the excess X-ray absorption in the spectra of some X-ray clusters. The absorbing material is probably in the form of cold clouds pressure-confined by the surrounding, hot, X-ray emitting gas. The cold clouds could remain relatively static until they are des

Saleem Zaroubi, Yehuda Hoffman, Avishai Dekel

We present an alternative, Bayesian method for large-scale reconstruction from observed peculiar velocity data. The method stresses a rigorous treatment of the random errors and it allows extrapolation into poorly sampled regions in real space or in k-space. A likelihood analysis is used to determine the fluctuation power spectrum, followed by a Wiener Filte

Albert A. Zijlstra

The effect of metallicity on the AGB mass loss is reviewed. Observations have mainly been limited to the Magellanic Clouds but are observationally feasible throughout the Local Group. Expansion velocities are predicted to depend strongly on Z but the peak mass-loss rates appear not to. The Mira PL relation shows no evidence for a Z-dependence, giving a power

V. Charmandaris, O. Laurent, I. F. Mirabel, P. Gallais

We present mid-infrared images at $6.7 μm$ and $15 μm$ of ``The Cartwheel&#39;&#39; (AM~0035-33), the prototypical collisional ring galaxy. The observations, taken with ISOCAM, reveal the distribution of hot dust in the galaxy and its two companions in the north-east. The intensity of the mid-IR emission from the outer star forming ring of the Cartwheel show

Noah Brosch, Ana Heller, Elchanan Almoznino

We studied the morphology of star formation in dwarf irregular galaxies and found that, in general, this takes place on one side of a galaxy and far from the center. This is mainly true for low surface brightness galaxies; in high surface brightness dwarf irregulars the star formation tends to be more centrally concentrated, as well as being more intense. We

A. MacFadyen, S. E. Woosley

Using a two-dimensional hydrodynamics code (PROMETHEUS), we study the continued evolution of rotating massive helium stars whose iron core collapse does not produce a successful outgoing shock, but instead forms a black hole. We study the formation of a disk, the associated flow patterns, and the accretion rate for disk viscosity parameter, alpha ~ 0.001 and

Benjamin D. Wandelt, Eric Hivon, Krzysztof M. Gorski

Much attention has been given to the problem of estimating cosmological parameters from the $C_l$ measured by future experiments. Many of the approaches which are being used either invoke poorly controlled approximations or are computationally expensive. We derive exact results as well as fast and highly accurate approximations for mapping a theoretical mode

R. A. Vázquez

If gamma ray bursts produce a total energy of 10^54 ergs and this energy is concentrated on the high energy tail of the spectrum E> 1 TeV, then they may account for the observed diffuse extragalactic gamma ray emission for energies > 100 MeV. Such an energy could be released if the GRB&#39;s are produced by the burning of the total mass of a neutron star in

Michael H. Freedman, David A. Meyer

Cellulations of the projective plane RP^2 define single qubit topological quantum error correcting codes since there is a unique essential cycle in H_1(RP^2;Z_2). We construct three of the smallest such codes, show they are inequivalent, and identify one of them as Shor&#39;s original 9 qubit repetition code. We observe that Shor&#39;s code can be constructe

M. Ardehali

We describe in detail the method for Particle-in cell/Monte-Carlo simulation of electron cyclotron resonance (ECR) discharges. In the simulation, electric and magnetic fields are obtained by solving Maxwell equations, and electrons and ions are accelerated by solving equations of motion. We consider two different cases: (i) propagation of electromagnetic wav

M. Ardehali

Particle-in-cell/Monte Carlo technique is used to simulate low pressure electro-negative and electro-positive plasmas at a frequency of 10 MHz. The potential, electric field, electron and ion density, and currents flowing across the plasma are presented. To compare the physical properties of the electro-positive gas with those of an electro-negative gas, the

Michael Farber

It is shown that the Novikov inequalities for critical points of closed 1-forms hold with the von Neumann Betti numbers replacing the Novikov numbers. As a corollary we obtain a vanishing theorem for $L^2$ cohomology, generalizing a theorem of W. Lueck. We also prove that von Neumann Betti numbers coincide with the Novikov numbers for free abelian coverings.

Mihaela Time

The space-time foliation Sigma compatible with the gravitational field g on a 4-manifold M determines a fibration pi of M, pi : M -> N is a surjective submersion over the 1-dimensional leaves space N. M is then written as a disjoint union of the leaves of Sigma, which are 3-dimensional spacelike surfaces on M. The decomposition, TM=Sigma + T^0 M, also implie

Henk van Elst, George F R Ellis

We employ the extended 1+3 orthonormal frame formalism for fluid spacetime geometries $({\cal M}, {\bf g}, {\bf u})$, which contains the Bianchi field equations for the Weyl curvature, to derive a 44-D evolution system of first-order symmetric hyperbolic form for a set of geometrically defined dynamical field variables. Describing the matter source fields ph

S. I. Tertychniy

An example of application of the specialized computer algebra system Grg-EC to the searching for solutions to the source-free Maxwell and Einstein--Maxwell equations is demonstrated. The solution involving five arbitrary functions of two variables is presented in explicit form (up to quadratures). An emphasis is made on the characterizing of the software uti

George Davies

This article outlines our derivation of the second order perturbations to a Schwarzschild black hole, highlighting our use of, and necessary reliance on, computer algebra. The particular perturbation scenario that is presented here is the case of the linear quadrapole seeding the second order quadrapole. This problem amounts to finding the second order Zeril

P. Fiziev

We propose a novel self consistent minimal coupling principle in presence of torsion dilaton field. This principle yields a new local dilatation symmetry and predicts the interactions of torsion dilaton with the real matter and with metric. The soft violation of this symmetry yields a physical dilaton and a simple relation between Cartan scalar curvature and

M. Hilke, D. Shahar, S. H. Song, D. C. Tsui

We present experimental results on the quantized Hall insulator in two dimensions. This insulator, with vanishing conductivities, is characterized by the quantization (within experimental accuracy) of the Hall resistance in units of the quantum unit of resistance, h/e^2. The measurements were performed in a two dimensional hole system, confined in a Ge/SiGe

R. Eder

We discuss the excitation spectrum of a disordered, isotropic and translationally invariant spin state in the 2D Heisenberg antiferromagnet. The starting point is the nearest-neighbor RVB state which plays the role of the vacuum of the theory, in a similar sense as the Neel state is the vacuum for antiferromagnetic spin wave theory. We discuss the elementary

David H. Hughes, James Dunlop, Michael Rowan-Robinson, Steve Serjeant

The advent of sensitive sub-mm array cameras now allows a proper census of dust-enshrouded massive star-formation in very distant galaxies, previously hidden activity to which even the deepest optical images are insensitive. We present the deepest sub-mm survey, taken with the SCUBA camera on the James Clerk Maxwell Telescope (JCMT) and centred on the Hubble

Ari Laor

IZw1 is the prototype narrow line quasar. This type of AGNs show a number of common peculiar characteristics whose physical origin is not yet well understood. Here, I review the results of a detailed study by Laor et al. (1997b) of the UV emission properties of IZw1, based on a high quality HST FOS spectrum. The main results are: 1) The Mg II and the Al III

Katharine C. Walker, Bradley E. Schaefer, E. E. Fenimore

We have performed searches for isolated flares and for steady flickering in Gamma Ray Burst light curves on the microsecond to millisecond time scales. Two bursts out of our sample of 20 revealed four isolated flares with time scales from $256 μs$ to $2048 μs$. A wavelet analysis for our sample showed low level flickering for all bursts on time scales from $

Bradley E. Schaefer, Katharine C. Walker

The Gamma Ray Burst GRB920229 has four extreme and unprecedented properties; a rise in brightness with an e-folding time scale of $220 \pm 30 μs$, a fall in brightness with an e-folding time scale of $400 \pm 100 μs$, a large change in spectral shape over a time of $768 μs$, and a sharp spectral cutoff to high energies with $ΔE/E = 18 %$. The rapid changes o

Noah Brosch, Yehuda Hoffman

We observed the large and faint planetary nebula (PN) around IN Com in H-alpha and [NII] light with a coronagraphic CCD device on the Wise Observatory reflector blocking the light from the central star. Our goal was to provide a second image of the object with which to confirm the features seen in the only published photograph from the paper reporting the di

K. A. Williams, W. Brinkmann, G. Wiedenmann

The large-scale (~ 20&#39;) diffuse x-ray background surrounding a sample of quasars observed during ROSAT PSPC pointed observations is studied using a new source-detection algorithm, the scaling-index method. This algorithm, which can identify individual photons as belonging to a source or background, is useful for detecting faint, extended sources in noisy

M. N. Tamashiro, Yan Levin, Marcia C. Barbosa

The one-component plasma (OCP) represents the simplest statistical mechanical model of a Coulomb system. For this reason, it has been extensively studied over the last forty years. The advent of the integral equations has resulted in a dramatic improvement in our ability to carry out numerical calculations, but came at the expense of a physical insight gaine

Dmitri Diakonov, Victor Petrov

We argue that asymptotically linear static potential is built in into the common procedure of extracting it from lattice Wilson loop measurements. To illustrate the point, we extract the potential by the standard lattice method in a model vacuum made of instantons. A beautiful infinitely rising linear potential is obtained in the case where the true potentia

J. M. Tranquada, N. Ichikawa, S. Uchida

We present the results of neutron-scattering studies on various aspects of crystalline and magnetic structure in single crystals of La(1.6-x)Nd(0.4)Sr(x)CuO(4) with x=0.12 and 0.15. In particular, we have reexamined the degree of stripe order in an x=0.12 sample. Measurements of the width for an elastic magnetic peak show that it saturates at a finite value

M. Pascaud, G. Montambaux

We have studied the appearance of chaos in the many-body spectrum of interacting Fermions. The coupling of a single state to the Fermi sea is considered. This state is coupled to a hierarchy of states corresponding to one or several particle-hole excitations. We have considered various couplings between two successive generations of this hierarchy and determ

M. M. Colavita, J. K. Wallace

The Palomar Testbed Interferometer (PTI) is a long-baseline infrared interferometer located at Palomar Observatory, California. It was built as a testbed for interferometric techniques applicable to the Keck Interferometer. First fringes were obtained in July 1995. PTI implements a dual-star architecture, tracking two stars simultaneously for phase referenci

Adonai S. Sant&#39;Anna, Daniel C. Freitas

We propose that the quantum vacuum may be considered as a gas of virtual photons which carry a non-vanishing linear momentum as well as a non-vanishing energy. We study, in particular, the Casimir effect in order to show that these virtual photons should satisfy a Fermi-Dirac statistics, which implies a non-zero temperature of the vacuum state.

Alexander Sergeev

Let V be a finite-dimensional superspace and G a simple (or a ``close&#39;&#39; to simple) matrix Lie superalgebra, i.e., a Lie subsuperalgebra in GL(V). Under the classical invariant theory for G we mean the description of G-invariant elements of the tensor algebra of V. We give such description for GL(V), SL(V) and OSP(V) and their ``odd&#39;&#39; analogs:

Vladimir Shander

There are two superanalogs of the general linear group: GL(m|n) and GQ(n). For any supercommutative superalgebra C let G(C) be the set of C-points of the supermanifold G. Here there are described the GQ(n; C)-invariant functions on Q(n; C) and GL(n; C)-invariant functions on the odd subspace of Mat (n|n; C), more exactly, the invariants of the action of Lie

Alexander Sergeev

Chevalley&#39;s theorem states that for any simple finite dimensional Lie algebra G (1) the restriction homomorphism of the algebra of polynomials on G onto the Cartan subalgebra H induces an isomorphism between the algebra of G-invariant polynomials on G with the algebra of W-invariant polynomals on H, where W is the Weyl group of G, (2) each G-invariant po

Alexander Sergeev

For the orthogonal Lie algebra O(2n+1), in addition to the conventional set of orthogonal polynomials, another set is produced with the help of the Lie superalgebra OSP(1|2n). Difficulties related with expression of Dyson&#39;s constant for the Lie superalgebras are discussed.

Alexander Sergeev

The description of irreducible finite dimensional representations of finite dimensional solvable Lie superalgebras over complex numbers given by V.~Kac is refined. In reality these representations are not just induced from a polarization but twisted, as infinite dimensional representations of solvable Lie algebras. Various cases of irreducibility (general an

Arturo Alvarez

In this paper we associate to t-motives with level structures a finite dimensional vector subspace (subspace of uniformizers). We study the particular case of elliptic sheaves finding some relations with some objects from conformal field theory.

Thomas Schick

In this paper, we investigate analytical and geometric properties of certain non-compact boundary-manifolds, namely manifolds of bounded geometry. One result are strong Bochner type vanishing results for the L^2-cohomology of these manifolds: if e.g. a manifold admits a metric of bounded geometry which outside a compact set has nonnegative Ricci curvature an

Ram Brustein

Scale factor duality, a truncated form of time dependent T-duality, is a symmetry of string effective action in cosmological backgrounds interchanging small and large scale factors. The symmetry suggests a cosmological scenario ("pre-big-bang") in which two duality related branches, an inflationary branch and a decelerated branch are smoothly joined into one

Roberto Soldati, Lorenzo Sorbo

Some new expressions are found, concerning the effective action as a regularized path-integral for Dirac&#39;s spinors in {\it 3+1} dimensions, in the presence of general uniform (i.e., constant and homogeneous) electric and magnetic fields. The rate of $e^+e^-$ pairs production is computed and briefly discussed.

D. V. Ivanov

The relativistic three-quark equations are found in the framework of the dispersion relation technique. The approximate solutions of these equations using the method based on the extraction of leading singularities of the amplitude are obtained. The calculated mass values of two ($ N=2, 56^* $) baryonic multiplets $ J^P ={1/2}^{+},{3/2}^{+} $ are in good agr

E. Oset, J. A. Oller, J. R. Peláez, Chiang Huan Ching

A new tool which combines chiral perturbation theory and unitarity in coupled channels is applied with success to the study of the meson-meson interaction, extending the theoretical predictions up to sqrt{s} = 1.2 GeV, hence improving considerably the convergence radius of conventional chiral perturbation theory. The method is applied to obtain the meson-mes

Vicente Azcoiti, Angelo Galante

We show how, contrary to physical intuition, thermal fluctuations of physical states having a non-vanishing baryonic number can be fully neglected in the thermodynamics of QCD at any physical temperature. We also discuss on the consistency between our results and the CPT theorem. The last part of this article is devoted to comment some interesting physical f

M. Kalelkar

We have measured the differential cross sections for the production of $π^{+}$, $K^{+}$, $K^{0}$, $K^{*0}$, $ϕ$, p, $Λ$ and their corresponding antiparticles in separate samples of flavor-tagged $Z^{0}\to$ light-flavor ($u\bar{u}$, $d\bar{d}$, or $s\bar{s}$), $Z^{0}\to c\bar{c}$ and $Z^{0}\to b\bar{b}$ events. Clear flavor dependences are observed, and the r

Redouane Fakir

We find that general relativity can be naturally free of cosmological singularities. Several nonsingular models are currently available that either assume ad hoc matter contents, or are nonsingular only over a sector of solution space of zero measure, or depart drastically from general relativity at high energies. After much uncertainty over whether cosmolog

Serge M. Nakhmanson, D. A. Drabold

We have performed an approximate ab initio calculation of vibrational properties of hydrogenated amorphous silicon (a-Si:H) using a molecular dynamics method. A 216 atom model for pure amorphous silicon (a-Si) has been employed as a starting point for our a-Si:H models with voids that were made by removing a cluster of silicon atoms out of the bulk and termi

R. S. Markiewicz, C. Kusko

Recent tunneling studies in Bi2Sr2CaCu2O8 suggest that the pseudogap is caused by superconducting fluctuations. By reanalyzing this data, we show that instead there is a second non-superconducting component of the gap which increases strongly with underdoping.

M. Amoruso, A. Minguzzi, S. Stringari, M. P. Tosi

We present a semiclassical three-fluid model for a Bose-condensed mixture of interacting Bose and Fermi gases confined in harmonic traps at finite temperature. The model is used to characterize the experimentally relevant behaviour of the equilibrium density profile of the fermions with varying composition and temperature across the onset of degeneracy, for

Ekkehard Lange

I employ an exactly soluble toy model to investigate why unrenormalized perturbation theory works better than fully self-consistent approaches in describing the correlation-driven metal-insulator transition.

C. Firmani, V. Avila-Reese

We study the evolution of disk galaxies within the frame of the cold dark matter (CDM) cosmologies. The hydrodynamics of a centrifugally supported gaseous disk and the growth of a stellar disk are calculated in detail taking into account the energy balance of the ISM and the gravitational instabilities that concern gas and stars. The halo density profile is

Eduardo L. D. Bica, Henrique R. Schmitt, Carlos, M. Dutra

A survey of extended objects in the Large Magellanic Cloud was carried out on the ESO/SERC R and J Sky Survey Atlases, checking entries in previous catalogs and searching for new objects. The census provided 6659 objects including star clusters, emission-free associations and objects related to emission nebulae. Each of these classes contains 3 subclasses wi

Henrique R. Schmitt, Thaisa Storchi-Bergmann, Roberto Cid Fernandes

We present the results of an optical spectral synthesis analysis for the nuclei of 20 Seyfert 2 and 4 Radio Galaxies, using a base of stellar population templates of different ages and metallicities and a power-law continuum. Compared with the stellar population of elliptical galaxies, we find that Seyfert 2s usually have a smaller contribution from old meta

Thomas S. Statler, Ivan R. King, Philippe Crane, Robert I. Jedrzejewski

We report observations of the double nucleus of M31 with the f/48 long-slit spectrograph of the HST Faint Object Camera. We obtain a total exposure of 19,000 sec. over 7 orbits, with the 0.063-arcsec-wide slit along the line between the two brightness peaks (PA 42). A spectrum of Jupiter is used as a spectral template. The rotation curve is resolved, and rea

Marco Chiaberge, Gabriele Ghisellini

Blazars are characterized by large amplitude and fast variability, indicating that the electron distribution is rapidly changing, often on time scales shorter than the light crossing time. The emitting region is sufficiently compact to let radiative losses dominate the cooling of high energy electrons. We study the time dependent behaviour of the electron di

John D. Monnier

This paper will review the technical progress of interferometric infrared observing techniques from the first 2-element interferometer 25 years ago to the 3+ element arrays now coming into service. To date, only the Infrared Spatial Interferometer (ISI) has published separate-element interferometric data on circumstellar dust shells in the infrared and many

Yoshiaki Taniguchi, Youichi Ohyama

In order to understand what controls the star formation process in luminous starburst mergers (e.g., NGC 6240, Arp 220, and so on), we investigate observational properties of two samples of high-luminosity starburst galaxies mapped in CO($J$=1--0) independently using both the Owens Valley Radio Observatory (Scoville et al. 1991) and the IRAM interferometer (

Ekkehard Lange, Gabriel Kotliar

We investigate the Hall effect and the magnetoresistance of strongly correlated electron systems using the dynamical mean-field theory. We treat the low- and high-temperature limits analytically and explore some aspects of the intermediate-temperature regime numerically. We observe that a bipartite-lattice condition is responsible for the high-temperature re

Eric L. Sandquist, Michael Bolte, G. E. Langer, James E. Hesser

We present new VI photometry for the halo globular cluster M30 (NGC 7099), and compute luminosity functions (LFs) in both bands for samples of about 15,000 hydrogen-burning stars from near the tip of the red giant branch (RGB) to over four magnitudes below the main-sequence (MS) turnoff. We confirm previously observed features of the LF that are at odds with

D. Boyanovsky, H. J. de Vega, Y. J. Ng, D. -S. Lee

In this article we study the dynamics of fermions in a fermion-scalar plasma. We begin by obtaining the effective in-medium Dirac equation in real time which is fully renormalized and causal and leads to the initial value problem. For a heavy scalar we find the novel result that the decay of the scalar into fermion pairs in the medium leads to damping of the

Duiliu-Emanuel Diaconescu, Jaume Gomis

We consider Type IIB Neveu-Schwarz five-branes transverse to C^2/Z_n orbifolds and conjecture that string theory on the near horizon geometry is dual to the decoupled theory on the branes. We analyze the conformal field theory describing the near horizon region and the world volume non-critical string theory. The modular invariance consistency condition of s

Hisakazu Minakata, Hiroshi Nunokawa

We perform an updated model-independent analysis using the latest solar neutrino data obtained by $^{37}$Cl and $^{71}$Ga radiochemical experiments, and most notably by a large water-Cherenkov detector SuperKamiokande with their 504 days of data taking. We confirm that the astrophysical solutions to the solar neutrino problem are extremely disfavored by the

Jian-Xin Zhu, C. S. Ting

The induction of an s-wave component in a d-wave superconductor is considered. Near the {110}-oriented edges of such a sample, the induced s-wave order parameter together with d-wave component forms a complex combination d+e^{iϕ} s, which breaks the time reversal symmetry (BTRS) of the pairing state. As a result, the spontaneous current is created. We numeri

Hirosi Ooguri, Kostas Skenderis

We study the dilaton/axion configuration near D-instantons in type IIB superstring theory. In the field theory limit, the metric near the instantons becomes flat in the string frame as well as in the Einstein frame. In the large N limit, the string coupling constant becomes zero except near the origin. The supersymmetry of this configuration is analyzed. An

M. Bayindir, Z. Gedik

We studied the effects of nonmagnetic impurities on high-temperature superconductors by solving the Bogoliubov-de Gennes equations on a two-dimensional lattice via exact diagonalization technique in a fully self-consistent way. We found that s-wave order parameter is almost unaffected by impurities at low concentrations while $d_{x^2-y^2}$-wave order paramet

S. Catani, M. Grazzini

We consider the singular behaviour of tree-level QCD amplitudes when the momenta of three partons become simultaneously parallel. We discuss the universal factorization formula that controls the singularities of the multiparton matrix elements in this collinear limit and present the explicit expressions of the corresponding splitting functions. The results f