March 1999 arXiv papers — page 11

A. Mastichiadis, J. G. Kirk

We present the expected variability features in the context of the Synchro- Self-Compton (SSC) model of emission from Active Galactic Nuclei (AGNs) and show that the homogeneous SSC model describes well the observed multi- wavelength spectrum and variability of objects such as Mkn 421 and Mkn 501; however in order to explain the very fast flaring timescales

R. Coziol, R. E. Carlos Reyes, S. Considere, E. Davoust

We show that the excess of nitrogen emission observed in a large sample of Starburst Nucleus Galaxies (SBNGs) can only be explained at a given metallicity by an overabundance of nitrogen with respect to normal HII regions in the disks of late-type spirals. The N/O ratios in the SBNGs are comparable to the values found in the bulges of normal early-type spira

N. Murray, M. Holman

Classical analytic theories of the solar system indicate that it is stable, but numerical integrations suggest that it is chaotic. This disagreement is resolved by a new analytic theory. The theory shows that the chaos among the Jovian planets results from the overlap of the components of a mean motion resonance among Jupiter, Saturn, and Uranus, and provide

Philip R. Maloney

The energy input into the interstellar medium in Ultraluminous Infrared Galaxies (ULIRGs) is enormous, regardless of the nature of the power source. I discuss some of the major consequences for the structure and energetics of the ISM in these galaxies. Observationally, the column densities in the nuclear regions of ULIRGs are known to be very high, which mak

Gary Bernstein, Philippe Fischer

The lensed double QSO 0957+561 has a well-measured time delay and hence is useful for a global determination of H0. Uncertainty in the mass distribution of the lens is the largest source of uncertainty in the derived H0. We investigate the range of \hn produced by a set of lens models intended to mimic the full range of astrophysically plausible mass distrib

N. Z. Scoville

Recent high resolution near infrared (HST-NICMOS) and mm-interferometric imaging have revealed dense gas and dust accretion disks in nearby ultra-luminous galactic nuclei. In the best studied ultraluminous IR galaxy, Arp 220, the 2 micron imaging shows dust disks in both of the merging galactic nuclei and mm-CO line imaging indicates molecular gas masses app

A. S. Evans

HST NICMOS observations of a sample of 24 luminous (LIGs: L_(IR) [8-1000 microns] = 10^(11.0-11.99) L_sun) and ultraluminous (ULIGs: L_(IR) > 10^(12.0) L_sun) infrared galaxies are presented. The observations provide, for the first time, high resolution HST imaging of the imbedded 1.1 - 2.2 micron nuclear regions of these mergers. All but one of the ULIGs ar

Dongsu Bak

A self-replicating system where the elements belonging to a solution category can replicate themselves by copying their own informations, is considered. The information carried by each element is defined by an element of all the n multiple tensor product of a base space that consists of m different base elements. We assume that in the replication the process

L. R. Abramo

Inflation leads us to expect a spectrum of gravitational waves (tensor perturbations) extending to wavelengths much bigger than the present observable horizon. Although these gravity waves are not directly observable, the energy density that they contribute grows in importance during the radiation- and dust-dominated ages of the universe. We show that the ba

Jerome Gauntlett, Chris Koehl, David Mateos, Paul Townsend

It is shown that the worldvolume field theory of a single D3-brane in a supergravity D3-brane background admits finite energy, and non-singular, abelian monopoles and dyons preserving 1/2 or 1/4 of the ${\cal N}=4$ supersymmetry and saturating a Bogomol'nyi-type bound. The 1/4 supersymmetric solitons provide a worldvolume realisation of string-junction d

Jean-Paul Blaizot, Edmond Iancu

We present a derivation of a Boltzmann equation for the QCD plasma, starting from the quantum field equations. The derivation is based on a gauge covariant gradient expansion which takes consistently into account all possible dependences on the gauge coupling assumed to be small. We point out a limitation of the gradient expansion arising when the range of t

Paul H. Frampton, P. Q. Hung, Marc Sher

The possibility of additional quarks and leptons beyond the three generations already established is discussed. The make-up of this Report is (I) Introduction: the motivations for believing that the present litany of elementary fermions is not complete; (II) Quantum Numbers: possible assignments for additional fermions; (III) Masses and Mixing Angles: mass l

Yasuyuki Kawahigashi, Roberto Longo, Michael Mueger

We describe the structure of the inclusions of factors A(E) contained in A(E')' associated with multi-intervals E of R for a local irreducible net A of von Neumann algebras on the real line satisfying the split property and Haag duality. In particular, if the net is conformal and the subfactor has finite index, the inclusion associated with two separ

B. Linet

We derive again the upper entropy bound for a charged object by employing thermodynamics of the Kerr-Newman black hole linearised with respect to its electric charge

Stefan Berceanu, Martin Schlichenmaier

For arbitrary quantizable compact Kaehler manifolds, relations between the geometry given by the coherent states based on the manifold and the algebraic (projective) geometry realised via the coherent state mapping into projective space, are studied. Polar divisors, formulas relating the scalar products of coherent vectors on the manifold with the correspond

A. Armoni, Y. Frishman, J. Sonnenschein

We review and elaborate on properties of the string tension in two-dimensional gauge theories. The first model we consider is massive QED in the $m\ll e$ limit. We evaluate the leading string tension both in the fermionic and bosonized descriptions. We discuss the next to leading corrections in $m/e$. The next-to-leading terms in the long distance behavior o

M. A. Jafarizadeh, A. Rezaei-Aghdam

All Bianchi bialgebras have been obtained. By introducing a non-degenerate adjoint invariant inner product over these bialgebras the associated Drinfeld doubles have been constructed, then by calculating the coupling matrices for these bialgebras several sigma-models with Poisson-Lie symmetry have been obtained. Two simple examples as prototypes of Poisson-L

Durmus A. Demir, Herman J. Mosquera Cuesta

The annihilation of pairs of very weakly interacting particles in the neibourghood of gamma-ray sources is introduced here as a plausible mechanism to overcome the baryon load problem. This way we can explain how these very high energy gamma-ray bursts can be powered at the onset of very energetic events like supernovae (collapsars) explosions or coalescence

Anton Galajinsky, Olaf Lechtenfeld

Motivated by the search for a space-time supersymmetric extension of the N=2 string, we construct a particle model which, upon quantization, describes (abelian) self-dual super Yang-Mills in 2+2 dimensions. The local symmetries of the theory are shown to involve both world-line supersymmetry and kappa symmetry.

Elisa Di Pietro, Jacques Demaret

We apply the scale factor duality transformations introduced in the context of the effective string theory to the anisotropic Bianchi-type models. We find dual models for all the Bianchi-types [except for types $VIII$ and $IX$] and construct for each of them its explicit form starting from the exact original solution of the field equations. It is emphasized

N. Sasakura

We propose an uncertainty relation of space-time. This relation is characterized by GhT \lesssim δV, where T and δV denote a characteristic time scale and a spatial volume, respectively. Using this uncertainty relation, we give qualitative estimations for the entropies of a black hole and our universe. We obtain qualitative agreements with the known results.

Izumi Hachisu, Mariko Kato

A new interpretation for the second peak of T Coronae Borealis (T CrB) outbursts is proposed based on a thermonuclear runaway (TNR) model. The system consists of a very massive white dwarf (WD) with a tilting accretion disk and a lobe-filling red-giant. The first peak of the visual light curve of T CrB outbursts is well reproduced by the TNR model on a WD cl

E. H. Rezayi, F. D. M. Haldane, Kun Yang

We report on numerical studies of two-dimensional electron systems in the presence of a perpendicular magnetic field, with a high Landau level index (N > 1) half filled by electrons. Strong and sharp peaks are found in the wave vector dependence of both static density susceptibility and equal-time density-density correlation function, in finite-size systems

Dariusz Grech

We deal with extensions of the Standard Model by adding horizontal interactions between particle generations. We calculate two loop corrections caused by the presence of coupling between hypothetical horizontal gauge bosons and matter fields, both at low and high energy. It is proved numerically, that the coupling of such extra bosons does not affect the pos

Kenneth Lane

We discuss the production and decay rates of the lightest color-singlet technihadrons, spin-one rho_T and omega_T and spin-zero pi_T, in a minimal ``straw-man'' model of low-scale techicolor. The revised rho_T and omega_T decay rates affect the technicolor searches planned for Run II of the Tevatron Collider.

Alex Karpelson

General equations of the unified field theory, obtained using the curved and torsional space-time, are presented. They contain only independent geometrical parameters (metric and connections) of the metric-affine space, and describe the distribution and motion of matter, which represents the curvature and torsion of the space-time. Equations, describing sphe

F. C. Santos, A. Tenorio, A. C. Tort

We apply the generalized zeta function method to compute the Casimir energy and pressure between an unusual pair of parallel plates at finite temperature, namely: a perfectly conducting plate and an infinitely permeable one. The high and low temperature limits of these quantities are discussed; relationships between high and low temperature limits are estabk

Julian Juhi-Lian Ting

The concept of stochastic resonance in nonlinear dynamics is applied to interpret the capacity of noisy quantum channels. The two-Pauli channel is used to illustrate the idea. The fidelity of the channel is also considered. Noise enhancement is found for the fidelity but not for the capacity.

R. Cleve, A. Ekert, L. Henderson, C. Macchiavello

Quantum computers use the quantum interference of different computational paths to enhance correct outcomes and suppress erroneous outcomes of computations. In effect, they follow the same logical paradigm as (multi-particle) interferometers. We show how most known quantum algorithms, including quantum algorithms for factorising and counting, may be cast in

J. Leon, J. Julve, P. Pitanga, F. J. de Urries

We introduce a formalism for the calculation of the time of arrival t at a detector of particles traveling through interacting environments. We develop a general formulation that employs quantum canonical transformations from the free to the interacting cases to compute t. We interpret our results in terms of a Positive Operator Valued Measure. We then compu

A. Beige, S. F. Huelga, P. L. Knight, M. B. Plenio

We investigate to what extent two trapped ions can be manipulated coherently when their coupling is mediated by a dipole-dipole interaction. We will show how the resulting level shift induced by this interaction can be used to create entanglement, while the decay of the states remains nearly negligible. This will allow us to implement conditional dynamics (a

Cristopher Moore

We propose definitions of QAC^0, the quantum analog of the classical class AC^0 of constant-depth circuits with AND and OR gates of arbitrary fan-in, and QACC^0[q], where n-ary Mod-q gates are also allowed. We show that it is possible to make a `cat' state on n qubits in constant depth if and only if we can construct a parity or Mod-2 gate in constant de

Xiaochun Mei

Based on the concept of ensemble, it is proved in the manuscript that the probability amplitude function can also been used to describe the classical statistical system. The motion equations of probability amplitude functions of classical statistical system are obtained, which are similar to that in quantum mechanics. It is also proved in the meantime that m

Dieter Biskamp, Wolf-Christian Mueller

Decay laws for three-dimensional magnetohydrodynamic turbulence are obtained from high-resolution numerical simulations using up to 512^3 modes....

Larry McLerran

I discuss the initial conditions for a parton cascade.

V. K. Magas, Cs. Anderlik, L. P. Csernai, F. Grassi

Freeze out of particles across a space-time hypersurface is discussed in kinetic models. The calculation of final momentum distribution of emitted particles is described for freeze out surfaces, with spacelike normals. The resulting non-equilibrium distribution does not resemble, the previously proposed, cut Juttner distribution, and shows non-exponential p_

E895 collaboration, C. Pinkenburg

We have measured the proton elliptic flow excitation function for the Au + Au system spanning the beam energy range 2 -- 8 AGeV. The excitation function shows a transition from negative to positive elliptic flow at a beam energy, $E_{tr} \sim$ 4 AGeV. Detailed comparisons with calculations from a relativistic Boltzmann-equation are presented. The comparisons

C. Dong, G. Mason

We prove some results which extend the classical theory, due to Hecke-Schoeneberg, of the transformation laws of theta functions. Although our results are classical in natural, they were suggested by recent work involving modular-invariance in conformal field theory.

V Kadets, B. Shumyatskiy, R. Shvidkoy, L. Tseytlin

The article presents a new method of integration of functions with values in Banach spaces. This integral and related notions prove to be a useful tool in the study of Banach space geomtry.

R. Shvidkoy

We find the largest linear space of bounded linear operators on L_1(Omega), that being restricted to any L_1(A), A \subset Omega, satisfy the Daugavet equation.

Karsten Grosse-Brauckmann, Robert B. Kusner, John M. Sullivan

We announce the classification of complete, almost embedded surfaces of constant mean curvature, with three ends and genus zero: they are classified by triples of points on the sphere whose distances are the asymptotic necksizes of the three ends.

Anton Deitmar

We generalize the first part of A. Connes paper (math/9811068) on the zeroes of the Riemann zeta function from a number field $k$ to any simple algebra $M$ over $k$. To a given automorphic representation $π$ of the reductive group $M^\times$ of invertible elements of $M$ we find a Hilbert space $H_π$ and an operator $D_π$ (Polya-Hilbert operator), which is t

S. L. Dubovsky, D. S. Gorbunov, M. V. Libanov, V. A. Rubakov

It is shown that global fermionic charges induced in vacuum by slowly varying, topologically non-trivial background scalar fields are not renormalized provided that expansion in momenta of background fields is valid. This suggests that strongly coupled theories obey induced charge matching conditions which are analogous, but generally not equivalent, to &#39

M. A. Jafarizadeh, A. Rezaei-Aghdam

It is shown that the T-duality in σ-model with Kaluza-Klein metric, without or with a torsion term, can be interpreted as electric-magnetic duality for some of their solitonic solutions. Actually Buscher's duality transformation interchanges the topological and Noether charges.

Maciej Pindor

We study the applicability of Pade Approximants (PA) to estimate a "sum" of asymptotic series of the type appearing in QCD. We indicate that one should not expect PA to converge for positive values of the coupling constant and propose to use PA for the Borel transform of the series. If the latter has poles on the positive semiaxis, the Borel integral

C. Ekstrand

Current superalgebras and corresponding Schwinger terms in 1 and 3 space dimensions are studied. This is done by generalizing the quantization of chiral fermions in an external Yang-Mills potential to the case of a Z_2-graded potential coupled to bosons and fermions.

C. Ekstrand

Z_2-graded Schwinger terms for neutral particles in 1 and 3 space dimensions are considered.

C. Ekstrand

An expression for the curvature of the "covariant" determinant line bundle is given in even dimensional space-time. The usefulness is guaranteed by its prediction of the covariant anomaly and Schwinger term. It allows a parallel derivation of the consistent anomaly and Schwinger term, and their covariant counterparts, which clarifies the similarities

Csaba Csaki, John Terning

We review the calculation of the spectrum of glueball masses in non-supersymmetric Yang-Mills theory using the conjectured duality between supergravity and large N gauge theories. The glueball masses are obtained by solving the supergravity wave equations in a black hole geometry. The glueball masses found this way are in unexpected agreement with the availa

J. M. Hernandez, M. A. Perez, G. Tavares-Velasco, J. J. Toscano

A complete study of the one-loop induced decay Z -> neutrino antineutrino photon is presented within the framework of the Standard Model. The advantages of using a nonlinear gauge are stressed. We have found that the main contributions come from the electric dipole and the magnetic dipole transitions of the Z gauge boson and the neutrino, respectively. We ob

J. R. Forshaw, D. A. Ross, A. Sabio Vera

We examine the effect of suppressing the emission of gluons which are close by in rapidity in the BFKL framework. We show that, after removing the unphysical collinear logarithms which typically arise in formally higher orders of the perturbative expansion, the effect of the rapidity veto is greatly reduced. This is an important result, since it supports the

Stanley J. Brodsky, John R. Hiller, Gary McCartor

We apply Pauli-Villars regularization and discrete light-cone quantization to the nonperturbative solution of a (3+1)-dimensional model field theory. The matrix eigenvalue problem is solved for the lowest-mass state with use of the complex symmetric Lanczos algorithm. This permits the calculation of each Fock-sector wave function, and from these we obtain va

John Ellis, N. E. Mavromatos

We comment on CP, T and CPT violation in the light of interesting new data from the CPLEAR and KTeV Collaborations on neutral kaon decay asymmetries. Other recent data from the CPLEAR experiment, constraining possible violations of CPT and the $ΔS = ΔQ$ rule, exclude the possibility that the semileptonic-decay asymmetry $A_{T}$ measured by CPLEAR could be so

Mayumi Aoki, Gi-Chol Cho, Noriyuki Oshimo

We study a rate asymmetry in the inclusive decay $\Bsgamma$, assuming the supersymmetric standard model based on N=1 supergravity. A complex coefficient $A$ for scalar-trilinear couplings is the source of CP violation, which is contained in the mass-squared matrices for squarks. The model parameters are nontrivially constrained by experimental results for th

M. I. Konchatnij, N. P. Merenkov, O. N. Shekhovzova

The electron current tensor for the scattering of heavy photon on longitudinally polarized electron accompanied with additional hard electron-positron pair has been considered. The contribution of collinear and semicollinear kinematics is computed. The full analysis of both, spin-dependent and spin-independend parts of electron current tensor, is performed.

M. I. Konchatnij, N. P. Merenkov

The initial-state radiative events in electron-positron annihilation into hadrons at DAFNE have been considered. The coresponding cross-section with the full first order radiative correction has been calculated. The analytical calculations take into account the realistic angular acceptance and energy cut of DAFNE photon detector.

A. Djouadi

In the context of the Minimal Supersymmetric extension of the Standard Model, we discuss the impact of the decays of the neutral Higgs bosons into supersymmetric particles, charginos/neutralinos and sfermions. We show that these decay modes could be dominant, when they are kinematically accessible, thus strongly suppressing the branching ratios for the decay

W. Placzek, S. Jadach, M. Melles, B. F. L. Ward

For the small-angle Bhabha-scattering process, we consider the error budget for the calculation of the LEP/SLC luminosity in the Monte Carlo event generator BHLUMI 4.04, from the standpoint of new calculations of exact results for the respective O(alpha**2) photonic corrections in the context of the Yennie-Frautchi-Suura exponentiation. We find that an over-

M. Skrzypek, S. Jadach, W. Placzek, B. F. L. Ward

In this talk I present the current status of the family of Monte Carlo programs for four-fermion physics based on the Yennie-Frautschie-Suura resummation of soft real and virtual photons. I focus on their applications to LEP2.

Tran N. Truong

The problem of Gamma + Pi --> Pi + Pi is studied using the axial anomaly, elastic unitarity, analyticity and crossing symmetry. Single variable dispersion relation is assumed. Using elastic unitarity relation, an integral equation equation for the lowest partial wave amplitude is obtained. The solution for this integral equation is obtained by an iteration p

A. Gehrmann-De Ridder, G. Kramer, H. Spiesberger

The production of photons accompanied by jets in large-Q2 deep inelastic ep scattering is calculated in next-to-leading order. We describe how to consistently include contributions from quark-to-photon fragmentation and give numerical results relevant for HERA experiments.

Zhou Mian-Lai, Ma Wen-Gan, Han Liang, Jiang Yi

We present the detailed analytical and numerical investigations of the one-loop radiative corrections of all quarks and squarks in the MSSM to the lightest chargino pair production via $γγ$ fusion at the future NLC. The numerical corrections show that the cross sections of the subprocess and the parent process are typically enhanced by several percent. We st

Guido Müller, Ulf-G. Meißner

We construct the general Lagrangian for relativistic and heavy baryon chiral perturbation theory with virtual photons to fourth order. We work out the electromagnetic and strong isospin violating contributions to the nucleon self-energy, the nucleon mass and the scalar form factor of the nucleon. Electromagnetic effects for the shift to the Cheng-Dashen poin

R. Foot, G. Filewood

The alternative $SU(4) \otimes SU(2)_L \otimes SU(2)_R$ gauge model, which allows unification of the quarks and leptons at the TeV scale, is studied in detail. We discuss the implications for nucleon decay, B and K rare meson decays and neutrino masses. We also explain how this model solves the gauge hierarchy problem without using supersymmetry or extra lar

B. Abbott

We report on a search for bottom squarks produced in pbarp collisions at sqrt(s) = 1.8 TeV using the D0 detector at Fermilab. Bottom squarks are assumed to be produced in pairs and to decay to the lightest supersymmetric particle (LSP) and a b quark with branching fraction of 100%. The LSP is assumed to be the lightest neutralino and stable. We set limits on

Jorge P. Fernandez, representing the SLD Collaboration

We present the measurements of the leptonic asymmetries in $Z^0$ decays measured by the SLD experiment at SLAC. A data sample of approximately 550,000 $Z^0$ bosons are used for the preliminary measurement of $A_{LR}(A_{e})$ and the leptonic final state measurements of $A_{e}$, $A_μ$ and $A_τ$, representing the entire set of 1992-1998 SLD runs. When combining

Halina Abramowicz, Allen Caldwell

HERA, the first electron-proton collider, has been delivering luminosity since 1992. It is the natural extension of an impressive series of fixed-target lepton-nucleon scattering experiments. The increase of a factor ten in center-of-mass energy over that available for fixed-target experiments has allowed the discovery of several important results, such as t

Jemal Guven, Niall O' Murchadha

It is well known that a spherically symmetric constant density static star, modeled as a perfect fluid, possesses a bound on its mass m by its radial size R given by 2m/R \le 8/9 and that this bound continues to hold when the energy density decreases monotonically. The existence of such a bound is intriguing because it occurs well before the appearance of an

Giovanni Amelino-Camelia, Jerzy Lukierski, Anatol Nowicki

We investigate the implications for the measurability of distances of a covariant dimensionful ``$κ$'' deformation of D=4 relativistic symmetries, with quantum time coordinate and modified Heisenberg algebra. We show that the structure of the deformed mass-shell condition has significant implications for measurement procedures relying on light probes

E. Caccese, V. A. Cimmelli, A. R. Pace

A general formal definition of a theory of space and time compatible with the inertia principle is given. The formal definition of reference frame and inertial equivalence between reference frames are used to construct the class of inertial frames. Then, suitable cocycle relations among the coefficients of space-time transformations between inertial frames a

Kristin Schleich, Donald M. Witt

Classically, all topologies are allowed as solutions to the Einstein equations. However, one does not observe any topological structures on medium range distance scales, that is scales that are smaller than the size of the observed universe but larger than the microscopic scales for which quantum gravity becomes important. Recently, Friedman, Schleich and Wi

A. V. Balatsky

It is shown that the {\em complex} $d_{xy}$ component is generated in d-wave superconductor in the magnetic field. As one enters superconducting state at finite field the normal to superconducting transition occurs into bulk $d_{x^2-y^2}+i d_{xy}$ state . The driving force for the transition is the linear coupling between magnetic field and non zero magnetiz

Claudio Tebaldi, Mario De Menech, Attilio L. Stella

An analysis of moments and spectra shows that, while the distribution of avalanche areas obeys finite size scaling, that of toppling numbers is universally characterized by a full, nonlinear multifractal spectrum. Rare, large avalanches dissipating at the border influence the statistics very sensibly. Only once they are excluded from the sample, the conditio

A. Barrat, A. Vespignani, S. Zapperi

We perform numerical simulations of the sandpile model for non-vanishing driving fields $h$ and dissipation rates $ε$. Unlike simulations performed in the slow driving limit, the unique time scale present in our system allows us to measure unambiguously response and correlation functions. We discuss the dynamic scaling of the model and show that fluctuation-

V. Kolevzon

The dilational viscosity $ε'$ of Langmuir monolayer is considered in a theoretical model taking into account an orientational effect of the dilational wave on surface molecules. This orientational order is described by the surface order parameter Q; the orientational part of the free surface energy is given by Landau's expansion in powers of Q. The m

Aldo H. Romero, Jose M. Sancho

We present the implementation of an algorithm to generate Gaussian random noises with prescribed time correlations that can be either long or short ranged. Examples of Langevin dynamics with short and long range noises are presented and discussed.

Edward McCann, Klaus Richter

Disorder-induced spectral correlations of mesoscopic quantum systems in the non-diffusive regime and their effect on the magnetic susceptibility are studied. We perform impurity averaging for non-translational invariant systems by combining a diagrammatic perturbative approach with semiclassical techniques. This allows us to study the entire range from clean

M. V. Yakunin, Yu. G. Arapov, O. A. Kuznetsov, V. N. Neverov

An unusually wide plateau in the quantized Hall resistance has been revealed for a MQW heterostructure of wide p-GeSi / Ge / p-GeSi quantum wells with the Fermi energy comparable to the well bottom bending amplitude. This plateau exists in one of two metastable states of the sample, for which a symmetric quasi-double-quantum-well system is formed inside the

Rudolf Gorenflo, Gianni De Fabritiis, Francesco Mainardi

We propose a variety of models of random walk, discrete in space and time, suitable for simulating stable random variables of arbitrary index $α$ ($0< α\le 2$), in the symmetric case. We show that by properly scaled transition to vanishing space and time steps our random walk models converge to the corresponding continuous Markovian stochastic processes, tha

Vincent Hakim, Alain Karma

In a weakly excitable medium, characterized by a large threshold stimulus, the free end of an isolated broken plane wave (wave tip) can either rotate (steadily or unsteadily) around a large excitable core, thereby producing a spiral pattern, or retract causing the wave to vanish at boundaries. An asymptotic analysis of spiral motion and retraction is carried

T. A. Arias, T. D. Engeness

This paper develops the use of wavelets as a basis set for the solution of physical problems exhibiting behavior over wide-ranges in length scale. In a simple diagrammatic language, this article reviews both the mathematical underpinnings of wavelet theory and the algorithms behind the fast wavelet transform. This article underscores the fact that traditiona

E. N. Dancer, S. P. Hastings

Some new global results are given about solutions to the boundary value problem for the Euler-Lagrange equations for the Ginzburg-Landau model of a one-dimensional superconductor. The main advance is a proof that in some parameter range there is a branch of asymmetric solutions connecting the branch of symmetric solutions to the normal state. Also, simplifie

Yu. I. Latyshev, T. Yamashita, L. N. Bulaevskii, M. J. Graf

We study the c-axis transport of stacked, intrinsic junctions in Bi2Sr2CaCu2O8+y single crystals, fabricated by the double-sided ion beam processing technique from single crystal whiskers. Measurements of the I-V characteristics of these samples allow us to obtain the temperature and voltage dependence of the quasiparticle c-axis conductivity in the supercon

Kurt Fischer

It is shown that the half filled Hubbard model does not display the Mott metal-insulator transition, in the limit of infinite dimensions. The proposed transition on the Bethe lattice is proved to be an artifact. In the atomic limit, the model is always in the antiferromagnetic phase, which can be described by the Weiss mean field model.

Jean-Pierre Eckmann, Esa Jarvenpaa, Maarit Jarvenpaa

We introduce a concept of porosity for measures and study relations between dimensions and porosities for two classes of measures: measures on $R^n$ which satisfy the doubling condition and strongly porous measures on $R$.

H. Hernandez-Saldaña, J. Flores, T. H. Seligman

Semi-Poisson statistics are shown to be obtained by removing every other number from a random sequence. Retaining every (r+1)th level we obtain a family of secuences which we call daisy models. Their statistical properties coincide with those of Bogomolny&#39;s nearest-neighbour interaction Coulomb gas if the inverse temperature coincides with the integer r.

Scott M. Zoldi

By computing 254 unstable stationary solutions of the Kuramoto-Sivashinsky equation in the extensive chaos regime (Lyapunov fractal dimension D=8.8), we find that 30% satisfy the symmetry of the time-average pattern of the spatiotemporal chaos. Using a symmetry pruning of unstable stationary solutions, the escape-time weighting average converges to the time-

C. Akerlof, R. Balsano, S. Barthelmy, J. Bloch

The origin of gamma-ray bursts (GRBs) has been enigmatic since their discovery. The situation improved dramatically in 1997, when the rapid availability of precise coordinates for the bursts allowed the detection of faint optical and radio afterglows - optical spectra thus obtained have demonstrated conclusively that the bursts occur at cosmological distance

M. Henriksen, S. Cousineau

Results are reported from the first survey of X-ray emission from galaxies in pairs. The sample consists of fifty-two pairs of galaxies from the Catalog of Paired Galaxies Karachentsev (1972) whose coordinates overlap ROSAT Position Sensitive Proportional Counter pointed observations. The mean observed log l_x for early-type pairs is 41.35 +/-0.21 while the

K. Hurley, C. Kouveliotou, P. Woods, E. Mazets

We present Ulysses, KONUS-WIND, and BATSE observations of bursts from a new soft gamma repeater which was active in 1998 June and July. Triangulation of the bursts results in a ~ 1.8 degree by 16 &#39;&#39; error box whose area is ~ 7.6 arcminutes^2, which contains the Galactic supernova remnant G337.0-0.1. This error box intersects the position of a BeppoSA

Peter M. Woods, Chryssa Kouveliotou, Jan van Paradijs, Kevin Hurley

We report the discovery of a new soft gamma repeater (SGR), SGR 1627-41, and present BATSE observations of the burst emission and BeppoSAX NFI observations of the probable persistent X-ray counterpart to this SGR. All but one burst spectrum are well fit by an optically thin thermal bremsstrahlung (OTTB) model with kT values between 25 and 35 keV. The spectru

J. E. Hibbard, M. S. Yun

We present VLA HI observations and UH88 deep optical B- and R-band observations of the IR luminous merger Arp 299 (= NGC 3690 + IC 694). These data reveal a gas-rich, optically faint tidal tail with a length of over 180 kpc. The size of this tidal feature necessitates an old interaction age for the merger (~750 Myr since first periapse), which is currently e

F. Prada, C. M. Gutierrez

We present a detailed study of the stellar kinematics in the barred galaxy NGC 5728 based on I-band photometry and long-slit spectroscopic observations in the region of the near-IR Ca II triplet. The analysis of the stellar line-of-sight velocity distribution (LOSVD) has revealed, in the central regions of the bar, the presence of a cold (v/sigma~2.5) progra

M. Livio

Models for Type Ia Supernovae (SNe Ia) are reviewed. It is shown that there are strong reasons to believe that SNe Ia represent thermonuclear disruptions of C-O white dwarfs, when these white dwarfs reach the Chandrasekhar limit and ignite carbon at their centers. Progenitor scenarios are reviewed critically and the strengths and weaknesses of each scenario

T. C. Weekes

The development of the atmospheric Cherenkov imaging technique has led to significant advances in gamma-ray detection sensitivity in the energy range from 200 GeV to 50 TeV. The Whipple Observatory 10m reflector has detected the first galactic and extragalactic sources in the Northern Hemisphere; the Crab Nebula has been established as the standard candle fo

M. Lopez-Corredoira, F. Garzon, J. E. Beckman, T. J. Mahoney

This paper is the second part of Garzon et al. (1997: ApJ 491, L31) in which we presented an outline of the analysis of 60 spectra from a follow-up program to the Two Micron Galactic Survey (TMGS) project in the l=27 deg., b=0 deg. area. In this second part, we present a more detailed explanation of the analysis as well a library of the spectra for more comp

James G. Bartlett

This is a course on cosmic microwave background (CMB) anisotropies in the standard cosmological model, designed for beginning graduate students and advanced undergraduates. ``Standard cosmological model&#39;&#39; in this context means a Universe dominated by some form of cold dark matter (CDM) with adiabatic perturbations generated at some initial epoch, e.g

H. Hirashita

We discuss the time evolution of dust-to-gas mass ratio in the context of multi-phase model of interstellar medium. Phase transition of interstellar gas is considered to occur on a timescale of $10^{7--8}$ yr, according to a nonlinear open system model of interstellar medium. Since the phase transition changes the dust formation and destruction rates, the du

Jorick S. Vink, Sara R. Heap, Allen V. Sweigart, Thierry Lanz

We have analyzed the far UV-spectrum of the globular cluster M79. We show that the nearly Gaussian mass distribution of zero-age horizontal-branch stars, as derived by Dixon et al.(1996), is able to reproduce the far-UV Hopkins Utraviolet Telescope (HUT) spectrum, if there is a luminous UV-bright star of about an effective temperature of 9,500 K within the H

T. D. Arber, A. W. Longbottom, R. A. M. Van der Linden

We present numerical studies of the nonlinear, resistive magnetohydrodynamic (MHD) evolution of coronal loops. For these simulations we assume that the loops carry no net current, as might be expected if the loop had evolved due to vortex flows. Furthermore the initial equilibrium is taken to be a cylindrical flux tube with line-tied ends. For a given amount