November 1999 arXiv papers — page 8

Werner Krauth, Jan Plefka, Matthias Staudacher

SU(N) Yang-Mills integrals form a new class of matrix models which, in their maximally supersymmetric version, are relevant to recent non-perturbative definitions of 10-dimensional IIB superstring theory and 11-dimensional M-theory. We demonstrate how Monte Carlo methods may be used to establish important properties of these models. In particular we consider

T. Harmark, N. A. Obers

General spinning brane bound states are constructed, along with their near-horizon limits which are relevant as dual descriptions of non-commutative field theories. For the spinning D-brane world volume theories with a B-field a general analysis of the gauge coupling phase structure is given, exhibiting various novel features, already at the level of zero an

Alex Lewis

We discuss the relation between singletons in AdS_3 and logarithmic operators in the CFT on the boundary. In 2 dimensions there can be more logarithmic operators apart from those which correspond to singletons in AdS, because logarithmic operators can occur when the dimensions of primary fields differ by an integer instead of being equal. These operators may

G. W. Gibbons, S. Ichinose

The finiteness requirement for Euclidean Einstein gravity is shown to be so stringent that only the flat metric is allowed. We examine counterterms in 4D and 6D Ricci-flat manifolds from general invariance arguments.

Sumiyoshi Abe, A. K. Rajagopal

Given physical systems, counting rule for their statistical mechanical descriptions need not be unique, in general. It is shown that this nonuniqueness leads to the existence of various canonical ensemble theories which equally arise from the definite microcanonical basis. Thus, the Gibbs theorem for canonical ensemble theory is not universal, and the maximu

K. G. Chetyrkin, M. Steinhauser

The relation between the on-shell and $\bar{\rm MS}$ mass can be expressed through scalar and vector part of the quark propagator. In principle these two-point functions have to be evaluated on-shell which is a non-trivial task at three-loop order. Instead, we evaluate the quark self energy in the limit of large and small external momentum and use conformal

Daisuke Matsushita

We prove that every irreducible component of a fibre of a complex Lagrangian fibration is Lagrangian subvariety. Especially, complex Lagrangian fibations are equidimensional.

N. N. Nikolaev, J. Speth, V. R. Zoller

As noticed by Fadin, Kuraev and Lipatov in 1975 incorporation of asymptotic freedom into the BFKL equation splits the QCD pomeron into a series of isolated poles in complex angular momentum plane. Following our earlier work on the proton structure function we explore the phenomenological consequences of the emerging BFKL-Regge factorized expansion for the sm

Hyun Kyu Lee, G. E. Brown, R. A. M. J. Wijers

Several issues regarding the Blandford-Znajek process are discussed to demonstrate that it can be an effective mechanism for powering the gamma ray bursts. Using a simple circuit analysis it is argued that the disk power increases the effective power of the black hole-accretion disk system, although a part of disk power can be dissipated into black hole entr

V. Dzhunushaliev, H. -J. Schmidt

Vacuum solutions for multidimensional gravity on the principal bundle with the SU(2) structural group as the extra dimensions are found and discussed. This generalizes the results of Ref. \cite{vds3} from U(1) to the SU(2) gauge group. The spherically symmetric solution with the off-diagonal components of the multidimensional metric is obtained. It is shown

T. C. Choy

We verify that the van der Waals interaction and hence all dispersion interactions for the hydrogen molecule given by: W"= -{A/R^6}-{B/R^8}-{C/R^10}- ..., in which R is the internuclear separation, are exactly soluble. The constants A=6.4990267..., B=124.3990835 ... and C=1135.2140398... (in Hartree units) first obtained approximately by Pauling and Beac

Nima Arkani-Hamed, Lawrence Hall, David Smith, Neal Weiner

The supersymmetric ``shining'' of free massive chiral superfields in extra dimensions from a distant source brane can trigger exponentially small supersymmetry breaking on our brane of order e^{-2 pi R}, where R is the radius of the extra dimensions. This supersymmetry breaking can be transmitted to the superpartners in a number of ways, for instance

Roberto Fernandez, Pablo A. Ferrari, Nancy Garcia

We present a perfect simulation algorithm for measures that are absolutely continuous with respect to some Poisson process and can be obtained as invariant measures of birth-and-death processes. Examples include area- and perimeter-interacting point processes (with stochastic grains), invariant measures of loss networks, and the Ising contour and random clus

Hisao Suzuki, Eiichi Takasugi, Hiroshi Umetsu

By using an analytic solution of the Teukolsky equation in the Kerr-de Sitter and Kerr-Newman-de Sitter geometries, an analytic expression of the absorption rate formulae for these black holes is calculated.

Shinji Mukohyama

New exact solutions of brane-world cosmology are given. These solutions include an arbitrary constant C, which is determined by the geometry outside the brane and which affects the cosmological evolution in the brane-world. If C is zero, then the standard cosmology governs the brane-world as a low-energy effective cosmological theory. However, if C is not ze

H. Belich, G. Cuba, R. Paunov

By studying the {\it internal} Riemannian geometry of the surfaces of constant negative scalar curvature, we obtain a natural map between the Liouville, and the sine-Gordon equations. First, considering isometric immersions into the Lobachevskian plane, we obtain an uniform expression for the general (locally defined) solution of both the equations. Second,

Masao Matsumoto

We develop the formulation of the spin(SU(2)) coherent state path integrals based on arbitrary fiducial vectors. The resultant action in the path integral expression extensively depends on the vector; It differs from the conventional one in that it has a generalized form having some additional terms. We also study, as physical applications, the geometric pha

F. Encinas-Sanz, I. Leyva, J. M. Guerra

We have measured quasi-instantaneous transverse patterns in a broad aperture laser. Non-ordered patterns yielding to boundary determined regular structures in progressive time-integrated recording are observed. The linear analysis and numerical integration of the full Maxwell-Bloch equations allow us to interpret the features of the experiment. We show that

C. I. Barbosa, T. Guhr, H. L. Harney

In the present paper we investigate the effect of symmetry breaking in the statistical distributions of reduced transition amplitudes and reduced transition probabilities. These quantities are easier to access experimentally than the components of the eigenvectors and were measured by Adams et al. for the electromagnetic transitions in ^{26}Al. We focus on i

Y. Tanushi, S. Saito, M. Uehara

The spin-averaged electromagnetic polarizabilities of the hyperons $Λ$ and $Σ$ are calculated within the one-loop approximation by use of the dispersion theory. The photon and meson couplings to hyperons are determined so as to satisfy the large N_c consistency condition. It is shown that in order for the large N_c consistency condition to hold exotic hypero

J. C. R. Bloch, C. D. Roberts, S. M. Schmidt

A covariant, composite scalar diquark, Fadde'ev amplitude model for the nucleon is used to calculate pseudoscalar, isoscalar- and isovector-vector, axial-vector and scalar nucleon form factors. The last yields the nucleon sigma-term and on-shell sigma-nucleon coupling. The calculated form factors are soft, and the couplings are generally in good agreemen

V. S. Vladimirov

Part I. Some Facts From p-Adic Analysis. Part II. Tables of Integrals.

Christopher B. Croke, Bruce Kleiner

We study discrete, cocompact, isometric actions of groups on Hadamard spaces, and the induced actions on ideal boundaries. For a class of groups generalizing fundamental groups of three-dimensional graph manifolds, we find a set of invariants for the action which determine the boundary action up to equivariant homeomorphism. This work was inspired by (and an

T. D. Palev, N. I. Stoilova, J. Van der Jeugt

A description of the quantum superalgebra U_q[sl(n+1|m)] via creation and annihilation generators (CAGs) is given. A statement that the Fock representations of the CAGs provide microscopic realizations of exclusion statistics is formulated.

Manfred Einsliedler, Graham Everest, Thomas Ward

A system of transformations is associated to a rational point on an elliptic curve. The sequence entropy is connected to the canonical height, and in some cases there is a canonically defined quotient system whose entropy is the canonical height and for which the fibre entropy is accounted for by local heights at primes of bad reduction. The proofs use trans

Miles Reid

Let M be a quasiprojective algebraic manifold with K_M=0 and G a finite automorphism group of M acting trivially on the canonical class K_M; for example, a subgroup G of SL(n,C) acting on C^n in the obvious way. We aim to study the quotient variety X=M/G and its resolutions Y -> X (especially under the assumption that Y has K_Y=0) in terms of G-equivariant g

Daisuke Matsushita

We classify singular fibres over general points of the discriminant locus of projective complex Lagrangian fibrations on 4-dimensional holomorphic symplectic manifolds. The singular fibre F is the following either one: F is isomorphic to the product of an elliptic curve and a Kodaira singular fibre up to finite unramified covering or F is a normal crossing v

Erik Koelink, Jasper Stokman, Mizan Rahman

The main goal is to interpret the Askey-Wilson function and the corresponding transform pair on the quantum SU(1,1) group. A weight on the C^*-algebra of continuous functions vanishing at infinity on the quantum SU(1,1) group is studied, which is left and right invariant in a weak sense with respect to a product defined using Wall functions. The Haar weight

Ciro Ciliberto, Gerard van der Geer

In this paper we give a lower bound for the codimension of the Andreotti-Mayer loci in the moduli space of principally polarized complex abelian varieties. We also present a conjecture on this codimension.

Eloy Ayón-Beato, Alberto García

Using a nonlinear electrodynamics coupled to General Relativity a new regular exact black hole solution is found. The nonlinear theory reduces to the Maxwell one in the weak limit, and the solution corresponds to a charged black hole for |q| \leq 2s_c m \approx 1.05 m, with metric, curvature invariants, and electric field regular everywhere.

J. Sonnenschein, A. Loewy

We explicitly show the area law behavior of a circular Wilson loop in confining theories from supergravity. We calculate the correlator of two Wilson loops from supergravity in confining backgrounds. We find that it is dominated by an exchange of a ``scalarball'' that is lighter than the glueballs. We interpret these results in terms of the meson-meson poten

A. A. Kirillov

It is found that the existence of spacetime foam leads to a situation in which the number of fundamental quantum bosonic fields is a variable quantity. The general aspects of an exact theory that allows for a variable number of fields are discussed, and the simplest observable effects generated by the foam are estimated. It is shown that in the absence of pr

B. M. Zupnik

We consider the modified superfield constraints with constant terms for the D=3, N=2 Goldstone-Maxwell gauge multiplet which contains Goldstone fermions, real scalar and vector fields. The partial spontaneous breaking N=2 to N=1 is possible for the non-minimal self-interaction of this modified gauge superfield including the linear Fayet-Iliopoulos term. The

S. Odake

In this lecture we discuss `beyond CFT' from symmetry point of view. After reviewing the Virasoro algebra, we introduce deformed Virasoro algebras and elliptic algebras. These algebras appear in solvable lattice models and we study them by free field approach.

Jun Gao, Bing An Li

An addtional intrinsic form factors of pion and kaons have been studied.

Thorsten Ohl

The interactions of electroweak gauge bosons are severely constrained by the symmetries inferred from low energy observables. The exploration of the dynamics of electroweak symmetry breaking requires therefore both an experimental sensitivity and a theoretical precision that is better than the natural scale of deviations from minimal extrapolations of the lo

R. Flores-Mendieta, C. P. Hofmann, E. Jenkins

Tree amplitudes for baryon-pion scattering are studied in the 1/N_c expansion. Generalized large-N_c consistency conditions are obtained to all orders in baryon mass splittings. For baryons with spin J ~ O(1), the leading order in N_c tree amplitudes can be evaluated keeping only terms up to a given finite order in baryon mass splittings.

Y. Nemoto, K. Naito, M. Oka

We study the O(N) symmetric linear sigma model at finite temperature as the low-energy effective models of quantum chromodynamics(QCD) using the Cornwall-Jackiw-Tomboulis(CJT) effective action for composite operators. It has so far been claimed that the Nambu-Goldstone theorem is not satisfied at finite temperature in this framework unless the large N limit

Kenichiro Aoki, Dimitri Kusnezov

The dynamics of classical $ϕ^4$ theory under weak and strong thermal gradients is studied. We obtain the thermal conductivity of the theory including its temperature dependence. Under moderately strong thermal gradients, the temperature profiles become visibly non-linear, yet the phenomenon can be understood using the linear response theory. When we move fur

JLQCD Collaboration, S. Aoki, M. Fukugita, S. Hashimoto

We present results for I=2 pion scattering length with the Wilson fermions in the quenched approximation. The finite size method presented by Lüscher is employed, and calculations are carried out at $β=5.9$, 6.1, and 6.3. In the continuum limit, we obtain a result in reasonable agreement with the experimental value.

Jean-Baptiste de VIVIE

HIGGS and SUSY searches performed by the ALEPH Experiment at LEP are interpreted in the framework of two constrained R-parity conserving models: Minimal Supergravity and minimal Gauge Mediated Supersymmetry Breaking.

B. Winstein

I will here make some brief comments on the T- and CP- odd asymmetry observed by KTeV in the KL -> pi^+pi^-e^+e^- decay.

Yungui Gong

The holographic bound in Brans-Dicke $k=1$ matter dominated Cosmology is discussed. In this talk, both the apparent horizon and the particle horizon are taken for the holographic bound. The covariant entropy conjecture proposed by Bousso is also discussed.

M. Novello, V. A. De Lorenci, J. M. Salim, R. Klippert

We analyze the propagation of light in the context of nonlinear electrodynamics, as it occurs in modified QED vacua. We show that the corresponding characteristic equation can be described in terms of a modification of the effective geometry of the underlying spacetime structure. We present the general form for this effective geometry and exhibit some new co

Eloy Ayón-Beato, Alberto García

A non-singular exact black hole solution in General Relativity is presented. The source is a non-linear electromagnetic field, which reduces to the Maxwell theory for weak field. The solution corresponds to a charged black hole with |q| \leq 2s_c m \approx 0.6 m, having metric, curvature invariants, and electric field bounded everywhere.

Sergei M. Kopeikin

The Lorentz covariant theory of precise Doppler measurements (PDM) based on the retarded Liénard-Wiechert solution of the Einstein equations is described. An exact solution of equations of light propagation in the field of arbitrary moving bodies, which drastically extends the range of applicability of the new theory of PDM, is obtained. An explicit formula

László Á. Gergely

The dynamics of a binary system with two spinning components on an eccentric orbit is studied, with the inclusion of the spin-spin interaction terms appearing at the second post-Newtonian order. A generalized true anomaly parametrization properly describes the radial component of the motion. The average over one radial period of the magnitude of the orbital

Yurij V. Baryshev

It is shown that detecting or setting an upper limit on the scalar gravitational radiation is a good experimental test of relativistic gravity theories. The relativistic tensor-field theory of gravitation is revised and it is demonstrated that the scalar monopole gravitational radiation must be added to the usual quadrupole radiation. In the case of the bina

G Filewood

The problem of unification of Gravitation and Electromagnetism in four dimensions; some new ideas involving mixtures of commuting and anti-commuting co-ordinates. Maxwell's equations are extracted in terms of the curvature of the anti-commuting component of space-time. The profound difference in the size of the coupling constants of the two forces is int

Marlon E. Pierce, Efstratios Manousakis

We investigate the first layer of helium adsorbed on graphite with path-integral Monte Carlo, examining the role of substrate corrugations on the phase diagram. When no corrugations are present, the equilibrium state of the system is a liquid phase, with solidification occurring only under compression but before layer promotion. We determine the solid-liquid

Michael T. Woodside, Chris Vale, Kent L. McCormick, Paul L. McEuen

Using a low-temperature atomic force microscope as a local voltmeter, we measure the Hall voltage profile in a quantum Hall conductor in the presence of a gate-induced non-equilibrium edge state population at n=3. We observe sharp voltage drops at the sample edges which are suppressed by re-equilibrating the edge states.

Wojciech Florek

It is shown that in the case of free electron in a spatially periodic magnetic field the concept of magnetic translations operators is still valid and, moreover, these operators can be defined in the same way as for a Bloch electron in a uniform magnetic field. The results can be a useful tool in investigation of lately observed phenomena in 2DEG with spatia

R. Renan, M. H. Pacheco, C. A. S. Almeida

The ambiguity involved in the definition of effective-mass Hamiltonians for nonrelativistic models is resolved using the Dirac equation. The multistep approximation is extended for relativistic cases allowing the treatment of arbitrary potential and effective-mass profiles without ordering problems. On the other hand, if the Schrodinger equation is supposed

Marcus Fleck, Alexander I. Lichtenstein, Andrzej M. Oles, L. Hedin

We present spectral and optical properties of the Hubbard model on a two-dimensional square lattice using a generalization of dynamical mean-field theory to magnetic states in finite dimension. The self-energy includes the effect of spin fluctuations and screening of the Coulomb interaction due to particle-particle scattering. At half-filling the quasipartic

C. M. Newman, D. L. Stein

We consider zero-temperature, stochastic Ising models with nearest-neighbor interactions and an initial spin configuration chosen from a symmetric Bernoulli distribution (corresponding physically to a deep quench). Whether a final state exists, i.e., whether each spin flips only finitely many times as time goes to infinity (for almost every initial spin conf

T. Schneider, J. M. Singer

We analyze high precision, high resolution microcalorimetric specific heat data of detwinned YBa2Cu3O(7-delta) single crystals. It is shown that a finite size effect must be taken into account when attempting to extract critical properties. Contrary to previous claims, there is no contradiction to a regular second order phase transition. Consistency with 3D-

A. Crisanti, F. Ritort

We analyze the properties of the energy landscape of {\it finite-size} fully connected p-spin-like models whose high temperature phase is described, in the thermodynamic limit, by the schematic Mode Coupling Theory of super-cooled liquids. We show that {\it finite-size} fully connected p-spin-like models, where activated processes are possible, do exhibit pr

Moonsoo Kang, A. Pinczuk, B. S. Dennis, M. A. Eriksson

We report observations of collective gap excitations of the fractional quantum Hall (FQH) states at filling factors ν=p/(2p+1) (p=integer), for 1/3 <= ν<= 2/3, by inelastic light scattering. The collective gap energies at ν= 1/3, 2/5 and 3/7 show a drastic decrease as the value ν=1/2 is approached. These energies and the one at ν=3/5 display the linear scali

D. Bolle&#39;, G. Jongen

The parallel dynamics of the asymmetric extremely diluted Ashkin-Teller neural network is studied using signal-to-noise analysis techniques. Evolution equations for the order parameters are derived, both at zero and finite temperature. The retrieval properties of the network are discussed in terms of the four-spin coupling strength and the temperature. It is

C. Godreche, J. M. Luck

We investigate the non-equilibrium two-time correlation and response functions and the associated fluctuation-dissipation ratio for the ferromagnetic Ising chain with Glauber dynamics. The scaling behavior of these quantities at low temperature and large times is studied in detail. This analysis encompasses the self-similar domain-growth (aging) regime, the

Oleg Tchernyshyov, Frank Wilczek

We motivate and perform a calculation of the energy of a cold fluid of charged fermions in the presence of a striped magnetic background. We find that a non-trivial value for the doping density on the walls is preferred

L. Frachebourg, Ph. A. Martin, ; J. Piasecki

The adhesive dynamics of a one-dimensional aggregating gas of point particles is rigorously described. The infinite hierarchy of kinetic equations for the distributions of clusters of nearest neighbours is shown to be equivalent to a system of two coupled equations for a large class of initial conditions. The solution to these nonlinear equations is found by

M. W. Pieper, F. Wiekhorst, T. Wolf

We investigated the charge distribution in Pr_{1+x}Ba_{2-x}Cu_3O_{6+y}-crystals at liquid-He temperature by means of ^{63,65}Cu- and ^{141}Pr-NMR and NQR. The electric field gradients determined for the different oxygen coordinations of Cu(1) on the chains confirm the model that the hole states are localized in the O 2p - pi-orbitals of the CuO_(2)-planes. T

Keir E. Novik, Peter V. Coveney

We investigate the domain growth and phase separation of hydrodynamically-correct binary immiscible fluids of differing viscosity as a function of minority phase concentration in both two and three spatial dimensions using dissipative particle dynamics. We also examine the behavior of equal-viscosity fluids and compare our results to similar lattice-gas simu

C Rascon, AO Parry

We report results of wetting on non-planar and heterogeneous surfaces calculated from an effective interfacial Hamiltonian model. The lack of translational invariance along the substrate induces a series of structural changes on the interface such as unbending and a number of non-thermodynamic singularities and can modify the location of the wetting transiti

Jörg Lehmann, Peter Reimann, Peter Hänggi

Thermally activated escape over a potential barrier in the presence of periodic driving is considered. By means of novel time-dependent path-integral methods we derive asymptotically exact weak-noise expressions for both the instantaneous and the time-averaged escape rate. The agreement with accurate numerical results is excellent over a wide range of drivin

A. O. Sousa, S. Moss de Oliveira

We introduce a square lattice into the Penna bit-string model for biological ageing and study the evolution of the spatial distribution of the population considering different strategies of child-care. Two of the strategies are related to the movements of a whole family on the lattice: in one case the mother cannot move if she has any child younger than a gi

Bruce M. Boghosian, Peter V. Coveney

We show that a phenomenological hydrodynamic lattice-gas model of two-phase flow, developed by Rothman and Keller in 1988 and used extensively for numerical simulations since then, can be derived from an underlying model of particle interactions. From this result, we elucidate the nature of the hydrodynamic limit of the Rothman-Keller model.

L. Dobrosavljević-Grujić, R. Zikić, Z. Radović

The quasiparticles energy spectrum in clean ferromagnetic weak links between conventional superconductors is calculated. Large peaks in DOS, due to a special case of Andreev reflection at the ferromagnetic barrier, correspond to spin-splitt bound states. Their energies are obtained as a function of the barrier thickness, exchange field strength, and of the m

Mario Nicodemi

We study the dynamical properties of recently introduced frustrated lattice gas models (IFLG and Tetris) for granular media under gentle shaking. We consider both the case where grains have inter-grain surface interactions and the case where they have not, corresponding, for instance, to the presence or absence of moisture in the packs. To characterise the g

M. Yu. Kagan, R. Fresard, M. Capezzali, H. Beck

We calculate the one-electron spectral function of the attractive-U Hubbard model in two dimensions. We work in the intermediate coupling and low density regime and evaluate analytically the self-energy. The results are obtained in a framework based on the self-consistent T-matrix approximation. We also calculate the chemical potential of the bound pairs as

T. Nikuni, A. Griffin, E. Zaremba

We extend our recent work on the two-fluid hydrodynamics of the condensate and non-condensate in a trapped Bose gas by including the dissipation associated with viscosity and thermal conduction. For purposes of illustration, we consider the hydrodynamic modes in the case of a uniform Bose gas. A finite thermal conductivity and shear viscosity give rise to a

Erik Koch, Olle Gunnarsson

We use the doped Fullerenes as an example of how realistic systems can be described by simple models. Starting from the band structure we set up a tight-binding model that describes the t_{1u} conduction band. Adding correlation terms we arrive at a generalized Hubbard Hamiltonian that we treat using quantum Monte Carlo. To address the problem of superconduc

Z. Maassarani

The authors of cond-mat/9911072 claim to introduce &#34;new representations of the Hecke algebra.&#34; These representations are shown to be the XXC models introduced two years ago in solv-int/9712008, and repeatedly studied and referred to in subsequent papers. They are in fact representations of the Temperley-Lieb algebra. Several other remarks are made an

Akira Shimizu, Hiroaki Kato

In order to specify a nonequilibrium steady state of a quantum wire (QWR), one must connect reservoirs to it. Since reservoirs should be large 2d or 3d systems, the total system is a large and inhomogeneous 2d or 3d system, in which e-e interactions have the same strength in all regions. However, most theories of interacting electrons in QWR considered simpl

Kwai-Kong Ng, Manfred Sigrist

The odd-parity spin-triplet Cooper pairing states show a six-fold degeneracy for a quasi-two-dimensional electron system. In this article we show how spin-orbit coupling can lift this degeneracy for Sr_2RuO_4 taking the band structure based on the three relevant t_{2g}-orbitals of the Ru-ions into account. The stabilized state depends on the relative strengt

Olaf Herbst, Martin Huthmann, Annette Zippelius

We investigate the free cooling of inelastic rough spheres in the presence of Coulomb friction. Depending on the coefficients of normal restitution $ε$ and Coulomb friction $μ$, we find qualitatively different asymptotic states. For nearly complete normal restitution ($ε$ close to 1) and large $μ$, friction does not change the cooling properties qualitativel

D. A. Ivanov

In the presence of strong disorder, the statistics of quasiparticle levels in the core of a vortex in a two-dimensional p-wave superconductor belongs to the universality class B corresponding to the ensemble of orthogonal matrices in odd dimensions. This novel universality class appears as a consequence of the O(2) spin symmetry of p-wave pairing. It is pres

Kimberly Ann Coble

Observations of the microwave sky using the Python telescope in its fifth season of operation at the Amundsen-Scott South Pole Station in Antarctica are presented. The system consists of a 0.75 m off-axis telescope instrumented with a HEMT amplifier-based radiometer having continuum sensitivity from 37-45 GHz in two frequency bands. With a $0.91^{\circ} \tim

Franco Pacini

I briefly summarize some facts and ideas concerning the presence of neutron stars in Supernova remnants. While sources similar to the Crab Nebula require the presence of a central energetic object, shell-type remnants such as Cas A are compatible with the presence of neutron stars releasing a weak relativistic wind.

Rino Bandiera

The synchrotron emission observed in plerions depends on the characteristics of the magnetic fields and relativistic electrons in these supernova remnants. Therefore an analysis of the spectral and spatial properties of this emission, combined with models for the evolution and structure of plerions, would allow one to investigate the evolution of the synchro

Richard de Grijs, Reynier F. Peletier

(Abbreviated) Optical observations of a statistically complete sample of edge-on disc galaxies are used to study the intrinsic vertical colour gradients in the galactic discs, to constrain the effects of population gradients, residual dust extinction and gradients in the galaxies&#39; metal abundance. It appears that the intrinsic vertical colour gradients a

G. B. Taylor

Multi-frequency polarimetry with the Very Long Baseline Array (VLBA) telescope has revealed absolute Faraday Rotation Measures (RMs) in excess of 1000 rad/m/m in the central regions of 7 out of 8 strong quasars studied (e.g., 3C 273, 3C 279, 3C 395). Beyond a projected distance of ~20 pc, however, the jets are found to have |RM| < 100 rad/m/m. Such sharp RM

Paul Goudfrooij

The properties of dust in giant elliptical galaxies are reviewed, with particular emphasis on the influence of the environment. After normalizing by the optical luminosities, a strong anti-correlation between the masses of dust and hot gas in X-ray bright ellipticals is found. Furthermore, large-scale, regularly-shaped dust lanes (which are symmetric with re

Yu. Chornij, B. Novosyadlyj

The evolution of two-point space correlation function of QSOs is analyzed in the framework of the theory of the large scale structure formation. For given cosmological models the agreement between theoretical predictions and observational data on correlation function of QSOs is achieved by determination of scales of structures R(z), in which could be formed

Giovanni Carraro, Antonella Vallenari

We report on near IR (J and K bands) observations of an $8^{\prime} \times 8^{\prime}$ region centered on the poorly studied open cluster King 5, for which only optical photometry existed. We found that the cluster is of moderate age (1.0 Gry old), intermediate in age between the Hyades and NGC 752. Combining optical and IR photometry we obtain estimates for

G. Gavazzi, P. Franzetti, M. Scodeggio, A. Boselli

We present near-infrared H-band (1.65 micron) surface photometry of 558 galaxies in the Coma Supercluster and in the Virgo cluster. This data set, obtained with the Arcetri NICMOS3 camera ARNICA mounted on the Gornergrat Infrared Telescope, is aimed at complementing, with observations of mostly early-type objects, our NIR survey of spiral galaxies in these r

Sergei M. Kopeikin, Vladimir A. Potapov

The influence of the low-frequency timing noise on the precision of measurements of the Keplerian and post-Keplerian orbital parameters in binary pulsars is studied. Fundamental limits on the accuracy of tests of alternative theories of gravity in the strong-field regime are established. The gravitational low-frequency timing noise formed by an ensemble of b

K. Kifonidis, T. Plewa, H. -Th. Janka, E. Mueller

We present results of high-resolution two-dimensional simulations which follow the first five minutes of a core collapse supernova explosion in a 15 solar mass blue supergiant progenitor. The computations start shortly after core bounce and include neutrino-matter interactions by using a light-bulb approximation for the neutrinos, and a treatment of the nucl

A. Boselli, G. Gavazzi, P. Franzetti, D. Pierini

We present near-infrared (H band) surface photometry of 170 galaxies, obtained in 1997 using the Calar Alto 2.2m telescope equipped with the NICMOS3 camera MAGIC. The majority of our targets are selected among bright members of the Virgo cluster, however galaxies in the A262 and Cancer clusters and in the Coma/A1367 supercluster are also included. This data

Jean-Claude Mermilliod, Michel Mayor

Coravel observations of 103 F5-K0 stars in the Praesepe cluster yielded 24 spectroscopic binaries (3 are non-members), and 20 orbits were determined, with periods from 4 to 7400 days. Based on a complete sample in the colour range 0.40 < B-V < 0.80 (80 stars, including KW 244 = TX Cnc), the companion star fraction CSF = 0.45. The percentage of spectroscopic

B. Czerny, A. Abrassart, S. Collin-Souffrin, A. -M. Dumont

There are strong suggestions that the disk-like accretion flow onto massive black hole in AGN is disrupted in its innermost part (10-100 Rg), possibly due to the radiation pressure instability. It may form a hot optically thin quasi spherical (ADAF) flow surrounded by or containing denser clouds due to the disruption of the disk. Such clouds might be optical

Vladimir V. Usov

We discuss plausible locations of radiating regions in the magnetospheres of pulsars and argue that the mechanisms of pulsar radiation at different frequencies are closely connected with the locations of the radiating regions, especially in the radio range. If the region that is responsible for the bulk of the non-thermal radiation at some frequency is local

Habib G. Khosroshahi, Yogesh Wadadekar, Ajit Kembhavi

Using a two-dimensional galaxy image decomposition technique, we extract global bulge and disk parameters for a complete sample of early type disk galaxies in the near infrared K band. We find significant correlation of the bulge parameter n with the central bulge surface brightness $μ_b(0)$ and with effective radius r_e. Using bivar iate analysis techniques

R. J. Smith, B. J. Boyle, S. J. Maddox

An angular correlation of low significance (2 sigma) is observed between 0.3 < z < 0.5 QSOs and V < 23 galaxies. Overall, the cross-correlation function between 82 intermediate-redshift (0.3 < z < 0.7), X-ray selected QSOs and V < 24 galaxies is investigated, but no signal is detected for the z > 0.5 QSOs. After converting to an excess of galaxies physically

Marcos J. Montes

We present new radio observations of the supernova SN 1979C made with the VLA at 20, 6, 3.6, and 2 cm from 1991 July to 1998 October, which extend our previously published observations (Weiler et al.1986, 1991), beginning 8 days after optical maximum in 1979 April and continuing through 1990 December. We find that the radio emission from SN 1979C has stopped

F. Abe, I. Bond, E. Budding, A. Daniel

A search for ultra-high energy gamma-rays emitted by the young, nearby supernova remnant that was discovered recently by the COMPTEL and ROSAT satellites was made using the JANZOS database for the period 1987-1993. A 95% confidence upper limit on the flux above 100 TeV of 3x10^(-13)cm^(-2)sec^(-1) was obtained. This is an order of magnitude below the expecte

Simone Bianchi

This thesis presents an original model for the FIR emission in spirals, developed from an existing radiative transfer code (Bianchi, Ferrara & Giovanardi, 1996, ApJ, 465, 127). The model&#39;s main features are: a complete treatment of multiple scattering within geometries appropriate for spirals; a full coverage of spectral range of stellar emission; the us

C. P. Burgess, R. C. Myers, F. Quevedo

There appears to be no natural explanation for the cosmological constant&#39;s small size within the framework of local relativistic field theories. We argue that the recently-discussed framework for which the observable universe is identified with a p-brane embedded within a higher-dimensional `bulk&#39; spacetime, has special properties that may help circu

Michael Gronau

Electroweak penguin (EWP) amplitudes are studied model-independently in $B$ meson decays to charmless final states consisting of a vector meson ($V$) and a pseudoscalar meson ($P$). A set of SU(3) relations is derived between EWP contributions and tree amplitudes, in the approximation of retaining only the dominant EWP operators $Q_9$ and $Q_{10}$ . Two appl