September 1997 arXiv papers — page 5

C. J. Wheeler, P. Hoeflich, R. Harkness, J. Spyromillio

Models of infrared spectra of Type Ia supernovae around maximum light are presented. The underlying dynamic models are delayed detonation explosions in Chandrasekhar mass carbon/oxygen white dwarfs. In combination with the radiative transport codes employed here, these models provide plausible fits to the optical spectra of "normal" Type Ia supernova

Barbara Wiebel-Sooth, Peter L. Biermann, Hinrich Meyer

Based on the earlier papers in this series, we discuss here the errors in the prediction of the model, and compare with the error ranges in the spectra for individual elements. The predictions are spectra of $E^{-2.75 \pm 0.04}$ for hydrogen, and $E^{-2.67 -0.02 \pm 0.02}$ for helium and heavier elements below the knee. For particle energies above $10 Z$ GeV

Peter L. Biermann, Hyesung Kang, Joerg P. Rachen, Dongsu Ryu

The simulations of the formation of cosmological structure allows to determine the spatial inhomogeneity of cosmic magnetic fields. Such simulations, however, do not give an absolute number for the strength of the magnetic field due to insufficient spatial resolution. Combining these simulations with observations of the Rotation Measure to distant radio sour

Youri Dabrowski

A decrement in the Cosmic Microwave Background (CMB) has been observed by the Ryle Telescope towards a pair of, possibly lensed, quasars (PC1643+4631 A&B). Assuming that the decrement is due to the Sunyaev-Zel'dovich (S-Z) effect, this is indicative of a very rich intervening cluster, although no X-ray emission has yet been observed in that direction. In

Peter L. Biermann, Hyesung Kang, Dongsu Ryu

The recent discoveries of several reliable events of high energy cosmic rays at an energy above 10^20 eV raise questions about their path through the nearby universe. The two analyses of the Haverah Park data set and the Akeno data set appear to have an inconsistent pattern. Both data sets showed some measure of a correlation with the supergalactic plane, th

Andrew W. Clegg, Alan L. Fey, T. Joseph W. Lazio

We consider the geometrical optics for refraction of a distant radio source by an interstellar plasma lens, with application to a lens with a Gaussian electron column density profile. The refractive properties of the lens are specified completely by a dimensionless parameter, alpha, which is a function of the wavelength of observation, the lens' electron

A. N. Parmar, T. Oosterbroek, F. Favata, S. Pightling

The 7 s X-ray pulsar 1E2259+586 and the supernova remnant (SNR) G109.1-1.0 (CTB 109) were observed by BeppoSAX in 1996 November. The pulse period of 6.978914 +/- 0.000006 s implies that the source continues its near constant spin-down trend. The 0.5-10 keV pulse shape is characterized by a double peaked profile, with the amplitude of the second peak ~50% of

Kazuhiro Yamamoto, Naoshi Sugiyama, Humitaka Sato

The evolution of small scale cosmological perturbations is carefully re-examined. Through the interaction with photons via electrons, baryon perturbations show interesting behavior in some physical scales. Characteristic features of the evolution of baryon density fluctuations are discussed. In CDM models, it is found a power-law growing phase of the small-s

E. Athanassoula, A. Bosma, J. -C. Lambert, J. Makino

The performance and accuracy of a GRAPE-3 system for collisionless N-body simulations is discussed. After a description of the hardware configurations available to us at Marseille, and the usefulness of on-line analysis, we concentrate on the performance and accuracy of the direct summation and tree code software. For the former we discuss the sources of rou

Paolo Molaro

In this paper we review the present status of observations of the Big Bang elements D, 3He, 4He and 7Li and of their extrapolation to the primordial values. It is shown that, within the errors, the abundances are consistent with the predictions of the standard Big Bang nucleosynthesis for 1 < eta_10 < 6, which corresponds to 0.004 < Omega_b h_{0}^2 < 0.02$.

M. A. Garrett, Simon T. Garrington

We have selected a field from the VLA FIRST Survey which is typical in all aspects except one: it contains a bright, but extremely compact VLBI calibrator - J1159+291. 127 unresolved FIRST sources with $S_{FIRST}\ge 10$ mJy lie within $2.5^{\circ}$ of this calibrator. $λ6$ cm MERLIN observations with a resolution $\sim 60$ mas detect around half the sources.

P. Molaro, P. Bonifacio, L. Pasquini

A search for lithium is performed on seven metal poor dwarfs with metallicities ranging from [Fe/H]=-1.5 down to [Fe/H]=-3.0 but showing disk-like kinematics. These stars belong to the metal poor tail of the Galactic thick disk and they may be also the result of an accretion event (Beers and Sommer-Larsen 1995). The Li 6707.8 A line is present in all the sev

S. Andreon

In Coma and two other clusters of galaxies the primary morphological segregation is the one with respect to a privileged direction. Only when this segregation is not considered it appears that the morphological types are segregated in density or in clustercentric distance.

Edward Bierstone, Pierre D. Milman

This article is an exposition of an elementary constructive proof of canonical resolution of singularities in characteristic zero, presented in detail in Invent. Math. 128 (1997), 207-302. We define a new local invariant and get an algorithm for canonical desingularization by successively blowing up its maximum loci. The invariant can be described by local c

Shinobu Hosono, Masa-Hiko Saito, Jan Stienstra

In this paper, we verify a part of the Mirror Symmetry Conjecture for Schoen&#39;s Calabi-Yau 3-fold, which is a special complete intersection in a toric variety. We calculate a part of the prepotential of the A-model Yukawa couplings of the Calabi-Yau 3-fold directly by means of a theta function and Dedekind&#39;s eta function. This gives infinitely many Gr

Kailash C. Sahu, Richard A. Shaw, Mary Elizabeth Kaiser, Stefi A. Baum

The cluster RX J1347.5-1145, the most luminous cluster in the X-ray wavelengths, was imaged with the newly installed Space Telescope Imaging Spectrograph (STIS) on-board HST. Its relatively high redshift (0.451) and luminosity indicate that this is one of the most massive of all known clusters. The STIS images unambiguously show several arcs in the cluster.

Thomas Appelquist, Andreas Nyffeler, Stephen B. Selipsky

We compare gap equation predictions for the spontaneous breaking of global symmetries in supersymmetric Yang-Mills theory to nonperturbative results from holomorphic effective action techniques. In the theory without matter fields, both approaches describe the formation of a gluino condensate. With $N_f$ flavors of quark and squark fields, and with $N_f$ bel

Arnon Dar

The observed afterglows of gamma ray bursts, in particular that of GRB 970228 six months later, seem to rule out relativistic fireballs and relativistic firecones driven by merger or accretion induced collapse of compact stellar objects in galaxies as the origin of GRBs. GRBs can be produced by superluminal jets from such events.

Peter Arnold, Laurence G. Yaffe

We discuss the sequence of effective theories needed to understand the qualitative, and quantitative, behavior of real-time correlators < A(t) A(0) > in ultra-relativistic plasmas. We analyze in detail the case where A is a gauge-invariant conserved current. This case is of interest because it includes a correlation recently measured in lattice simulations o

Stephen L. Adler

We discuss the problem of gauge fixing for the partition function in generalized quantum (or trace) dynamics, deriving analogs of the De Witt-Faddeev-Popov procedure and of the BRST invariance familiar in the functional integral context.

Yeong E. Kim, Alexander L. Zubarev

Based on an approach introduced byGerjuoy, Rau, and Spruch, we constract variational principles in a systematic way for the nonlinear Schroedinger equation and obtain new variational principles for the case of Ginzburg-Pitaevskii-Gross equation (PGP) which is belived to describe accurately the Bose-Einstein condensation at zero temperature. As an application

Ming-Tsung Lee, Wei-Min Zhang, Cheng-Li Wu

In this paper, we study the influence of quantum effects to chaotic dynamics, especially the influence of Pauli effect and dynamical symmetry breaking to chaotic motions. We apply the semiquantal theory to the Sp(6) fermion symmetry model in nuclear collective motion. We demonstrate that quantum chaos appears when dynamical symmetry is broken. We further sho

Lev I. Deych, Alexander A. Lisyansky

We consider propagation of coupled waves (polaritons) formed by a scalar electromagnetic wave and excitations of a finite one dimensional chain of dipoles. It is shown that a microscopic defect (an impurity dipole) embedded in the chain causes resonance tunneling of the electromagnetic wave with the frequency within the forbidden band between two polariton b

E. A. Baltz, P. Gondolo

We compute the neutralino decay rate in the minimal supersymmetric standard model with the addition of explicit R-parity violation. We include the complete squark and slepton mixing matrices, previously neglected, and we improve and correct published formulas. These decays are relevant to accelerator and non-accelerator searches for R-parity violation, and a

Bruce A. Bassett

Inflationary reheating is almost completely controlled by the Floquet indices, $\mu_k$. Using spectral theory we demonstrate that the stability bands (where $\mu_k = 0$) of the Mathieu and Lam\'e equations are destroyed even in Minkowski spacetime, leaving a fractal Cantor set or a measure zero set of stable modes in the cases where the inflaton evolves in a

Vadim Ponomarenko, Naoto Nagaosa

Finite length of a one channel wire results in crossover from a Tomonaga-Luttinger to Fermi liquid behavior with lowering energy scale. In condition that voltage drop $(V)$ mostly occurs across a tunnel barrier inside the wire we found coefficients of temperature/voltage expansion of low energy conductance as a function of constant of interaction, right and

C. Giunti, C. W. Kim, M. Monteno

A comprehensive formalism for the description of neutrino oscillations in the Earth in a general scheme with three massive neutrinos and the mass hierarchy m_1<<m_2<<m_3 is presented. Using this formalism, which is valid both in vacuum and in a medium, the matter effect on the oscillations of low-energy neutrinos is discussed, pointing out the existence of v

Ph. de Forcrand, J. E. Hetrick, T. Takaishi, A. J. van der Sijs

1. We compare Monte Carlo results with analytic predictions for the fermion condensate, in the massive one-flavour Schwinger model. 2. We illustrate on the Schwinger model how to facilitate transitions between topological sectors by a simple reweighting method. 3. We discuss exact, non-perturbative improvement of the gauge sector.

A. M. Gavrilik, N. Z. Iorgov

For the nonstandard $q$-deformed algebras $U_q(so_n)$, defined recently in terms of trilinear relations for generating elements, most general finite dimensional irreducible representations directly corresponding to those of nondeformed algebras $so(n)$ (i.e., characterized by the same sets of only integers or only half-integers as in highest weights of the l

E. I. Guendelman, A. B. Kaganovich

We show that it is possible to obtain inflation and also solve the cosmological constant problem. The theory is invariant under changes of the Lagrangian density $L$ to $L+const$. Then the constant part of a scalar field potential $V$ cannot be responsible for inflation. However, we show that inflation can be driven by a condensate of a four index field stre

C. Anastopoulos

The theme of this paper is the multiplicity of the consistent sets appearing in the consistent histories approach to quantum mechanics. We propose one criterion for choosing preferred families among them: that the physically realizable quasiclassical domain ought to be one corresponding to classical histories. We examine the way classical mechanics arises as

Nurit Krausz, M. S. Marinov

Free quantal motion on group manifolds is considered. The Hamiltonian is given by the Laplace -- Beltrami operator on the group manifold, and the purpose is to get the (Feynman&#39;s) evolution kernel. The spectral expansion, which produced a series of the representation characters for the evolution kernel in the compact case, does not exist for non-compact

R. Adams, R. Bates, C. Da Via, N. P. Johnson

Thick epitaxial layers have been grown using Low Pressure Vapour Phase Epitaxy techniques with low free carrier concentrations . This type of material is attractive as a medium for X-ray detection, because of its high conversion efficiency for X-rays in the medically interesting energy range.

R. L. Bates, C. Da&#39;Via, V. O&#39;Shea, A. Pickford

The motivation for investigating the use of GaAs as a material for detecting particles in experiments for High Energy Physics (HEP) arose from its perceived resistance to radiation damage. This is a vital requirement for detector materials that are to be used in experiments at future accelerators where the radiation environments would exclude all but the mos

M. D. Gould, N. I. Stoilova

A full set of Casimir operators for the Lie superalgebra $gl(m/\infty)$ is constructed and shown to be well defined in the category $O_{FS}$ generated by the highest weight irreducible representations with only a finite number of non-zero weight components. The eigenvalues of these Casimir operators are determined explicitly in terms of the highest weight. C

R. A. Ritchie, H. G. Miller, F. C. Khanna

Based on recent studies of the temperature dependence of the energy and specific heat of liquid nuclear matter, a phase transition is suggested at a temperature $\sim .8$ MeV. We apply Landau Ginzburg theory to this transition and determine the behaviour of the energy and specific heat close to the critical temperature in the condensed phase.

Helmut Haberzettl

Based on an effective field theory of hadrons in which quantum chromodynamics is assumed to provide the necessary bare cutoff functions, a gauge-invariant theory of pion photoproduction with fully dressed nucleons is described. The formalism provides consistent dynamical descriptions of pi-N --> pi-N scattering and Gamma-N --> pi-N production mechanisms in t

G. Krein, R. S. Marques de Carvalho, D. P. Menezes, M. Nielsen

The optimized $δ$-expansion is a nonperturbative approach for field theoretic models which combines the techniques of perturbation theory and the variational principle. This technique is discussed in the $λϕ^4$ model and then implemented in the Walecka model for the equation of state of nuclear matter. The results obtained with the $δ$ expansion are compared

M. Schwamb, H. Arenhoevel, P. Wilhelm, T. Wilbois

Photodisintegration of the deuteron above pi-threshold is studied in a coupled channel approach including N Delta- and pi d-channels with pion retardation in potentials and exchange currents. A much improved description of total and differential cross sections in the energy region between pi-threshold and 400-450 MeV is achieved.

Guangjun Mao, L. Neise, H. Stöcker, W. Greiner Zhuxia Li

A self-consistent relativistic integral-differential equation of the Boltzmann-Uehling-Uhlenbeck-type for the $N^{*}$(1440) resonance is developed based on an effective Lagrangian of baryons interacting through mesons. The closed time-path Green&#39;s function technique and semi-classical, quasi-particle and Born approximations are employed in the derivation

D. C. Brody, A. Ritz

A natural geometry, arising from the embedding into a Hilbert space of the parametrised probability measure for a given lattice model, is used to study the symmetry properties of real-space renormalisation group (RG) flow. In the projective state space this flow is shown to have two contributions: a gradient term, which generates a projective automorphism of

Michele Bourdeau, Gabriel Lopes Cardoso

We show that a large class of supersymmetric solutions to the low-energy effective field theory of heterotic string theory compactified on a seven torus can have finite energy, which we compute. The mechanism by which these solutions are turned into finite energy solutions is similar to the one occurring in the context of four-dimensional stringy cosmic stri

M. Blagojević, D. Popović, B. Sazdović

A general method of constructing canonical gauge invariant actions is used to establish the equivalence between 2D induced gravity and a WZNW system, defined by a difference of two simple WZNW actions fo the SL(2,R) group. The diffeomorphism invariance of the induced gravity is generated by the SL(2,R) Kac-Moody structure of the WZNW system.

Sascha Vongehr

This is a revised and shortened version of a MSc thesis submitted to the University of Sussex, UK. An introduction into the pre-string physics of black holes and related thermodynamics is given. Then, starting with an introduction of how superstring theory is approaching the problem of black hole entropy, work on that and closely related topics like Hawking

Ulf H. Danielsson, Gabriele Ferretti

D-particle quantum mechanics in a type I&#39; background is reviewed. It is also discussed how a string is created when a D-particle is taken through a D8-brane. The process is found to be dual to the creation of a D3-brane when a NS5 and D5 brane are passed through each other.

Isard Dunietz

CP violation is observed to date only in K^0 decays and is parameterizable by a single quantity epsilon. Because it is one of the least understood phenomena in the Standard Model and holds a clue to baryogenesis, it must be investigated further. Highly specialized searches in K^0 decays are possible. Effects in B decays are much larger. In addition to the tr

C. H. Chen, C. Q. Geng, C. C. Lih

We study the T violating transverse muon polarization in the decay of $K^+\to μ^+νγ$ due to CP violation in theories beyond the standard model. We find that the polarization asymmetry could be large in some CP violation models and it may be detectable at the ongoing KEK experiment of E246 as well as the proposed BNL experiment.

B. L. Ioffe

The determination of twist-4 corrections to the structure functions of polarized $e(μ)N$ scattering by QCD sum rules is reviewed and critically analyzed. It is found that in the case of the Bjorken sum rule the twist-4 correction is small at $Q^2 > 5 GeV^2$. However, the accuracy of the today experimental data is insufficient to reliably determine $α_s$ from

Paul Hoyer

There is considerable freedom in setting boundary conditions to perturbation theory at $t=\pm\infty$. The standard PQED and PQCD expansions are based on the (empty) perturbative vacuum. Since the true QCD ground state is expected to have a condensate of low momentum gluons, I propose studying expansions around states containing free particles. A specific bou

R. S. Thorne, R. G. Roberts

At low Q^2, charm production in deep-inelastic scattering is adequately described by assuming generation in electroweak boson-light parton scattering (dominantly boson-gluon fusion) which naturally incorporates the correct threshold behaviour. At high Q^2 this description is inadequate, since it does not sum logs in Q^2/m_c^2, and is replaced by the treatmen

A. Pich

A brief overview of flavour-changing phenomena is presented. The main topics discussed are the universality and Lorentz structure of the leptonic charged-current couplings, our present knowledge of the quark-mixing matrix and the future prospects for CP--violation studies.

J. C. Collins, A. D. Martin, M. G. Ryskin

We outline the existing descriptions of the charm component of the deep inelastic proton structure function F2. We discuss recent approaches to include charm mass effects in the parton evolution equations and the coefficient functions.

John W. Flanagan, John G. Learned, Sandip Pakvasa

We propose a simple test of underground neutrino data to discriminate amongst neutrino oscillation models. It uses the asymmetry between downward-going events and upward-going events, for electron and muon events separately. Because of the symmetry of typical underground detectors, an asymmetry can be compared with calculations with little need for the inter

Francesco Sannino

In this thesis we show that the effective Lagrangian models, encoding the relevant symmetries of the underlying fundamental gauge theory for strong interactions (QCD), provide a reasonable understanding of the interactions among Light Mesons at intermediate energies as well as of the properties of Heavy Baryons.

Hiroko Ichie, Hideo Suganuma, Atsunori Tanaka

Color confinement can be understood by the dual Higgs theory, where monopole condensation leads to the exclusion of the electric flux from the QCD vacuum. We study the role of the monopole for color confinement by investigating the monopole current system. When the self-energy of the monopole current is small enough, long and complicated monopole world-lines

P. Hasenfratz

The fixed-point (FP) action in QCD, although it is local and determined by classical equations, is difficult to parametrize well and is expensive to simulate. But the stake is high: the FP action has scale invariant instanton solutions, has no topological artifacts, satisfies the index theorem on the lattice, does not allow exceptional configurations, requir

Hiroko Ichie, Hideo Suganuma

The nonperturbative phenomena of QCD like color confinement is well described through the dual superconductor picture in the Maximally Abelian (MA) gauge. In this gauge, monopoles appear as important degrees of freedom composed by nonabelian gauge fields. We investigate the peculiar size $R_c$ of the monopole in the MA gauge, considering the theoretical simi

Z. Sroczynski, S. M. Pickles, S. P. Booth

UKQCD&#39;s dynamical fermion project uses the Generalised Hybrid Monte-Carlo (GHMC) algorithm to generate QCD gauge configurations for a non-perturbatively O(a) improved Wilson action with two degenerate sea-quark flavours. We describe our implementation of the algorithm on the Cray-T3E, concentrating on issues arising from code verification and performance

M. Garcia Perez, A. Gonzalez-Arroyo, A. Montero, C. Pena

We study a series of problems in classical Yang-Mills theories using lattice methods. We first investigate SU(N) self-dual configurations on the torus with twisted boundary conditions. We also study the zero modes of the Dirac equation in topological non-trivial background Yang-Mills fields.

G. Burgio, F. Di Renzo, G. Marchesini, E. Onofri

A review of new developments in numerical stochastic perturbation theory (NSPT) is presented. In particular, the status of the extension of the method to gauge fixed lattice QCD is reviewed and a first application to compact (scalar) QED is presented. Lacking still a general proof of the convergence of the underlying stochastic processes, a self-consistent m

G. Burgio, F. Di Renzo, G. Marchesini, E. Onofri

From the analysis of the perturbative expansion of the lattice regularized gluon condensate, toghether with MC data, we present evidence of OPE-unexpected dim-2 power corrections in the scaling behaviour of the Wilson loop. These can be interpreted as an indication that in lattice gauge theories the running coupling at large momentum contains contributions o

H. Markum, R. Pullirsch, K. Rabitsch, T. Wettig

We study complete eigenvalue spectra of the staggered Dirac matrix in quenched QCD on a $6^3\times 4$ lattice. In particular, we investigate the nearest-neighbor spacing distribution $P(s)$ for various values of $β$ both in the confinement and deconfinement phase. In both phases except far into the deconfinement region, the data agree with the Wigner surmise

M. E. Berbenni-Bitsch, A. D. Jackson, S. Meyer, A. Schäfer

We analyze complete spectra of the lattice Dirac operator in SU(2) gauge theory and demonstrate that the distribution of low-lying eigenvalues is described by random matrix theory. We present possible practical applications of this random-matrix universality. In particular, reliable extrapolations of lattice gauge data to the thermodynamic limit are discusse

Pietro Menotti

Starting from the De Witt supermetric and limiting ourselves to a family of geometries characterized by a finite number of geometric invariants we extract the unique integration measure. Such a measure turns out to be a geometric invariant, i.e. independent of the gauge fixed metric used for describing the geometries. The measure is also invariant in form un

K. Orginos, W. Bietenholz, R. Brower, S. Chandrasekharan

We evaluate a perfect quark-gluon vertex function for QCD in coordinate space and truncate it to a short range. We present preliminary results for the charmonium spectrum using this quasi-perfect action.

H. S. Egawa, N. Tsuda, T. Yukawa

Two kinds of statistical properties of dynamical-triangulated manifolds (DT mfds) have been investigated. First, the surfaces appearing on the boundaries of 3D DT mfds were investigated. The string-susceptibility exponent of the boundary surfaces ($\tildeγ_{st}$) of 3D DT mfds with $S^{3}$ topology near to the critical point was obtained by means of a MINBU

Ferenc Csikor, Zoltan Fodor, Jochen Heitger

We study the finite-temperature electroweak phase transition by numerical simulations of the four-dimensional SU(2)-Higgs model on anisotropic lattices with temporal extension $L_t=2$. The physically interesting parameter region of Higgs masses near 80 GeV is reached, and recent results on some thermodynamic quantities are presented.

Jemal Guven, Niall O Murchadha

We establish sufficient conditions for the appearance of apparent horizons in spherically symmetric initial data when spacetime is foliated extrinsically. Let $M$ and $P$ be respectively the total material energy and the total material current contained in some ball of radius $\ell$. Suppose that the dominant energy condition is satisfied. We show that if $M

Jemal Guven, Niall O Murchadha

We establish necessary conditions for the appearance of both apparent horizons and singularities in the initial data of spherically symmetric general relativity when spacetime is foliated extrinsically. When the dominant energy condition is satisfied these conditions assume a particularly simple form. Let $ρ_{Max}$ be the maximum value of the energy density

Jemal Guven, Niall O Murchadha

We exploit an arbitrary extrinsic time foliation of spacetime to solve the constraints in spherically symmetric general relativity. Among such foliations there is a one parameter family, linear and homogeneous in the extrinsic curvature, which permit the momentum constraint to be solved exactly. This family includes, as special cases, the extrinsic time gaug

Dieter R. Brill

Solutions of Einstein&#39;s equations are discussed in which the ``gravitational force&#34; is balanced by an electrical force, and which can serve as models for the Cavendish experiment.

Hyeong-Chan Kim, Min-Ho Lee, Jeong-Young Ji

It is shown that that the area law for the entropy of a quantum field in the Schwarzschild black hole is due to the quantum statistics. The entropies for one particle, a Boltzmann gas, a quantum mechanical gas obeying Bose-Einstein or Fermi-Dirac statistics, and a quantum field in the Schwarzschild black hole are calculated using the microcanonical ensemble

I. L. Egusquiza, A. Feinstein, M. A. Perez Sebastian, M. A. Valle Basagoiti

We look at the transition to the semiclassical behaviour and the decoherence process for the inhomogeneous perturbations in the inflationary universe. Two different decoherence mechanisms appear: one dynamical, accompanied with a negligible, if at all, entropy gain, and the other, effectively irreversible dephasing, due to a rapid variation in time of the of

George F R Ellis, Henk van Elst

The geodesic deviation equation (`GDE&#39;) provides an elegant tool to investigate the timelike, null and spacelike structure of spacetime geometries. Here we employ the GDE to review these structures within the Friedmann--Lema\^ıtre--Robertson--Walker (`FLRW&#39;) models, where we assume the sources to be given by a non-interacting mixture of incoherent ma

Udo Hertrich-Jeromin

A quaternionic calculus for surface pairs in the conformal 4-sphere is elaborated. This calculus is then used to discuss the relation between curved flats in the symmetric space of point pairs and Darboux and Christoffel pairs of isothermic surfaces. A new viewpoint on relations between surfaces of constant mean curvature in certain space forms is presented

J. S. Langer, Alexander E. Lobkovsky

We have examined a class of cohesive-zone models of dynamic mode-I fracture, looking both at steady-state crack propagation and its stability against out-of-plane perturbations. Our work is an extension of that of Ching, Langer, and Nakanishi (CLN) (Phys. Rev. E, vol. 53, no. 3, p. 2864 (1996)), who studied a non-dissipative version of this model and reporte

Arno Schindlmayr, R. W. Godby

Inspired by earlier work on the band-gap problem in insulators, we reexamine the treatment of strongly correlated Hubbard-type models within density-functional theory. In contrast to previous studies, the density is fully parametrized by occupation numbers and overlap of orbitals centered at neighboring atomic sites, as is the local potential by the hopping

A. F. Barabanov, O. V. Urazaev, E. Zasinas, L. A. Maksimov

In the framework of the three-band model for CuO_2 plane in high-temperature superconductors the spectrum of the spin-polaron hole exitation is investigated. The problem is treated taking into account the coupling of a local polaron with the antiferromagnetic spin wave with Q=(pi,pi). This leads to the essential changes of the lowest polaron band E(k) and th

W. Hubner, G. P. Zhang

The spin dynamics in Ni is studied by an exact diagonalization method on the ultrafast time scale. It is shown that the femtosecond relaxation of the magneto-optical response results from exchange interaction and spin-orbit coupling. Each of the two mechanisms affects the relaxation process differently. We find that the intrinsic spin dynamics occurs during

Attila Szolnoki

A two-temperature lattice gas model with repulsive nearest-neighbour interactions is studied using Monte Carlo simulations and dynamical mean-field approximation. The evolution of the two-dimensional, half-filled system is described by an anisotropic Kawasaki dynamics assuming that the hopping of particles along the principal directions is governed by two he

You-Quan Li

The quantum theory for mesoscopic electric circuit is briefly described. The uncertainty relation for electric charge and current modifies the tranditional Heisenberg uncertainty relation. The mesoscopic ring is regarded as a pure L-design, and the persistent current is obtained explicitly. The Coulomb blockade phenomenon appears when applying to the pure C-

F. Igloi, H. Rieger

We study the critical and off-critical (Griffiths-McCoy) regions of the random transverse-field Ising spin chain by analytical and numerical methods and by phenomenological scaling considerations. Here we extend previous investigations to surface quantities and to the ferromagnetic phase. The surface magnetization of the model is shown to be related to the s

S. Giorgini

Damping in a dilute Bose gas is investigated using a mean-field approximation which describes the coupled oscillations of condensate and non-condensate atoms in the collisionless regime. Explicit results for both Landau and Beliaev damping rates are given for non-uniform gases. In the case of uniform systems we obtain results for the damping of phonons both

S. E. Korshunov, Vik. S. Dotsenko

We consider a one-dimensional directed polymer in a random potential which is characterized by the Gaussian statistics with the finite size local correlations. It is shown that the well-known Kardar&#39;s solution obtained originally for a directed polymer with delta-correlated random potential can be applied for the description of the present system only in

A. L. Chernyshev, P. W. Leung, R. J. Gooding

Exact diagonalization numerical results are presented for a 32-site square cluster, with two holes propagating in an antiferromagnetic background described by the t-J model. We characterize the wave function of the lowest energy bound state found in this calculation, which has d_{x^2-y^2} symmetry. Analytical work is presented, based on a Lang-Firsov-type ca

C. Pépin, M. Lavagna

We propose a new approach to the Kondo lattice in order to describe simultaneously the Kondo effect and the local magnetism. This approach relies on an original representation of the $S=1/2$ impurity spin in which the different degrees of freedom are represented by fermionic as well as bosonic variables. The magnetic instability is found at $J_c/D =0.67$ in

Shuly Wintner, Evgeniy Gabrilovich, Nissim Francez

Contemporary linguistic theories (in particular, HPSG) are declarative in nature: they specify constraints on permissible structures, not how such structures are to be computed. Grammars designed under such theories are, therefore, suitable for both parsing and generation. However, practical implementations of such theories don&#39;t usually support bidirect

Laurence Tresse, Steve J. Maddox

We have measured the Ha+[N II] fluxes of the I-selected Canada-France Redshift Survey (CFRS) galaxies lying at a redshift z below 0.3, and hence derived the Ha luminosity function. The magnitude limits of the CFRS mean that only the galaxies with M(B) > -21 mag were observed at these redshifts. We obtained a total Ha luminosity density of at least 10^{39.44\

E. Baron, Peter H. Hauschildt

We describe an important addition to the parallel implementation of our generalized NLTE stellar atmosphere and radiative transfer computer program PHOENIX. In a previous paper in this series we described data and task parallel algorithms we have developed for radiative transfer, spectral line opacity, and NLTE opacity and rate calculations. These algorithms

S. D. Ryder, L. E. Allen, M. G. Burton, M. C. B. Ashley

The newly-commissioned University of New South Wales Infrared Fabry-Perot (UNSWIRF) has been used to image molecular hydrogen emission at 2.12 and 2.25 microns in the reflection nebula Parsamyan 18. P 18 is known to exhibit low values of the (1-0)/(2-1) S(1) ratio suggestive of UV-pumped fluorescence rather than thermal excitation by shocks. Our line ratio m

Ivanio Puerari, Carlos Garcia-Gomez, Antonio Garijo

The projected directions of the rotation axes of interacting binary disk galaxies tend to align orthogonal to each other. Sofue (1992) has suggested that this could be due to shorter merger times for galaxies with paralel spins. We show by means of N-body simulations that this suggestion is correct.

Rene D. Oudmaijer, Graeme Busfield, Janet E. Drew

We have compared the B-V colour excess, E(B-V), obtained for a sample of five optically visible massive YSOs both from diffuse interstellar bands (DIBs) in their spectra and from their optical continuum slopes. Our targets are HD 200775, BD+40 4124, MWC 1080, MWC 297 and MWC 349A. First, E(B-V) towards each of the targets is derived by dereddening the observ

J. H. Knapen, S. Laine, J. A. Yates, A. Robinson

We have studied the core morphology of the ultraluminous infrared galaxy Mrk 273 by combining a high-resolution adaptive optics near-infrared image with an optical image from the Hubble Space Telescope and interferometric radio continuum data, all at spatial resolutions of 150 mas or better. The near-infrared image reveals that the nucleus has two main compo

Peter Hoeflich, F. K. Thielemann, J. Craig Wheeler

The influence of the initial composition of the exploding white dwarf on the nucleosynthesis, light curves and spectra of Type Ia supernovae has been studied in order to evaluate the size of evolutionary effects on cosmological time scales, how the effects can be recognized and how one may be able to correct for them. The calculations are based on a set of d

Torsten A. Ensslin, Peter L. Biermann

Relativistic electrons, seen in the large diffuse radio halo of the Coma cluster of galaxies, should scatter background photons to higher energies. We calculate the inverse Compton contributions from the microwave background, from the local radiation field of elliptical galaxies and from the thermal X-ray emission of the intra cluster medium to the different

J. S. Bagla

We show that the galaxy correlation function does not evolve in proportion with the correlation function of the underlying mass distribution. Earliest galaxies cluster very strongly and the amplitude of the galaxy correlation function decreases from this large value. This continues till the average peaks have collapsed, after which, the galaxy correlation fu

Matthias Bartelmann, Andreas Huss, Joerg M. Colberg, Adrian Jenkins

The gravitational lens effect of galaxy clusters can produce large arcs from source galaxies in their background. Typical source redshifts of ~ 1 require clusters at z ~ 0.3 for arcs to form efficiently. Given the cluster abundance at the present epoch, the fewer clusters exist at z ~ 0.3 the higher Omega_0 is, because the formation epoch of galaxy clusters

M. J. Hardcastle, M. Birkinshaw, D. M. Worrall

We report on ROSAT HRI observations of the nearby powerful radio galaxies 3C33 and 3C111, which both have detected optical hot spots. We find nuclear X-ray sources in both objects, but no X-ray emission from the hot spots. This confirms the presence of a high-energy cutoff in the spectrum of synchrotron-emitting electrons. Since these electrons necessarily s

M. J. Drinkwater, J. K. Webb, J. D. Barrow, V. V. Flambaum

We have compared the frequency of high-redshift Hydrogen HI 21 cm absorption with that of associated molecular absorption in two quasars to place new (1 sigma) upper limits on any variation in y = g_p.alpha^2 (where alpha is the fine structure constant and g_p is the proton g-factor) of |Delta(y)/y| < 5.10^{-6} at redshifts z=0.25 and z=0.68.

I. Neill Reid, John E. Gizis

We have obtained HST Planetary Camera observations of a total of fifty-three low-mass (M < 0.3 M_solar) members of the Hyades cluster. Nine of these stars are resolved as binaries, with separations between 0.1 and 3.1 arcseconds, while a further three are probably equal-mass systems at smaller separations. Allowing for observational selection effects, this c