August 1998 arXiv papers — page 6

A. Lima-Santos, Wagner Utiel

Using the KMS condition and exchange algebras we discuss the monodromy and modular properties of two-point KMS states of the critical Ising model.

Zixiang Zhou

Using the nonlinear constraint and Darboux transformation methods, the (m_1,...,m_N) localized solitons of the hyperbolic su(N) AKNS system are constructed. Here "hyperbolic su(N)" means that the first part of the Lax pair is F_y=JF_x+U(x,y,t)F where J is constant real diagonal and U^*=-U. When different solitons move in different velocities, each co

J. Dittmann

The aim of this paper is to derive explicit formulae for the Riemannian Bures metric on the manifold of (finite dimensional) nondegenerate density matrices. The computation of the Bures metric using the presented equations does not require any diagonalization procedure and uses matrix products, determinants and traces, only.

Pawel Masiak, Peter L. Knight

We investigate the degree to which entanglement survives when a correlated pair of two-state systems are copied using either local or non-local processes. We show how the copying process degrades the entanglement, due to a residual correlation between the copied output and the copying machine (itself made of qubits).

S. I. Tzenov, P. L. Colestock

In this work we derive evolution equations for the nonlinear behavior of a coasting beam under the influence of a resonator impedance. Using a renormalization group approach we find a set of coupled nonlinear equations for the beam density and the resonator voltage. Under certain conditions, these may be analytically solved yielding solitary wave behavior, e

Paolo Sibani, Ruud van der Pas, J. Christian Schoen

The `lid' algorithm performs an exhaustive exploration of neighborhoods of local energy minima of energy landscapes. This paper describes an implementation of the algorithm, including issues of parallel performance and scalability. To illustrate the versatility of the approach and to stress the common features present in landscapes of quite different sys

Vasyl Gafiychuk, Ihor Lubashevsky, Roman Andrushkiw

The response of the living tissue to the effects of strong heating or cooling can cause the blood flow rate to vary by an order of magnitude. A mathematical model for the freezing of living tissue is formulated which takes into account the nonlocal temperature dependence of the blood flow rate when the temperature distribution in the tissue is substantially

Fedor Bogomolov

This article contains a new argument which proves vanishing of the first cohomology for negative vector bundles over a complex projective variety if the rank of the bundle is smaller than the dimension of the base. Similar argument is applied to the construction of holomorphic functions on the universal covering of the complex projective variety .

E. Ballico, B. Russo

Let X be a smooth complex projective curve of genus g bigger or equal to 1. If g is bigger than 1 assume further that X is either bielliptic or with general moduli. Under a natural condition on slopes, we prove that there exists a short exact sequence of semistable vector bundles with given ranks and degrees. The importance of the paper consists of the new m

Huai-Dong Cao, Jian Zhou

We develop a Chern-Weil theory for compact Lie group action whose generic stabilizers are finite in the framework of equivariant cohomology. This provides a method of changing an equivariant closed form within its cohomological class to a form more suitable to yield localization results. This work is motivated by our work on reproving wall crossing formulas

Thomas Jech, Saharon Shelah

We investigate reflection of stationary sets in P_kappa lambda and prove a consistency result for the case when lambda is the successor of kappa.

Valeri V. Dvoeglazov

We argue that the self/anti-self charge conjugate states of the (1/2,0)\oplus (0,1/2) representation possess the axial charge. Furthermore, we analyze the recent claims of the \sim σ\cdot [A \times A^*] interaction terms for `fermions'. Finally, we briefly discuss the problem in the (1,0)\oplus (0,1) representation.

S. Groot Nibbelink, J. W. van Holten

Generalized matter couplings to four-dimensional supersymmetric sigma models on general Kaehler manifolds are presented, preserving all holomorphic symmetries. Our generalization allows assignment of arbitrary U(1) charges to additional matter fermions, in all representations of (the holomorphic part of) the isometry group. This can be used to eliminate unwa

Dongsu Bak, Sang Pyo Kim, Sung Ku Kim, Kwang-Sup Soh

We have studied the underlying algebraic structure of the anharmonic oscillator by using the variational perturbation theory. To the first order of the variational perturbation, the Hamiltonian is found to be factorized into a supersymmetric form in terms of the annihilation and creation operators, which satisfy a q-deformed algebra. This algebraic structure

Ashoke Sen

We construct the SO(32) spinor state in weakly coupled type I string theory as a kink solution of the tachyon field on the D-string - anti-D-string pair and calculate its mass. We also give a description of this system in terms of an exact boundary conformal field theory and show that in this description this state can be regarded as a non-supersymmetric D0-

C. Macesanu, L. H. Orr

We study the effects of gluon radiation on top production and decay processes at an $e^+e^-$ collider.The matrix elements are computed without any approximations, using spinor techniques. We use a Monte Carlo event generator which takes into account the infrared singularity due to soft gluons and differences in kinematics associated with radiation in the pro

Cheuk-Yin Wong

In order to understand the J/psi suppression arising from the possible occurrence of the quark-gluon plasma in high-energy heavy-ion collisions, it is necessary to have a comprehensive picture how the J/psi and its precursors are produced, what their properties after production are, and how the J/psi and its precursors propagate inside nuclear matter. There

T. Gherghetta, G. F. Giudice, A. Riotto

In gauge-mediated supersymmetry breaking theories the next-to-lightest supersymmetric particle can decay during or after the nucleosynthesis epoch. The decay products such as photons and hadrons can destroy the light element abundances. Restricting the damage that these decays can do leads to constraints on the abundance and lifetime of the NLSP. We compute

Zhen Cao, Rudolph C. Hwa

A comprehensive model, called ECOMB, is proposed to describe multiparticle production by soft interaction. It incorporates the eikonal formalism, parton model, color mutation, branching and recombination. The physics is conceptually opposite to the dynamics that underlies the fragmentation of a string. The partons are present initially in a hadronic collisio

Michael C. Birse, Judith A. McGovern, Keith G. Richardson

Nonrelativistic two-body scattering by a short-ranged potential is studied using the renormalisation group. Two fixed points are identified: a trivial one and one describing systems with a bound state at zero energy. The eigenvalues of the linearised renormalisation group are used to assign a systematic power-counting to terms in the potential near each of t

E. Baron, R. N. Mohapatra, V. L. Teplitz

We consider nuclei produced in core collapse supernovae and subjected to a high neutron flux. We show that an accelerator mass spectrometry experiment that searched for traces of anomalous iron isotopes could set limits on the order of $10^{-20}-10^{-25}$ on (or perhaps discover) Pauli principle violation by neutrons. A similar search for anomalous Co isotop

O. G. Miranda, V. B. Semikoz, J. W. F. Valle

Low-energy high-resolution neutrino-electron scattering experiments may play an important role in testing the gauge structure of the electroweak interaction. We discuss the use of strong radioactive neutrino sources (e.g. $^{51}$Cr) in underground experiments such as BOREXINO, HELLAZ and LAMA. We display the sensitivity of these detectors in testing the poss

T. S. Biro, P. Levai, J. Zimanyi, C. T. Traxler

We present a model of fast hadronization of constituent quark matter in relativistic heavy ion collisions based on rate equations and capture cross sections in non-relativistic potential. We utilize a thermodynamically consistent approach with a non-ideal equation of state including correlation terms based on string phenomenology. We investigate strange and

T. Binoth, A. Ghinculov

We show in this paper that the 1/N expansion is a reliable tool to calculate the properties of a heavy Higgs boson. The 1/N expansion sums up all orders in perturbation theory, and therefore avoids the renormalization scheme dependence of the conventional perturbative approach. It is explained how effects due to the Landau pole of the Higgs sector are isolat

Dario Grasso, Victor Semikoz

In this letter we introduce a new method to determine the radiative neutrino decay rate in the presence of a medium. Our approach is based on the generalisation of the optical theorem at finite temperature and density. Differently from previous works on this subject, our method allows to account for dispersive and dissipative electromagnetic properties of th

A. V. Belitsky

We study the renormalization of the Wilson loop with a path corresponding to the Drell-Yan lepton pair production in two-loop approximation of perturbation theory. We establish the renormalization group equation in next-to-leading order and find a process specific anomalous dimension Gamma_DY in the corresponding approximation.

R. Foot, R. R. Volkas

We show that the SuperKamiokande atmospheric neutrino results explain electric charge quantisation, provided that the oscillation mode is $ν_μ \to ν_τ$ and that the neutrino mass is of Majorana type.

P. Minkowski

We study the lowest lying $π^+ π^-$ resonance R, bound by the long range Coulomb potential and destabilized by short range strong interactions mediating the dominant decay into two neutral pions. Parametrizing the corresponding partial decay width by $Γ(R \to 2 π^0) = 2/9 α^3 \sqrt{m_{π^+}^2 - m_{π^0}^2} (Δa_{D} m_{π^+})^2$ the quantity $Δa_{D}$ depends with

Claude Bernard, Maarten Golterman, Craig McNeile

We calculate the perturbative scales (q*) for the axial and vector currents for the Wilson action, with and without tadpole improvement, using Lepage and Mackenzie's formalism. The scale for the pseudoscalar density (times the mass) is computed as well. Contrary to naive expectation, tadpole improvement reduces q* by only a small amount for the operators

Guy D. Moore

I present a technique for measuring the broken phase sphaleron rate nonperturbatively. There are three parts to the calculation: determination of the probability distribution of Chern-Simons number NCS; measurement of <| d\NCS/dt |> at NCS=1/2, the mean rate of change of NCS at the barrier; and measurement of the ``dynamical prefactor,&#39;&#39; the fraction

Xiang-Qian Luo

I describe a mechanism to understand the relation between chiral-symmetry breaking and eigenmodes of the Dirac operator in lattice QCD with Kogut-Susskind sea quarks. It can be shown that if chiral symmetry is spontaneously broken, the eigenvalues $λ_i$ should behave as $z(i)/V$ for large volume $V$, where $z(i)$ is the i-th zero of the Bessel function. With

The OPAL Collaboration, K. Ackerstaff et al

We present an observation at LEP of the production of chi_c2 mesons in the collisions of two quasi-real photons using the OPAL detector. The chi_c2 mesons are reconstructed in the decay channel Chi_c2 to J/psi gamma to l+l- gamma (with l= e,mu) using all data taken at e+e- centre-of-mass energies of 91 and 183 GeV, corresponding to integrated luminosities of

László Á. Gergely, Zoltán I. Perjés, Mátyás Vasúth

The secular evolution of a spinning, massive binary system in eccentric orbit is analyzed, expanding and generalizing our previous treatments of the Lense-Thirring motion and the one-spin limit. The spin-orbit and spin-spin effects up to the 3/2 post-Newtonian order are considered, both in the equations of motion and in the radiative losses. The description

M. Marklund, M. Bradley

The properties of LRS class II perfect fluid space-times are analyzed using the description of geometries in terms of the Riemann tensor and a finite number of its covariant derivatives. In this manner it is straightforward to obtain the plane and hyperbolic analogues to the spherical symmetric case. For spherically symmetric static models the set of equatio

H. -J. Schmidt

We report on the cited papers refs. 1 - 18 from the following points of view: What do we exactly know about solutions when no exact solution (in the sense of &#34;solution in closed form&#34;) is available? In which sense do these solutions possess a singularity? In which cases do conformal relations and/or dimensional reductions simplify the deduction? Furt

G. J. Stephens, E. A. Calzetta, B. L. Hu, S. A. Ramsey

We study the nonequilibrium dynamics leading to the formation of topological defects in a symmetry-breaking phase transition of a quantum scalar field with λΦ^4 self-interaction in a spatially flat, radiation-dominated Friedmann-Robertson-Walker Universe. The quantum field is initially in a finite-temperature symmetry-restored state and the phase transition

Edith Hemaspaandra, Lane A. Hemaspaandra, Harald Hempel

Hemaspaandra et al. proved that, for $m > 0$ and $0 < i < k - 1$: if $Σ_i^p \BoldfaceDelta DIFF_m(Σ_k^p)$ is closed under complementation, then $DIFF_m(Σ_k^p) = coDIFF_m(Σ_k^p)$. This sharply asymmetric result fails to apply to the case in which the hypothesis is weakened by allowing the $Σ_i^p$ to be replaced by any class in its difference hierarchy. We so

Jae Dong Noh, Hyunggyu Park, Marcel den Nijs

We present a realization of directed Ising (DI) type dynamic absorbing state phase transitions in the context of one-dimensional interfaces, such as the relaxation of a step on a vicinal surface. Under the restriction that particle deposition and evaporation can only take place near existing kinks, the interface relaxes into one of three steady states: rough

Alain Rochefort, Dennis R. Salahub, Phaedon Avouris

The electronic structure of finite-length armchair carbon nanotubes has been studied using several ab-initio and semi-empirical quantum computational techniques. The additional confinement of the electrons along the tube axis leads to the opening of a band-gap in short armchair tubes. The value of the band-gap decreases with increasing tube length, however,

Panayotis Benetatos, M. Cristina Marchetti

In this paper we use non-Gaussian hydrodynamics to study the magnetic response of a flux-line liquid in the mixed state of a type-II superconductor. Both the derivation of our model, which goes beyond conventional Gaussian flux liquid hydrodynamics, and its relationship to other approaches used in the literature are discussed. We focus on the response to a t

L. Bellaiche, J. Padilla, David Vanderbilt

Using first-principles supercell calculations, we have investigated energetic, structural and dielectric properties of three different A(B&#39;B&#39;&#39;)O_3 perovskite alloys: Ba(Zn_{1/3}Nb_{2/3})O_3 (BZN), Pb(Zn_{1/3}Nb_{2/3})O_3 (PZN), and Pb(Zr_{1/3}Ti_{2/3})O_3 (PZT). In the homovalent alloy PZT, the energetics are found to be mainly driven by atomic r

D. W. Hess, J. J. Deisz, J. W. Serene

We present calculations of the single-particle excitation spectrum for a 2D strong-coupling superconductor in a conserving approximation. Spectral weight at low frequency is substantially reduced as the superconducting transition is approached from the normal state. The suppression of low-energy excitations is a consequence of Cooper-pair fluctuations that a

D. B. Abraham, F. H. L. Essler, F. T. Latremoliere

We solve exactly a Terrace-Ledge-Kink (TLK) model describing a crystal surface at a microscopic level. We show that there is a faceting transition driven either by temperature or by the chemical potential that controls the slope of the surface. In the rough phase we investigate thermal fluctuations of the surface using Conformal Field Theory.

Jonathan Doye, Mark Miller, David Wales

The 38-atom Lennard-Jones cluster has a paradigmatic double-funnel energy landscape. One funnel ends in the global minimum, a face-centred-cubic (fcc) truncated octahedron. At the bottom of the other funnel is the second lowest energy minimum which is an incomplete Mackay icosahedron. We characterize the energy landscape in two ways. Firstly, from a large sa

Girish S. Setlur, Yia-Chung Chang

This is a sort of tutorial where we present many of the tedious details involved in deriving the correspondence between the number conserving product of two fermi/bose fields with spin and the corresponding sea/condensate displacements also with spin. This time we include finite temperature effects differently by coupling the sea-bosons to an inhomogeneous c

Alessandro Chessa, H. Eugene Stanley, Alessandro Vespignani, Stefano Zapperi

We perform extensive numerical simulations of different versions of the sandpile model. We find that previous claims about universality classes are unfounded, since the method previously employed to analyze the data suffered a systematic bias. We identify the correct scaling behavior and conclude that sandpiles with stochastic and deterministic toppling rule

Rama Cont

After a brief review of option pricing theory, we introduce various methods proposed for extracting the statistical information implicit in options prices. We discuss the advantages and drawbacks of each method, the interpretation of their results in economic terms, their theoretical consequences and their relevance for applications.

R. Eder

We present a theory for the spin excitations of the Kondo lattice. We derive an effective Hamiltonian, which describes Fermionic spin 1/2 charge fluctuations interacting with Bosonic triplet spin fluctuations. We show that already the simplest approximation possible, i.e. replacing the magnon self-energy by the free polarization bubble for the charge excitat

K. Walasek, K. Lukierska- Walasek, M. Wodawski

We consider the Ising spin glass for the arbitrary spin S with the short- ranged interaction using the Bethe- Peierls approximation previously formulated by Serva and Paladin for the same system but limited to S=1/2. Results obtained by us for arbitrary S are not a simple generalization of those for S=1/2. In this paper we mainly concentrate our studies on t

Axel Gross

Reactions on surfaces play an important role in many technological applications. Since these processes are often rather complex, one tries to understand single steps of these complicated reactions by investigating simpler system. In particular the hydrogen dissociation on surfaces serves as such a model system. There has been much progress in recent years in

Axel Gross, Ching-Ming Wei, Matthias Scheffler

We report calculations of the dissociative adsorption of H_2 at Pd (100) covered with 1/4 monolayer of sulfur using quantum dynamics as well as molecular dynamics and taking all six degrees of freedom of the two H atoms fully into account. The ab initio potential-energy surface (PES) is found to be very strongly corrugated. In particular we discuss the influ

Axel Gross

Due to the development of efficient algorithms and the improvement of computer power it is now possible to map out potential energy surfaces (PES) of reactions at surfaces in great detail. This achievement has been accompanied by an increased effort in the dynamical simulation of processes on surfaces. The paradigm for simple reactions at surfaces -- the dis

C. Stampfl, M. Scheffler

Knowledge of the atomic geometry of a surface is a prerequisite for any detailed understanding of the surface&#39;s electronic structure and chemical properties. Previous studies have convincingly demonstrated that density functional theory (DFT) yields accurate surface atomic geometries and that reliable predictions concerning stable and metastable phases c

Hiroshi Kuratsuji, Hiroyuki Yabu

Based on the Landau-Ginzburg Lagrangian, the dynamics of a vortex is studied for superfluid He3-A characterized by the l-texture. The resultant equation of motion for a vortex leads to the Magnus-type force caused by the l-texture. The force is explicitly written in terms of the mapping degree from the compactified 2-dimensional plane to the space of l-vecto

G. I. Japaridze, A. P. Kampf

A one-dimensional model of interacting electrons with on-site $U$, nearest-neighbor $V$, and correlated-hopping interaction $T^{\ast}$ is studied at half-filling using the continuum-limit field theory approach. The ground state phase diagram is obtained for a wide range of coupling constants. In addition to the insulating spin- and charge-density wave phases

J. -M. Robin, A. Romano, J. Ranninger

The Boson-Fermion model, describing a mixture of tightly bound electron pairs and quasi-free electrons hybridized with each other via a charge exchange term, is studied in the limit of infinite dimensions, using the Non-Crossing Approximation within the Dynamical Mean Field Theory. It is shown that a metal-insulator crossover, driven by strong pair fluctuati

Y. Hanein, D. Shahar, J. Yoon, C. C. Li

The observation of a carrier-density driven metal-insulator transition in n-type GaAs-based heterostructure is reported. Although weaker than in comparable-quality p-type GaAs samples, the main features of the transition are rather similar.

Roland Faller, Mathias Puetz, Florian Mueller-Plathe

We investigate mutual local chain order in systems of fully flexible polymer melts in a simple generic bead-spring model. The excluded-volume interaction together with the connectivity leads to local ordering effects which are independent of chain length between 25 and 700 monomers, i.e. in the Rouse as well as in the reptation regime. These ordering phenome

Paolo Ruggerone, Alex Kley, Matthias Scheffler

Density functional theory (DFT) primarily provides a good description of the electronic structure. Thus, DFT primarily deals with length scales as those of a chemical bond, i.e. 10^-10 meter, and with time scales of the order of atomic vibrations, i.e. 10^-13 seconds. However, several interesting phenomena happen and/or become observable on different scales,

The MACHO Collaboration, C. Alcock, R. A. Allsman, D. R. Alves

MACHO Project photometry of 45 LMC FO/SO beat Cepheids which pulsate in the first and second overtone (FO and SOo, respectively) has been analysed to determine the lightcurve characteristics for the SO mode of Cepheid pulsation. We predict that singly-periodic SO Cepheids will have nearly sinusoidal lightcurves; that we will only be able to discern SO Cephei

Brad M. S. Hansen

The recent discovery of microlensing of stars in the Large Magellanic Cloud has excited much interest in the nature of the lensing population. Detailed analyses indicate that the mass of these objects ranges from 0.3-0.8 solar masses, suggesting that they might be white dwarfs, the faint remnants of stellar evolution. The confirmation of such an hypothesis w

Rohan Mahadevan

We calculate the flux and spectrum of synchrotron radiation produced by high energy electrons and positrons (\epm) in an advection dominated accretion flow (ADAF) around a black hole. The \epm are from the decay of charged pions which are created through proton-proton collisions. We consider both a thermal and power-law energy distribution of protons, and sh

F. -X. Desert, A. Benoit, S. Gaertner, J. -P. Bernard

We report on the first observation of the Sunyaev-Zel&#39;dovich effect with the Diabolo experiment at the IRAM 30 metre telescope. A significant brightness decrement is detected in the direction of three clusters (Abell 665, Abell 2163 and CL0016+16). With a 30 arcsecond beam and 3 arcminute beamthrow, this is the highest angular resolution observation to d

John Barrow, Roy Maartens

Anisotropic stress contributions to the gravitational field can arise from magnetic fields, collisionless relativistic particles, hydrodynamic shear viscosity, gravitational waves, skew axion fields in low-energy string cosmologies, or topological defects. We investigate the effects of such stresses on cosmological evolution, and in particular on the dissipa

Keivan G. Stassun, Kenneth Wood

We employ a Monte Carlo radiation transfer code to investigate the multi- wavelength photopolarimetric variability arising from a spotted T Tauri star surrounded by a dusty circumstellar disk. Our aim is to assess the ability of the magnetic accretion model to explain the observed photopolarimetric variability of classical T Tauri stars, and to identify pote

G. R. Knapp

Elliptical galaxies outside dense clusters are observed to contain small amounts (relative to spiral galaxies) of cold interstellar gas. This review discusses the atomic gas, the molecular gas, and the dust in elliptical galaxies. Field elliptical galaxies contain about 0.01 to 0.1 of the cold interstellar matter content of spiral galaxies of similar luminos

R. G. Ohl, R. W. O&#39;Connell, R. C. Bohlin, N. R. Collins

We discuss far-UV (1500 A) surface photometry and FUV-B color profiles for 8 E/S0 galaxies from images taken with the Ultraviolet Imaging Telescope, primarily during the Astro-2 mission. In three cases, the FUV radial profiles are more consistent with an exponential than a de Vaucouleurs function, but there is no other evidence for the presence of a disk or

Claudia Maraston

Evolutionary synthesis models for stellar populations of various ages and chemical compositions are constructed with the approach described in Maraston (1998), in which the Fuel Consumption Theorem is used to evaluate the energetics of Post Main Sequence stars. We present here the synthetic `stellar&#39; mass-to-light ratios (M*/L) in the U,B,V,R,I,J,H,K pho

D. Thomas

I discuss the formation of alpha-enhanced metal-rich stellar populations in the nuclei of luminous ellipticals. Based on hierarchical clustering, different galaxy formation scenarios, which imply different star formation histories, are considered. In contrast to the fast clumpy collapse mode, the late merger of two spiral galaxies fails to reproduce signific

G. Giovannini, W. D. Cotton, L. Feretti, L. Lara

We present here two epochs of Space VLBI Observations at 18 cm of the BL-Lac type object MKN 501. Thanks to the high resolution of these new data, we have found that the inner jet is centrally brightened at its beginning, but becomes extended and limb brightened at ~8 mas from the core. Moreover a comparison between the two epochs shows the presence of a pro

Seb Oliver, Carlotta Gruppioni, Stephen Serjeant

We present a new determination of the co-moving star formation density at redshifts z~<0.35 from the 1.4 GHz luminosity function of sub-mJy star-burst galaxies. Our sample, taken from Benn et al. (1993), is insensitive to dust obscuration. The shape of the Luminosity function of this sample is indistinguishable from a number of reasonable a prior models of t

P. Richter, H. Widmann, K. S. de Boer, I. Appenzeller

We present a study of molecular hyrogen (H_2) in the SMC gas, based on space shuttle Far UV spectroscopy with ORFEUS and the Tuebingen echelle spectrograph, in the line of sight to the SMC star HD 5980. 17 absorption lines from the Lyman band have been analysed. Our line of sight crosses two clouds within the SMC. We detect a cool molecular component near +1

Joerg M. Colberg, Simon D. M. White, Thomas J. MacFarland, Adrian Jenkins

We report on analyses of cluster samples obtained from the Hubble Volume Simulations. These simulations, an $Ω=1$ model named $τ$CDM and a flat low $Ω$ model with a cosmological constant ($Λ$CDM), comprise the largest computational efforts to date in numerical cosmology. We investigate the presence of massive galaxy clusters at $z\approx 0.8$. The $τ$CDM mod

K. S. de Boer, P. Richter, D. J. Bomans, A. Heithausen

We present the first detection of molecular hydrogen (H_2) UV absorption profiles on the line of sight to the LMC. The star LH 10:3120 in the LMC was measured with the ORFEUS telescope and the Tuebingen echelle spectrograph during the space shuttle mission of Nov./Dec. 1996. 16 absorption lines from the Lyman band are used to derive the column densities of H

H. Widmann, K. S. de Boer, P. Richter, G. Kraemer

FUV high resolution spectra of 18 stars, particularly chosen to observe the interstellar medium (ISM), were obtained during the second ORFEUS-SPAS free flight space shuttle mission in December 1996. Among these were 6 objects with a distance to the galactic plane larger than 1 kpc, one SMC and 4 LMC stars. This selction of targets is part of the ORFEUS progr

Koji Nobuta, Tomoyuki Hanawa

We investigate time-dependent inviscid hydrodynamical accretion flows onto a black hole using numerical simulations. We consider the accretion that consists of hot tenuous gas with low specific angular momentum and cold dense gas with high specific angular momentum. The former accretes continuously and the latter highly intermittently as blobs. The high spec

David R. Alves, Ata Sarajedini

Color-magnitude diagrams of globular clusters often exhibit a prominent horizontal branch (HB) and may also show features such as the red giant branch (RGB) bump and the asymptotic giant branch (AGB) bump. Stellar evolution theory predicts that the luminosities of these features will depend on the metallicity and age of the cluster. We calculate theoretical

Rosanne Di Stefano

Are microlensing searches likely to discover planets that harbor life? Given our present state of knowledge, this is a difficult question to answer. We therefore begin by asking a more narrowly focused question: are conditions on planets discovered via microlensing likely to be similar to those we experience on Earth? In this paper I link the microlensing ob

M. -R. Li, P. J. Hirschfeld, P. Woelfle

We examine the effects of nonlocal electrodynamics for a d-wave superconductor on the field dependence of the magnetic penetration depth. The linear field dependence predicted in the local limit, commonly known as the nonlinear Meissner effect, is instead found to be quadratic, $δλ\sim H^2$ for fields below a crossover scale $H^*$. This crossover is shown to

Ya. Azimov

Decays of neutral D-mesons are considered phenomenologically without invoking any particular models. Special attention is given to cascade decays with intermediate neutral kaons where coherent double-flavor oscillations (CDFO) become possible. We show necessity and unique possibilities of experiments on CDFO. They allow to relate with each other widths and m

Kevin E. Cahill, Roy J. Glauber

The mathematical methods that have been used to analyze the statistical properties of boson fields, and in particular the coherence of photons in quantum optics, have their counterparts for Fermi fields. The coherent states, the displacement operators, the P-representation, and the other operator expansions all possess surprisingly close fermionic analogues.

Arthur Jaffe

We identify a positivity property for partition functions in quantum systems with a unitary symmetry group, and we call this &#34;twist positivity.&#34; The existence of Feynman-Kac measures and the existence of zero-mass limits are both related to this property. Twist positivity arises from the occurrence of complex conjugate representations on an energy ei

William Arveson

A notion of curvature is introduced in multivariable operator theory and an analogue of the Gauss-Bonnet-Chern theorem is established for graded (contractive) Hilbert modules over the complex polynomial algebra in d variables, d=1,2,3,.... The curvature invariant, Euler characteristic, and degree are computed for some explicit examples based on varieties in

Lane A. Hemaspaandra, Joerg Rothe

Rabi and Sherman [RS97] presented novel digital signature and unauthenticated secret-key agreement protocols, developed by themselves and by Rivest and Sherman. These protocols use ``strong,&#39;&#39; total, commutative (in the case of multi-party secret-key agreement), associative one-way functions as their key building blocks. Though Rabi and Sherman did p

Simon Cozens

It has been argued that, when learning a first language, babies use a series of small clues to aid recognition and comprehension, and that one of these clues is word length. In this paper we present a statistical part of speech tagger which trains itself solely on the number of letters in each word in a sentence.

R. Benzi, F. Toschi, R. Tripiccione

In this paper we discuss some theoretical aspects concerning the scaling laws of the Nusselt number versus the Rayleigh number in a Rayleigh-Benard cell. We present a new set of numerical simulations and compare our findings against the predictions of existing models. We then propose a new theory which relies on the hypothesis of Bolgiano scaling. Our approa

Robert Fender, Ralph Spencer, Tasso Tzioumis, Kinwah Wu

In observations with the Australia Telescope Compact Array we have resolved the radio counterpart of the unusual X-ray binary Cir X-1 into an asymmetric extended structure on arcsecond scales. In order to quantify the asymmetry we have redetermined as accurately as possible both the optical and radio coordinates of the source. The extended emission can be un

Fred C. Adams, Greg Laughlin, Manasse Mbonye, Malcolm J. Perry

We consider the long term fate and evolution of cold degenerate stars under the action of gravity alone. Although such stars cannot emit radiation through the Hawking mechanism, the wave function of the star will contain a small admixture of black hole states. These black hole states will emit radiation and hence the star can lose its mass energy in the long

M. Beneke, G. Buchalla, C. Greub, A. Lenz

We compute the QCD corrections to the decay rate difference in the $B_s-\bar B_s$ system, $ΔΓ_{B_s}$, in the next-to-leading logarithmic approximation using the heavy quark expansion approach. Going beyond leading order in QCD is essential to obtain a proper matching of the Wilson coefficients to the matrix elements of local operators from lattice gauge theo

Peter Sheridan Dodds, Daniel H. Rothman

Scaling laws that describe the structure of river networks are shown to follow from three simple assumptions. These assumptions are: (1) river networks are structurally self-similar, (2) single channels are self-affine, and (3) overland flow into channels occurs over a characteristic distance (drainage density is uniform). We obtain a complete set of scaling

Marius Grigorescu, Mahi R. Singh

Macroscopic quantum coherence oscillations in mesoscopic antiferromagnets may appear when the anisotropy potential creates a barrier between the antiferromagnetic states with opposite orientations of the Neel vector. This phenomenon is studied for the physical situation of the nuclear spin system of eight Xe atoms arranged on a magnetic surface along a chain

Igor F. Lyuksyutov, Valery Pokrovsky

We propose two statistical models for description the metal-insulator phase transition coupled with paramagnetic-ferromagnetic phase transition in manganites of the type La_{1-x}Sr_xMnO_3. The first one based on the competition of small polarons and delocalized carriers. In the second one the conductivity appears as a result of overlapping of large polarons.

Danuta Makowiec

This paper is the continuation of our earlier considerations on cellular automata with Toom local rule (TCA) as the alternative to kinetic Ising systems. The arguments for TCA stationary states not being the equilibrium states are found in simulations.

Tin-Lun Ho, Sungkit Yip

Motivated by the recent success of optical trapping of alkali Bose condensate, we have studied the superfluid state of optically trapped alkali fermions, which can have Cooper pairs with total spin $J\geq 2$. In this paper, we shall discuss the general structure of these large spin Cooper pairs and their close relation with singlet Cooper pairs with non-zero

Taeseung Choi, Chang-Mo Ryu, A. M. Jayannavar

We considered the circulating current induced by the current magnification and the persistent current induced by Aharonov-Casher flux. The persistent currents have directional dependence on the direct current flow, but the circulating currents have no directional dependence. Hence in the equilibrium, only the persistent current can survives on the ring. For

C. M. Bezborodov, J. V. Mustsevaya, V. V. Mustsevoy

The stability of thin homogeneous gaseous disk with step discontinuity of velocity and density profile has been investigated analytically in the limitary case of large compressibility and numerically at spatially separated velocity and density kinks. The expressions for reflection and transmission coefficients at the axisymmetrical vortex sheet are derived.

C. M. Bezborodov, V. V. Mustsevoy

Linear stability analysis of the axisymmetric interface of velocity and density discontinuity in rotating gaseous disk has been performed numerically and analytically. Physical mechanisms leading to development of centrifugal and Kelvin-Helmholtz instability at the kink has been analysed in detail. In the incompressible limit it has been shown in the first t

J. V. Mustsevaya, V. V. Mustsevoy

Linear analysis of vortex sheet stability in the rotating gaseous disk or shallow water layer shows that presence of a central reflecting surface changes system stability significantly. An effect of absence of vortex sheet stabilization has been found as compressibility exceeds Landau criterion. The properties of multimode short-scale instability of acoustic

A. V. Khoperskov, S. S. Khrapov

Dynamics of linear perturbations in a differentially rotating accretion disk with non-homogeneous vertical structure is investigated. It has been found that turbulent viscosity results in instability of both pinching oscillations, and bending modes. Not only the low-frequency fundamental modes, but also the high-frequency reflective harmonics appear to be un

A. V. Khoperskov, S. S. Khrapov

The model of a geometrically thin gaseous disk in the external gravitational potential is considered. The dinamics of small nonaxisymmetric perturbations in the plane of the accretion disk with dissipative effects is investigated. It is showed, that conditions of development and parameters of unstable oscillation modes in the opticaly thick accretion disk ar