October 2000 arXiv papers — page 10

Machiko Hatsuda, Makoto Sakaguchi

Open superstring theory is formulated in terms of a nondegenerate supertranslation algebra. A supercharge for a tachyonic superstring can be also defined classically by taking into account the leakage of the supercurrent which is compensated by fermionic and bosonic auxiliary fields. The anticommutator of two supercharges of the tachyonic superstring does no

Giuseppe Castagnoli, David Ritz Finkelstein

Insofar as quantum computation is faster than classical, it appears to be irreversible. In all quantum algorithms found so far the speed-up depends on the extra-dynamical irreversible projection representing quantum measurement. Quantum measurement performs a computation that dynamical computation cannot accomplish as efficiently.

M. B. Plenio, V. Vedral

We present upper and lower bounds to the relative entropy of entanglement of multi-party systems in terms of the bi-partite entanglements of formation and distillation and entropies of various subsystems. We point out implications of our results to the local reversible convertibility of multi-party pure states and discuss their physical basis in terms of del

S. Cruz-Barrios, J. Gomez-Camacho

The motion of neutral particles with magnetic moments in an inhomogeneous magnetic field is described in a semi-classical framework. The concept of Coherent Internal States is used in the formulation of the semiclassical approximation from the full quantum mechanical expression. The classical trajectories are defined only for certain spin state, that satusfy

Yunhai Cai, Alexander W. Chao, Stephan I. Tzenov, Toshi Tajima

We have developed an efficacious algorithm for simulation of the beam-beam interaction in synchrotron colliders based on the nonlinear $δf$ method, where $δf$ is the much smaller deviation of the beam distribution from the slowly evolving main distribution $f_0$. In the presence of damping and quantum fluctuations of synchrotron radiation it has been shown t

C. Hanhart, G. A. Miller, F. Myhrer, T. Sato

We develop a toy model of pion production in nucleon-nucleon collisions that reproduces some of the features of the chiral Lagrangian calculations. We calculate the production amplitude and examine some common approximations.

Nir Barnea, Victor D. Efros, Winfried Leidemann, Giuseppina Orlandini

Two conceptually different hyperspherical harmonics expansions are used for the calculation of the total 4He photoabsorption cross section. Besides the well known method of CHH the recently introduced effective interaction approach for the hyperspherical formalism is applied. Semi-realistic NN potentials are employed and final state interaction is fully take

A. F. Krutov, V. E. Troitsky

In the paper nucl-ex/0010009 by The Jefferson Lab F_pi Collaboration the new results for the charged pion electromagnetic form factor are presented. The approach given in our paper hep-ph/9811318, "On a possible estimation of the constituent--quark parameters from Jefferson Lab experiments on the pion form factor" makes it possible to estimate the ma

Travis Norsen, Sanjay Reddy

We study the role of Coulomb and surface effects on the phase transition from dense nuclear matter to a mixed phase of nuclear and kaon-condensed matter. We calculate corrections to the bulk calculation of the equation of state (EOS) and the critical density for the transition by solving explicitly for spherical, cylindrical, and planar structures. The impor

K. Yoshida, M. Matsuo, Y. R. Shimizu

We construct a microscopic model of thermally excited superdeformed states that describes both the barrier penetration mechanism, leading to the decay-out transitions to normal deformed states, and the rotational damping causing fragmentation of rotational E2 transitions. We describe the barrier penetration by means of a tunneling path in the two-dimensional

M. Veselsky

The production mechanism of highly excited nuclei in the Fermi energy domain is investigated. A phenomenological approach, based on the exciton model, is used for the description of pre-equilibrium emission. A model of deep inelastic transfer is employed for the peripheral collisions in the post-pre-equilibrium stage. An approach to describe more central col

S. Das Gupta, A. Z. Mekjian, M. B. Tsang

The equation of state of nuclear matter suggests that at suitable beam energies the disassembling hot system formed in heavy ion collisions will pass through a liquid-gas coexistence region. Searching for the signatures of the phase transition has been a very important focal point of experimental endeavours in heavy ion collisions, in the last fifteen years.

M. Menzel, I. Boettcher, M. Debowski, F. Dohrmann

Differential production cross sections of K$^-$ and K$^+$ mesons have been measured as function of the polar emission angle in Ni+Ni collisions at a beam energy of 1.93 AGeV. In near-central collisions, the spectral shapes and the widths of the rapidity distributions of K$^-$ and K$^+$ mesons are in agreement with the assumption of isotropic emission. In non

P. Senger

Experimental data on the production of kaons and antikaons in heavy ion collisions at relativistic energies are reviewed with respect to in-medium effects. The $K^-/K^+$ ratios measured in nucleus-nucleus collisions are 1 - 2 orders of magnitude larger than in proton-proton collisions. The azimuthal angle distributions of $K^+$ mesons indicate a repulsive ka

Wentao T. Lu, Kristi Pance, Prabhakar Pradhan, S. Sridhar

We show that the autocorrelation of quantum spectra of an open chaotic system is well described by the classical Ruelle-Pollicott resonances of the associated chaotic strange repeller. This correspondence is demonstrated utilizing microwave experiments on 2-D n-disk billiard geometries, by determination of the wave-vector autocorrelation C(κ) from the experi

Damian H. Zanette

A dynamical model for the distribution of resources between competing agents is studied. While global competition leads to the accumulation of all the resources by a single agent, local competition allows for a wider resource distribution. Multiplicative processes give rise to almost-ordered spatial structures, thourgh the enhancement of random fluctuations.

Frédéric Hélein, Joseph Kouneiher

We discuss in this paper the canonical structure of classical field theory in finite dimensions within the {\it{pataplectic}} Hamiltonian formulation, where we put forward the role of Legendre correspondance. We define the generalized Poisson $\mathfrak{p}$-brackets which are the analogues of the Poisson bracket on forms. We formulate the equations of motion

Semion Gutman, Alexander G. Ramm

An identification of a spherically symmetric potential by its phase shifts is an important physical problem. Recent theoretical results assure that such a potential is uniquely defined by a sufficiently large subset of its phase shifts at any one fixed energy level. However, two different potentials can produce almost identical phase shifts. That is, the inv

Alexander G. Ramm, Semion Gutman

It has recently been shown that spherically symmetric potentials of finite range are uniquely determined by the part of their phase shifts at a fixed energy level $k^2>0$. However, numerical experiments show that two quite different potentials can produce almost identical phase shifts. It has been guessed by physicists that such examples are possible only fo

Chi-Ok Hwang, Michael Mascagni

A discrete random walk method on grids was proposed and used to solve the linearized Poisson-Boltzmann equation (LPBE) \cite{Rammile}. Here, we present a new and efficient grid-free random walk method. Based on a modified `` Walk On Spheres" (WOS) algorithm \cite{Elepov-Mihailov1973} for the LPBE, this Monte Carlo algorithm uses a survival probability di

G. Carnovale, T. H. Koornwinder

In this paper we study a q-analogue of the convolution product on the line in detail. A convolution product on the braided line was defined algebraically by Kempf and Majid. We adapt their definition in order to give an analytic definition for the q-convolution and we study convergence extensively. Since the braided line is commutative as an algebra, all res

M. Paredes

We obtain new families of (1,2)-symplectic invariant metrics on the full complex flag manifolds F(n). For n > 4, we characterize n-3 different n-dimensional families of (1,2)-symplectic invariant metrics on F(n). Any of these families corresponds to a different class of non-integrable invariant almost complex structure on F(n).

Jose Maria Ancochea, Otto Rutwig Campoamor

In this work large families of naturally graded nilpotent Lie algebras in arbitrary dimension and characteristic sequence (n,q,1), with n odd, satisfying the centralizer property, are given. This condtion constitutes a generalization, for a nilpotent Lie agebra, of the structural properties charactrizing the Lie algebra $Q_{n}$. By considering certain cohomo

Michel Brion

Let $X$ be a projective variety, homogeneous under a linear algebraic group. We show that the diagonal of $X$ belongs to a unique irreducible component $H_X$ of the Hilbert scheme of $X\times X$. Moreover, $H_X$ is isomorphic to the ``wonderful completion'' of the connected automorphism group of $X$; in particular, $H_X$ is non-singular. We describe

V. A. Smirnov

The Adams spectral sequence was invented by J.F.Adams almost fifty years ago for calculations of stable homotopy groups of topological spaces and in particular of spheres. The calculation of differentials of this spectral sequence is one of the most difficult problem of Algebraic Topology. Here we consider an approach to solve this problem in the case of Z/2

Stuart Dowker, Peter Gilkey, Klaus Kirsten

The spectral problem where the field satisfies Dirichlet conditions on one part of the boundary of the relevant domain and Neumann on the remainder is discussed. It is shown that there does not exist a classical asymptotic expansion for short time in terms of fractional powers of $t$ with locally computable coefficients.

Ralph Blumenhagen, Lars Goerlich, Boris Kors, Dieter Lust

We discuss the compactification of type I strings on a torus with additional background gauge flux on the D9-branes. The solutions to the cancellation of the RR tadpoles display various phenomenologically attractive features: supersymmetry breaking, chiral fermions and the opportunity to reduce the rank of the gauge group as desired. We also point out the eq

Rajesh R. Parwani

Given a truncated perturbation expansion of a physical quantity, one can, under certain circumstances, obtain lower or upper bounds (or both) to the sum of the full perturbation series by using the Borel transform and a variational conformal map. The method is illustrated by applying it to various mathematical toy-models for which exact results are known. On

Eric Bergshoeff, Antoine Van Proeyen

The d=10 type II string theories, d=11 M-theory and d=12 F-theory have the same symmetry group. It can be viewed either as a subgroup of a conformal group OSp(1|64) or as a contraction of OSp(1|32). The theories are related by different identifications of their symmetry operators as generators of OSp(1|32). T- and S-dualities are recognized as redefinitions

Eric Bergshoeff, Antoine Van Proeyen

We show how OSp(1|32) gives a unifying framework to describe d=10 type II string theories, d=11 M-theory and d=12 F-theory. The theories are related by different identifications of their symmetry operators as generators of OSp(1|32). T- and S-dualities are recognized as redefinitions of generators. Some (s,t) signatures of spacetime allow reality conditions

Barton Zwiebach

A discrete symmetry of the string field tachyon condensate noted by Hata and Shinohara is identified as a discrete subgroup of an SU(1,1) symmetry acting on the ghost coordinates. This symmetry, known from early studies of free gauge invariant string field actions, extends to off-shell interactions only for very restricted kinds of string vertices, among the

Aharon Davidson, Philip D. Mannheim

We show that the thin wall limit of the thick domain wall associated with a sine-Gordon soliton in a single non-compactified patch of 5-dimensional spacetime explicitly yields the Randall-Sundrum localized gravity two patch brane, with its discrete $Z_2$ symmetry arising from the discrete symmetry of the potential, and with the thin Minkowski brane $Λ_5+κ^2_

Nikolay M. Nikolov, Ivan T. Todorov

Rationality of the Wightman functions is proven to follow from energy positivity, locality and a natural condition of global conformal invariance (GCI) in any number D of space-time dimensions. The GCI condition allows to treat correlation functions as generalized sections of a vector bundle over the compactification of Minkowski space and yields a strong fo

J. Ignatius, Dominik J. Schwarz

We analyze a new mechanism for the cosmological QCD first-order phase transition: inhomogeneous nucleation. The primordial temperature fluctuations are larger than the tiny temperature interval, in which bubbles would form in the standard picture of homogeneous nucleation. Thus the bubbles nucleate at cold spots. We find the typical distance between bubble c

Carl H. Albright

The present experimental situation regarding neutrino oscillations is first summarized, followed by an overview of selected grand unified models which have been proposed to explain the various scenarios with three active neutrinos and their right-handed counterparts. Special attention is given to the general features of the models and their ability to favor

K. Funakubo, A. Kakuto, S. Otsuki, F. Toyoda

The preheating after the inflation, which can be interpreted as particle creation in the oscillating inflaton background, provides a state far from thermal equilibrium. We extend the field theoretical treatment of the preheating by Linde et al. to the case of multicomponent complex scalars to show that some charges are created in this process, if C and CP ar

Johan Bijnens

An overview is given of weak interaction physics of the light flavours. It starts with the definition of the CKM matrix and the measurement of its components in the light-flavour sector via semi-leptonic decays. The main part of the lectures is devoted to non-leptonic decays with a main emphasis on analytical calculations of $K\toππ$ and $K^0\leftrightarrow

Christer Friberg

A model for total cross sections with virtual photons is presented. In particular gamma*-p and gamma*-gamma* cross sections are considered. Our approach extends on a model for photoproduction, where the total cross section is subdivided into three distinct event classes: direct, VMD and anomalous. With increasing photon virtuality, the latter two decrease in

O. I. Piskounova

The character of asymmetry between the spectra of Lambda_c and antiLambda_c in the E781 experiment (FNAL) is discussed on the basis of the Quark Gluon String Model(QGSM). As it was shown in the description of the asymmetry between the spectra of leading and nonleading charmed mesons measured in Sigma^--A interactions at p_L= 340 GeV/c in the WA89 experiment

M. Wakamatsu

The theoretical predictions of the chiral quark soliton model for the unpolarized and longitudinally polarized structure functions of the nucleon are compared with recent high energy data. The theory is shown to explain all the qualitatively noticeable features of the existing experiments, including the light flavor sea-quark asymmetry for the unpolarized di

L. B. Okun

In order to directly demonstrate that in static gravitational field the rate of clocks increases with their distance from the source a simple thought experiment is proposed.

Nguyen Van Hieu

We propose to study the superconducting pairing of quarks with the formation of the diquarks as well as the quark-antiquark pairing in QCD by means of the functional integral technique. The dynamical equations for the superconducting order parameters are the nonlinear integral equations for the composite quantum fields describing the quark-quark or quark-ant

The KTeV Collaboration, A. Alavi-Harati

We report on a study of the decay $K_L \to e^+e^-γγ$ carried out as a part of the KTeV/E799 experiment at Fermilab. The 1997 data yielded a sample of 1543 events, including an expected background of $56 \pm 8$ events. An effective form factor was determined from the observed distribution of the $e^+e^-$ invariant mass. Using this form factor in the calculati

Babar Collaboration, T. I. Meyer

We discuss the design, implementation and performance of the radiation monitoring and protection system used by the Silicon Vertex Tracker (SVT) in the BaBar detector. Using 12 reverse-biased PIN photodiodes mounted around the beampipe near the IP, we are able to provide instantaneous radiation dose rates, absorbed dose integrals, and active protection that

H Bialkowska, W Retyk

Data on kaon and $Φ$ production in nuclear collisions as a function of centrality are analysed both at AGS and SPS energy range. We compare the results of several experiments, looking for common trend in `participant scaling' of production yields. We find a smooth description of scaled kaon and $Φ$ yields as a function of participant density. We also sho

G. Giacomelli, A. Margiotta

After a brief presentation of the MACRO detector we discuss the data on atmospheric neutrinos and neutrino oscillations, on high energy (E> 1 GeV) neutrino astronomy, on indirect searches for WIMPs and low energy (E >7 MeV) stellar collapse neutrinos.

J. Podolsky

A class of radiative solutions of Einstein's field equations with a negative cosmological constant and a pure radiation is investigated. The space-times, which generalize the Defrise solution, represent exact gravitational waves which interact with null matter and propagate in the anti-de Sitter universe. Interestingly, these solutions have homogeneous a

V. A. Berezin

We demonstrate how the Einstein's equations for the $D$-dimensional spherical gravity can be written in the covariant vector-like form. These equations reveal easily the causal structure of curved spherically symmetric manifolds and may appear useful in investigation of different models of brane universes.

S. P. Drake

The formation of energetic rings of matter in a Kerr spacetime with an outward pointing acceleration field does not appear to have previously been noted as a relativistic effect. In this paper we show that such rings are a gravimagneto effect with no Newtonian analog, and that they do not occur in the static limit. The energy efficiency of these rings can, d

Andre Kempe

This article describes an algorithm for reducing the intermediate alphabets in cascades of finite-state transducers (FSTs). Although the method modifies the component FSTs, there is no change in the overall relation described by the whole cascade. No additional information or special algorithm, that could decelerate the processing of input, is required at ru

Weihong Zheng, C. J. Hamer, R. R. P. Singh, Simon Trebst

We develop strong-coupling series expansion methods to study two-particle spectra of quantum lattice models. At the heart of the method lies the calculation of an effective Hamiltonian in the two-particle subspace. We explicitly consider an orthogonality transformation to generate this block diagonalization, and find that maintaining orthogonality is crucial

P. Punyindu, S. Das Sarma

This is a Comment on a recent publication: Y.-P. Zhao et al., Phys. Rev. Lett. 85, 3229 (2000). In the Letter, the authors report on an experimental investigation of polymeric (p-xylene) thin film growth and propose a new universality class not previously known. Here, we point out that the critical exponents reported in the Letter are consistent with the cri

Alexandre Diehl, Marcia C. Barbosa, Yan Levin

We explore the effects of counterion condensation on fluid-fluid phase separation in charged colloidal suspensions. It is found that formation of double layers around the colloidal particles stabilizes suspensions against phase separation. Addition of salt, however, produces an instability which, in principle, can lead to a fluid-fluid separation. The instab

M. Hondoh, I. R. Mukhamedshin, M. Nasu, H. Suzuki

The nuclear magnetic relaxation in scandium metal is investigated at liquid helium temeprature for both single crystal and powder samples. The obtained temperature and field dependence of the Korringa constant are described by the means of the spin uctuation theory. It is shown that one of the reason for the high field decreasing of the relaxation rate is th

M. A. Topinka, B. J. LeRoy, R. M. Westervelt, S. E. J. Shaw

Semiconductor nanostructures based on two dimensional electron gases (2DEGs) have the potential to provide new approaches to sensing, information processing, and quantum computation. Much is known about electron transport in 2DEG nanostructures and many remarkable phenomena have been discovered (e.g. weak localization, quantum chaos, universal conductance fl

Geza Odor

A directed percolation process with two symmetric particle species exhibiting exclusion in one dimension is investigated numerically. It is shown that if the species are coupled by branching ($A\to AB$, $B\to BA$) a continuous phase transition will appear at zero branching rate limit belonging to the same universality class as that of the dynamical two-offsp

W. Strepp, S. Sengupta, P. Nielaba

The nature of freezing and melting transitions for a system of hard disks in a spatially periodic external potential is studied using extensive Monte Carlo simulations. Detailed finite size scaling analysis of various thermodynamic quantities like the order parameter, its cumulants etc. are used to map the phase diagram of the system for various values of th

T. A. Gloor, M. E. Zhitomirsky, T. M. Rice

We investigate multiexciton bound states in a semiconducting phase of divalent hexaborides. Due to three degenerate valleys in both the conduction and valence bands the binding energy of a 6-exciton molecule is greatly enhanced by the shell effect. The ground state energies of multiexciton molecules are calculated using the density functional formalism. We a

Wolfgang Kinzel

An overview is given about the statistical physics of neural networks generating and analysing time series. Storage capacity, bit and sequence generation, prediction error, antipredictable sequences, interacting perceptrons and the application on the minority game are discussed. Finally, as a demonstration a perceptron predicts bit sequences produced by huma

G. Schwarz, J. Neugebauer, M. Scheffler

The basic properties of point defects (atomic geometry, the position of charge-transfer levels, and formation energies) on the (110) surface of GaAs, GaP, and InP have been calculated employing density-functional theory. Based on these results we discuss the electronic properties of surface defects, defect segregation, and compensation.

Meghmalhar Manekar, Sujeet Chaudhary, M. K. Chattopadhyay, Kanwal Jeet Singh

We present results of dc magnetisation study showing that the low temperature antiferromagnetic state in various CeFe$_2$-based pseudobinary alloys can be transformed into ferromagnetic state through a magnetic field induced phase transition. We highlight the presence of hysteresis and phase coexistence across this metamagnetic transition and argue that the

K. Hirota

This paper reviews studies of the spatial modulation of spin in La2-xSrxCuO4 (LSCO) through neutron-scattering measurements of the elastic magnetic peaks, with emphasis on Zn-doped LSCO. The elastic incommensurate magnetic peaks can be categorized in two classes with respect to the temperature dependence. Nd-doped LSCO, La2CuO4+y and LSCO with x ~ 1/8 exhibi

D. E. Cox, T. Iglesias, E. Moshopoulou, K. Hirota

The structural phase diagram of the La1-xSrxMnO3 system in the compositional range 0.08 <= x <= 0.125 has been investigated by high-resolution synchrotron x-ray powder diffraction techniques between 20-600 K. Recent studies have reported that there is an unusual rentrant-type phase transition in this range involving an abrupt change in lattice parameters but

H. Yoshioka

Based on the tight binding method with hopping integral between the nearest-neighbor atoms, an oscillator strength $\int_0^{\infty} \d ω{\rm Re} σ(ω)$ is discussed for armchair and metallic zigzag carbon nanotubes. The formulae of the oscillator strength are derived for both types of nanotubes and are compared with the result obtained by a linear chain model

M. Gutmann, E. S. Bozin, S. J. L. Billinge

We report an anomalous local structural response in the CuO2 planes associated with the appearance of charge inhomogeneities at low temperature in underdoped but superconducting La2-x(Sr,Ba)xCuO4. We used pair distribution function analysis of neutron powder diffraction data. The increase in the Cu-O bond length distribution at low temperature has an onset t

A. Kathy Romer, Pedro T. P. Viana, Andrew R. Liddle, Robert G. Mann

This paper describes a serendipitous galaxy cluster survey that we plan to conduct with the XMM X-ray satellite. We have modeled the expected properties of such a survey for three different cosmological models, using an extended Press-Schechter (Press & Schechter 1974) formalism, combined with a detailed characterization of the expected capabilities of the E

Abraham Loeb, Rennan Barkana

The first light from stars and quasars ended the ``dark ages'' of the universe and led to the reionization of hydrogen by redshift 7. Current observations are at the threshold of probing this epoch. The study of high-redshift sources is likely to attract major attention in observational and theoretical cosmology over the next decade.

A. R. McDonald, T. W. B. Muxlow, A. Pedlar, M. A. Garrett

Observations of the starburst galaxy, M82, have been made with a 20-station global VLBI array at $λ$18cm. Maps are presented of the brightest young supernova remnants (SNR) in M82 and the wide-field mapping techniques used in making images over a field of view of $\sim$1 arcminute with 3 milliarcsecond resolution are discussed. A limit has been placed on the

Fumitaka Nakamura, Masayuki Umemura

The collapse and fragmentation of filamentary primordial gas clouds are explored using 1D and 2D hydrodynamical simulations coupled with the nonequilibrium processes of H2 formation. The simulations show that depending upon the initial density,there are two occasions for the fragmentation of primordial filaments. If a filament has relatively low initial dens

P. C. Freire, M. Kramer, A. G. Lyne

We present a simple novel method for determining the orbital parameters of binary pulsars. This method works with any sort of orbital sampling, no matter how sparse, provided that information on the period derivatives is available with each measurement of the rotational period of the pulsar, and it is applicable to binary systems with nearly circular orbits.

S. A. Cora, P. B. Tissera, D. G. Lambas, M. B. Mosconi

We present preliminary results on the effects of mergers on the chemical properties of galactic objects in hierarchical clustering scenarios. We adopt a hydrodynamical chemical code that allows to describe the coupled evolution of dark matter and baryons within a cosmological context. We found that disk-like and spheroid-like objects have distinctive metalli

John E. Gizis, Michael F. Skrutskie

We introduce the properties of the Two Micron All-Sky Survey (2MASS) survey for IAU Symposium 204. 2MASS is a near-infrared survey of the entire sky characterized by high reliability and completeness. Catalogs and images for 47% of the sky are now available online. This data release has been used by Wright (2000) and Cambresy et al. (2000) to subtract the st

J. Silk, J. Devriendt

The far infrared background is a sink for the hidden aspects of galaxy formation. At optical wavelengths, ellipticals and spheroids are old, even at $z \sim 1.$ Neither the luminous formation phase nor their early evolution is seen in the visible. We infer that ellipticals and, more generally, most spheroids must have formed in dust-shrouded starbursts. In t

Y. -Z. Qian, G. J. Wasserburg

We present a three-component mixing model for the evolution of O abundance relative to Fe, taking into account the contributions of the first very massive (> 100 solar masses) stars formed from Big Bang debris. We show that the observations of O and Fe abundances in metal-poor stars in the Galaxy by Israelian et al. and Boesgaard et al. can be well represent

Gijs Nelemans, Lev R. Yungelson, Simon F. Portegies Zwart, Frank Verbunt

We model the population of double white dwarfs in the Galaxy and find a better agreement with observations compared to earlier studies, due to two modifications. The first is the treatment of the first phase of unstable mass transfer and the second the modelling of the cooling of the white dwarfs. A satisfactory agreement with observations of the local sampl

J. S. Greaves, W. S. Holland, D. Ward-Thompson

Molecular outflows from young protostars are widely believed to be collimated by magnetic fields, but there has been little observational evidence to support this hypothesis. Using the new technique of millimetre-wavelength spectro-polarimetry, we demonstrate the existence of a magnetic field in the NGC2024-FIR5 outflow lobe. The 1.3mm J=2-1 transition of ca

N. Christlieb, L. Wisotzki, D. Reimers

We report on the exploitation of the stellar content of the Hamburg/ESO objective prism survey by quantitative selection methods, such as automatic spectral classification, and first results obtained.

E. Xanthopoulos, F. Combes, T. Wiklind

We have searched for molecular absorption lines at millimeter wavelengths in eleven gravitational lens systems discovered in the JVAS/CLASS surveys of flat spectrum radio sources. Spectra of only one source 1030+074 were obtained in the 3-, 2- and 1.3-millimeter band at the frequencies corresponding to common molecular transitions of CO and HCO+ as continuum

Dominik J. Schwarz, Jerome Martin, Alain Riazuelo

Inflationary predictions of the cosmic microwave background anisotropy are often based on the slow-roll approximation. We study the precision of these predictions and compare them with the recent data from BOOMERanG and MAXIMA-1.

A. Lavagno, P. Quarati

We describe the physical motivations why we are urged to look for an ionic equilibrium distribution function slightly different from the Maxwellian to calculate nuclear reaction rates in the solar core plasma answering, at the same time, to a recent paper by Bahcall et al. (astro-ph/0010055).

M. C. Bento, O. Bertolami, P. T. Silva

We analyse the implications of recent Cosmic Microwave Background (CMB) data for a specific cosmological model, based on the higher-dimensional Einstein-Yang-Mills System compactified on a $R\times S^3\times S^d$ topology and conclude that the model parameters are tightly constrained by CMB spectra. Moreover, the model predicts a relationship between the dec

A. Finoguenov, C. Jones

We analyzed a deep Chandra observation of M84, a bright elliptical galaxy in the core of the Virgo cluster. We find that the spatial distribution of the soft X-ray emission is defined by the radio structure of the galaxy. In particular we find two low density regions associated with the radio lobes and surrounded by higher density X-ray filaments. In additio

S. Charnoz, A. Brahic, C. Ferrari, I. Grenier

Observations of the November 1995 Sun crossing of the Saturn&#39;s ring-plane made with the 3.6m CFH telescope, using the UHAO adaptive optics system, are presented here. We report the detection of four arcs located in the vicinity of the F ring. They can be seen one day later in HST images. The combination of both data sets gives accurate determinations of

M. A. Barstow, M. R. Burleigh, N. P. Bannister, J. B. Holberg

We present a series of systematic abundance measurements for a group of hot DA white dwarfs in the temperature range 20,000-75,000K, based on far-UV spectroscopy with STIS on HST, IUE and FUSE. Using our latest heavy element blanketed non-LTE stellar atmosphere calculations we have addressed the heavy element abundance patterns for the hottest stars for the

M. A. Barstow, M. R. Burleigh, N. P. Bannister, J. B. Holberg

We report early FUSE observations of the very hot DA white dwarfs PG1342+444 and REJ0558-371. Detection of photospheric absorption lines allows us to estimate the abundances of C, O, Si, P, S and Fe, the first measurements reported for DA stars at such high temperatures. Values of Teff and log g determined for PG1342+444 from the Lyman line series disagree w

L. L. Kiss, B. Csak, K. Szatmary, G. Furesz

New CCD observations of the pre-cataclysmic binary HW Virginis are presented and discussed. The R-filtered CCD photometry was supplemented with medium-band (Cousins VRI) spectrophotometry based on low-resolution objective-prism spectra. The period variation is reanalysed by means of the standard O-C technique. The new data support the conclusions of Kilkenny

Steve Rawlings, Steve Eales, Mark Lacy

This is the second of two papers presenting basic observational data on the 6CE sample of extragalactic radio sources. It presents the results of optical spectroscopy which has yielded virtually complete redshift information for the 6CE sample: 56 of the 59 sample members have spectroscopic redshifts which, with the exception of seven cases, are secure. The

D. L. Wiltshire

Quintessence models with a dark energy generated by pseudo Nambu-Goldstone bosons provide a natural framework in which to test the possibility that type Ia supernovae luminosity distance measurements are at least partially due to an evolution of the sources, since these models can have parameter values for which the expansion of the Universe is decelerating

J. Machalski, M. Jamrozy

A radio source of the Fanaroff--Riley type II with the angular size of 11.3 arc min is identified with an optical galaxy at z=0.229. Thus, the projected linear extent of the radio structure is 3.14 Mpc which makes it the third largest classical double radio source known after 3C236 and WNB2147+816. The high-frequency VLA observations, a galaxy identification

Andrzej M. Soltan, Radoslaw Marcinkowski

Fluctuations of the gamma-ray background (GRB) are investigated. It is assumed that the GRB is produced by discrete sources. Two basic classes of objects as dominant contributors to the GRB are considered: a) blazars and b) starburst galaxies. Predicted logN-logS counts are calculated for these two models. To produce substantial fraction of the XRB, both cla

Michio Hashimoto, Masaharu Tanabashi, Koichi Yamawaki

We critically examine a version of the top mode standard model recently cast in extra dimensions by Arkani-Hamed, Cheng, Dobrescu, and Hall, based on the (improved) ladder Schwinger-Dyson (SD) equation for the D-(=6,8-)-dimensional gauge theories. We find that the bulk QCD cannot have larger coupling beyond the non-trivial ultraviolet (UV) fixed point, the e

Maurice H. P. M. van Putten, Eve C. Ostriker

We analyze the temporal evolution of accretion onto rotating black holes subject to large-scale magnetic torques. Wind torques alone drive a disk towards collapse in a finite time $\sim t_{ff} E_k/E_B$, where $t_{ff}$ is the initial free-fall time and $E_k/E_B$ is the ratio of kinetic-to-poloidal magnetic energy. Additional spin-up torques from a rapidly rot

Stephan Dürr

Some key points out of my recent study of the characteristic features of the small ($x \ll 1$), intermediate ($x \simeq 1$) and large ($x \gg 1$) Leutwyler-Smilga regimes for QCD-type theories in a finite volume ($x = V Σm$) are presented, and a few immediate consequences for full QCD simulations are discussed.

Nikolaj M. Glazunov

This paper describes some validated numerics aspects of Riemann zeta function, Dirichlet L-functions, Dedekind zeta functions and Hasse-Weil L-functions.

Omar Mustafa, Maen Odeh

Magnetic fingerprints on the spectra of an interacting electron with a negatively charged ion in a parabolic quantum dot (QD), and of two interacting electrons in such a dot, are investigated via a pseudoperturbative methodical proposal. The effect of ion-electron and electron-electron interactions on the spectra are studied. The effect of the symmetry of su

V. Dzhunushaliev

A recent investigation of SU(2) Yang-Mills theory found several classical solutions with bad behaviour at infinity : one of the potential components oscillated and another tended to infinity. In this paper we apply an idea due to Heisenberg about the quantization of strongly interacting nonlinear fields to these classical singular solutions. We find that thi

Gregory L. Eyink

We establish local balance equations for smooth functions of the vorticity in the DiPerna-Majda weak solutions of 2D incompressible Euler, analogous to the balance proved by Duchon and Robert for kinetic energy in 3D. The anomalous term or defect distribution therein corresponds to the ``enstrophy cascade&#39;&#39; of 2D turbulence. It is used to define a ra

Qiong-gui Lin

The partial wave series for the Coulomb scattering amplitude in three dimensions is evaluated in a very simple way to give the closed result.

Florin A. Ghergu, Dumitru N. Vulcanov

The article presents some aspects on the use of computer in teaching general relativity for undergraduate students with some experience in computer manipulation. The article presents some simple algebraic programming (in REDUCE+EXCALC package) procedures for obtaining and the study of some exact solutions of the Einstein equations in order to convince a dedi

Dumitru N. Vulcanov, Gabriela Ciobanu

We present some Maple procedures using the GrTensorII package for teaching purposes in the study of the canonical version of the general relativity based on the ADM formalism