June 1998 arXiv papers — page 9

M. Boettcher, S. D. Bloom

The multiwavelength spectrum of BL Lacertae during its July 1997 outburst is analyzed in terms of different variations of the homogeneous leptonic jet model for the production of high-energy radiation from blazars. We find that a two-component gamma-ray spectrum, consisting of a synchrotron self-Compton and an external Compton component, is required in order

M. Hillery, V. Buzek, A. Berthiaume

Secret sharing is a procedure for splitting a message into several parts so that no subset of parts is sufficient to read the message, but the entire set is. We show how this procedure can be implemented using GHZ states. In the quantum case the presence of an eavesdropper will introduce errors so that his presence can be detected. We also show how GHZ state

S. Sivakumar

The states $|α,m>$, defined as ${a^{\dagger}}^{m}|α>$ up to a normalization constant and $m$ is a nonnegative integer, are shown to be the eigenstates of $f(\hat{n},m)\hat{a}$ where $f(\hat{n},m)$ is a nonlinear function of the number operator $\hat{n}$. The explicit form of $f(\hat{n},m)$ is constructed. The eigenstates of this operator for negative values

Per Elmfors, Kari Enqvist, Kimmo Kainulainen

We consider the effect of the presence of a hypermagnetic field at the electroweak phase transition. Screening of the Z-component inside a bubble of the broken phase delays the phase transition and makes it stronger first order. We show that the sphaleron constraint can be evaded for m_H up to 100 GeV if a B_Y\gsim 0.3 T^2 exists at the time of the EW phase

N. Q. Balaban, U. Meirav, I. Bar-Joseph

We have studied the conductivity peak in the transition region between the two lowest integer Quantum Hall states using transmission measurements of edge magnetoplasmons. The width of the transition region is found to increase linearly with frequency but remains finite when extrapolated to zero frequency and temperature. Contrary to prevalent theoretical pic

Dongsu Bak, Joohan Lee, Hyunsoo Min

The Dirac-Born-Infeld action with transverse scalar fields is considered to study the dynamics of various BPS states. We first describe the characteristic properties of the so-called 1/2 and 1/4 BPS states on the D3 brane, which can be interpreted as F/D-strings ending on a D3-brane in Type IIB string theory picture. We then study the response of the BPS sta

S. Groote, J. G. Körner, A. A. Pivovarov

We introduce an efficient configuration space technique which allows one to compute a class of Feynman diagrams which generalize the scalar sunset topology to any number of massive internal lines. General tensor vertex structures and modifications of the propagators due to particle emission with vanishing momenta can be included with only a little change of

Ken-ichi Hikasa, K. Whisnant, Jin Min Yang, Bing-Lin Young

We study the effects of dimension-six operators contributing to the $gt\bar t$ vertex in top quark pair production at the Tevatron collider. We derive both the limits from Run 1 data and the potential bounds from future runs (Run 2 and 3). Although the current constraints are not very strong, the future runs are quite effective in probing these operators. We

Sergei M. Kuzenko

We analyse the relationship between the N=2 harmonic and projective superspaces which are the only approaches developed to describe general N=2 super Yang-Mills theories in terms of off-shell supermultiplets with conventional supersymmetry. The structure of low-energy hypermultiplet effective action is briefly discussed.

Massimiliano Capezzali, Hans Beck

We calculate the one-electron Green's function of the 2D attractive Hubbard model by coupling the electrons to pair fluctuations. The latter are approximated by homogeneous amplitude fluctuations and phase correlations corresponding to the XY-model. The electronic density of states shows a pseudogap at temperatures well above the transition temperature $

Oleg Y. Gnedin, Hyung Mok Lee, Jeremiah P. Ostriker

We present new Fokker-Planck models of the evolution of globular clusters, including gravitational tidal shocks. We extend our calculations beyond the core collapse by adopting three-body binary heating. Effects of the shocks are included by adding the tidal shock diffusion coefficients to the ordinary Fokker-Planck equation: the first order heating term, <d

L. D. Almeida, F. Kokubun, D. Hadjimichef

One of the best systems for the study of quantum chaos is the atomic nucleus. A confined particle with general boundary conditions can present chaos and the eigenvalue problem can exhibit this fact. We study a toy model in which the potential has a Cantor-like form. The eigenvalue spectrum presents a Devil&#39;s staircase ordering in the semi-classical limit

A. Lambrecht, M. T. Jaekel, S. Reynaud

We study the generation of photon pulses from thermal field fluctuations through opto-mechanical coupling to a cavity with an oscillatory motion. Pulses are regularly spaced and become sharp for a high finesse cavity.

Rodolfo Gambini

It is well known, that the causal Schrödinger evolution of a quantum state is not compatible with the reduction postulate, even when decoherence is taken into account. The violation of the causal evolution, introduced by the standard reduction postulate distinguishes certain systems (as the measurement devices), whose states are very close to statistical mix

J. I. Katz

Is it possible to create a small volume of equilibrium pair plasma in the laboratory with an intense laser pulse? No. The required power would exceed 10^{18} W. The number of seed particles required to absorb the laser energy would approach the number of pairs in the desired plasma, and their radiation in a visible laser field would occur at extremely high f

Gunn Quznetsov

The Clifford pentad of 4X4 complex matrices defines the currents of the particles. The weak isospin transformation scatters the particle on two components into the 2-dimensional space of the antidiagonal Clifford matrices. The physics particles move in the 3-dimensional space of the diagonal Clifford matrices. Such sectioning of the 5-dimensional space on tw

Frieder Kleefeld, Fernando Pilotto, Manfred Dillig

We investigate the exclusive proton-induced $K^+$ production near the kaon threshold. Compared are two models: a meson-exchange model, which includes $π$, ρ$, $K$ and $K^\ast$ exchange, together with the dominant baryon resonances, and a quark-gluon model, where momentum sharing is provided via the exchange of two gluons. Based on covariant bound state wave

Frieder Kleefeld, Manfred Dillig

To study the characteristic features of relativistic bound systems, the Bethe-Salpeter equation (BSE) for two equal mass spin 1/2 particles (like the deuteron) is solved in the cm-frame for a covariant separable interaction kernel. For that purpose the BSE is transformed to an eigenvalue problem which is diagonalized numerically. The Bethe--Salpeter amplitud

F. Barranco, R. A. Broglia, H. Esbensen, E. Vigezzi

The inner crust of a neutron star is a superfluid and inhomogeneous system, consisting of a lattice of nuclei immersed in a sea of neutrons. We perform a quantum calculation of the associated pairing gap and compare it to the results one obtains in the Local Density Approximation (LDA). It is found that the LDA overestimates the spatial dependence of the gap

Manoj K. Banerjee

Using a relativistic Dirac-Brueckner analysis the OPEP contribution to the ground state energy of nuclear matter is studied. In the study the pion is derivative-coupled. We find that the role of the tensor force in the saturation mechanism is substantially reduced compared to its dominant role in a usual nonrelativistic treatment. We show that the damping of

T. Siiskonen, J. Suhonen, M. Hjorth-Jensen

Recently many authors have performed shell-model calculations of nuclear matrix elements determining the rates of the ordinary muon capture in light nuclei. These calculations have employed well-tested effective interactions in large scale shell-model studies. For one of the nuclei of interest, namely $^{28}$Si, there exists recent experimental data which ca

W. Cassing

The properties of $π, η, K^+$ and $K^-$ mesons are studied in nuclear reactions from SIS to SPS energies within the covariant transport approach HSD in comparison to the experimental data. Whereas the pion, $η$ and kaon abundancies and spectra indicate little or vanishing selfe-nergies for these mesons in the medium, antikaons (as well as antiprotons) are fo

Hans Thunberg

We consider perturbations of quadratic maps $f_a$ admitting an absolutely continuous invariant probability measure, where $a$ is in a certain positive measure set $\mathcal{A}$ of parameters, and show that in any neighborhood of any such an $f_a$, we find a rich fauna of dynamics. There are maps with periodic attractors as well as non-periodic maps whose cri

Guoguang Lin, Hongjun Gao, Jinqiao Duan, Vincent J. Ervin

In this paper the difference in the asymptotic dynamics between the nonlocal and local two-dimensional Swift-Hohenberg models is investigated. It is shown that the bounds for the dimensions of the global attractors for the nonlocal and local Swift-Hohenberg models differ by an absolute constant, which depends only on the Rayleigh number, and upper and lower

Hugh Nelson Howards

One can embed arbitrarily many disjoint, non-parallel, non-boundary parallel, incompressible surfaces in any three manifold with at least one boundary component of genus two or greater [4]. This paper proves the contrasting, but not contradictory result that although one can sometimes embed arbitrarily many surfaces in a 3-manifold it is impossible to ever e

Dan Abramovich, Frans Oort

On July 26, 1995, at the University of California, Santa Cruz, a young Dutch mathematician by the name Aise Johan de Jong made a revolution in the study of the arithmetic, geometry and cohomology theory of varieties in positive or mixed characteristic. The talk he delivered, first in a series of three entitled &#34;Dominating Varieties by Smooth Varieties&#3

Jan-R. Lahmann, Michael Plum

The Orr-Sommerfeld equation is a spectral problem which is known to play an important role in hydrodynamic stability. For an appropriate operator theoretical realization of the equation, we will determine the essential spectrum, and calculate an enclosure of the set of all eigenvalues by elementary analytical means.

Terrence M. Adams, Karl E. Petersen

Denote by $x$ a random infinite path in the graph of Pascal&#39;s triangle (left and right turns are selected independently with fixed probabilities) and by $d_n(x)$ the binomial coefficient at the $n$&#39;th level along the path $x$. Then for a dense $G_δ$ set of $θ$ in the unit interval, $\{d_n(x)θ\}$ is almost surely dense but not uniformly distributed mo

D. Yafaev

We study a class of pseudo-differential operators with oscillating symbols or osc illating amplitudes appearing in the long-range scattering theory. We develop the basic calc ulus for operators from such classes and solve some concrete problems posed by applications to scattering theory, especially to the scattering matrix. In particular, we show tha t under

Denis V. Juriev

In the paper there are investigated various approximate representations of the infinite dimensional $\Bbb Z$--graded Lie algebras: the Witt algebra of all Laurent polynomial vector fields on a circle and its one-dimensional nontrivial central extension, the Virasoro algebra, by the infinite dimensional hidden symmetries in the Verma modules over the Lie alge

A. Brandhuber, N. Itzhaki, J. Sonnenschein, S. Yankielowicz

We study the construction of baryons via supergravity along the line suggested recently by Witten and by Gross and Ooguri. We calculate the energy of the baryon as a function of its size. As expected the energy is linear with N. For the non-supersymmetric theories (in three and four dimensions) we find a linear relation which is an indication of confinement.

O. Bergman, M. R. Gaberdiel

It is shown that the orbifold of type IIB string theory by (-1)^{F_L} I_4 admits a stable non-BPS Dirichlet particle that is stuck on the orbifold fixed plane. It is charged under the SO(2) gauge group coming from the twisted sector, and transforms as a long multiplet of the D=6 supersymmetry algebra. This suggests that it is the strong coupling dual of the

Dmitri Antonov, Dietmar Ebert

By making use of the path integral duality transformation, we derive the string representation for the partition function of an extended Dual Abelian Higgs Model containing gauge fields of external currents of electrically charged particles. By the same method, we obtain the corresponding representations for the generating functionals of gauge field and mono

Jens Hoppe, Shing-Tung Yau

The method introduced in [hep-th/9805020] is simplified, and used to calculate the asymptotic form of all SU(2) \times SO(d=3, resp. 5) invariant wave functions satisfying $Q_{\hatβ} Ψ= 0, \hatβ = 1 ... 4$ resp. 8, where $Q_{\hatβ}$ are the supercharges of the SU(2) matrix model related to supermembranes in d+2=5 (resp. 7) space-time dimensions. For d=3, the

Martin Cederwall

This is the written version of an invited talk delivered at the workshop ``Quantum gravity in the Southern Cone&#39;&#39; held in San Carlos de Bariloche, Argentina, January 7-10, 1998. After giving a brief introduction to the concept of branes and their role in string theory, this talk describes a method for formulating the dynamics of branes, especially th

K. Zarembo

Static charges are introduced in Yang-Mills theory via coupling to heavy fermions. The states containing static color charges are constructed using integration over gauge transformations. A functional representation for interquark potential is obtained. This representation provides a simple criterion for confinement.

Ramesh Anishetty, Pushan Majumdar, H. S. Sharatchandra

2+1-dimensional Yang-Mills theory is reinterpreted in terms of metrics on 3-manifolds. The dual gluons are related to diffeomorphisms of the 3-manifold. Monopoles are identified with points where the Ricci tensor has triply degenerate eigenvalues. The dual gluons have the desired interaction with these monopoles. This would give a mass for the dual gluons re

Roman Lietava, Jan Pisut, Neva Pisutova, Petr Zavada

We propose a simple model of production of strange baryons and antibaryons in nuclear collisions at the CERN SPS. The model takes into account both the increase of strangeness production in collisions of lighter ions and a possibility of the formation of anomalous, strangeness rich matter in central PbPb interactions. It is shown that ratios like $<Ω>:<Ξ>:<Λ

H. J. Drescher, M. Hladik, S. Ostapchenko, K. Werner

Our ultimate goal is the construction of a model for interactions of two nuclei in the energy range between several tens of GeV up to several TeV per nucleon in the centre-of-mass system. Such nuclear collisions are very complex, being composed of many components, and therefore some strategy is needed to construct a reliable model. The central point of our a

T. Appelquist, F. Sannino

We investigate the physical spectrum of vector-like SU(N) gauge theories with infrared coupling close to but above the critical value for a conformal phase transition. We use dispersion relations, the momentum dependence of the dynamical fermion mass and resonance saturation. We show that the second spectral function sum rule is substantially affected by the

H. J. Drescher, M. Hladik, S. Ostapchenko, K. Werner

Understanding hadronic interactions at high energies represents a very important ingredient for modeling high energy cosmic ray air showers. In this paper, we present a new approach to simulate hadronic interactions, including hadron-hadron, hadron-nucleus, and nucleus-nucleus scattering, in the energy range roughly between 10^11 and 10^17 eV. Such collision

L. Frankfurt, A. Freund, M. Strikman

We demonstrate that perturbative QCD allows one to calculate the absolute cross section of diffractive exclusive production of photons at large $Q^2$ at HERA, while the aligned jet model allows one to estimate the cross section for intermediate $Q^2 \sim 2 GeV^2$. Furthermore, we find that the imaginary part of the amplitude for the production of real photon

Lisa Everett

The properties of a class of quasi-realistic three-family perturbative heterotic string vacua are addressed. String models in this class generically contain an anomalous U(1), such that the nonzero Fayet-Iliopoulos term triggers certain fields to acquire string scale VEV&#39;s along flat directions. This vacuum shift reduces the rank of the gauge group and g

M. Gl&#34;uck, E. Reya, A. Vogt

Dynamical parton densities, generated radiatively from valence-like inputs at some low resolution scale, are confronted with recent small-x data on deep inelastic and other hard scattering processes. It is shown that within theoretical uncertainties our previous (1994) dynamical/radiative parton distributions are compatible with most recent data and still ap

Masako Bando, Koichi Yoshioka

The recent experimental results indicating the neutrino oscillations may strongly suggest that at least one more light neutrino species is required in order to reconcile the existing data. In the simple GUT frameworks, this fact seems difficult to preserve the parallelism between quarks and leptons. In this letter, we investigate an SO(10) grand unified mode

Finn Ravndal

Plenary talk at PASCOS-98, Boston, Massachusetts, USA, March 22-29, 1998.

F. Abe

The lifetimes of the B- and B0-bar mesons are measured using the partially reconstructed semileptonic decays B-bar -> D l- nu-bar X, where D is either a D0 or D*+ meson. The data were collected by the CDF detector at the Fermilab Tevatron collider during 1992-95 and correspond to about 110 pb-1 of p-bar p collisions at sqrt(s)=1.8 TeV. We measure decay lengt

H. C. Rosu

The formal Ermakov approach for empty FRW minisuperspace cosmological models of arbitrary Hartle-Hawking factor ordering and the corresponding squeezing features are briefly discussed as a possible means of describing cosmological evolution

A. G. Agnese, M. La Camera

We obtain the vacuum spherical symmetric solutions for the gravitational sector of a (4+d)-dimensional Kaluza-Klein theory. In the various regions of parameter space, the solutions can describe either naked singularities or black-holes or wormholes. We also derive, by performing a conformal rescaling, the corresponding picture in the four-dimensional space-t

M. Gasperini

In the context of the pre-big bang scenario the large-scale CMB anisotropy can be seeded by a primordial background of very light (or massless) axion fluctuations. In that case the slope of the temperature anisotropy spectrum, allowed by present observations, defines an allowed range of values for the string mass scale. Conversely, from the theoretical expec

Paulo S. Kuhn, Yan Levin, Marcia C. Barbosa

The interaction between polyelectrolyte and ionic surfactant is of great importance in different areas of chemistry and biology. In this paper we present a theory of polyelectrolyte ionic-surfactant solutions. The new theory successfully explains the cooperative transition observed experimentally, in which the condensed counterions are replaced by ionic-surf

Daniel Braak, Natan Andrei

We reply to the comment (cond-mat/9806125) by Essler, Goehmann and Korepin, and show that their points are unfounded.

Jan R. Engelbrecht, Alexander B. Nazarenko

We study the superconducting transition in the attractive Hubbard model in two dimensions using the self-consistent $T$-matrix approximation. We demonstrate that for large system sizes, this approximate method produces XY critical scaling in the correlation length and pair susceptibility. For the parameters we investigate, the critical regime is quite large,

A. Damascelli, D. van der Marel, J. Jegoudez, G. Dhalenne

We discuss the symmetry of NaV2O5 in the high temperature phase on the basis of optical conductivity data. Conclusive information cannot be obtained by studying the optically allowed lattice vibrations. However, intensity and polarization of the electronic excitations give a direct indication for a broken-parity electronic ground-state. This is responsible f

Dirk Helbing

The paper analyzes traffic data of the Dutch freeway A9 with respect to certain aspects which are relevant for traffic flow modeling as well as the calibration of model parameters and functions. Apart from the dynamic velocity distribution, the density-dependence and the temporal evolution of various, partly lane-specific quantities is investigated. The resu

M. Steiner, Yang Chen, M. Fabrizio, Alexander O. Gogolin

We study a one-dimensional model of disordered electrons (also relevant for random spin chains), which exhibits a delocalisation transition at half-filling. Exact probability distribution functions for the Wigner time and transmission coefficient are calculated. We identify and distinguish those features of probability densities that are due to rare, trappin

Edward McCann, Klaus Richter

We study disorder-induced spectral correlations and their effect on the magnetic susceptibility of mesoscopic quantum systems in the non-diffusive regime. By combining a diagrammatic perturbative approach with semiclassical techniques we perform impurity averaging for non-translational invariant systems. This allows us to study the crossover from clean to di

C. N. Hind, A. O. Gogolin

We study a simple model of the two-channel Kondo effect in a distorted crystal. This model is then used to investigate the interplay of the Kondo and Jahn-Teller effects, and also the Kondo effect in an impure crystal. We find that the Jahn-Teller interaction modifies the characteristic energy scale of the system below which non-Fermi-liquid properties of th

Frank Potthast

A minimal off-lattice model for alpha-helical proteins is presented. It is based on hydrophobicity forces and sequence independent local interactions. The latter are chosen so as to favor the formation of alpha-helical structure. They model chirality and alpha-helical hydrogen bonding. The global structures resulting from the competition between these forces

Dimitar I. Pushkarov

A full selfconsistent set of equations is deduced to describe the kinetics and dynamics of charged quasiparticles (electrons, holes etc.) with arbitrary dispersion law in crystalline solids subjected to time-varying deformations. The set proposed unifies the nonlinear elasticity theory equation, a kinetic equation for quasiparticle excitations and Maxwell&#3

Maxim Mostovoy, Daniel Khomskii

We suggest that the phase transition observed in NaV_2O_5 at T_c = 34K is not a spin-Peierls transition, but a charge ordering transition, related to the formal presence in this system of equal number of V^4+ and V^4- ions. Below T_c, V^4+ ions form a zigzag structure, which is consistent with the experimentally observed doubling of the lattice period in a a

Jysoo Lee

We study the motion of strongly inelastic particles in a narrow vibrating tube using molecular dynamics simulation. At low frequency of the vibration, we observe qualitative changes of the motion, as the depth of the pile increases. The center of mass of the particle cloud can be described by a superposition of modes of different frequencies. For certain val

J. -B. Fournier, L. Peliti

We consider the effects of the coupling between the orientational order of the two monolayers in flat nematic bilayers. We show that the presence of a topological defect on one bilayer generates a nontrivial orientational texture on both monolayers. Therefore, one cannot consider isolated defects on one monolayer, but rather associated pairs of defects on ei

Kunihiko Yamaji, Takashi Yanagisawa, Takeshi Nakanishi, Soh Koike

The possibility of superconductivity (SC) in the 2D Hubbard model (2DH) was investigated by means of the variational Monte Carlo method. The energy gain of the d-wave SC state, obtained as the difference of the minimum energy with a finite gap and that with zero gap, was examined with respect to dependences on U, electron density rho and next nearest neighbo

Martin Zwaan

The local HI mass function (HIMF), like the optical luminosity function, is an important observational input into models of cosmology and galaxy evolution. It is a helpful framework for assessing the number density of gas rich dwarf galaxies, which are easily missed in optically selected galaxy samples, as well as for determining the cosmological density of

John C. Martin, Heather L. Morrison

Full space velocities are computed for a sample of 130 nearby RR Lyrae variables using both ground-based and Hipparcos proper motions. In many cases proper motions from multiple sources have been averaged to produce a significant improvement in the transverse space velocity errors. In most cases, this exceeds the accuracy of Hipparcos proper motions alone. T

Neal Katz, Lars Hernquist, David H. Weinberg

We investigate the clustering of high redshift galaxies in five variants of the cold dark matter (CDM) scenario, using hydrodynamic cosmological simulations that resolve the formation of systems with circular velocities $v_c \geq 100 \kms$ ($Ω=1$) or $v_c \geq 70 \kms$ ($Ω=0.4$). Although the five models differ in their cosmological parameters and in the sha

Brad M. S. Hansen, Chigurupati Murali

We propose that the cosmological gamma ray bursts arise from the collapse of neutron stars to black holes triggered by collisions or mergers with main sequence stars. This scenario represents a cosmological history qualitatively different from most previous theories because it contains a significant contribution from an old stellar population, namely the glo

Vijay K. Narayanan, Rupert A. C. Croft

We present a comparative study of six different methods for reversing the gravitational evolution of a cosmological density field to recover the primordial fluctuations: linear theory, the Gaussianization mapping scheme, two different quasi-linear dynamical schemes based on the Zel&#39;dovich approximation, a Hybrid dynamical-Gaussianization method and the P

T. Corbard, M. P. Di Mauro, T. Sekii, the GOLF team

The low degree splittings obtained from one year of GOLF data analysis are combined with the MDI medium-l 144-day splittings in order to infer the solar internal rotation as a function of the radius down to $0.2R_\odot$. Several inverse methods are applied to the same data and the uncertainties on the solution as well as the resolution reachable are discusse

M. Arnaboldi, K. C. Freeman, O. Gerhard, M. Matthias

We present a study of the kinematics of the outer regions of the early-type galaxy NGC 1316, based on radial velocity measurements of 43 planetary nebulae as well as deep integrated-light absorption line spectra. The smoothed velocity field of NGC 1316 indicates fast rotation at a distance of 16 kpc, possibly associated with an elongated feature orthogonal t

Tod E. Strohmayer, William Zhang, Jean H. Swank, Iosif Lapidus

We report on the long term stability of the millisecond oscillations observed with the Rossi X-ray Timing Explorer (RXTE) during thermonuclear X-ray bursts from the low mass X-ray binaries (LMXB) 4U 1728-34 and 4U 1636-53. We show that bursts from 4U 1728-34 spanning more than 1.5 years have observed asymptotic oscillation periods which are within 0.2 micros

Luis N. Epele, Esteban Roulet

We show that the photodisintegration of heavy cosmic ray nuclei with energies above 10^20 eV is dominated by interactions with photons from the cosmic microwave background radiation, rather than from infrared ones. This implies that the observed air shower events with energies 2-3 10^20 eV cannot originate from Fe nuclei coming from distances beyond 10 Mpc

T. Kelsall, J. L. Weiland, B. A. Franz, W. T. Reach

The COBE Diffuse Infrared Background Experiment (DIRBE) was designed to search for the cosmic infrared background (CIB) radiation. Scattered light and thermal emission from the interplanetary dust (IPD) are major contributors to the diffuse sky brightness at most infrared wavelengths. Accurate removal of this zodiacal light foreground is a necessary step tow

M. V. Sazhin, V. E. Zharov, A. V. Volynkin, T. A. Kalinina

The fluctuation of the angular positions of reference extragalactic radio and optical sources under the influence of the irregular gravitational field of visible Galactic stars is considered. It is shown that these angular fluctuations range from a few up to hundreds of microarcseconds. This leads to a small rotation of the celestial reference frame. The non

F. P. Israel, P. P. van der Werf, T. G. Hawarden, C. Aspin

Images in the J, H and K bands and in the the v=1-0 S(1) line of H2 of the central region of the almost edge-on galaxy NGC 3079 reveal contributions from direct and scattered starlight, emission from hot dust and molecular gas, and extinction gradients. The central 100 pc suffers an extinction of 6 mag. Extremely red near-infrared colours require the presenc

L. van Zee, E. D. Skillman, J. J. Salzer

We present the results of high spatial resolution HI observations of five intrinsically compact dwarf galaxies which are currently experiencing a strong burst of star formation. The HI maps indicate that these systems have a complex and clumpy interstellar medium. Unlike typical dwarf irregular galaxies, these Blue Compact Dwarf (BCD) galaxies exhibit strong

S. V. Zharikov, V. V. Sokolov, Yu. V. Baryshev

Optical observations of the GRB 970508 optical remnant were continued with the 6-m telescope of SAO RAS in standard BVRcIc bands in Oct.-Dec.1997 and in Jan. 1998. The results of the photometry of GRB970508 remnant and of three nearby galaxies are presented. The BVRcIc light curves of the GRB970508 remnant may be described by a power law plus a constant F(t)

Zurab Kakushadze, S. -H. Henry Tye

Generalizing the recent work on three-family Type I compactifications, we classify perturbative Type I vacua obtained via compactifying on the T^6/Z_2 X Z_2 X Z_3 orbifold with all possible Wilson lines. In particular, we concentrate on models with gauge groups containing the Standard Model gauge group SU(3)_c X SU(2)_w X U(1)_Y as a subgroup. All of the vac

C. M. Hull

T-Duality on a timelike circle does not interchange IIA and IIB string theories, but takes the IIA theory to a type $IIB^*$ theory and the IIB theory to a type $IIA^*$ theory. The type $II^*$ theories admit E-branes, which are the images of the type II D-branes under timelike T-duality and correspond to imposing Dirichlet boundary conditions in time as well

Isabel P. Ennes, Stephen G. Naculich, Henric Rhedin, Howard J. Schnitzer

One-instanton predictions are obtained from certain non-hyperelliptic Seiberg-Witten curves derived from M-theory for N=2 supersymmetric gauge theories. We consider SU(N_1) x SU(N_2) gauge theory with a hypermultiplet in the bifundamental representation together with hypermultiplets in the defining representations of SU(N_1) and SU(N_2). We also consider SU(

P. Dargis, Z. Maassarani

We introduce a transformation which allows the fermionization of operators of any one-dimensional spin-chain. This fermionization procedure is independent of any eventual integrable structure and is compatible with it. We illustrate this method on various integrable and non-integrable chains, and deduce some general results. In particular, we fermionize XXC

Thomas G. Rizzo

We examine the influence of gauge kinetic mixing on the couplings of a TeV scale $Z&#39;$ in both $E_6$ and SO(10) models. The strength of such mixing, which arises due to the existence of incomplete matter representations at low scale, can be described by a single parameter, $δ$. The value of this parameter can significantly influence the ability of both ha

Ryoichi Yamamoto, Akira Onuki

Highly supercooled liquids with soft-core potentials are studied via molecular dynamics simulations in two and three dimensions in quiescent and sheared conditions.We may define bonds between neighboring particle pairs unambiguously owing to the sharpness of the first peak of the pair correlation functions. Upon structural rearrangements, they break collecti

J. C. Anjos, J. Magnin, F. R. A. Simao, J. Solano

We present a study on hyperon/anti-hyperon production asymmetries in the framework of the recombination model. The production asymmetries for Lambda 0/Lambda 0-bar, Xi-/Xi+ and Omega-/Omega+ are studied as a function of x_F. Predictions of the model are compared to preliminary data on hyperon/anti-hyperon production asymmetries in 500 GeV/c pi- p interaction

Frank Wilczek

After a very brief overview recollecting the `classic&#39; parts of QCD, that is its application to describe hard processes and static properties of hadrons, I survey recent work -- some very recent -- on QCD at non-zero temperature and density. At finite temperature and zero density there is a compelling theoretical framework allowing us to predict highly s

Gianguido Dall&#39;Agata, Kurt Lechner, Mario Tonin

We present a manifestly Lorentz invariant and supersymmetric component field action for $D = 10$, type $IIB$ supergravity, using a newly developed method for the construction of actions with chiral bosons, which implies only a single scalar non propagating auxiliary field. With the same method we construct also an action in which the complex two-form gauge p

H. Itoyama, T. Matsuo

Berry&#39;s connection is computed in the USp(2k) matrix model. In T dualized quantum mechanics, the Berry phase exhibits a residual interaction taking place at a distance m_(f) from the orientifold surface via the integration of the fermions in the fundamental representation. This is interpreted as a coupling of the magnetic D2 with the electric D4 branes.

A. Aguado, A. Ayuela, J. M. Lopez, J. A. Alonso

Ab initio calculations using the Perturbed Ion model, with correlation contributions included, are presented for nonstoichiometric (NaI)_nNa+ and (CsI)_nCs+ (n=1-14) cluster ions. The ground state and several low-lying isomers are identified and described. Rocksalt ground states are common and appear at cluster sizes lower than in the corresponding neutral s

M. Magliocchetti, G. Pucacco, E. Vesperini

In this paper we investigate the gravothermal instability of spherical stellar systems endowed with a radially anisotropic velocity distribution. We focus our attention on the effects of anisotropy on the conditions for the onset of the instability and in particular we study the dependence of the spatial structure of critical models on the amount of anisotro

J. R. Forshaw, A. Sabio Vera

The contributions to the deep inelastic scattering structure function which arise from emission of zero, one, two or three resolvable gluons and any number of unresolvable ones are computed to order ${\bar α}_{S}^{3}$. Coherence effects are taken into account via angular ordering and are demonstrated to yield (at the leading logarithm level) the identical re

Michael Haack, Michael G. Schmidt

We investigate the radiative decay of the axion into two photons in an external electromagnetic field to one loop order. Our approach is based on the world-line formalism, which is very suitable to take into account the external field to all orders. Afterwards we discuss how the calculation could be generalized to finite temperature.

Matthias Weber, Michael Wolf

We develop Teichmuller theoretical methods to construct new minimal surfaces in $\BE^3$ by adding handles and planar ends to existing minimal surfaces in $\BE^3$. We exhibit this method on an interesting class of minimal surfaces which are likely to be embedded, and have a low degree Gaußmap for their genus; the (Weierstrass data) period problem for these su

Jim McCarthy, Leonard Susskind, Andy Wilkins

We compute the effective action for scattering of three well-separated extremal brane solutions, in 11d supergravity, with zero p_ transfer and small transverse velocities. Using an interpretation of the conjecture of Maldacena, following Hyun, this can be viewed as the large N limit of the Matrix theory description of three supergraviton scattering at leadi

D. B. Cannon, T. J. Ponman, I. S. Hobbs

Abell 2218 is one of a handful of clusters in which X-ray and lensing analyses of the cluster mass are in strong disagreement. It is also a system for which X-ray data and radio measurements of the Sunyaev-Zel&#39;dovich decrement have been combined in an attempt to constrain the Hubble constant. However, in the absence of reliable information on the tempera

Dumitru Baleanu, V. M. Dubovik, S. Misicu

In this work we introduce the Killing-Yano symmetry on the phase space and we investigate the symplectic structure on the space of Killing-Yano tensors. We perform the detailed analyze of the $n$-dimensional flat space and the Riemaniann manifolds with constant scalar curvature. We investigate the form of some multipole tensors, which arise in the expansion

Rachel S. Somerville, Joel R. Primack, S. M. Faber

This paper has been withdrawn because the models on which it was based have undergone significant changes and improvements. A new paper with the same title, based on the improved models, is accepted for publication in MNRAS and is available at astro-ph/0006364. We have withdrawn this paper to avoid confusion.

R. Aguirre, M. Schvellinger

The equation of state of symmetric nuclear matter with the inclusion of non-strange dibaryons is studied. We pay special attention to the existence of a dibaryon condensate at zero temperature. These calculations have been performed in an extended quark-meson coupling model with density-dependent parameters, which takes into account the finite size of nucleo

Pawel Horodecki, Michal Horodecki, Ryszard Horodecki

Bound entanglement is the noisy entanglement which cannot be distilled to a singlet form. Thus it cannot be used alone for quantum communication purposes. Here we show that, nevertheless, the bound entanglement can be, in a sense, pumped into single pair of free entangled particles. It allows for teleportation via the pair with the fidelity impossible to ach

Mark Burgess

The phenomenological two-level atom is re-analysed using the methods of effective field theory. By presenting the Dicke-Jaynes-Cummings model in real space, an exact diagonalization is accomplished going beyond the rotating wave approximation. The meaning of the symmetries and conserved quantities in the theory is discussed and the model is related to non-eq