November 1994 arXiv papers — page 5

Jiri Dolejsi, Wojciech Florkowski, Joerg Huefner

The enhancement of pions and kaons observed at small transverse momenta in ultra-relativistic heavy-ion collisions may at least partly reflect critical scattering expected to occur in the neighborhood of a second order phase transition. Kinetic equations in the relaxation time approximation are proposed for the time evolution of the quark distribution functi

R. Arnowitt, Pran Nath

{\tenrm The possibility of detecting supersymmetric dark matter is examined within the framework of the minimal supergravity model (MSGM), where the $\tilde{Z}_{1}$ is the LSP for almost the entire parameter space. A brief discussion is given of experimental strategies for detecting dark matter. The relic density is constrained to obey 0.10 $\leq Ω_{\tilde{Z

Tanmay Vachaspati

The Dirac equations for leptons and quarks in the background of an electroweak $Z-$string have zero mode solutions. If two loops of electroweak string are linked, the zero modes on one of the loops interacts with the other loop via an Aharanov-Bohm interaction. The effects of this interaction are briefly discussed and it is shown that the fermions induce a b

Rathin ADhikari, Biswarup Mukhopadhyaya

We consider the decays of a $B_s$-meson into a pair of lightest supersymmetric particles (LSP) in the minimal supersymmetric standard model. It is found that the parameter space for light LSP's in the range of 1 GeV can be appreciably constrained by looking for such decays.

Ludwik Turko

We consider an ideal gas of massive hadrons in thermal and chemical equilibrium. The gas expands longitudinally in accordance with Bjorken law. Strangeness and baryon number conservation is taken into account. This gas has different features as compared to the pion gas.

Otto Nachtmann

High energy hadron-hadron collisions are discussed. It is argued that soft collisions should involve in an essential way nonperturbative QCD. A way is outlined how to calculate properties of high energy elastic hadron-hadron scattering using field theoretic methods. The functional integrals occuring there are evaluated using the ``stochastic vacuum model&#39

TAekoon Lee

We present the anomalous cross section for baryon number violation in the standard model from the perturbation of large-order behavior of forward scattering amplitudes to the order $\left(ε/n\right)^{8/3} \ln\left(ε/n\right)$. An improved high energy behavior of the anomalous cross section is observed. We also argue that the asymptotic form of $F(εg) \equiv

Ulvi Yurtsever

Recently, Larry Ford and Tom Roman have discovered that in a flat cylindrical space, although the stress-energy tensor itself fails to satisfy the averaged null energy condition (ANEC) along the (non-achronal) null geodesics, when the ``Casimir-vacuum" contribution is subtracted from the stress-energy the resulting tensor does satisfy the ANEC inequality

M. Heusler

Requiring that the matter fields are subject to the dominant energy condition, we establish the lower bound $(4π)^{-1} κ{\cal A}$ for the total mass $M$ of a static, spherically symmetric black hole spacetime. (${\cal A}$ and $κ$ denote the area and the surface gravity of the horizon, respectively.) Together with the fact that the Komar integral provides a s

Claude LeBrun

Using the new diffeomorphism invariants of Seiberg and Witten, a uniqueness theorem is proved for Einstein metrics on compact quotients of irreducible 4-dimensional symmetric spaces of non-compact type. The proof also yields a Riemannian version of the Miyaoka-Yau inequality.

B. R. Trees, A. J. Fedro, M. R. Norman

In this paper, we examine the mean field electronic structure of the $f^1-f^2$ Anderson lattice model in a slave boson approximation, which should be useful in understanding the physics of correlated metals with more than one f electron per site such as uranium-based heavy fermion superconductors. We find that the multiplet structure of the $f^2$ ion acts to

Peter F Arndt, Thomas Heinzel, C M Yung

Based on the Temperley--Lieb algebra we define a class of one-dimensional Hamiltonians with nearest and next-nearest neighbour interactions. Using the regular representation we give ground states of this model as words of the algebra. Two point correlation functions can be computed employing the Temperley--Lieb relations. Choosing a spin-1/2 representation o

Jorge Ibsen, Rodrigo Soto, Patricio Cordero

We report and explain a convective phenomenon observed in molecular dynamics simulations that cannot be classified either as a hydrodynamics instability nor as a macroscopically forced convection. Two complementary arguments show that the velocity field by a thermalizing wall is proportional to the ratio between the heat flux and the pressure. This predictio

Rodolfo Cuerno, Albert-Laszlo Barabasi

We derive a stochastic nonlinear equation to describe the evolution and scaling properties of surfaces eroded by ion bombardment. The coefficients appearing in the equation can be calculated explicitly in terms of the physical parameters characterizing the sputtering process. We find that transitions may take place between various scaling behaviors when expe

Sangeeta Malhotra

We present full modeling of tangent point emission of HI as seen in the 21 cm transition in the inner Galaxy ($R \simeq 3-8 \kpc$). The model used takes into account emission from a large path length along the line of sight, corresponding to an interval ($ΔR$) of typically $\le 1 \kpc$ in galactic radius; and is parametrized by the scale height of the gas, t

Charles C. Dyer, Francine R. Marleau

We find solutions of Einstein's field equation for topologically stable strings associated with the breaking of a U(1) symmetry. Strings form in many GUTs and are expected whenever the homotopy group $Π_1(M_0)$ is non-trivial. The behavior of the fields making up the string is described by the Euler-Lagrange equations. These fields appear in the energy-m

Karl Mannheim

Consequences of anisotropic cascade radiation in AGN are investigated. The anisotropic cascades are produced by protons accelerated in a nuclear jet. The protons are assumed to cool in the UV photon field of an accretion disk by photo-production of secondary particles. Most cascade photons are produced in the direction of the accretion disk leading to strong

Sangeeta Malhotra, Edwin L Turner

Most physical properties derived for quasars, as single entities or as a population, depend upon the cosmology assumed. In this paper, we calculate the quasar luminosity function and some related quantities for a flat universe dominated by a cosmological constant $Λ$ ($Λ=0.9, Ω=0.1$) and compare them with those deduced for a flat universe with zero cosmologi

J. G. Kirk, P. Duffy, Lewis Ball

When applied to the blast wave formed by the explosion of a massive star as a supernova (SN), the theory of diffusive particle acceleration at shock fronts predicts a very high energy density in cosmic rays. Almost immediately after particles begin to be injected into the process, the cosmic ray pressure rises until comparable to the ram-pressure encountered

Peter Magyar

We present a generalization of the classical Schur modules of $GL(N)$ exhibiting the same interplay among algebra, geometry, and combinatorics. A generalized Young diagram $D$ is an arbitrary finite subset of $\NN \times \NN$. For each $D$, we define the Schur module $S_D$ of $GL(N)$. We introduce a projective variety $\FF_D$ and a line bundle $\LL_D$, and d

William Arveson

We classify all continuous tensor product systems of Hilbert spaces which are ``infinitely divisible" in the sense that they have an associated logarithmic structure. These results are applied to the theory of E_0 semigroups to deduce that every E_0 semigroup which possesses sufficiently many ``decomposable" operators must be cocycle conjugate to a C

Maxim Raykin

A theory of the t-J model in the presence of an external electromagnetic field is presented. The 1/N expansion for this model in the slave-fermion representation is developed, and it is shown that all the general properties of the theory are satisfied in every order of the 1/N expansion separately. A convenient procedure of the gauge fixing is suggested. It

R. M. Kashaev

The cyclic quantum dilogarithm is interpreted as a cyclic 6j-symbol of the Weyl algebra, considered as a Borel subalgebra $BU_q(sl(2))$. Using modified 6j-symbols, an invariant of triangulated links in triangulated 3-manifolds is constructed. Apparently, it is an ambient isotopy invariant of links.

H. C. Rosu

I discuss a phenomenological model of the nucleon in which a small anti-de Sitter bag is placed into the Skyrmion configuration. Such a bag has a timelike boundary and allows naturally the Cheshire Cat Principle. Very important in this model is the membrane of the bag, the 3-dimensional time-space manifold S^{1}\times S^{2}, in which topological techniques w

M. V. Stoitsov, M. L. Cescato, P. Ring, M. M. Sharma

The breathing-mode giant monopole resonance is studied within the framework of the relativistic mean-field (RMF) theory. Using a broad range of parameter sets, an analysis of constrained incompressibility and excitation energy of isoscalar monopole states in finite nuclei is performed. It is shown that the non-linear scalar self-interaction and the resulting

N. Seiberg

We demonstrate electric-magnetic duality in N=1 supersymmetric non-Abelian gauge theories in four dimensions by presenting two different gauge theories (different gauge groups and quark representations) leading to the same non-trivial long distance physics. The quarks and gluons of one theory can be interpreted as solitons (non-Abelian magnetic monopoles) of

Paul Demkin

Some general properties of the relativistic $p$-dimensional surface imbedded into $D$-dimensional spacetime and its reduction to the sim\-plest case of the quadratic Lagrangian (the linearized model) are considered. The solutions of the equations of motion of the linearized model for the $p$-brane with arbitrary topology and massless eigenstates, as well as

S. Guruswamy, P. Vitale

We derive explicit forms of the two--point correlation functions of the $O(N)$ non-linear sigma model at the critical point, in the large $N$ limit, on various three dimensional manifolds of constant curvature. The two--point correlation function, $G(x, y)$, is the only $n$-point correlation function which survives in this limit. We analyze the short distanc

Jan Ambjorn, Gudmar Thorleifsson, Mark Wexler

We study $q=10$ and $q=200$ state Potts models on dynamical triangulated lattices and demonstrate that these models exhibit continuous phase transitions, contrary to the first order transition present on regular lattices. For $q=10$ the transition seems to be of 2nd order, while it seems to be of 3rd order for $q=200$. For $q=200$ the phase transition also i

I. B. Khriplovich

The influence of radiative corrections on the photon propagation in a gravitational background is investigated without the low-frequency approximation $ω\ll m$. The conclusion is made in this way that the velocity of light can exceed unity.

Zhi-zhong Xing

The Wolfenstein parametrization of the $3\times 3$ Kobayashi-Maskawa (KM) matrix $V$ is modified by keeping its unitarity up to the accuracy of $O(λ^{6})$. This modification can self-consistently lead to the off-diagonal asymmetry of $V$: $|V_{ij}|^{2}-|V_{ji}|^{2}$ = $Z\displaystyle\sum_{k}ε^{~}_{ijk}$ with $Z=\approx A^{2}λ^{6} (1-2ρ)$, which is comparable

Thomas Jech

Let $j$ be an elementary embedding of $V_λ$ into $V_λ$ that is not the identity, and let $κ$ be the critical point of $j$. Let $\Cal A$ be the closure of $\{j\}$ under the operation $a (b)$ of application, and let $Ω$ be the closure of $\{κ\}$ under the operation $\min \{ξ: a(ξ) \ge b(α)\}$. We give a complete description of the set $Ω$ under an assumption (

M. B. Hindmarsh, T. W. B. Kibble

The topic of cosmic strings provides a bridge between the physics of the very small and the very large. They are predicted by some unified theories of particle interactions. If they exist, they may help to explain some of the largest-scale structures seen in the Universe today. They are `topological defects' that may have been formed at phase transitions

Paolo Lipari, Maurizio Lusignoli, Francesca Sartogo

The charged current cross section for neutrinos with energy of a few GeV is reanalysed. In this energy range the cross section for the lowest multiplicity exclusive channels is an important fraction of $σ_{CC}$ and the approximation of describing the cross section with deep inelastic scattering formulae may be inaccurate. Possible consequences of our reanaly

Paul Langacker

The status of the solar neutrino problem is reviewed. Attempts to explain the observed deficit and spectral distortion, both by astrophysical and particle physics methods, are described. It is argued that the comparison of all experiments strongly prefers the particle physics solutions.

Dieter Müller

The evolution of the pion distribution amplitude in next-to-leading order is studied for a fixed and a running coupling constant. In both cases, the evolution provides a logarithmic modification in the endpoint region. Assuming a simple parameterization of the distribution amplitude at a scale of $Q_0\sim 0.5\ \rm GeV$, it is shown numerically that these eff

Christopher S. Kochanek

Standard $Ω_0=1$ cold dark matter (CDM) needs $0.27 < σ_8 < 0.63$ ($2σ$) to fit the observed number of large separation lenses, and the constraint is nearly independent of $H_0=100h^{-1}\kms$ Mpc$^{-1}$. This range is strongly inconsistent with the COBE estimate of $σ_8=(2.8\pm0.2)h$. Tilting the primordial spectrum $\propto k^n$ from $n=1$ to $0.3 \ltorder

Patrick L. Nash

$O(\hbar)$ effects that modify the classical orbit of a charged particle are described for the case of a classical spin-1/2 particle moving in a constant magnetic field, using a manifestly covariant formalism reported previously. It is found that the coupling between the momentum and spin gives rise to a shift in the cyclotron frequency, which is explicitly

M. A. Novotny

A class of Monte Carlo algorithms which incorporate absorbing Markov chains is presented. In a particular limit, the lowest-order of these algorithms reduces to the $n$-fold way algorithm. These algorithms are applied to study the escape from the metastable state in the two-dimensional square-lattice nearest-neighbor Ising ferromagnet in an unfavorable appli

Bas V. de Bakker

We consider a dynamical triangulation model of euclidean quantum gravity where the topology is not fixed. This model is equivalent to a tensor generalization of the matrix model of two dimensional quantum gravity. A set of moves is given that allows Monte Carlo simulation of this model. Some preliminary results are presented for the case of four dimensions.

S. Borgani, M. Plionis, P. Coles, L. Moscardini

We present extended simulations of the distribution of galaxy clusters in different dark matter models, using an optimized version of the Zel&#39;dovich approximation. Six different dark matter models are studied: Standard CDM, Open CDM, Tilted CDM, Cold + Hot DM, low-density CDM with cosmological constant, and low Hubble constant ($h=0.3$) CDM. We compare s

Chiang-Mei Chen, James M. Nester, Roh Suan Tung

From a covariant Hamiltonian formulation, using symplectic ideas, we obtain covariant quasilocal energy-momentum boundary expressions for general gravity theories. The expressions depend upon which variables are fixed on the boundary, a reference configuration and a displacement vector field. We consider applications to Einstein&#39;s theory, black hole ther

W. Buchmuller, O. Philipsen

We derive a set of gauge independent gap equations for Higgs boson and vector boson masses for the SU(2) Higgs model in three dimensions. The solutions can be associated with the Higgs phase and the symmetric phase, respectively. In the Higgs phase the calculated masses are in agreement with results from perturbation theory. In the symmetric phase a non-pert

Kjell Rosquist

An ADM-like Hamiltonian approach is proposed for static spherically symmetric relativistic star configurations. For a given equation of state the entire information about the model can be encoded in a certain 2-dimensional minisuperspace geometry. We derive exact solutions which arise from symmetries corresponding to linear and quadratic geodesic invariants

G. Montagna, O. Nicrosini, G. Passarino, F. Piccinini

In view of the forthcoming experiments at high energy $e^+ e^-$ colliders, LEP2 and beyond, the process $e^+ e^- \to W^+ W^- \to 4f$ has been investigated for {\it off-shell} $W$&#39;s. After deriving the matrix element for the process within the helicity amplitude formalism, QED radiative corrections to the initial state leptons have been included at the le

C. Kaiser, L. Turban

Two-dimensional directed site percolation is studied in systems directed along the x-axis and limited by a free surface at y=\pm Cx^k. Scaling considerations show that the surface is a relevant perturbation to the local critical behaviour when k<1/z where z=ν_\parallel/νis the dynamical exponent. The tip-to-bulk order parameter correlation function is calcul

Jean Gaschler, Mathieu Lafourcade

This paper presents a methodology for building and manipulating human-oriented dictionaries. This methodology has been applied in the construction of a French-English-Malay dictionary which has been obtained by &#34;crossing&#34; semi-automatically two bilingual dictionaries. We use only Microsoft Word, a specialized language for writing transcriptors and a

Michael J. Dinneen

Broadcasting concerns the dissemination of a message originating at one node of a network to all other nodes. This task is accomplished by placing a series of calls over the communication lines of the network between neighboring nodes, where each call requires a unit of time and a call can involve only two nodes. We show that for bounded-degree networks dete

J. Lyn Miller

In this paper we will define analogs of Gröbner bases for $R$-subalgebras and their ideals in a polynomial ring $R[x_1,\ldots,x_n]$ where $R$ is a noetherian integral domain with multiplicative identity and in which we can determine ideal membership and compute syzygies. The main goal is to present and verify algorithms for constructing these Gröbner basis c

V. Chari, A. N. Pressley

We prove a highest weight theorem classifying irerducible finite--dimensional representations of quantum affine algebras and survey what is currently known about the structure of these representations.

V. Chari

We describe the underlying U_q(g)--module structure of representations of quantum affine algebras.

Stephen G. Naculich, Harold A. Riggs

Compact string expressions are found for non-intersecting Wilson loops in SU(N) Yang-Mills theory on any surface (orientable or nonorientable) as a weighted sum over covers of the surface. All terms from the coupled chiral sectors of the 1/N expansion of the Wilson loop expectation values are included.

F. G. Scholtz, A. N. Theron, H. B. Geyer

We discuss the equivalence between the path integral representations of spin dynamics for anti-commuting (Grassmann) and commuting variables and establish a bosonization dictionary for both generators of spin and single fermion operators. The content of this construction in terms of the representations of the spin algebra is discussed in the path integral se

D. R. Grigore

Symmetries in the Lagrangian formalism of arbitrary order are analysed with the help of the so-called Anderson-Duchamp-Krupka equations. For the case of second order equations and a scalar field we establish a polynomial structure in the second order derivatives. This structure can be used to make more precise the form of a general symmetry. As an illustrati

Hoi-Kwong Lo

Owing to subtle issues concerning quantum fluctuations and gauge fixing, a formulation of a general procedure to specify the realization of non-Abelian gauge symmetry has evaded all earlier attempts. In this Letter, we discuss these subtleties and present two sets of order parameters for non-Abelian gauge theories. Such operators directly probe the manifest

P. Berglund, T. Hubsch

A residue-theoretic representation is given for massless matter fields in (quotients) of (weighted) \CY\ complete intersection models and the corresponding chiral operators in \LGO{s}. The well known polynomial deformations are thus generalized and the universal but somewhat abstract Koszul computations acquire a concrete realization and a general but more h

Chung Kao

The leading weak corrections to the production of top quark pairs via $q\bar{q} \to t\bar{t}$ in $p\bar{p}$ collisions are evaluated. The chromo-anapole form factor of the top quark and effects of parity violation are studied in the Standard Model (SM) and the Minimal Supersymmetric Model (MSSM). The parity violation effect in $q\bar{q} \to g \to t\bar{t}$ f

N. Arbex, U. Ornik, M. Plümer, A. Timmermann

Using a three-dimensional hydrodynamic simulation of the collision and an equation of state containing a first order phase transition to the quark-gluon plasma, we study thermal photon production for $Au+Au$ collisions at $E_{lab}=11.5$ AGeV and for $Pb+Pb$ collisions at $160$ AGeV. We obtain surprisingly high rates of thermal photons even at the lower energ

Gerhard O. Koehler, Emmanuel A. Paschos

We examine the possibility of extracting CP-violating terms in the decay K0 -> Pi0 e+ e- by studying the time evolution of a K0 beam. We focus on the interference region and search for clear effects. We find that experiments which average over the electron and positron momenta can detect CP violation as an oscillation in the decay rate. The branching ratio i

Kingman Cheung, Roger J. N. Phillips, Apostolos Pilaftsis

We investigate the potential of future TeV linear e^+e^- colliders to observe singly-charged Higgs bosons ($H^\pm$) via the coupling $H^\pm W^\mp Z$, which would signal the existence of exotic Higgs representations. In the context of a Higgs-triplet model compatible with the electroweak oblique parameters, we estimate the cross section for pro- ducing charge

C. A. Dominguez

Fits to the ARGUS data on hadronic decays of the tau-lepton, which determine the vector and axial-vector spectral functions, are used in order to determine the size of a dimension $d=2$ term in the Operator Product Expansion. Constraints from the first Weinberg sum rule (in the chiral limit) are enforced in order to reduce the uncertainty of this determinati

Hai-Yang Cheng

The long distance vector-meson-dominance (VMD) effects on the weak radiative decays $\bb\toργ$ and $\bb^0\to D^{*0}γ$ are studied. For $\bb\toργ$ decays, the VMD contribution is $(10-20)\%$ of the short-distance penguin amplitude. The pole effect is as important as the VMD one in the decay $B^-\toρ^-γ$, but it is suppressed in $\bb^0\to ρ^0γ$. The branching

Michael Creutz

I review some of the difficulties associated with chiral symmetry in the context of a lattice regulator. I discuss the structure of Wilson Fermions when the hopping parameter is in the vicinity of its critical value. Here one flavor contrasts sharply with the case of more, where a residual chiral symmetry survives anomalies. I briefly discuss the surface mod

S. Hioki

We propose a simple method to construct staples in lattice gauge theory with Wilson action on a parallel computer. This method can be applicable to any dimensional system and to any dimensional division without difficulty. Furthermore this requires rather small working area to realize gauge simulation on a parallel computer.

A. Bonanno, S. Droz, W. Israel, S. M. Morsink

The internal structure of a charged spherical black hole is still a topic of debate. In a nonrotating but aspherical gravitational collapse to form a spherical charged black hole, the backscattered gravitational wave tails enter the black hole and are blueshifted at the Cauchy horizon. This has a catastrophic effect if combined with an outflux crossing the C

M. M. Som, Marcelo de Oliveira Souza

We obtain an exact solution of the coupled Einstein-scalar-gauge field equations for a local infinitely long supermassive cosmic string. The solution correponds to that of Hiscock-Gott . The string appears to be due to the freezing of the scalar field at the null value giving rise to a constant linear energy density.

Ulrich Bunke, Martin Olbrich

We propose a new method for studying $n$- and $Γ$-cohomology of globalizations of Harish-Chandra modules, where $G=KAN$ is a rank one semisimple Lie group, $Γ$ is a discrete subgroup of $G$ and $n=Lie(N)$. We prove a conjecture of Patterson relating the singularities of Selberg zeta functions with the $Γ$-cohomology of principal series representations if $Γ$

A. Sanchez, F. Dominguez-Adame, G. Berman, F. Izrailev

We propose an explanation of the bands of extended states appearing in random one dimensional models with correlated disorder, focusing on the Continuous Random Dimer model [A.\ Sánchez, E.\ Maciá, and F.\ Dom\&#39;ınguez-Adame, Phys.\ Rev.\ B {\bf 49}, 147 (1994)]. We show exactly that the transmission coefficient at the resonant energy is independent of th

Subir Sachdev

Nuclear relaxation in half-integer spin chains at low temperatures (T << J, the antiferromagnetic exchange constant) is dominated by dissipation from a gas of thermally-excited, overdamped, spinons. The universal low temperature dependence of the relaxation rates $1/T_1$ and $1/T_{2G}$ is computed.

T. Einarsson, S. L. Sondhi, S. M. Girvin, D. P. Arovas

We investigate the issue of whether quasiparticles in the fractional quantum Hall effect possess a fractional intrinsic spin. The presence of such a spin $S$ is suggested by the spin-statistics relation $S=θ/2π$, with $θ$ being the statistical angle, and, on a sphere, is required for consistent quantization of one or more quasiparticles. By performing Berry-

S. Krishna Prasad, D. S. Shankar Rao, S. Chandrasekhar, M. E. Neubert

We report the first observation of the smectic C--smectic I (C--I) critical point by Xray diffraction studies on a binary system. This is in confirmity with the theoretical idea of Nelson and Halperin that coupling to the molecular tilt should induce hexatic order even in the C phase and as such both C and I (a tilted hexatic phase) should have the same symm

Ian A. Bonnell, Matthew R. Bate

A viable solution to the origin of close binary systems, unaccounted for in recent theories, is presented. Fragmentation, occurring at the end of the secondary collapse phase (during which molecular hydrogen is dissociating), can form binary systems with separations less than 1 au. Two fragmentation modes are found to occur after the collapse is halted. The

Laerte Sodre, Hector Cuevas

We investigate the integrated spectra of a sample of 24 normal galaxies. A principal component analysis suggests that most of the variance present in the spectra is due to the differences in morphology of the galaxies in the sample. We show that spectroscopic parameters extracted from the spectra, like the amplitude of the 4000 Å~ break or of the CN band, co

J. Kaluzny, M. Kubiak, M. Szymanski, A. Udalski

The central area of the Sculptor dwarf galaxy was surveyed for variable stars as a side-program of the OGLE project. Light curves in the V band were obtained for 226 RR Lyr stars and for 3 anomalous cepheids. One previously unknown anomalous cepheid was identified. We discovered also two variables located at the tip of the red giant branch of Sculptor. Out o

Janusz Kaluzny, Wojtek Krzeminski, Beata Mazur

Deep color-magnitude diagrams are presented for poorly known open clusters Cr 261, Be 18, Be 54, Tr 5 and BH176. All clusters are old objects with age\geq 4 Gyr. BH176 is either old open cluster or young globular cluster. Extremely red giants with V-I>3 were identified in the central parts of Cr 261, Be 54 and BH176. These three objects are candidates for ve

L. Feretti, R. Fanti, P. Parma, S. Massaglia

We report X-ray observations of the radio galaxies B2 1615+35 (NGC 6109) and B2 1621+38 (NGC 6137), which belong to poor groups of galaxies and are characterized by a &#34;head-tail&#34; structure. We also analyze the X-ray behaviour of the radio galaxy NGC 6107, present within the field of view and showing a symmetric extended radio structure. The X-ray emi

S. Cristiani, S. D&#39;Odorico, A. Fontana, E. Giallongo

The spectrum of the quasar Q0055-269 ($z=3.66$) has been observed at the resolution of 14 km s$^{-1}$ in the wavelength interval 4750--6300 Å. We give a list of Lyman$-α$ lines and metal-line systems for which column densities and Doppler widths have been derived by a fitting procedure. The statistical distribution of the Doppler parameter for the Lyman$-α$

Dan Kiselman, Bertrand Plez

We study the formation of Li lines in a case study of an S-type AGB star in the SMC. AGB stars may be important providers of $^7$Li to the interstellar medium. Abundance analysis of these stars is difficult due to the heavy molecular blanketing, uncertainties in the model atmospheres and possible departures from LTE in the Li atomic level populations. We add

A. Belkasri, M. Hamade

A new approach to find all the transitive orientations for a comparability graph (finite or infinite) is presented. This approach is based on the link between the notion of ``strong&#39;&#39; partitive set and the forcing theory (notions of simplices and multiplices). A mathematical algorithm is given for the case of a comparability graph which has only non

I. A. McDonald

In systems subject to periodic boundary conditions, Haldane has shown that states at arbitrary filling fraction possess a degeneracy with respect to center of mass translations. An analysis is carried out for multi-component electron systems and extra degeneracies are shown to exist. Their application to numerical studies is discussed.

Evalyn I. Gates, Geza Gyuk, Michael S. Turner

We discuss the implications of the more than 50 microlensing events seen by the EROS, MACHO, and OGLE collaborations for the composition of the halo of our galaxy. The event rates indicate that the halo mass fraction in MACHO&#39;s is less than 30\%, consistent with expectations for a universe whose primary component is cold dark matter. We caution that the

S. Ying

We explore a consistent way to extend the partially conserved axial vector current (PCAC) relationship and corresponding current algebra results in two strongly correlated directions: 1) towards a search for a set of systematic rules for the establishment of PCAC related relationships in a finite low momentum transfer region and for the extrapolation of the

K. M. Rabe, U. V. Waghmare

A systematic method is presented for constructing effective Hamiltonians for general phonon-related structural transitions. The key feature is the application of group theoretical methods to identify the subspace in which the effective Hamiltonian acts and construct for it localized basis vectors, which are the analogue of electronic Wannier functions. The r

I. Andrić, V. Bardek, L. Jonke

In the Bogomol&#39;nyi limit of the Calogero-Sutherland collective-field model we find static-soliton solutions. The solutions of the equations of motion are moving solitons, having no static limit for $ł>1$. They describe holes and lumps, depending on the value of the statistical parametar $ł$.

A. B. Eriksson, T. Einarsson, S. Ostlund

The two-dimensional extended Hubbard model that includes a nearest- neighbor Heisenberg interaction is studied using a mean-field theory where quasiparticles are defined by an U(8) group of canonical transformations. The theory is a generalization of the ordinary BCS theory, and Balian and Werthamer&#39;s theory of He-3 that permits both broken gauge, spin a

Kentaro Hori

New relations of correlation functions are found in topological string theory; one for each second cohomology class of the target space. They are close cousins of the Deligne-Dijkgraaf-Witten&#39;s puncture and dilaton equations. When combined with the dilaton equation and the ghost number conservation, the equation for the first chern class of the target sp

J. Madore, T. Masson, J. Mourad

A general definition of a linear connection in noncommutative geometry has been recently proposed. Two examples are given of linear connections in noncommutative geometries which are based on matrix algebras. They both possess a unique metric connection.

D. Makovoz, G. A. Miller

The opportunity to observe color transparency (CT) is determined by how rapidly a small-sized hadronic wave packet expands. Here we use SU(2) lattice gauge theory with Wilson fermions in the quenched approximation to investigate the expansion. The wave packet is modeled by a point hadronic source, often used as an interpolating field in lattice calculations.

Steven Nerney, Edward J. Schmahl, Z. E. Musielak

The vector Burgers equation is extended to include pressure gradients and gravity. It is shown that within the framework of the Cole-Hopf transformation there are no physical solutions to this problem. This result is important because it clearly demonstrates that any extension of Burgers equation to more interesting physical situations is strongly limited.

Simon Capstick, B. D. Keister

Current matrix elements and observables for electro- and photo-excitation of baryons from the nucleon are studied in a light-front framework. Relativistic effects are estimated by comparison to a nonrelativistic model, where we use simple basis states to represent the baryon wavefunctions. Sizeable relativistic effects are found for certain transitions, for

W. ~Zhong, David Vanderbilt

We study the antiferrodistortive instability and its interaction with ferroelectricity in cubic perovskite compounds. Our first-principles calculations show that coexistence of both instabilities is very common. We develop a first-principles scheme to study the thermodynamics of these compounds when both instabilities are present, and apply it to SrTiO$_3$.

Anthony Giaquinto, J. J. Zhang

We introduce a general theory of twisting algebraic structures based on actions of a bialgebra. These twists are closely related to algebraic deformations and also to the theory of quasi-triangular bialgebras. In particular, a deformation produced from a universal deformation formula (UDF) is a special case of a twist. The most familiar example of a deformat

Valeri V. Dvoeglazov

I start from the Bargmann-Wigner equations and introduce an interaction in the form which is similar to a $j=1/2$ case [M. Moshinsky & A. Szczepaniak, {\it J. Phys. A}{\bf 22} (1989) L817]. By means of the expansion of the wave function in the complete set of $γ$- matrices one can obtain the equations for a system which could be named as the $j=0$ Kemmer-Dir

R. Paunov

It is shown that the algebraic--geometrical (or quasiperiodic) solutions of the Conformal Affine $sl(2)$ Toda model are generated from the vacuum via dressing transformations. This result generalizes the result of Babelon and Bernard which states that the $N$--soliton solutions are generated from the vacuum by dressing transformations.

S. Aoki, R. B. Levien

We test perturbatively a recent scheme for implementing chiral fermions on the lattice, proposed by Kaplan and modified by Narayanan and Neuberger, using as our testing ground the chiral Schwinger model. The scheme is found to reproduce the desired form of the effective action, whose real part is gauge invariant and whose imaginary part gives the correct ano

Kentaro Hori

A study of the gauged Wess-Zumino-Witten models is given focusing on the effect of topologically non-trivial configurations of gauge fields. A correlation function is expressed as an integral over a moduli space of holomorphic bundles with quasi-parabolic structure. Two actions of the fundamental group of the gauge group is defined: One on the space of gauge

L. Griguolo

Using a cohomological characterization of the consistent and the covariant Lorentz and gauge anomalies, derived from the complexification of the relevant algebras, we study in $d=2$ the definition of the Weyl determinant for a non-abelian theory with Riemannian background. We obtain two second order operators that produce, by means of $ζ$-function regulariza

F. T. Brandt, J. Frenkel, J. C. Taylor

It has been shown that the high-temperature limit of perturbative thermal QCD is easily obtained from the Boltzmann transport equation for `classical&#39; coloured particles. We generalize this treatment to curved space-time. We are thus able to construct the effective stress-energy tensor. We give a construction for an effective action. As an example of the

Saurya Das, Parthasarathi Majumdar

We consider possible mixing of electromagnetic and gravitational shock waves, in the Planckian energy scattering of point particles in Minkowski space. By boosting a Reissner-Nordström black hole solution to the velocity of light, it is shown that no mixing of shock waves takes place for arbitrary finite charge carried by the black hole. However, a similar b

Amit Ghosh, P. Mitra

We reinterpret recent work on extremal Reissner- Nordstrøm black holes to argue that the mass is a measure of the gravitational entropy. We also find that the entropy of scalar fields in this background has a stronger divergence than usual.