April 1997 arXiv papers — page 13

Philip Resnik

We describe a prototype system for multilingual gisting of Web pages, and present an evaluation methodology based on the notion of gisting as decision support. This evaluation paradigm is straightforward, rigorous, permits fair comparison of alternative approaches, and should easily generalize to evaluation in other situations where the user is faced with de

Bruce Margon, Eric W. Deutsch

The poorly-studied, faint (18<m_pg<19.5) variable star CC Bootis has been noted in the literature as a candidate for a halo red giant. It proves instead to be a quasi-stellar object of redshift z=0.172, and is detected as an X-ray source by ROSAT. In addition to its odd heritage, CC Boo exhibits unusually high amplitude optical variability for an optically-s

Michael S. Turner

These lecture notes are organized into ten lessons that summarize the status of inflationary cosmology.

G. M. Frichter, T. K. Gaisser, T. Stanev

We employ a simple multiple scattering model to investigate the inclusive reaction p + A --> p + X for projectile momenta in the 100-200 GeV/c range. We find that data are consistent with a class of interaction models in which the stopping power of nuclei is rather low. We discuss extrapolation to ultra-high energy and the application to interpretation of co

D. Barrado y Navascues, J. R. Stauffer

We have derived accurate and homogeneous Lithium abundances in 49 main sequence binary systems belonging to the Hyades Open Cluster by using a deconvolution method to determine individual magnitudes and colors for the primary and secondary components of the binary. The input parameters of the model are the observed Li equivalent width, the actual distance to

Eduard Masso

A light pseudoscalar coupled to two photons would be copiously emitted by the core of a supernova and part of this flux would be converted to gamma-rays by the galactic magnetic field. Measurements on the SN1987A gamma-ray flux by the Gamma-Ray Spectrometer on the Solar Maximum Mission satellite imply stringents bounds on such process. The improved generatio

E. Kuulkers, M. van der Klis, T. Oosterbroek, J. van Paradijs

We investigated the properties of the Z pattern of the low-mass X-ray binary GX 17+2 in the X-ray colour-colour diagrams (CDs) and hardness-intensity diagrams (HIDs), and of the power spectra as a function of position in the Z, using all EXOSAT ME data. The Z pattern in the CD does not move to within 2 per cent between observations separated by 1 day to 1.5

K. M. Bekarian, A. A. Melkonian

We represent the further development of S-tree technique of the study the structure of clusters of galaxies. The S-tree technique developed by Gurzadyan et al enables one to analyse the substructures of clusters via self-consistent use of 2D positional, 1D kinematical and magnitude information on the galaxies. First, the generalization of the method for the

David A. Lowe

M-theory suggests the large N limit of the matrix description of a collection of N Type IA D-particles should provide a nonperturbative formulation of heterotic string theory. In this paper states in the matrix theory corresponding to fundamental heterotic strings are identified, and their interactions are studied. Comments are made about analogous states in

Daniel P. Arovas, A. J. Berlinsky, C. Kallin, Shou-Cheng Zhang

We show that a superconducting vortex in underdoped high T_c superconductors could have an antiferromagnetic core. This type of vortex configuration arises as a topological solution in the recently constructed SO(5) nonlinear sigma model and in Ginzburg-Landau theory with competing antiferromagnetic and superconducting order parameters. Experimental detectio

I. Rudychev, E. Sezgin

Actions for two-superparticle system in (10,2) dimensions and three-superparticle systems in (11,3) dimensions are constructed. These actions have worldline bosonic and fermionic local symmetries, and target space global supersymmety generalizing the reparametrization, kappa-symmetry and Poincare supersymmetry of the usual superparticle. With the second part

A. Brandhuber, J. Sonnenschein, S. Theisen, S. Yankielowicz

We study brane configurations which correspond to field theories in four dimension with N=2 and N=1 supersymmetry. In particular we discuss brane motions that translate to Seiberg&#39;s duality in N=1 models recently studied by Elitzur, Giveon and Kutasov. We investigate, using the brane picture, the moduli spaces of the dual theories. Deformations of these

R. Oppermann, B. Rosenow

We provide evidence for spin glass related magnetic gaps in the fermionic density of states below the freezing temperature. Model calculations are presented and proposed to be relevant for explaining resistivity measurements which observe a crossover from variable-range- to activated behavior. The magnetic field dependence of a hardgap and the low temperatur

Carlos Castro

Since the lightcone self dual spherical membrane, moving in flat target backgrounds, has a direct correspondence with the SU(\infty) Nahm equations and the continuous Toda theory, we construct the quantum/Moyal deformations of the self dual membrane in terms of the q-Moyal star product . The q deformations of the SU(\infty) Nahm equations are studied and exp

Satoru Saito

The duality of dual resonance models is shown to imply that the four point string correlation function solves the Yang-Baxter equation. A reduction of transfer matrices to $A_l$ symmetry is described by a restriction of the KP $τ$ function to Toda molecules.

Satoru Saito

The correspondence between two geometrical descriptions of the KP-hierarchy, one by discrete surface and another by difference analogue of differential geometry, is given.

R. Myrzakulov, S. Vijayalakshmi, G. N. Nugmanova, M. Lakshmanan

A non-isospectral (2+1) dimensional integrable spin equation is investigated. It is shown that its geometrical and gauge equivalent counterparts is the (2+1) dimensional nonlinear Schrödinger equation introduced by Zakharov and studied recently by Strachan. Using a Hirota bilinearised form, line and curved soliton solutions are obtained. Using certain freedo

John H. Brodie, Amihay Hanany

We study N=1 four dimensional gauge theories as the world volume theory of D4-branes between NS 5-branes. We find constructions for a number of known field theory dualities involving $SU(N_c)\times SU(N_c&#39;)$ groups, coupled by matter fields F in the $(N_c, \bar N_c)$ representation, in terms of branes of type IIA string theory. The dual gauge group follo

T. Li, J. Lopez, D. Nanopoulos

We compactify the M-theory proposed by Horava and Witten on a Calabi-Yau manifold with boundary $S_1/Z_2$. A no-scale-like Kähler potential, the superpotential, and the gauge kinetic function are obtained in this 4-dimensional $E_6\times E_8$ model. We also study the general phenomenological consequences of the resulting M-theory-inspired model, which may in

Robert G. Leigh, Lisa Randall, Riccardo Rattazzi

We examine the models with gauge group U(1)^{k-1}\times\prod_{i=1}^k SU(n_i), which are obtained from decomposing the supersymmetry breaking model of Affleck, Dine and Seiberg containing an antisymmetric tensor field. We note that all of these models are distinct vacua of a single SU(N) gauge theory with an adjoint superfield. The dynamics of this model may

L. Giusti

In this talk we present the results obtained from a study of ${\cal O}(2000)$ (quenched) lattice configurations from the APE collaboration, at $6.0\leβ\le 6.4$, using both the Wilson and the SW-Clover fermion action. We determine the light hadronic spectrum and the meson decay constants. For the light-light systems we find an agreement with the experimental

Fotini Markopoulou

We illustrate the relationship between spin networks and their dual representation by labelled triangulations of space in 2+1 and 3+1 dimensions. We apply this to the recent proposal for causal evolution of spin networks. The result is labelled spatial triangulations evolving with transition amplitudes given by labelled spacetime simplices. The formalism is

Kirill A. Bronnikov

We consider multidimensional cosmologies in even-dimensional space-times (D=2n) containg perfect fluid and a multidimensional generalization of the Maxwell field, preserving its conformal invariance (the F field, an n-form). Among models with an isotropic physical 3-space some integrable cases are found: vacuum models (which are integrable in the general cas

Shiyi Chen, Katepalli R. Sreenivasan, Mark Nelkin, Nianzheng Cao

We argue on the basis of empirical data that Kolmogorov&#39;s refined similarity hypothesis (RSH) needs to be modified for transverse velocity increments, and propose an alternative. In this new form, transverse velocity increments bear the same relation to locally averaged enstrophy (squared vorticity) as longitudinal velocity increments bear in RSH to loca

Douglas Singleton

It is proven that if more than a single magnetic charge exists it is impossible to define a proper quantum mechanical angular momentum operator for an electrically charged particle in the field of the magnetic charges. Assuming that quantum mechanics is correct we conclude that free magnetic charges (i.e. magnetic charges with a Coulomb-like magnetic field)

Satoru Saito, Noriko Saitoh, Hisao Konuma, Katsuhiko Yoshida

We study a small piece of two dimensional Toda lattice as a complex dynamical system. In particular the Julia set, which appears when the piece is deformed, is shown analytically how it disappears as the system approaches to the integrable limit.

P. Danielewicz

Dynamics of central collisions of heavy nuclei in the energy range from few tens of MeV/nucleon to a couple of GeV/nucleon is discussed. As the beam energy increases and/or the impact parameter decreases, the maximum compression increases. It is argued that the hydrodynamic behavior of matter sets in the vicinity of balance energy. At higher energies shock f

P. Bozek

The particle production in the intermediate energy heavy ion collisions is discussed in the framework of the nonequilibrium Green&#39;s functions formalism. The evolution equations of the Green&#39;s functions for fermions allows for the discussion of the off-shell fermion propagator and of the large momentum component in the initial state. For the case of a

Franck Barthe

We give a new proof of the sharp form of Young&#39;s inequality for convolutions, first proved by Beckner [Be] and Brascamp-Lieb [BL]. The latter also proved a sharp reverse inequality in the case of exponents less than $1$. Our proof is simpler and gives Young&#39;s inequality and its converse altogether.

Kevin Whyte

We determine when a quasi-isometry between discrete spaces is at bounded distance from a bilipschitz map. From this we prove a geometric version of the Von Neumann conjecture on amenability. We also get some examples in geometric groups theory which show that the sign of the Euler characteristic is not a coarse invariant. Finally we get some general results

C. Devchand, Jean Nuyts

We generalise the notions of supersymmetry and superspace by allowing generators and coordinates transforming according to more general Lorentz representations than the spinorial and vectorial ones of standard lore. This yields novel SO(3,1)-covariant superspaces, which we call hyperspaces, having dimensionality greater than (4|4) of traditional super-Minkow

I. Bigi, M. Shifman, N. Uraltsev, A. Vainshtein

The leading term in the semileptonic width of heavy flavor hadrons depends on the fifth power of the heavy quark mass. We present an analysis where this power can be self-consistently treated as a free parameter n and the width can be studied in the limit n -> oo. The resulting expansion elucidates why the small velocity (SV) treatment is relevant for the in

G. M. de Divitiis, R. Petronzio, L. Silvestrini

Flavour changing top decays $t \to c Z^0, t \to c g$ and $t \to c γ$ are predicted with invisible rates within the standard model and may represent a window on new physics. We consider these processes in supersymmetric extensions of the standard model and we show that observable rates can be obtained only if the SUSY breaking is non universal and flavour dep

Hans-Reinhard Mueller

Discrete lattice simulations of an one-dimensional phi^4 theory coupled to an external heat bath are being carried out. Great care is taken to remove the effects of lattice discreteness and finite size and to establish the correct correspondence between simulations and the desired, finite-temperature continuum limit.

Giorgio Parisi

We show that at short time aging is realized in a simple model of binary glasses. We find that below the transition point the off-equilibrium correlation functions and response functions are compatible with the relations that were originally derived Cugliandolo Kurchan for generalized spin glasses.

G. Bilalbegovic

The high-temperature properties of the Al(111) surface are studied by molecular-dynamics simulation. This surface does not melt below the bulk melting point, but can be superheated. Superheating of metal surfaces has been recently observed in several experiments. A molecular-dynamics study of the structural properties reveals how after going through the supe

L. P. Rokhinson, V. J. Goldman

We have studied temperature dependence of both diagonal and Hall resistivity in the vicinity of $ν=1/2$. Magnetoresistance was found to be positive and almost independent of temperature: temperature enters resistivity as a logarithmic correction. At the same time, no measurable corrections to the Hall resistivity has been found. Neither of these results can

Mulugeta Bekele, G Ananthakrishna

We consider a model proposed earlier by us for describing a form of plastic instability found in creep experiments . The model consists of three types of dislocations and some transformations between them. The model is known to reproduce a number of experimentally observed features. The mechanism for the phenomenon has been shown to be Hopf bifurcation with

J. Girash

We have developed a two-dimensional orbit averaged Fokker-Planck model of stellar clusters which expands on spherically symmetric one-dimensional models to include rotation and ellipticity. Physical effects such as collisions, finite stellar lifetimes and bar formation (i.e., a non-axisymmetric component of the potential) can also be included. The first use

Pedro G. Ferreira, Joao Magueijo

In this paper we explore the connection between anisotropic Gaussian fluctuations and isotropic non-Gaussian fluctuations. We first set up a large angle framework for characterizing non-Gaussian fluctuations: large angle non-Gaussian spectra. We then consider anisotropic Gaussian fluctuations in two different situations. Firstly we look at anisotropic space-

Judith G. Cohen, Anton Ryzhov

We present the results from a study of the dynamics of the system of globular clusters around M87. After eliminating foreground galactic stars and background galaxies, we end up with a sample of 205 bona fide M87 globular clusters for which we have radial velocities determined from multi-slit spectra taken with the LRIS on the Keck Telescope. We find that th

CDF Collaboration

This Letter describes a direct search for charged Higgs boson production in proton-antiproton collisions at sqrt(s)=1.8 TeV recorded by the Collider Detector at Fermilab. Two-Higgs-doublet extensions to the standard model predict the existence of charged Higgs bosons. In such models, the branching fraction for top quarks B(t --> H b --> tau nu b) can be larg

V. Delgado, J. G. Muga

A self-adjoint operator with dimensions of time is explicitly constructed, and it is shown that its complete and orthonormal set of eigenstates can be used to define consistently a probability distribution of the time of arrival at a spatial point.

Steven G. Harris

The purpose of this note is to establish, in a categorical manner, the universality of the Geroch-Kronheimer-Penrose causal boundary when considering the types of causal structures that may profitably be put on any sort of boundary for a spacetime. Actually, this can only be done for the future causal boundary (or the past causal boundary) separately; furthe

J. de Boer, K. Skenderis

A new heterotic N=2 string with manifest target space supersymmetry is constructed by combining a conventional N=2 string in the right-moving sector and a Green-Schwarz-Berkovits type string in the left-moving sector. The corresponding sigma model is then obtained by turning on background fields for the massless excitations. We compute the beta functions and

Horacio M. Pastawski, Jose Gascon

In metallic nanoparticles, the different electronic environment seen by each magnetic nucleus produces a distribution of Knight shifts of the NMR frequencies which is observed as an inhomogeneously broadened lineshape. We study the fluctuations in the local density of states for s electrons at the Fermi energy in a simple LCAO model. We resort to a Matrix Co

Lluis Balcells, Oscar Iglesias, Amilcar Labarta

We critically discuss relaxation experiments in magnetic systems that can be characterized in terms of an energy barrier distribution, showing that proper normalization of the relaxation data is needed whenever curves corresponding to different temperatures are to be compared. We show how these normalization factors can be obtained from experimental data by

S. Jadach, B. F. L. Ward, Z. Was

We discuss the allowed parameter regime in the coupling-mass plane implied by the existing LEP2 data on e+ e- -> hadrons at 172.3 GeV for the leptoquark interpretation of the anomalous DESY positron-jet events for four different models of the leptoquark charges and chiral couplings to quarks, for both a loose cut on s&#39;/s and a tight cut on s&#39;/s. We f

Ken Umeno

A unified view is given to recent developments about a systematic method of constructing rational mappings as ergodic transformations with non-uniform invariant measures on the unit interval I=[0,1]. All of the rational ergodic mappings of I with explicit non-uniform invariant densities can be obtained by addition theorems of elliptic functions. It is shown

S. Bellucci

We re-examine the OSp(N,4) invariant interacting model of massless chiral and gauge superfields, whose superconformal invariance was instrumental, both in proving the all-order no-renormalization of the mass and chiral self-interaction lagrangians, and in determining the linear superfield renormalization needed. We show that the renormalization of the gravit

Michal J. Chodorowski

I derive up to second order in Eulerian perturbation theory a new relation between the weakly nonlinear density and velocity fields. In the case of unsmoothed fields, density at a given point turns out to be a purely local function of the expansion (divergence) and shear of the velocity field. The relation depends on the cosmological parameter Omega, strongl

M. Plumacher

The baryon asymmetry of the universe can be explained by the out-of-equilibrium decays of heavy right-handed neutrinos. We analyse this mechanism in the framework of a supersymmetric extension of the Standard Model and show that lepton number violating scatterings are indispensable for baryogenesis, even though they may wash-out a generated asymmetry. By ass

A. Stephan

We investigate the dark matter constraints for the nonminimal SUSY standard model (NMSSM). The cosmologically restricted mass spectra of the NMSSM are compared to the minimal SUSY standard model (MSSM). The differences of the two models concerning the neutralino, sfermion and Higgs sector are discussed. The dark matter condition leads to cosmologically allow

Aleksey I. Alekseev, Boris A. Arbuzov

It is shown, that the possibility of a freezing of QCD running coupling constant at zero in the approach with &#34;forced analyticity&#34; can not be in accord with Schwinger-Dyson equation for gluon propagator. We propose to add to the analytic expression the well-known infrared singular term $1/q^2$ as well as pole term corresponding to &#34;excited gluon&

Andrei A. Bytsenko, Luciano Vanzo, Sergio Zerbini

The Ray-Singer torsion for a compact smooth hyperbolic 3-dimensional manifold ${\cal H}^3$ is expressed in terms of Selberg zeta-functions, making use of the associated Selberg trace formulae. Applications to the evaluation of the semiclassical asymptotics of the Witten&#39;s invariant for the Chern-Simons theory with gauge group SU(2) as well as to the sum

F. Fucito, M. Martellini, S. P. Sorella, A. Tanzini

We discuss the quantum equivalence, to all orders of perturbation theory, between the Yang-Mills theory and its first order formulation through a second rank antisymmetric tensor field. Moreover, the introduction of an additional nonphysical vector field allows us to interpret the Yang-Mills theory as a kind of perturbation of the topological BF model.

Shun-ichi Yamaguchi

We study the two-dimensional critical Ising model on a Möbius strip based on a duality relation between conformally invariant boundary conditions. By using a Majorana fermion field theory, we obtain explicit representations of crosscap states corresponding to the boundary states. We also discuss the duality structure of the partition functions.

Savely G. Karshenboim

The work is a comments on the article of V. G. Pal&#39;chikov, Yu. L. Sokolov, and V. P. Yakovlev, devoted to the measurement of the Lamb shift in the hydrogen atom and published in Physica Scripta, 55 (1997) 33-40.

Fumiaki Shibata, Masahiro Morikawa, Tetsuya Shiromizu, Masahide Yamaguchi

Back reaction of the particle creation on the quantum tunneling process is analyzed in real time formalism. We use quantum potential method in which whole quantum dynamics is exactly projected to a classical Hamilton-Jacobi equation with quantum corrections. We derive the reduction of the tunneling rate due to this particle creation effect.

C. Spieles, H. Stoecker, C. Greiner

Measured hadron yields from relativistic nuclear collisions can be equally well understood in two physically distinct models, namely a static thermal hadronic source vs.~a time-dependent, nonequilibrium hadronization off a quark-gluon plasma droplet. Due to the time-dependent particle evaporation off the hadronic surface in the latter approach the hadron rat

Sourav Sarkar, Dinesh Kumar Srivastava, Bikash Sinha, Pradip Kumar Roy

We evaluate the production of large mass diphotons from quark annihilation at BNL RHIC and CERN LHC energies from central collisions of gold nuclei. The collision is assumed to lead to either a thermally and chemically equilibrated quark gluon plasma, or a free-streaming quark gluon gas having an identical initial entropy, or a chemically equilibrating quark

A. Bianconi, M. Radici

The nuclear response to longitudinally polarized electrons, detected in coincidence with out-of-plane high-energy protons, is discussed in a simple model where the ejectile wave function is approximated as a plane wave with a complex wave vector. This choice is equivalent to solve the problem of Final-State Interactions (FSI) in homogeneous nuclear matter, a

W. Trautmann, ALADIN collaboration

We report on new measurements of breakup temperatures for target spectators from 197Au + 197Au reactions at 1000 MeV per nucleon. The temperatures rise with decreasing impact parameter from 4 MeV for peripheral to about 10 MeV for the most central collisions, in good agreement with previous results for projectile spectators at 600 MeV per nucleon. The measur

Gilles Pisier, Quanhua Xu

We prove the analogue of the classical Burkholder-Gundy inequalites for non-commutative martingales. As applications we give a characterization for an Ito-Clifford integral to be an $L^p$-martingale via its integrand, and then extend the Ito-Clifford integral theory in $L^2$, developed by Barnett, Streater and Wilde, to $L^p$ for all $1<p<\infty$. We include

Timur Oikhberg, Gilles Pisier

In analogy with the maximal tensor product of $C^*$-algebras, we define the ``maximal&#34; tensor product $E_1\otimes_μE_2$ of two operator spaces $E_1$ and $E_2$ and we show that it can be identified completely isometrically with the sum of the two Haagerup tensor products: \ $E_1\otimes_h E_2 + E_2\otimes_h E_1$. Let $E$ be an $n$-dimensional operator spac

Anna Okopińska

The method of the effective action for the composite operators $Φ^2(x)$ and $Φ^4(x)$ is applied to the termodynamics of the scalar quantum field with $λΦ^4$ interaction. An expansion of the finite temperature effective potential in powers of $\hbar$ provides successive approximations to the free energy with an effective mass and an effective coupling determi

Thomas Curtright, David Fairlie, Cosmas Zachos

Cubic interactions are considered in 3 and 7 space dimensions, respectively, for bosonic membranes in Poisson Bracket form. Their symmetries and vacuum configurations are discussed. Their associated first order equations are transformed to Nahm&#39;s equations, and are hence seen to be integrable, for the 3-dimensional case, by virtue of the explicit Lax pai

H. Fujisaki, K. Nakagawa, S. Sano

Physical aspects of the thermofield dynamics of the D=10 heterotic thermal string theory are exemplified through the infrared behaviour of the one-loop dual symmetric cosmological constant in association with the global phase structure of the thermal string ensemble.

Rajesh Gopakumar

Matrix string theory (or more generally U-Duality) requires Super Yang-Mills theory to reflect a stringy degeneracy of BPS short multiplets. These are found as supersymmetric states in the Yang-Mills carrying (fractionated) momentum, or in some cases, instanton number. Their energies also agree with those expected from M(atrix) theory. A nice parallel also e

Raymond Frey, David Gerdes, John Jaros, Steve Vejcik

(Report of the Top Physics working group at the 1996 DPF/DPB Snowmass workshop, to appear in the proceedings). We discuss the study of the top quark at future experiments and machines. Top&#39;s large mass makes it a unique probe of physics at the natural electroweak scale. We emphasize measurements of the top quark&#39;s mass, width, and couplings, as well

A. N. Kuznetsov, P. G. Tinyakov

It is shown that periodic instanton solutions may have bifurcations which qualitatively change the behaviour of the finite temperature transition rate. These bifurcations are studied numerically in a quantum mechanical model and in the massive two-dimensional sigma model with the Skyrme term. General rules which determine the behaviour of periodic instantons

C. S. Lam

Symmetrization of bosonic wave functions produces bunching and low temperature phenomena like Bose-Einstein condensation, superfludity, superconductivity, as well as laser. Since probability is conserved, one might expect such bunchings at one place would lead to a depletion or a destructive interference at another place. This indeed takes place in high-ener

R. K. Ellis, D. A. Ross, S. Veseli

We consider the production of $γ^*, W$ and $Z$ vector bosons in hadron-hadron collisions in perturbative QCD. We present results from a new numerical program which gives a full description of the production of the vector bosons and of their decay products. At small $\qt$ the calculation includes resummation of large logarithms and non-perturbative effects. T

J. L. Chkareuli, A. B. Kobakhidze

The missing VEV solution to the doublet-triplet splitting problem in general SU(N) SUSY GUTs is found. Remarkably enough, it requires a strict equality of numbers of the fundamental colours and flavours in SU(N) and for the even-order groups (N=2k) gives the predominant breaking channel $SU(N) \to SU(k-1)_c\otimes SU(k-1)_f\otimes SU(2)_w\otimes U(1)\otimes

G. Veneziano

This will be more of an outlook than a summary ...

V. L. Eletsky, B. L. Ioffe

We reply to the Comment by Hatsuda and Lee on our recent paper &#34;Meson Masses in Nuclear Matter&#34; (Phys.Rev.Lett. 78, 1010, (1997)). We argue that, contrary to the claim in the Comment, the short distance operator product expansion is not applicable for calculation of meson mass shifts in nuclear matter, since they are determined by long distance physi

C. S. Lam, K. F. Liu

We study the pion-baryon scattering process $π+B \to (n-1)π+B$ in a QCD theory with a large number (N_c) of colors. It is known that this scattering amplitudes decreases with N_c like N_c^{1-n/2}, and that its individual tree diagrams grow like N_c^{n/2}. The only way these two can be consistent is for n-1 powers of N_c to be cancelled when the Feynman diagr

Shaaban Khalil, Antonio Masiero, Qaisar Shafi

We exploit the measured branching ratio for $b \rightarrow sγ$ to derive lower limits on the sparticle and Higgs masses in the minimal string unification models. For the LSP(&#39;bino&#39;), chargino and the lightest Higgs, these turn out to be 50, 90 and 75 GeV respectively. Taking account of the upper bounds on the mass spectrum from the LSP relic abundanc

J. Bijnens

I give a short overview of Chiral Perturbation Theory, its underlying assumptions and underpinnings. A few examples are included.

R. N. Lee, A. I. Milstein, V. M. Strakhovenko

The helicity amplitudes of the high-energy photon splitting in the external Coulomb field are obtained exactly in the parameter $\al$. The cases of screened and unscreened potentials are investigated. The consideration is based on the quasiclassical approach, valid for small angles between all photon momenta. New representation of the quasiclassical electron

R. Casalbuoni, S. De Curtis, D. Dominici, M. Grazzini

A linear realization of a model of dynamical electroweak symmetry breaking describing additional heavy vector bosons is proposed. The model is a SU(2)_L x U(1) x SU(2)_L&#39; x SU(2)_R&#39; gauge theory, breaking at some high scale u to SU(2)_weak x U(1)_Y and breaking again in the standard way at the electroweak scale v to U(1)_(em). The model is renormaliz

Apostolos Pilaftsis

CP violation induced by resonant transitions of a scalar to a pseudoscalar intermediate state is analyzed within a gauge-invariant resummation approach based on the pinch technique. Necessary conditions governing the resonant enhancement of CP violation in transition amplitudes are derived. The results of this study are then applied to describe the indirect

Zong-Guo Si, Qun Wang, Qu-Bing Xie

A strict method to calculate the color rearrangement probability at partonic level in hadronic $W^+W^-$ decays is proposed. The color effective Hamiltonian $H_c$ is constructed from invariant amplitude for the process $e^+e^- \to W^+W^- \to q_1\bar{q}_2 q_3\bar{q}_4+ng$ (n=0, 1, 2, ...) and is used to calculate the cross sections of various color singlets an

M. Rogalla, Th. Eich, N. Evans, S. Joost

The radiation damage in 200 um thick Schottky diodes made on semi-insulating (SI) undoped GaAs Liquid Encapsulated Czochralski (LEC) bulk material with resistivities between 0.4 and 8.9*10E7 Ohm*cm were studied using alpha-spectroscopy, signal response to minimum ionising particles (MIP), I-V and CV-measurements. The results have been analysed to investigate

E. Calzetta, A. Campos, E. Verdaguer

We consider the classical stochastic fluctuations of spacetime geometry induced by quantum fluctuations of massless non-conformal matter fields in the Early Universe. To this end, we supplement the stress-energy tensor of these fields with a stochastic part, which is computed along the lines of the Feynman-Vernon and Schwinger-Keldysh techniques; the Einstei

Alexander K. Hartmann

A method is presented for the calculation of all exact ground states of diluted antiferromagnets and random field systems in an arbitrary range of fields. It works by calculating all jump-fields B,Δwhere the system changes it&#39;s ground state. For each field value all degenerated ground states are represented by a set of (anti-) ferromagnetic clusters and

F. Brosens, J. T. Devreese, L. F. Lemmens

Two basic correlation functions are calculated for a model of $N$ harmonically interacting identical particles in a parabolic potential well. The density and the pair correlation function of the model are investigated for the boson case. The dependence of these static response properties on the complete range of the temperature and of the number of particles

Hitoshi Seo, Hidetoshi Fukuyama

The magnetic structure of antiferromagnetically ordered phases of quasi-one-dimensional organic conductors is studied theoretically at absolute zero based on the mean field approximation to the quarter-filled band with on-site and nearest-neighbor Coulomb interaction. The differences in magnetic properties between the antiferromagnetic phase of (TMTTF)$_2$X

Joerg Buenemann, Florian Gebhard, Werner Weber

We introduce Gutzwiller-correlated wave functions for the variational investigation of general multi-band Hubbard models. We set up a diagrammatic formalism which allows us to evaluate analytically ground-state properties in the limit of infinite spatial dimensions. In this limit recent results obtained within the Gutzwiller approximation are seen to become

M. I. Dykman, H. Rabitz, V. N. Smelyanskiy, B. E. Vugmeister

We analyze the probabilities of large infrequent fluctuations in systems driven by external fields. In a broad range of the field magnitudes, the logarithm of the fluctuation probability is linear in the field magnitude, and the response can be characterized by a logarithmic susceptibility. This susceptibility is used to analyze optimal control of large fluc

Kevin Scott Brown, Kevin E. Bassler, Dana A. Browne

We study the phase diagram and critical behavior of an interacting one dimensional two species monomer-monomer catalytic surface reaction model with a reactive phase as well as two equivalent adsorbing phase where one of the species saturates the system. A mean field analysis including correlations up to triplets of sites fails to reproduce the phase diagram

D. C. Dender, P. R. Hammar, Daniel H. Reich, C. Broholm

Neutron scattering from copper benzoate, Cu(C6D5COO)2 3D2O, provides the first direct experimental evidence for field-dependent incommensurate low energy modes in a one-dimensional spin S = 1/2 antiferromagnet. Soft modes occur for wavevectors q=π+- dq(H) where dq(H) ~ 2 πM(H)/gμ_B as predicted by Bethe ansatz and spinon descriptions of the S = 1/2 chain. Un

Eduardo Canale, Roberto Markarian, Sylvie Oliffson Kamphorst, Sonia Pinto de Carvalho

The elliptical stadium is a plane region bounded by a curve constructed by joining two half-ellipses by two parallel segments of equal length. The billiard inside it, as a map, generates a two parameters family of dynamical systems. It is known that the system is ergodic for a certain region of the parameter space. In this work we study the stability of a pa

Eyal Maoz, Christopher F. McKee

SHORT VERSION: The rapidly rotating, masing circumnuclear disk in the central sub-parsec region of the galaxy NGC 4258 is remarkably circular and Keplerian, yet a striking asymmetry appears in the maser spectrum: the red-shifted, high- velocity sources are much more numerous and significantly more intense than the blue-shifted ones. A similar strong asymmetr

D. W. Hoard, Raymundo Baptista, Michael Eracleous, Keith Horne

We present time-resolved HST UV spectroscopy and ground-based optical photometry of the dwarf nova IP Peg in a quiescent state. The observations were obtained prior to an eclipse, when the bright spot caused by the impact of the accretion stream with the edge of the disk dominates the light output. The optical light curve is strongly correlated with the UV s

V. Reshetnikov, N. Sotnikova

We present an analysis of structural features of all known galaxies with optical polar rings. We find a clear dichotomy for objects of this peculiar class. Bulge-dominated S0 galaxies possess only short narrow rings, while disk-dominated objects always have wide extended polar rings. We try by gas dynamical simulations to explain such a segregation by depend

A. R. Beresnyak, Ya. N. Istomin, V. I. Pariev

We developed theory of particle acceleration inside the relativistic rotating electron-positron force-free jet with spiral magnetic field. We considered perturbation of stationary magnetic field structure and found that acceleration takes place in the regions where the Alfven resonant condition with the eigenmodes in the jet is fulfilled. Acceleration proces

Hans Kjeldsen, Timothy R. Bedding

We review techniques for measuring stellar oscillations in solar-type stars. Despite great efforts, no unambiguous detections have been made. A new method, based on monitoring the equivalent widths of strong lines, shows promise but is yet to be confirmed. We also discuss several subtleties, such as the need to correct for CCD non-linearities and the importa

Hong-Guang Bi, Li-Zhi Fang

Combining the observations of spatial abundance and two-point correlation function of QSOs, we can effectively set constraints on models of cosmic structure formation. Both the abundance of gravitationally confined halos and their two-point correlation functions can be calculated in the conventional Press-Schechter formalism. We apply this method to examine

Heng Fan, Bo-yu Hou, Kang-jie Shi, Wen-li Yang

We extend the work of Foda et al and propose an elliptic quantum algebra $A_{q,p}(\hat {sl_n})$. Similar to the case of $A_{q,p}(\hat {sl_2})$, our presentation of the algebra is based on the relation $RLL=LLR^*$, where $R$ and $R^*$ are $Z_n$ symmetric R-matrices with the elliptic moduli chosen differently and a factor is also involved. With the help of the