July 1996 arXiv papers — page 4

J. Groth, C. Reichhardt, C. J. Olson, Stuart Field

We present simulations, without electrodynamical assumptions, of $B(x,y,H(t)), M(H(t))$, and $J_c(H(t))$, in hard superconductors, for a variety of twin-boundary pinning potential parameters, and for a range of values of the density and strength of the pinning sites. We numerically solve the overdamped equations of motion of up to 10^4 flux-gradient-driven v

Jane' Kondev

We develop a coarse-graining procedure for two-dimensional models of fluctuating loops by mapping them to interface models. The result is an effective field theory for the scaling limit of loop models, which is found to be a Liouville theory with imaginary couplings. This field theory is {\it completely specified} by geometry and conformal invariance {\it al

William Bialek, Curtis G. Callan, S. P. Strong

Imagine being shown $N$ samples of random variables drawn independently from the same distribution. What can you say about the distribution? In general, of course, the answer is nothing, unless we have some prior notions about what to expect. From a Bayesian point of view we need an {\it a priori} distribution on the space of possible probability distributio

M. Capone, W. Stephan

The optical conductivity of a polaronic charge carrier in the intermediate and strong-coupling regimes is calculated for a tight-binding electron using exact diagonalization. Two different simple models of the electron-phonon coupling are considered: the Holstein model, with coupling of the lattice displacement to the local electron density, and the Su-Schri

Kyung-Soo Yi, J. J. Quinn

The charge and spin response of a spin--polarized electron gas is investigated including terms beyond the random phase approximation. We evaluate the charge response, the longitudinal and transverse spin response, and the mixed spin--charge response self--consistently in terms of the susceptibility functions of a non--interacting system. Exchange--correlatio

Cecile Paris, Keith Vander Linden

Automated text generation requires a underlying knowledge base from which to generate, which is often difficult to produce. Software documentation is one domain in which parts of this knowledge base may be derived automatically. In this paper, we describe \drafter, an authoring support tool for generating user-centred software documentation, and in particula

Michael J. Davis

Numerical calculations studying bound eigenstates in chaotic regions of phase space, including those of the stadium billiard, are summarized. These calculations demonstrate that the scars of periodic orbit model is seriously flawed. An alternative picture of localization in chaotic regions is outlined.

G. F. Bertsch, V. Visuthikraisee

We examine the magnetic response of free clusters considering the spin direction and the cluster orientation as the only active degrees of freedom. The average magnetization in small fields approaches the Langevin value for paramagnets, depending on the degree to which the Hamiltonian preserves symmetries. Superparamagnetic behavior is not achievable within

Alex Lazarian, Michael Efroimsky

This paper provides a quantitative account of a recently introduced mechanism of mechanical alignment of suprathermally rotating grains. These rapidly rotating grains are essentially not susceptible to random torques arising from gas-grain collisions, as the timescales for such torques to have significant effect are orders of magnitude greater than the mean

Elisabete M. de Gouveia Dal Pino, Mark Birkinshaw

We present fully three-dimensional hydrodynamical simulations of radiative cooling jets propagating into stratified isothermal ambient media with power-law density and pressure distributions. The parameters used are mainly suitable for protostellar jets but results applicable to extragalactic jets are also presented. Comparisons are made with previous simula

R. A. Mendez, R. M. Rich, W. F van Altena, T. M. Girard

We present preliminary results from the deepest and largest photographic proper-motion survey ever undertaken of the Galactic bulge. Our first-epoch plate material (from 1972-3) goes deep enough (V_lim = 22) to reach below the bulge main-sequence turnoff. These plates cover an area of approximately 25 arc-min X 25 arc-min of the bulge in the low-extinction (

Geza Gyuk

We analyze the first-year MACHO collaboration observations of microlensing towards the Galactic center using a new direct likelihood technique that is sensitive to the distribution of the events on the sky. We consider the full set of 41 events, and calculate the direct likelihood against a simply-parameterized Galactic model consisting of either a gaussian

George Davies, Lawrence M. Widrow

The Schrödinger Method is a novel approach for modeling numerically self-gravitating, collisionless systems that may have certain advantages over N-body and phase space methods. In particular, smoothing is part of the dynamics and not just the force calculation. This paper describes test-bed simulations which illustrate the viability of the Schrödinger Metho

Curtis S. Gehman, Fred C. Adams, Richard Watkins

We study the linear evolution of small perturbations in self-gravitating fluid systems with magnetic fields. We consider wave-like perturbations to nonuniform filamentary and sheet-like hydrostatic equilibria in the presence of a uniform parallel magnetic field. Motivated by observations of molecular clouds that suggest substantial nonthermal (turbulent) pre

Hui Li, Edward E. Fenimore

We propose a new, simple but powerful algorithm to analyze the gamma-ray burst temporal structures based on identifying non-statistical variations (``peaks'') in the time histories. Detailed analyses of the bursts from the third BATSE catalog show that $\sim 30$ bursts have more than 20 peaks individually. Upon identifying most of the peaks in those

R. R. Caldwell, R. A. Battye, E. P. S. Shellard

We examine the spectrum of gravitational radiation emitted by a network of cosmic strings, with emphasis on the observational constraints and the opportunities for detection. The analysis improves over past work, as we use a phenomenological model for the radiation spectrum emitted by a cosmic string loop. This model attempts to include the effect of the gra

M. Marengo, G. Canil, G. Silvestro, L. Origlia

Radiative transfer modelling of AGB circumstellar envelopes is applied to a sample of AGB stars previously observed with the mid-IR imaging camera TIRCAM (Busso et al. 1996: Paper I). We present the results of our simulations, aimed at deriving the physical parameters of the envelope, such as the optical depth and the radial thermal structure, the mass loss

Jeff Secker

Deep CCD photometry and positions for a new sample of $\simeq 250$ dwarf elliptical (dE) galaxies in the Coma cluster core are analyzed. A significant color gradient is detected in their projected radial distribution, given by $Δ(B$--$R)/Δ(\log R_{\rm cc}) = -0.08\pm0.02$ mag. Calibrating these dE galaxies against Galactic globular clusters yields a correspo

Theodore T. Lee, Vahe Petrosian

We perform several nonparametric correlation tests on the BATSE 3B data to search for evidence of cosmological time dilation. These tests account for the effects of data truncation due to threshold effects in both limiting brightness and limiting duration, enabling us to utilize a larger number of bursts than in previous analyses. We find little significant

U. Zuelicke, A. H. MacDonald

We present microscopic derivations of the one-dimensional low-energy boson effective Hamiltonians of quantum wire and quantum Hall bar systems. The quantum Hall system is distinguished by its spatial separation of oppositely directed electrons. We discuss qualitative differences in the plasmon collective mode dispersions and the ground state correlation func

C. -H. Chen, M. Drees, J. F. Gunion

We investigate the phenomenology of an orbifold string model in which supersymmetry breaking is dominated by the overall `size' modulus field and all matter fields are in the untwisted sector. The possibly close degeneracy of the lightest neutralino and chargino and the possibly small splitting between the gluino and chargino/LSP mass imply that discover

Sora Cho, Matthew P. A. Fisher

The two-dimensional (2D) random-bond Ising model has a novel multicritical point on the ferromagnetic to paramagnetic phase boundary. This random phase transition is one of the simplest examples of a 2D critical point occurring at both finite temperatures and disorder strength. We study the associated critical properties, by mapping the random 2D Ising model

Daniel R. Phillips, Thomas D. Cohen

We discuss a number of constraints on the effects of zero-range potentials in quantum mechanics. We show that for such a potential $p \cot(δ)$, where $p$ is the momentum of the nucleon in the center of mass frame and $δ$ is the S-wave phase shift, must be a monotonically decreasing function of energy. This implies that the effective range of the potential is

S. Ambrosanio, G. L. Kane, Graham D. Kribs, Stephen P. Martin

We present a refined and expanded analysis of the CDF $eeγγ+ \Et$ event as superpartner production, assuming the lightest neutralino is the lightest supersymmetric particle. A general low-energy Lagrangian is constrained by a minimum cross section times branching ratio into two electrons and two photons, kinematics consistent with the event, and LEP1-LEP130

M. Hosch, K. Whisnant, Bing-Lin Young

If there is new physics associated with the top quark, it could show up as anomalous couplings of the top quark to weak gauge bosons, such as $Z\ttbar$ and $W\tbbar$ vector and axial-vector couplings. We use the processes $\ttbar\to Z^0Z^0$, $\ttbar\to W^+W^-$, and $\ttbar\to Z^0H$ to obtain the unitarity constraints on these anomalous couplings, and combine

Masayasu Harada, Asif Qamar, Francesco Sannino, Joseph Schechter

We investigate the hyperfine splitting of the heavy baryons in the bound-state approach. We start with an ordinary relativistic Lagrangian which has been extensively used to discuss finite mass corrections to the heavy limit predictions. It turns out that the dominant contribution arises from terms which do not manifestly break the heavy spin symmetry. The a

Antal Jevicki

We present an approach to membrane quantization using matrix quantum mechanics at large N. We show that this leads (through a simple field theory of two-dimensional open strings and the associated SU(\infty) current algebra) to a 4-D dynamics of self-dual gravity plus matter.

C. Reichhardt, J. Groth, C. J. Olson, Stuart Field

We present simulations of flux-gradient-driven superconducting rigid vortices interacting with square and triangular arrays of columnar pinning sites in an increasing external magnetic field. These simulations allow us to quantitatively relate spatio-temporal microscopic information of the vortex lattice with typically measured macroscopic quantities, such a

Kai Hencken, George Bertsch, Henning Esbensen

We calculate the nuclear induced breakup of Be11 and B8 using a more realistic treatment of the diffraction and stripping processes than in previous work. The breakup is treated in the eikonal approximation with a profile function calculated from a realistic optical potential at low energies and from free nucleon-nucleon cross sections at high energies. This

A. Sibirtsev, W. Cassing, U. Mosel

We study the production of $K^+, ρ, ω$ and $ϕ$ mesons in $p + ^{12}C$ reactions on the basis of empirical spectral functions. The high momentum, high removal energy part of the spectral function is found to be negligible in all cases close to the absolute threshold. Furthermore, the two-step process ($pN \rightarrow πN N; πN \rightarrow N + K^+, ρ, ω, ϕ$) do

G. Chanfray, M. Ericson, J. Wambach

The temperature evolution of the quark condensate is studied using three different methods. In the spirit of a many-body approach we make an expansion in the scalar density up to second order. Our result is consistent chiral perturbation theory to two-loop order.

Tomohiro Mitsumori, Nobuo Noda, Hiroaki Kouno, Akira Hasegawa

The effects of higher order corrections of ring diagrams for the quark condensate are studied by using the bare vertex Nuclear Schwinger Dyson formalism based on $σ$-$ω$ model. At the high density the quark condensate is reduced by the higher order contribution of ring diagrams more than the mean field theory or the Hartree-Fock .

L. G. Moretto, L. Phair, G. J. Wozniak

First order phase transitions are described in terms of the microcanonical and canonical ensemble, with special attention to finite size effects. Difficulties in interpreting a "caloric curve" are discussed. A robust parameter indicating phase coexistence (univariance) or single phase (bivariance) is extracted for charge distributions.

L. G. Moretto, R. Ghetti, K. X. Jing, L. Phair

The experimental emission probabilities of complex fragments by low energy compound nuclei and their dependence upon energy and atomic number are compared to the transition state rates. Intermediate-mass-fragment multiplicity distributions for a variety of reactions at intermediate energies are shown to be binomial and thus reducible at all measured transver

Philip C. Argyres, Keith R. Dienes

Despite recent evidence indicating the existence of a new kind of self-dual six-dimensional superstring, no satisfactory worldsheet formulation of such a string has been proposed. In this note we point out that a theory built from Z_4 parafermions may have the right properties to describe the light-cone conformal field theory of this string. This indicates a

Emilio Elizalde, Sergei D. Odintsov, August Romeo

We discuss the influence of gravitational effects on the stabilization of the chromomagnetic vacuum. The one-loop effective potential for a covariantly constant SU(2) gauge field in ${\bf S}^2 \times {\bf R}^2$ and ${\bf T}^2 \times {\bf R}^2$ is calculated. A possibility of curvature-induced phase transitions between zero and nonzero chromomagnetic vacua is

Carlo Becchi

The aim of these lectures is to describe a construction, as self-contained as possible, of renormalized gauge theories. Following a suggestion of Polchinski, we base our analysis on the Wilson renormalization group method. After a discussion of the infinite cut-off limit, we study the short distance properties of the Green functions verifying the validity of

V. C. Spanos, W. J. Stirling

The most general form of the $WWZ$ and $WWγ$ interaction contains a $CP$-violating term which has the same threshold behaviour as the Standard Model $\ee \to \ww$ cross section. We calculate the cross section as a function of the corresponding anomalous coupling, and estimate the bounds which can be obtained from a measurement of the threshold cross section

S. M. Barr

Several experimental results could be interpreted as evidence that certain neutrino mixing angles are large, of order unity. However, in the context of grand unified models the neutrino angles come out characteristically to be small, like the KM angles. It is shown how to construct simple grand-unified models in which neutrino angles are not only large but c

C. Glenn Boyd, Ira Z. Rothstein

We utilize inclusive sum rules to construct both upper and lower bounds on the form factors for B to D, D*, rho, pi, omega, K and K* semi-leptonic and radiative decays. We include the leading nonperturbative 1/E corrections and point out cases when alpha_s corrections are equally important. We compute the alpha_s correction to the lower bound on the B to D*

Rudnei O. Ramos

We study the importance of thermal fluctuations during the electroweak phase transition. We evaluate in detail the equilibrium number density of large amplitude subcritical fluctuations and discuss the importance of phase mixing to the dynamics of the phase transition. Our results show that, for realistic Higgs masses, the phase transition can be completed b

Rudnei O. Ramos

We apply the $δ$-expansion perturbation scheme to the $λϕ^{4}$ self-interacting scalar field theory in 3+1 D at finite temperature. In the $δ$-expansion the interaction term is written as $λ(ϕ^{2})^{ 1 + δ}$ and $δ$ is considered as the perturbation parameter. We compute within this perturbative approach the renormalized mass at finite temperature at a finit

Yosef Nir

We discuss the discovery potential for New Physics of various measurements of CP violation. If nature is supersymmetric, then the flavor problem is even more mysterious than in the standard model. We show how we can learn about the mechanism that solves the supersymmetric flavor problem from measurements of mixing and CP violation in $K$, $D$ and $B$ decays.

V. Gimenez, G. Martinelli, C. T. Sachrajda

We present a high-statistics lattice calculation of the kinetic energy $-λ_1/2 m_b$ of the heavy quark inside the $B$-meson and of the chromo-magnetic term $λ_2$, related to the $B^*$--$B$ mass splitting, performed in the HQET. Our results have been obtained from a numerical simulation based on 600 gauge field configurations generated at $β=6.0$, on a lattic

Tsuneo Suzuki, Yoshimi Matsubara, Shun-ichi Kitahara, Shinji Ejiri

Three topics about monopole dynamics after abelian projection are reported. The first is the new and detailed analyses of $SU(2)$ monopole action obtained after the block-spin transformation on the dual lattice. The $b=na(β)$ dependence for all couplings are well fitted with a universal curve. The distance dependence of the couplings is well reproduced by a

A. Carlini, I. D. Novikov

We consider the action principle to derive the classical, relativistic motion of a self-interacting particle in a 4-D Lorentzian spacetime containing a wormhole and which allows the existence of closed time-like curves. In particular, we study the case of a pointlike particle subject to a `hard-sphere' self-interaction potential and which can traverse th

J. Ibáñez, I. Olasagasti

The asymptotic behaviour of a class of inhomogeneous scalar field cosmologies with a Liouville type of potential is studied. We define a set of new variables for which the phase space of the system of Einstein equations is bounded. This allows us to perform a complete analysis of the evolution of these cosmologies. We also discuss the extension of the cosmic

J. Carot, A. M. Sintes

A brief summary of results on homotheties in General Relativity is given, including general information about space-times admitting an r-parameter group of homothetic transformations for r>2, as well as some specific results on perfect fluids. Attention is then focussed on inhomogeneous models, in particular on those with a homothetic group $H_4$ (acting mul

J. Madore, J. Mourad

A method has been recently proposed for defining an arbitrary number of differential calculi over a given noncommutative associative algebra. As an example a version of quantized space-time is considered here. It is found that there is a natural differential calculus using which the space-time is necessarily flat Minkowski space-time. Perturbations of this c

J. Hwang

Recently, we presented a unified way of analysing classical cosmological perturbation in generalized gravity theories. In this paper, we derive the perturbation spectrums generated from quantum fluctuations again in unified forms. We consider a situation where an accelerated expansion phase of the early universe is realized in a particular generic phase of t

Alexander L. Fetter

A two-parameter trial condensate wave function is used to find an approximate variational solution to the Gross-Pitaevskii equation for $N_0$ condensed bosons in an isotropic harmonic trap with oscillator length $d_0$ and interacting through a repulsive two-body scattering length $a>0$. The dimensionless parameter ${\cal N}_0 \equiv N_0a/d_0$ characterizes t

David A. Kessler, Herbert Levine, Douglas Ridgway, Lev Tsimring

We study in detail a recently proposed simple discrete model for evolution on smooth landscapes. An asymptotic solution of this model for long times is constructed. We find that the dynamics of the population are governed by correlation functions that although being formally down by powers of $N$ (the population size) nonetheless control the evolution proces

Gabriel Kotliar, Chandra Varma

We interpret the upper-critical-field anomalies observed in some high- temperature superconductors as resulting from the proximity to a zero-temperature quantum critical point. We estimate the shape of the phase boundary between the normal and the superconducting phase by modeling the zero temperature critical point as the second-order endpoint of the first-

I. C. Charret, S. M. de Souza, M. T. Thomaz, E. V. Correa Silva

We exploit the grassmannian nature of the variables involved in the path integral expression of the grand canonical partition function for self--interacting fermionic models to show, in one-space dimension, a general relation among the terms of it expansion in the high temperature limit and a combination of co-factors of a suitable matrix with commuting entr

Carmem Lucia de Souza Batista, Dingping Li

We present a framework for the analytic calculations of the hierarchical wave functions and the composite fermion wave functions in the fractional quantum Hall effect on the sphere by using projective coordinates. Then we calculate the overlaps between these two wave functions at various fillings and small numbers of electrons. We find that the overlaps are

S. Dippel, G. G. Batrouni, D. E. Wolf

By means of Molecular Dynamics simulations, we investigate the elementary process of avalanches and size segregation by surface flow in 2 dimensions: a single ball confined to moving along an inclined line consisting of balls. The global characteristics of the motion depend strongly on the size of the moving ball relative to the size of the balls on the line

Ar. Abanov, A. Kashuba, V. L. Pokrovsky

In 2D XY ferromagnet the dipole force induces a strong interaction between spin-waves in the long-wavelength limit. The major effect of this interaction is the transformation of a propagating spin-wave into a diffusion mode. We study the anomalous dynamics of such diffusion modes. We find that the Janssen-De Dominics functional, which governs this dynamics,

W. Van Dyke Dixon, Mark Hurwitz, Henry C. Ferguson

We have searched the far-UV spectra of five clusters of galaxies observed with the Hopkins Ultraviolet Telescope (HUT) for emission in the resonance lines of O VI (1032,1038 A) and C IV (1548,1551 A). We do not detect significant emission from either species in any of the spectra. Lieu et al. [ApJ, 458, L5 (1996)] have recently proposed a warm [(5-10) * 10^5

Salvatore Capozziello, Ruggiero de Ritis, Vladimir Mank'o, Alma Angela Marino

We discuss the possibility that, besides the usual gravitational lensing, there may exist a sort of gravitational waveguiding in cosmology which could explain some anomalous phenomena which cannot be understood by the current gravitational lensing models as the existence of "brothers" objects having different brilliancy but similar spectra and redshi

Lawrence M. Widrow

We propose a new numerical technique for following the evolution of a self-gravitating collisionless system in general relativity. Matter is modeled as a scalar field obeying the coupled Klein-Gordon and Einstein equations. A phase space distribution function, constructed using covariant coherent states, obeys the relativistic Vlasov equation provided the de

S. Bonazzola, J. Frieben, E. Gourgoulhon

Triaxial neutron stars may be important sources of gravitational radiation for the forthcoming generation of interferometric gravitational wave detectors such as LIGO, VIRGO, and GEO600. We investigate the viscosity triggered bar mode secular instability of rapidly rotating neutron stars by means of a perturbation analysis of numerically constructed ``exact&

Alejandro Gangui

One of the most powerful tools to probe the existence of cosmic defects in the early universe is through the Cosmic Microwave Background (CMB) radiation. It is well known that computations with causal sources are more involved than the adiabatic counterparts based on inflation, and this fact has in part hampered the development of fine detailed predictions.

Trinh X. Thuan, Yu. I. Izotov, V. A. Lipovetsky

We present HST WFPC2 V and I images and GHRS UV spectrophotometry of the spectral regions around Ly$_alpha$ and OI 1302 of the extremely metal-deficient (Z~Zsun/41) blue compact dwarf (BCD) galaxy SBS 0335-052. All the star formation in the BCD occurs in six super-star clusters (SSC) with ages =< 3-4 Myr. Dust is clearly present and mixed spatially with the

Indranil Biswas, A. K. Raina

For a compact Riemann surface $X$ of any genus $g$, let $L$denote the line bundle $K_{X\times X}\otimes {\cal O}_{X\times X}(2Δ)$ on $X\times X$, where $K_{X\times X}$ is the canonical bundle of $X\times X$ and $Δ$ is the diagonal divisor. We show that $L$ has a canonical trivialisation over the nonreduced divisor $2Δ$. Our main result is that the space of p

Hitoshi Nishino, Ergin Sezgin

We present a model for supersymmetric Yang-Mills theory in 10+2 dimensions. Our construction uses a constant null vector, and leads to a consistent set of field equations and constraints. The model is invariant under generalized translations and an extra gauge transformation. Ordinary dimensional reduction to ten dimensions yields the usual supersymmetric Ya

G. López Castro, D. A. López Falcón

Using the vector meson dominance model we get predictions for the Cabibbo-favored $\tom$ and $\tphi$ decays. We show how the measurements of these two decays can provide information on the nature of the violation of the OZI rule.

E. L. Grossman, T. Zhou, E. Ben-Naim

We study steady-state properties of inelastic gases in two-dimensions in the presence of an energy source. We generalize previous hydrodynamic treatments to situations where high and low density regions coexist. The theoretical predictions compare well with numerical simulations in the nearly elastic limit. It is also seen that the system can achieve a noneq

Oren Bergman

String-bit models are both an efficient way of organizing string perturbation theory, and a possible non-perturbative composite description of string theory. This is a summary of ideas and results of string-bit and superstring-bit models, as presented in the Strings &#39;96 conference.

Y. -F. Wu, U. Heinz, B. Tomasik, U. A. Wiedemann

The Yano-Koonin-Podgoretskii (YKP) parametrisation of Hanbury Brown-Twiss (HBT) two-particle correlation functions opens new strategies for extracting the emission duration and testing the longitudinal expansion in heavy-ion collisions. Based on the recently derived model-independent expressions, we present a detailed parameter study of the YKP parameters fo

J. Gegenberg, G. Kunstatter, T. Strobl

We calculate the statistical mechanical entropy associated with boundary terms in the two-dimensional Euclidean black holes in deSitter gravity.

John Cardy

This is the text of a talk given at the conference in memory of Claude Itzykson at Saclay in June 1996. It contains an introductory survey and an account of recent developments in the field theoretic RG approach to reaction-diffusion problems.

Kengo Maeda, Akihiro Ishibashi

We investigate the instability of the Cauchy horizon caused by causality violation in the compact vacuum universe with the topology $B\times {\bf S}^{1}\times {\bf R}$, which Moncrief and Isenberg considered. We show that if the occurrence of curvature singularities are restricted to the boundary of causality violating region, the whole segments of the bound

S. M. A. Nimour, N. Zekri, R. Ouasti

The effect of electric field on the electron resonant tunnelling into a double barrier structure is studied. We show for particular field strengths an increase of the tunnelling time which leads us to explain the Stark-ladder localization and Bloch oscillations in superlattices and to discuss the quenching of luminescence in multiple quantum wells.

Carlo Becchi

This paper contains a revised version of the lecture notes of a short course on the quantization of gauge theories. Starting from a sketchy review of scattering theory, the paper describes the lines of BRST-Faddeev-Popov quantization considering the problem of a non-perturbative extension of this method. The connection between Slavnov-Taylor identity and S-m

Stefan K. Kehrein, Andreas Mielke

We introduce a new theoretical approach to dissipative quantum systems. By means of a continuous sequence of infinitesimal unitary transformations, we decouple the small quantum system that one is interested in from its thermodynamically large environment. This yields a trivial final transformed Hamiltonian. Dissipation enters through the observation that ge

R. A. Mendez, D. Minniti, G. de Marchi, A. Baker

Stellar sources are identified in the Hubble Deep Field, and accurate colours and magnitudes are presented. The predictions of a Galactic starcounts model are compared with the faint stellar counts in this field. The model reproduces the observations very well in the magnitude range 21.0 < V < 26.4, while it overpredicts the counts by a factor of four in the

Patrick Petitjean, Bertrand Theodore, Alain Smette, Yannick Lespine

We report on the detection of a z_gal=0.101 galaxy projected on the sky at 4.2 arcsec (or 5.2 h^{-1} kpc for q_o=0.5) from the quasar Q 0439-433 (z_em=0.594). The HST spectrum of the quasar shows strong MgII, FeII, SiII, AlII and CIV absorption lines at the same redshift as the galaxy. The equivalent width ratios of the low ionization lines indicate that thi

Valter Moretti

The thermal Euclidean Green functions for Photons propagating in the Rindler wedge are computed employing an Euclidean approach within any covariant Feynman-like gauge. This is done by generalizing a formula which holds in the Minkowskian case. The coincidence of the found $(\be=2π)$-Green functions and the corresponding Minkowskian vacuum Green functions is

Michael Dine, Yosef Nir, Yuri Shirman

We study various modifications to the minimal models of gauge mediated supersymmetry breaking. We argue that, under reasonable assumptions, the structure of the messenger sector is rather restricted. We investigate the effects of possible mixing between messenger and ordinary squark and slepton fields and, in particular, violation of universality. We show th

A. G. Cohen, D. B. Kaplan, A. E. Nelson

Effective Supersymmetry is presented as a theory of physics above the electroweak scale which has significant theoretical advantages over both the standard model and the Minimal Supersymmetric Standard Model (MSSM). The theory is supersymmetric at short distances but differs significantly from the MSSM. Flavor symmetry violation is intimately related to supe

M. Jimbo, M. Lashkevich, T. Miwa, Y. Pugai

The BRST property of Lukyanov&#39;s screening operators in the bosonic representation of the deformed Virasoro algebra is proven.

Miyuki Kawamura, Kayoko Maeda, Makoto Sakamoto

Working in a Hamiltonian formulation with $A_0 = 0$ gauge and also in a path integral formulation, we show that the vacuum wave functional of four-dimensional pure Yang-Mills theory has the form of the exponential of a {\it three}-dimensional Yang-Mills action. This result implies that vacuum expectation values can be calculated in Yang-Mills theory but one

K. L. Vaninsky

We present two independent approaches for computing the thermodynamics for classical particles interacting via the Moser--Calogero potential. Combining the results we propose the form of equation of state or, what is equivalent, the asymptotics of the Jacobian between volume elements corresponding two symplectic structures on the phase space.

Nalini Joshi, Gopala K. Srinivasan

In this paper we obtain explicit lower bounds for the radius of convergence of the Painlevé expansions of the Korteweg-de-Vries equation around a movable singularity manifold ${\Cal S}$ in terms of the sup norms of the arbitrary functions involved. We use this estimate to prove the well-posedness of the singular Cauchy problem on ${\Cal S}$ in the form of co

Zhenping Li

The reaction $γ+ p\to η^\prime + p$ is investigated in the quark model approach. The quark model predicts that the off-shell contributions from the resonance $S_{11}(1535)$ dominate the $\etap$ production in the threshold region. We find that the coulping constant $α_{\etap NN}$ from the fit to a few total cross section data is small. The results of the tota

Steffen Wilke, Morrel H. Cohen, Matthias Scheffler

The quantity w^N(r) = ( 1/ k^2 T_el)[partial n(r, T_el) / partial T_el]_(v(r),N) is introduced as a convenient measure of the local isoelectronic reactivity of surfaces. It characterizes the local polarizability of the surface and it can be calculated easily. The quantity w^N(r) supplements the charge transfer reactivity measured e.g. by the local softness t

Kimball A. Milton, Y. Jack Ng

In the final few years of his life, Julian Schwinger proposed that the ``dynamical Casimir effect&#39;&#39; might provide the driving force behind the puzzling phenomenon of sonoluminescence. Motivated by that exciting suggestion, we have computed the static Casimir energy of a spherical cavity in an otherwise uniform material. As expected the result is dive

Bernard de Wit, Gabriel Lopes Cardoso, Dieter Lüst, Thomas Mohaupt

The restrictions of target--space duality are imposed at the perturbative level on the holomorphic Wilsonian couplings that encode certain higher-order gravitational interactions in $N=2, D=4$ heterotic string compactifications. A crucial role is played by non-holomorphic corrections. The requirement of symplectic covariance and an associated symplectic anom

S. Deser, M. Henneaux, C. Teitelboim

We generalize duality invariance for the free Maxwell action in an arbitrary background geometry to include the presence of electric and magnetic charges. In particular, it follows that the actions of equally charged electric and magnetic black holes are equal.

Khaled Abdel-Khalek

Taking into account the recent dualities we rederive the super p-brane scan. Our main results are the importance of the metric&#39;s signature and the existence of an S self-dual super 5-brane at D=14 with signature (7,7) or (11,3).

H. Fujisaki, K. Nakagawa, S. Sano

Physical aspects of the thermofield dynamics of the D=10 heterotic 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.

Carlos Pinheiro, J. A. Helayel-Neto, Gilmar S. Dias

The existence of an electromagnectic field with parallel electric and magnetic components is readdressed in the presence of a gravitational field. A non-parallel solution is shown to exist. Next, we analyse the possibility of finding stationary gravitational waves in de nature. Finaly, We construct a D=4 effective quantum gravity model. Tree-level unitarity

D. J. Broadhurst, J. A. Gracey, D. Kreimer

Counterterms that are not reducible to $ζ_{n}$ are generated by ${}_3F_2$ hypergeometric series arising from diagrams for which triangle and uniqueness relations furnish insufficient data. Irreducible double sums, corresponding to the torus knots $(4,3)=8_{19}$ and $(5,3)=10_{124}$, are found in anomalous dimensions at ${\rm O}(1/N^3)$ in the large-$N$ limit

D. -U. Jungnickel, C. Wetterich

Quark mass ratios are expressed within the linear meson model by universal relations involving only the masses and decay constants of the flavored pseudoscalars as well as their wave function renormalization. Quantitative results are in agreement with those obtained from chiral perturbation theory, with a tendency to a somewhat higher strange quark mass.

W. L. van Neerven, M. Buza, Y. Matiounine, J. Smith

Using renormalization group techniques we have derived analytic formulae for the next-to-leading order heavy-quark coefficient functions in deep inelastic lepton hadron scattering. These formulae are only valid in the kinematic regime Q^2 >> m^2, where Q^2 and m^2 stand for the masses squared of the virtual photon and heavy quark respectively. Some of the ap

Hanxin He, Xiangdong Ji

The nucleon&#39;s tensor charges (isovector $g^v_T=δu-δd$ and isoscalar $g^s_T=δu+δd$) are calculated using the QCD sum rules in the presence of an external tensor field. In addition to the standard quark and gluon condensates, new condensates described by vacuum susceptibilities are induced by the external field. The latter contributions to $g^v_T$ and $g^s

A. Khodjamirian, R. Rückl

We describe the calculation of the $B\rightarrow π$ hadronic matrix element from operator product expansion near the light-cone in QCD. In the resulting sum rules, the form factors $f^+$ and $F_0$ determining this matrix element are expressed in terms of pion light-cone wave functions. We present predictions for $f^+$ and $F_0$ in the region of momentum tran

Gian Franco Bonini

We use transport equations to compute the evolution of the quark plasma at the electroweak phase transition in the two-doublet Higgs model, obtaining in a more rigorous and quantitatively accurate way results consistent with previous work. We discuss the model in connection with the electroweak baryogenesis scenario, and claim that the observed baryon asymme

A. Brignole, L. E. Ibáñez, C. Muñoz

It is known that a Higgs $μ$ term can be naturally generated through the Kähler potential in orbifold string models in which one of the three compactified complex planes has order two. In this class of models explicit expressions for both the $μ$ parameter and the soft SUSY-breaking parameters can be obtained under the assumption that the goldstino is an arb

John Ellis, Einan Gardi, Marek Karliner, Mark A. Samuel

We study the renormalization-scheme (RS) dependence of Pade Approximants (PA&#39;s), and compare them with the Principle of Minimal Sensitivity (PMS) and the Effective Charge (ECH) approaches. Although the formulae provided by the PA, PMS and ECH predictions for higher-order terms in a QCD perturbation expansion differ in general, their predictions can be ve