January 1997 arXiv papers — page 12

Reinhold Egger, Hermann Grabert

We investigate the role of charging effects in a voltage-biased quantum wire. Both the finite range of the Coulomb interaction and the long-ranged nature of the Friedel oscillation imply a finite capacitance, leading to a charging energy. While observable Coulomb blockade effects are absent for a single impurity, they are crucial if islands are present. For

Christian Schulze, János Hajdu, Bodo Huckestein, Martin Janssen

We consider a disordered two-dimensional system of independent lattice electrons in a perpendicular magnetic field with rigid confinement in one direction and generalized periodic boundary conditions (GPBC) in the other direction. The objects investigated numerically are the orbits in the plane spanned by the energy eigenvalues and the corresponding center o

Alberto Alvarez, Emilio Hernandez-Garcia, Joaquin Tintore

We study the development of mean structures in a nonlinear model of large scale ocean dynamics with bottom topography and dissipation, and forced with a noise term. We show that the presence of noise in this nonlinear model leads to persistent average currents directed along isobaths. At variance with previous works we use a scale unselective dissipation, so

Chi-Chao Wu, D. Michael Crenshaw, Andrew J. S. Hamilton, Robert A. Fesen

We have obtained a far-ultraviolet spectrum (1150 - 1600 Ang.) of a hot subdwarf star behind the remnant of SN 1006 with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope. The high-quality spectrum is used to test previous identifications of the strong absorption features discovered with the International Ultraviolet Explorer. These features

R. F. Peletier, M. Balcells

We present optical and near-infrared (NIR) surface brightness and colour profiles,in bands ranging from U to K, for the disk and bulge components of a complete sample of 30 nearby S0 to Sbc galaxies with inclinations larger than 50 degrees. We describe in detail the observations and the determination of colour parameters. Calibrated monochromatic and real-co

Ethan T. Vishniac

Recent work has shown that the speed of the cooling front in soft X-ray transients may be an important clue in understanding the nature of accretion disk viscosity. In a previous paper (Vishniac and Wheeler 1996) we derived the scaling law for the cooling front speed. Here we derive a similarity solution for the hot inner part of disks undergoing cooling. Th

J. G. Cohen, J. K. McCarthy

We have analyzed high dispersion and high precision spectra of 5 blue horizontal branch stars in the globular cluster M92 to establish that the projected rotational velocity for these stars ranges from 15 to 40 \kms. This is larger than that expected based on the rotation of their main sequence progenitors, the spin down of rotation with age, and the conserv

T. W. Jones, Joseph B. Gaalaas, Dongsu Ryu, Adam Frank

We have carried out high resolution MHD simulations of the nonlinear evolution of Kelvin-Helmholtz unstable flows in 2 1/2 dimensions. The modeled flows and fields were initially uniform except for a thin shear layer with a hyperbolic tangent velocity profile and a small, normal mode perturbation. The calculations consider periodic sections of flows containi

Uffe Hellsten, Romeel Dave, Lars Hernquist, David H. Weinberg

We study metal line absorption of CIV, CII, SiIV, and NV at redshifts z=3.5 to z=2 within the framework of a cosmological model for the Lyman alpha forest, comparing the results of numerical simulations to recent observations by Songaila & Cowie (1996, SC). In agreement with Rauch, Haehnelt & Steinmetz (1996), we find that the observed mean value of the CIV/

Simon F. Portegies Zwart, Piet Hut, Frank Verbunt

Star clusters with a high central density contain an ecological network of evolving binaries, affected by interactions with passing stars, while in turn affecting the energy budget of the cluster as a whole by giving off binding energy. This is the first paper in a series aimed at providing the tools for increasingly realistic simulations of these ecological

Jian Ge, Jill Bechtold

We present a new ultra-violet spectrum of the QSO 0013-004 with 0.9 Åresolution obtained with the MMT Blue spectrograph. The \upsilon = 0 - 0, 1 - 0, 2 - 0 and 3 - 0 Lyman bands of H_2 associated with the z = 1.9731 damped Ly alpah absorption line system have been detected. The H_2 column density is N(H_2) = 6.9 (\pm 1.6)\times 10^{19} cm^{-2}, and the Doppl

Rupert A. C. Croft, Gavin B. Dalton, George Efstathiou, Will Sutherland

We analyse the spatial clustering properties of a new catalogue of very rich galaxy clusters selected from the APM Galaxy Survey. These clusters are of comparable richness and space density to Abell Richness Class $\geq 1$ clusters, but selected using an objective algorithm from a catalogue demonstrably free of artificial inhomogeneities. Evaluation of the t

Daniel Loss, David P. DiVincenzo

We propose a new implementation of a universal set of one- and two-qubit gates for quantum computation using the spin states of coupled single-electron quantum dots. Desired operations are effected by the gating of the tunneling barrier between neighboring dots. Several measures of the gate quality are computed within a newly derived spin master equation inc

A. Klemm, B. Lian, S. -S. Roan, S. -T. Yau

We investigate topological properties of Calabi-Yau fourfolds and consider a wide class of explicit constructions in weighted projective spaces and, more generally, toric varieties. Divisors which lead to a non-perturbative superpotential in the effective theory have a very simple description in the toric construction. Relevant properties of them follow just

E. I. Guendelman, Aleksey Nudelman

In this paper we use a non-covariant gauge which makes some of the YM features manifest which otherwise do not appear explicitly in the Landau gauge used by Nielsen and Olesen.We show, in fact, that the unstable mode which makes a large contribution to the vacuum energy is non-perturbative even classically.

Philip E. Gibbs

A covariant formula for conserved currents of energy, momentum and angular-momentum is derived from a general form of Noethers theorem applied directly to the Einstein-Hilbert action of classical general relativity. Energy conservation in a closed big-bang cosmology is discussed as a special case. Special care is taken to distinguish between kinematic and dy

Jordi Comellas, Alex Travesset

Using Wegner-Houghton equation, within the Local Potential Approximation, we study critical properties of O(N) vector models. Fixed Points, together with their critical exponents and eigenoperators, are obtained for a large set of values of N, including N=0 and N\to\infty. Polchinski equation is also treated. The peculiarities of the large N limit, where a l

O. A. Starykh, A. W. Sandvik, R. R. P. Singh

Combining high-temperature expansions with the recursion method and quantum Monte Carlo simulations with the maximum entropy method, we study the dynamics of the spin-1/2 Heisenberg chain at temperatures above and below the coupling J. By comparing the two sets of calculations, their relative strengths are assessed. At high temperatures, we find that there i

M. Dominik

For a given spatial distribution of the lenses and distribution of the transverse velocity of the lens relative to the line-of-sight, a probability distribution for the lens mass for a single observed event is derived. In addition, similar probability distributions are derived for the Einstein radius and the separation of the lens objects and their rotation

Anne Schilling, S. Ole Warnaar

$q$-Analogues of the coefficients of $x^a$ in the expansion of $\prod_{j=1}^N (1+x+...+x^j)^{L_j}$ are proposed. Useful properties, such as recursion relations, symmetries and limiting theorems of the ``$q$-supernomial coefficients'' are derived, and a combinatorial interpretation using generalized Durfee dissection partitions is given. Polynomial id

Ch. Helm, Ch. Preis, F. Forsthofer, J. Keller

The recently reported subgap structures observed in the current-voltage characteristic of intrinsic Josephson junctions in the high-T_c superconductors Tl_2Ba_2Ca_2Cu_3O_{10+δ} and Bi_2Sr_2CaCu_2O_{8+δ} are explained by the coupling between c-axis phonons and Josephson oscillations. A model is developed where c-axis lattice vibrations between adjacent superc

Lubos Motl

We show a possibility that the matrix models recently proposed to explain (almost) all the physics of M-theory may include the superstring theories that we know perturbatively. The ``1st quantized'' physical system of one IIA string seems to be an exact consequence of M(atrix) theory with a proper mechanism to mod out a symmetry. The central point of

A. Hucht, K. D. Usadel

We demonstrate that the reorientation transition from out-of-plane to in-plane magnetization with decreasing temperature as observed experimentally in Ni-films on Cu(001) can be explained on a microscopic basis. Using a combination of mean field theory and perturbation theory, we derive an analytic expression for the temperature dependent anisotropy. The red

S. James Gates,, Lubna Rana

By an explicit construction, it is shown that the geometry of the SU(3) pion multiplet with respect to the group manifold SU_L(3) x SU_R(3) maybe deformed to admit a second pseudoscalar multiplet that is analogous to the Z_0 in unified theories of the electroweak interactions. This observation is found to play a key role in the construction of the N = 1 supe

Jiyu Fang, Ellis Teer, Charles M. Knobler, Kok-Kiong Loh

Domains in Langmuir monolayers support a texture that is the two-dimensional version of the feature known as a boojum. Such a texture has a quantifiable effect on the shape of the domain with which it is associated. The most noticeable consequence is a cusp-like feature on the domain boundary. We report the results of an experimental and theoretical investig

Charilaos Aneziris

While the problem of knot classification is far from solved, it is possible to create computer programs that can be used to tabulate knots up to a desired degree of complexity. Here we discuss the main ideas on which such programs can be based. We also present the actual results obtained after running a computer program on which knots are denoted through reg

David A. Kessler, Herbert Levine

Spiral waves are a ubiquitous feature of the nonequilibrium dynamics of a great variety of excitable systems. In the limit of a large separation in timescale between fast excitation and slow recovery, one can reduce the spiral problem to one involving the motion of a free surface separating the excited and quiescent phases. In this work, we study the free su

Bengt Friman, H. J. Pirner

We study the $p$-wave polarization operator of the $ρ$-meson due to $ρN$ interactions via the $N^*$ (1720) and $Δ(1905)$ resonances and compute the corresponding production rate for $e^+e^-$-pairs at finite temperature and baryon density. At high baryon density we find a significant shift of the spectrum to lower invariant masses.

J. M. Pawlowski

We calculate within an algebraic Bjorken-Johnson-Low (BJL) method anomalous Schwinger terms of fermionic currents and the Gauss law operator in chiral gauge theories. The current algebra is known to violate the Jacobi identity in an iterative computation. Our method takes the subtleties of the equal-time limit into account and leads to an algebra that fulfil

N. S. Manton

A non-dissipative model for vortex motion in thin superconductors is considered. The Lagrangian is a Galilean invariant version of the Ginzburg--Landau model for time-dependent fields, with kinetic terms linear in the first time derivatives of the fields. It is shown how, for certain values of the coupling constants, the field dynamics can be reduced to firs

V. I. Shevchenko, Yu. A. Simonov

Exact relations between gauge-invariant vacuum correlators in QCD are derived. Derivatives of the correlators are expressed in terms of higher orders correlators. The behaviour of the correlators at large and small distances due to these relations is discussed.

T. P. Cheng, Ling-Fong Li

The chiral quark model with a nonet of Goldstone bosons can yield an adequate description of the observed proton flavor and spin structure. In a previous publication we have compared the results of a SU(3) symmetric calculation with the phenomenological findings based on experimental measurements and SU(3) symmetry relations. In this paper we discuss their S

M. Klasen, G. Kramer

We have calculated jet shapes in low $Q^2$ $ep$ and $p\overline{p}$ collisions in perturbation theory at order $α_s^3$ for the hard parton-parton processes. For the $γp$ process resolved and direct contributions are superimposed. The dependence of the jet shapes on transverse energy, rapidity, and inner cone extension is studied. The numerical results of the

Silvano Bonazzola, Patrick Peter

A simple model is exhibited in which the remnant density of charged vortons is used to provide candidates for explaining the observed ultra high energy cosmic rays (above $10^{20}$ eV). These vortons would be accelerated in active galaxies and propagated through intergalactic medium with negligible losses of energy. The expected number density of observable

Odd Magne Ogreid

The sensitivity of various angular and energy distributions to the CP of a Higgs candidate are considered for the process $e^-e^- -> e^-e^-h$, where h is either a scalar or a pseudoscalar Higgs. This process may differ from the corresponding production at an $e^+e^-$ collider in the availability of both beams being polarized. Beam polarization enhances the s

Andre de Gouvea, Takeo Moroi, Hitoshi Murayama

We study the cosmology of supersymmetric models in which the supersymmetry breaking effects are mediated by gauge interactions at about the 10^5 GeV scale. We first point out that the gravitino is likely to overclose the Universe in this class of models. This requires an entropy production, which prefers a baryogenesis mechanism at a relatively low temperatu

M. Teper

We show that SU(N) gauge theories in 2+1 dimensions are close to N=\infty for N \geq 2. The dimensionful coupling, g^2, is proportional to 1/N, at large N, confirming the usual diagram-based expectation. Preliminary calculations in 3+1 dimensions indicate that the same is true there.

M. Teper

We compare the mass spectra and string tensions of SU(2), SU(3) and SU(4) gauge theories in 2+1 dimensions. We find that the ratios of masses are, to a first approximation, independent of N and that the remaining dependence can be accurately reproduced by a simple O(1/N^2) correction. This provides us with a prediction of these mass ratios for all SU(N) theo

M. W. Wu, E. M. Conwell

The field-effect mobility of hole polarons in $α$-sexithiophene, measured in thin film transistors, was shown to be well fitted by Holstein's small polaron theory. Unfortunately, Holstein's formulation is based on an integral that does not converge. We show that the data are well fitted by a theory of polaron transport that was successful in accounti

Karlo Penc, Karen Hallberg, Frederic Mila, Hiroyuki Shiba

We give the details of the calculation of the spectral functions of the 1D Hubbard model using the spin-charge factorized wave-function for several versions of the U -> +\infty limit. The spectral functions are expressed as a convolution of charge and spin dynamical correlation functions. A procedure to evaluate these correlation functions very accurately fo

S. Luding

We present simulations of static model sandpiles in two dimensions (2D) and focus on the stress distribution in such arrays made of discrete particles. We use the simplest possible model, i.e. spherical particles with a linear spring and a linear dashpot active on contact and without any frictional forces. Our model is able to reproduce several recent theore

P. Singha Deo

We take a negative delta function impurity in one arm of a quasi one dimensional Aharonov-Bohm ring and demonstrate abrupt phase changes across a quasi bound state of the negative delta function potential. We give a new mechanism for conductance oscillations with the strength of the negative delta potential. We also show that coupling to evanescent modes can

Fabio Siringo

A simple d-dimensional lattice model is proposed, incorporating some degree of frustration and thus capable of describing some aspects of molecular orientation in covalently bound molecular solids. For d=2 the model is shown to be equivalent to the standard two-dimensional Ising model, while for d>2 it describes a peculiar transition from an isotropic high t

W. R. Czart, T. Kostyrko, S. Robaszkiewicz

We study the basic thermodynamic and electromagnetic properties of the superconductor described by the negative-$U$ Hubbard model (gap parameter $Δ$, critical temperature $T_c$, London penetration depth $λ$, thermodynamic critical field $H_c$ and Ginzburg-Landau correlation length $ξ_{G-L}$).The calculations are performed for square (SQ, d=2), simple cubic (

David Lancaster, Giorgio Parisi

On the basis of long simulations of a binary mixture of soft spheres just below the glass transition, we make an exploratory study of the activated processes that contribute to the dynamics. We concentrate on statistical measures of the size of the activated processes.

Th. M. Nieuwenhuizen

The glass transition is considered within two toys models, a mean field spin glass and a directed polymer in a correlated random potential. In the spin glass model there occurs a dynamical transition, where the system condenses in a state of lower entropy. The extensive entropy loss, called complexity or information entropy, is calculated by analysis of the

Daniel Hone, A. H. Castro Neto

We study the properties of generalized striped phases of doped cuprate planar quantum antiferromagnets. We invoke an effective, spatially anisotropic, non-linear sigma model in two space dimensions. Our theoretical predictions are in quantitative agreement with recent experiments in La_{2-x}Sr_xCuO_4 with $0 \leq x \leq 0.018$. We focus on (i) the magnetic c

K. A. Matveev, A. I. Larkin

We study the superconductivity in small grains in the regime when the quantum level spacing $δ\varepsilon$ is comparable to the gap $Δ$. As $δ\varepsilon$ is increased, the system crosses over from superconducting to normal state. This crossover is studied by calculating the dependence of the ground state energy of a grain on the parity of the number of elec

Ann A. Esin

We consider non-local effects which arise when radiation emitted at one radius of an accretion disk either heats or cools gas at other radii through Compton scattering. We discuss three situations: 1. Radiation from the inner regions of an advection-dominated flow Compton cooling gas at intermediate radii and Compton heating gas at large radii. 2. Soft radia

M. R. Zapatero Osorio, E. L. Martin, R. Rebolo

We have obtained near-IR observations of some of the faintest objects so far known towards the Pleiades cluster, with the aim of investigating the sequence that connects cluster very low-mass (VLM) stars with substellar objects. We find that IR data combined with optical magnitudes are a useful tool to discriminate cluster members from foreground/background

Simon F. Portegies Zwart, Frank Verbunt, Ene Ergma

We calculate the formation rates of low-mass X-ray binaries with a black hole. Both a semi-analytic and a more detailed model predict formation rates two orders of magnitude lower than derived from the observations. Solution of this conundrum requires either that stars with masses less than 20M$_\odot$ can evolve into a black hole, or that stellar wind from

A. Vazdekis, R. F. Peletier, J. E. Beckman, E. Casuso

We present here the results of applying a new chemo-evolutionary stellar population model developed by ourselves in a previous paper (Vazdekis et al. 1996) to new high quality observational data of the nuclear regions of two representative elliptical galaxies and the bulge of the Sombrero galaxy. Here we fit in detail about 20 absorption lines and 6 optical

Antonaldo Diaferio, Margaret J. Geller

In hierarchical clustering, galaxy clusters accrete mass through the aggregation of smaller systems. Thus, the velocity field of the infall regions of clusters contains significant random motion superimposed on radial infall. Because the purely spherical infall model does not predict the amplitude of the velocity field correctly, methods estimating the cosmo

S. W. Allen, A. C. Fabian, E. Idesawa, H. Inoue

We report the results from an ASCA X-ray observation of the powerful Broad Line Radio Galaxy, 3C109. The ASCA spectra confirm our earlier ROSAT detection of intrinsic X-ray absorption associated with the source. The absorbing material obscures a central engine of quasar-like luminosity. The luminosity is variable, having dropped by a factor of two since the

Jon Bell

General relativity asserts that: energy and momentum conservation laws are valid, preferred frames do not exist, and the strong equivalence principle is obeyed. In this paper recent progress in testing these important principles using millisecond pulsars is summarised.

Andrew R Liddle, Ian J Grivell

Cosmic microwave anisotropy satellites promise extremely accurate measures of the amplitude of perturbations in the universe. We use a numerical code to test the accuracy of existing approximate expressions for the amplitude of perturbations produced by single-field inflation models. We find that the second-order Stewart-Lyth calculation gives extremely accu

Craig Sosin, Ivan R. King

Using the Faint Object Camera on the repaired Hubble Space Telescope, we have observed two fields in the globular cluster M15: the central density cusp, and a field at r = 20''. These are the highest-resolution images ever taken of this cluster's dense core, and are the first to probe the distribution of stars well below the main-sequence turnoff

Ricardo Garcia, Andras Nemethi

Given a polynomial map $f:\Bbb C^{n+1}\to\Bbb C$, one can attach to it a geometrical variation of mixed Hodge structures (MHS) which gives rise to a limit MHS. The equivariant Hodge numbers of this MHS are analytical invariants of the polynomial map and reflect its asymptotic behaviour. In this paper we compute them for a class of generic polynomials, in ter

A. N. Ramaprakash, Ranjan Gupta, A. K. Sen, S. N. Tandon

Taking advantage of the advances in array detector technology, an imaging polarimeter (IMPOL) has been constructed for measuring linear polarization in the wavelength band from 400-800 nm. It makes use of a Wollaston prism as the analyser to measure simultaneously the two orthogonal polarization components that define a Stoke's parameter. An achromatic h

Markus Finkemeier, Howard Georgi, Matt McIrvin

Reparameterization invariance, a symmetry of heavy quark effective theory, appears in different forms in the literature. The most commonly cited forms of the reparameterization transformation are shown to induce the same constraints on operators that do not vanish under the equation of motion to order $1/m^2$, and to be related by a redefinition of the heavy

F. T. Brandt, J. Frenkel

We calculate, to one-loop order, the ln (T) contributions of 3-point functions in the ϕ^3 and Yang-Mills theory at high temperature. We find that these terms are Lorentz invariant and have the same structure as the ultraviolet divergent contributions which occur at zero temperature. A simple argument, valid for all N-point Green functions, is given for this

C. Bachas

This is a concise foreword to, rather than a review of D-brane physics.

R. S. Thorne

We present calculations of the structure functions F_2(x,Q^2) and F_L(x,Q^2), concentrating on small x. After discussing the standard expansion of the structure functions in powers of α_s(Q^2) we consider a leading-order expansion in ln(1/x) and finally an expansion which is leading order in both ln(1/x) and α_s(Q^2), and which we argue is the only really co

Ivan G. Avramidi, G. Esposito

The quantization of gauge fields and gravitation on manifolds with boundary makes it necessary to study boundary conditions which involve both normal and tangential derivatives of the quantized field. The resulting one-loop divergences can be studied by means of the asymptotic expansion of the heat kernel, and a particular case of their general structure is

B. Alles, A. Buonanno, G. Cella

By using the results of a high-statistics (O(10^7) measurements) Monte Carlo simulation we test several predictions of perturbation theory on the O(n) non-linear sigma-model in 2 dimensions. We study the O(3) and O(8) models on large enough lattices to have a good control on finite-size effects. The magnetic susceptibility and three different definitions of

T. W. B. Kibble, G. Lozano, A. J. Yates

We examine current-carrying configurations of cosmic strings in non-Abelian gauge theories. We study the solutions numerically and point out that the currents will be at best dynamically stable and not subject to any topological quantisation or conservation, as in conventional models of string superconduction. We suggest that non-Abelian string loops may be

Patricia Ball, V. M. Braun

The existing calculations of the form factors describing the decay $B\toρe ν$ from QCD sum rules have yielded conflicting results at small values of the invariant mass squared of the lepton pair. We demonstrate that the disagreement originates from the failure of the short-distance expansion to describe the $ρ$ meson distribution amplitude in the region wher

D. Jaksch, C. W. Gardiner, P. Zoller

We present results of simulations of a em quantum Boltzmann master equation (QBME) describing the kinetics of a dilute Bose gas confined in a trapping potential in the regime of Bose condensation. The QBME is the simplest version of a quantum kinetic master equations derived in previous work. We consider two cases of trapping potentials: a 3D square well pot

Subhendra Mohanty, A. R. Prasanna

We derive the wave equation obeyed by electromagnetic fields in curved spacetime. We find that there are Riemann and Ricci curvature coupling terms to the photon polarisation which result in a polarisation dependent deviation of the photon trajectories from null geodesics. Photons are found to have an effective mass in an external gravitational field and the

Tsung-Wen Yeh, Hsiang-nan Li

The nonleptonic heavy meson decays $B\to D^{(*)}π(ρ), J/ψK^{(*)}$ and $D\to K^{(*)}π$ are studied based on the three-scale perturbative QCD factorization theorem developed recently. In this formalism the Bauer-Stech-Wirbel parameters a_1 and a_2 are treated as the Wilson coefficients, whose evolution from the W boson mass down to the characteristic scale of

Mario Vietri

I consider the recent discovery of a soft X-ray source inside the error box of the gamma ray burst GB 960720 by the SAX, ASCA and ROSAT satellites, in terms of the fireball model. I show that the ejecta shell, which, after causing the burst is cold and dense, but still relativistic, keeps plowing through the interstellar medium, heating up the just-shocked m

H. R. Karadayi, M. Gungormez

It is shown, for any irreducible representation of $E_8$ Lie algebra, that eigenvalues of Casimir operators can be calculated in the form of invariant polinomials which are decomposed in terms of $A_8$ basis functions. The general method is applied for degrees 8,12 and 14 for which 2,8 and 19 invariant polinomials are obtained respectively. For each particul

A. R. Prasanna, Sai Iyer

The Cumulative Drag Index defined recently by Prasanna has been generalised to include the centrifugal acceleration. We have studied the behaviour of the drag index for the Kerr metric and the Neugebauer-Meinel metric representing a self-gravitating rotating disk and their Newtonian approximations. The similarity of the behaviour of the index for a given set

Tomohiro Matsuda

The Higgs mixing term coefficient $μ$ is calculated in the supersymmetric theory which possesses a non-anomalous $U(1)_{R}$ symmetry in the limit of global supersymmetry. In this model, supersymmetry is assumed to be broken by gaugino condensation in the hidden sector when the supergravity effects are turned on. The soft breaking terms in the visible sector

A. M. Lallena

The role of the meson-exchange current correction to the nuclear charge operator is studied in electron scattering processes involving the excitation of medium and heavy nuclei to energies up to the quasi-elastic peak. The effect of these contributions in the quasi-free electron scattering process is a reduction of at most a 3% in the longitudinal response a

S. A. Gurvitz

We show that parton confinement in the final state generates large $1/Q^2$ (higher twist) corrections to Bjorken scaling. For treatment of these non-perturbative effects, we derive a new expansion in powers of $1/Q^2$ for the structure function that is free of infra-red singularities and which reduces corrections to the leading term. The leading term represe

H. Sorge

Transverse expansion of centrally produced matter in Pb on Pb collisions at beam energies around 158 AGeV appears to be rather `soft'. Two possible reasons -- an extended preequilibrium stage and a first order phase transition from a quark-gluon-plasma into hadronic matter -- are discussed. The softening of transverse expansion caused by preequilibrium d

A. Leclair, F. Lesage, S. Lukyanov, H. Saleur

In this letter, the problem of radiation in a fiber geometry interacting with a two level atom is mapped onto the anisotropic Kondo model. Thermodynamical and dynamical properties are then computed exploiting the integrability of this latter system. We compute some correlation functions, decay rates and Lamb shifts. In turn this leads to an analysis of the c

Peter Cho

We investigate the confining phase vacuum structure of supersymmetric SO(11) gauge theories with one spinor matter field and Nf \le 6 vectors. We describe several useful tricks and tools that facilitate the analysis of these chiral models and many other theories of similar type. The forms of the Nf=5 and Nf=6 quantum moduli spaces are deduced by requiring th

A. Bassetto, G. Nardelli, A. Shuvaev

We obtain a formal solution of an integral equation for $q\bar q$ bound states, depending on a parameter ηwhich interpolates between 't Hooft's (η=0) and Wu's (η=1) equations. We also get an explicit approximate expression for its spectrum for a particular value of the ratio of the coupling constant to the quark mass. The spectrum turns out to be

Robert Konik, Andre LeClair

We examine harmonic oscillator defects coupled to a photon field in the environs of an optical fiber. Using techniques borrowed or extended from the theory of two dimensional quantum fields with boundaries and defects, we are able to compute exactly a number of interesting quantities. We calculate the scattering S-matrices (i.e. the reflection and transmissi

Eric Braaten, Yu-Qi Chen

Contributions to the decay rates of P-wave charmonium states that are proportional to $n_f α_s^3$, where $n_f$ is the number of flavors of light quarks, are calculated in the framework of nonrelativistic QCD using the threshold expansion method. Dimensional regularization is used to regularize the infrared divergences that arise from the emission of a soft g

L. Houra-Yaou, P. Kessler, J. Parisi, F. Murgia

We present a formalism for studying the exclusive production or decay of mesons with any value of the internal orbital angular momentum L. As an application, we discuss the production of meson pairs (involving tensor and pseudotensor mesons) in photon-photon collisions.

Mariana Kirchbach, Andreas Wirzba

Two-point functions related to the pion weak decay constant f_πare calculated from the generating functional of chiral perturbation theory in the mean-field approximation and the heavy-baryon limit. The aim is to demonstrate that Lorentz invariance is violated in the presence of background matter. This fact manifests itself in the splitting of both f_πand th

E. Gotsman, E. Levin, U. Maor

The measured forward slope in elastic and inelastic leptoproduction of vector mesons differ by a substantial amount. In an attempt to describe this phenomenon we construct a two radii model for the target proton, and estimate the effective parameters of the hard Pomeron obtained from a pQCD dipole model with eikonal shadowing corrections (SC). We show that t

Pyungwon Ko, Jungil Lee, H. S. Song

The inclusive D-wave charmonium production rates in B decays are considered in the Bodwin-Braaten-Lepage (BBL) approach. We find that the color-octet subprocesses B->cc_(^3S_1^(8) or ^3P_J^(8))+s,d, followed by the transition cc_(^3S_1^(8) or ^3P_J^(8)) -> ^3D_J, strongly dominate over any other subprocess, due to the large Wilson coefficient for the ΔB = 1

Hai-Yang Cheng

In the heavy quark limit, there are three independent strong axial coupling constants in chiral Lagrangians for ground-state heavy hadrons: g in the meson sector, and g_1, g_2 in the baryon sector. The coupling g_2 is extracted from recent CLEO measurements of $Σ_c^*\toΛ_cπ$ to be $|g_2|=0.57\pm 0.10$, in agreement with the nonrelativistic quark model expect

Jeroen Snippe

We compute the one-loop coefficients for an alternative Symanzik improved pure gauge SU{N} lattice action (N=2 and N=3). For the standard Symanzik improved action we confirm previous results by Lüscher and Weisz.

Matthew W. Choptuik, Eric W. Hirschmann, Steven Liebling

We investigate the stability of a family of spherically symmetric static solutions in vacuum Brans-Dicke theory (with $ω=0$) recently described by van Putten. Using linear perturbation theory, we find one exponentially growing mode for every member of the family of solutions, and thus conclude that the solutions are not stable. Using a previously constructed

Anshu Gupta, Sai Iyer, A. R. Prasanna

We have evaluated the centrifugal force acting on a fluid element and the ellipticity of the fluid configuration, which is slowly rotating, using the Hartle-Thorne solution for different equations of state. The centrifugal force shows a maximum in every case, whereas the reversal in sign could be seen in only one case, and the system becomes unstable in othe

Weiping Li

We prove the Chern-Weil formula for SU(n+1)-singular connections over the complement of an embedded oriented surface in smooth four manifolds. The expression of the representation of a number as a sum of nonvanishing squares is given in terms of the representations of a number as a sum of squares. Using the number theory result, we study the irreducible SU(n

Boris Fain, Joseph Rudnick

We examine the elastic model of short circular DNA. We obtain analytic expressions for configurations, elastic energy, twist and linking number of our solutions. We find the onset of the plectonemic transition. We suggest ways to use our formalism to describe other elastic models, and to improve the current finite-element-analysis methods. We estimate the ef

David C. Dixon, Keith R. Wald, Paul L. McEuen, M. R. Melloch

We have used gated GaAs/AlGaAs heterostructures to explore nonlinear transport between spin-resolved Landau level (LL) edge states over a submicron region of two-dimensional electron gas (2DEG). The current I flowing from one edge state to the other as a function of the voltage V between them shows diode-like behavior---a rapid increase in I above a well-def

Klaus Ziegler, Alok Shukla

We consider the Bose-Einstein condensation of atoms in a trap where the density of particles is so high that the low density approach of Gross and Pitaevskii will not be applicable. For this purpose we use the slave boson representation which is valid for hard-core bosons at any density. This description leads to the same results as the Gross-Pitaevskii appr

Yan. V. Fyodorov, H. -J. Sommers

Assuming the validity of random matrices for describing the statistics of a closed chaotic quantum system, we study analytically some statistical properties of the S-matrix characterizing scattering in its open counterpart. In the first part of the paper we attempt to expose systematically ideas underlying the so-called stochastic (Heidelberg) approach to ch

A. Aldea, P. Gartner, A. Manolescu, M. Nita

The spectrum and the eigenstates of a finite 2D tight-binding electronic system, with Dirichlet boundary conditions, in magnetic field and external linear potential are studied. The eigenstates show an equipotential character and may cross the plaquette in the direction perpendicular to the electric field. When leads are added to the plaquette, the channels

C. N. A. van Duin, J. Zaanen

The bilayer Heisenberg antiferromagnet is known to exhibit a quantum-critical transition at a particular value of the inter-layer coupling. Using a new type of coherent state, appropriate to the special order parameter structure of the bilayer, we map the problem onto the quantum non-linear sigma model. It is found that the bare coupling constant diverges at

Giorgio Parisi

In these lectures I will study some properties that are shared by many glassy systems. I will shown how some of these properties can be understood in the framework of the mean field approach based on the replica method and I will discuss which are the difficulties which we have to face when we apply the replica method to realistic short range models. We fina

Silvio Franz, Giorgio Parisi

We study the mean-field phase diagram of glassy systems in a field pointing in the direction of a metastable state. We find competition among a ``magnetized'' and a ``disordered'' phase, that are separated by a coexistence line as in ordinary first order phase transitions. The coexistence line terminates in a critical point, which in principl

Giorgio Parisi

I present here some results on the statistical behaviour of large random matrices in an ensemble where the probability distribution is not a function of the eigenvalues only. The perturbative expansion can be cast in a closed form and the limits of validity of this expansion are carefully analyzed. A comparison is done with a similar model with quenched diso