September 1997 arXiv papers — page 10

Kenneth M. Lanzetta, Alberto Fernandez-Soto, Amos Yahil

We describe our application of broad-band photometric redshift techniques to faint galaxies in the Hubble Deep Field. To magnitudes AB(8140) < 26, the accuracy of the photometric redshifts is a few tenths and the reliability of the photometric redshifts approaches 100%. At fainter magnitudes the effects of photometric error on the photometric redshifts can b

D. M. Worrall

There is good evidence for X-ray emission associated with AGN jets which are relativistically boosted towards the observer. But to what jet radius does such X-ray emission persist? To attempt to answer this question one can look at radio galaxies; their cores are sufficiently X-ray faint that any unbeamed X-ray emission in the vicinity of the central engine

G. Leyshon

Many different methods exist for reducing data obtained when an astronomical source is studied with a two-channel polarimeter, such as a Wollaston prism system. This paper presents a rigorous method of reducing the data from raw aperture photometry, and evaluates errors both by a statistical treatment, and by propagating the measured sky noise from each fram

Cedric Lacey, Carlton Baugh, Shaun Cole, Carlos Frenk

I describe a semi-analytical model for the formation and evolution of galaxies in hierarchical clustering models, and its predictions for the properties of the galaxy population at high z. The predictions are found to agree well with the observed properties of the Lyman break galaxies found at z sim 3 by Steidel et al. The models predict that the star format

V. G. Klochkova, E. L. Chentsov, V. E. Panchuk

To understand the evolutionary stage of the peculiar supergiant IRC+10420, we have been taking spectra for several years at the 6m telescope. The optical spectrum of IRC+10420 of the years from 1992 through 1996 points to the increase in the temperature: spectral class A5 instead of the former F8, as was pointed out by Humpreys et al., (1973). Now it resembl

Vladimir Masek

Let M be a Q-divisor on a smooth surface over C. In this paper we give criteria for very ampleness of the adjoint of the round-up of M. (Similar results for global generation were given by Ein and Lazarsfeld and used in their proof of Fujita&#39;s Conjecture in dimension 3.) In the last section we discuss an example which suggests that this kind of criteria

Vladimir Masek

We study a useful numerical invariant of normal surface singularities, introduced recently by T. Kawachi. Using this invariant, we give a quick proof of the (well-known) fact that all log-canonical surface singularities are either elliptic Gorenstein or rational (without assuming a priori that they are Q-Gorenstein). The main result is a criterion (stated in

A. A. Tseytlin

We review some tests of the 0-brane and instanton matrix models based on comparing long-distance interaction potentials between branes and their bound states (with 1/2,1/4 or 1/8 of supersymmetry) in supergravity and in super Yang-Mills descriptions. We first consider the supergravity-SYM correspondence at the level of the leading term in the interaction pot

Dennis P. Clougherty, Frederick G. Anderson

A pseudo-Jahn-Teller model describing central atom distortions is proposed for endohedral fullerenes of the form A@C$_{60}$ where A is either a rare gas or a metal atom. A critical (dimensionless) coupling $g_c$ is found, below which the symmetric configuration is stable and above which inversion symmetry is broken. Vibronic parameters are given for selected

R. Moessner, Bhuvnesh Jain

The angular cross-correlation between two galaxy samples separated in redshift is shown to be a useful measure of weak lensing by large-scale structure. Angular correlations in faint galaxies arise due to spatial clustering of the galaxies as well as gravitational lensing by dark matter along the line-of-sight. The lensing contribution to the 2-point auto-co

Guy D. Moore

We compute the matching conditions between lattice and continuum 3-D SU(N) Higgs theories, with both adjoint and fundamental scalars, at O(a), except for additive corrections to masses and Higgs field operator insertions.

Philip Phillips, Yi Wan, Ivar Martin, Sergey Knysh

In a series of recent experiments, Kravchenko and colleagues observed unexpectedly that a two-dimensional electron gas in zero magnetic field can be a conductor. The two-dimensionality was imposed by confining the electron gas to move laterally at the interface between two semiconductors. The observation of a conductor in two dimensions (2D) is surprising as

P. Nason, C. Oleari

In this paper we describe the calculation of the process e+e- -> Z/gamma -> QQbar + X, where Q is a heavy quark, at order alpha_s^2.

I. Jack, D. R. T. Jones

We present an elegant exact formula for the gaugino $β$-function in a softly-broken supersymmetric gauge theory, of the form $β_M = {\cal O}(β_g/g)$, where $β_g$ is the gauge $β$ function and ${\cal O}$ is a simple differential operator acting on the gauge coupling $g$ and the Yukawa coupling.

P. Quemerais, S. Fratini

Considering the long range Coulomb interactions between large polarons in dielectrics, we propose a model for their crystallization when no bipolarons are formed. As the density increases, the melting is examined at $T=OK$. One possibility is the delocalization towards a liquid state of polarons. However, we show that this cannot happen if the electron-phono

Y. Hanein, U. Meirav, D. Shahar, C. C. Li

We report on a zero magnetic field transport study of a two-dimensional, variable-density, hole system in GaAs. As the density is varied we observe, for the first time in GaAs-based materials, a crossover from an insulating behavior at low-density, to a metallic-like behavior at high-density, where the metallic behavior is characterized by a large drop in th

E. Mukhin, A. Varchenko

We consider the quantized Knizhnik-Zamolodchikov difference equation (qKZ) with values in a tensor product of irreducible sl(2) modules, the equation defined in terms of rational R-matrices. We solve the equation in terms of multidimensional q-hypergeometric integrals. We identify the space of solutions of the qKZ equation with the tensor product of the corr

J. W. F. Valle

The present observational status of neutrino physics is sketched, with emphasis on the hints that follow from solar and atmospheric neutrino observations, as well as dark matter. I also briefly review the ways to account for the observed anomalies and some of their implications

Nathan Berkovits

Using linearized superfields, $R^4$ terms in the Type II superstring effective action compactified on $T^2$ are constructed as integrals in N=2 D=8 superspace. The structure of these superspace integrals allows a simple proof of the $R^4$ non-renormalization theorems which were first conjectured by Green and Gutperle.

B. Badełek, J. Kwieciński

A unified equation for the non-singlet spin dependent structure function $g_1^{ns}(x,Q^2)$ which incorporates the complete leading order Altarelli-Parisi evolution at finite $x$ and double logarithmic $ ln^2(1/x)$ effects at $x \to 0$ is formulated. The solution of this equation reasonably agrees with the recent data obtained by the Spin Muon Collaboration.

Andrea Brignole, Ferruccio Feruglio, Fabio Zwirner

If the gravitino is light and all the other supersymmetric particles are heavy, we can consider the effective theory describing the interactions of its goldstino components with ordinary matter. To discuss the model-dependence of these interactions, we take the simple case of spontaneously broken supersymmetry and only two chiral superfields, associated with

E864 Collaboration, T. A. Armstrong et al

We present the first results from the E864 collaboration on the production of antiprotons in 10% central 11.5 A GeV/c Au+Pb nucleus collisions at the Brookhaven AGS. We report invariant multiplicities for antiproton production in the kinematic region 1.4<y<2.2 and 50<p_T<300 MeV/c, and compare our data with a first collision scaling model and previously publ

S. Capitani, M. Goeckeler, R. Horsley, H. Perlt

We derive bases of improved operators for all bilinear quark currents up to spin two (including the operators measuring the first moment of DIS Structure Functions), and compute their one-loop renormalization constants for arbitrary coefficients of the improvement terms. We have thus control over O(a) corrections, and for a suitable choice of improvement coe

UA8 Collaboration, A. Brandt, J. B. Cheze, S. Erhan

The UA8 experiment previously reported the observation of jets in diffractive events containing leading protons (``hard diffraction&#39;&#39;), which was interpreted as evidence for the partonic structure of an exchanged Reggeon, believed to be the Pomeron . In the present Letter, we report the final UA8 hard-diffractive (jet) cross section results and their

Enrico Carlon, Andrzej Drzewinski

The properties of a fluid, or Ising magnet, confined in a $L \times \infty$ geometry with opposing surface fields at the walls are studied by density matrix renormalization techniques. In particular we focus on the effect of gravity on the system, which is modeled by a bulk field whose strength varies linearly with the distance from the walls. It is well kno

M. Grigorescu

The Brownian dynamics of the density operator for a quantum system interacting with a classical heat bath is described using a stochastic, non-linear Liouville equation obtained from a variational principle. The environment&#39;s degrees of freedom are simulated by classical harmonic oscillators, while the dynamical variables of the quantum system are two no

A. J. Schofield, J. R. Cooper

We present a theoretical study of the orbital magnetoresistance in a unixial anisotropic metal within the relaxation-time approximation. The appearance of a new dimensionless scale, delta=4t_perp/epsilon_F, allows the possibility of a new region at intermediate fields where the magnetoresistance is linear in applied magnetic field for currents flowing along

Masanori Kohno

We consider two aspects of the ground state of the $U=\infty$ Hubbard ladder: ferromagnetism and the metal-insulator transition at quarter-filling. First, we present rigorous results for the $U=\infty$ Hubbard ladder in the limit of the large inter-chain hopping ($t_{\perp}/t\to\infty$). In this limit, the total spin $S$ of the ground state is shown to be ze

Aiichi Iwazaki

The paper has been withdrawm. A completely new version on oscillating axionic boson stars will appear.

Kei-ichi Kondo

Starting from SU(2) Yang-Mills theory in 3+1 dimensions, we prove that the abelian-projected effective gauge theories are written in terms of the maximal abelian gauge field and the dual abelian gauge field interacting with monopole current. This is performed by integrating out all the remaining non-Abelian gauge field belonging to SU(2)/U(1). We show that t

Naoya Takahashi, Tsutomu Kambe, Tohru Nakano, Toshiyuki Gotoh

Two conditional averages for the increment Delta(x,x+r) = T(x)-T(x+r) of the scalar field are estimated for DNS data: H(Delta)=<nabla^2 Delta(x,x+r)|Delta(x,x+r)> and G(Delta)=<|nabla Delta(x,x+r)|^2| Delta(x,x+r)>. The probability density function P(Delta) for Delta(x,x+r) is also calculated. If Delta, P(Delta), H(Delta), and G(Delta) are expressed as theta

Stephen P. Martin

I provide a pedagogical introduction to supersymmetry. The level of discussion is aimed at readers who are familiar with the Standard Model and quantum field theory, but who have had little or no prior exposure to supersymmetry. Topics covered include: motivations for supersymmetry, the construction of supersymmetric Lagrangians, superspace and superfields,

Juan M. Maldacena

We consider a brane moving close to a large number of coincident branes. We compare the calculation of the effective action using the gauge theory living on the brane and the calculation using the supergravity approximation. We discuss some general features about the correspondence between large N gauge theories and black holes. Then we do a one loop calcula

M. Schvellinger

Recent developments in the density dependence of the MIT bag radius and parameters in nuclear matter are discussed. Starting from the MIT bag lagrangian density, the calculations are specialized for symmetric homogeneous isotropic nuclear matter. A simultaneous description of the density dependence of MIT bag model is derived from the Quantum Hadrodynamics a

L. Faccioli, F. Finelli, G. P. Vacca, G. Venturi

The identification of the particle creation and distruction operators is discussed.

S. Majid

We formulate quantum group Riemannian geometry as a gauge theory of quantum differential forms. We first develop (and slightly generalise) classical Riemannian geometry in a self-dual manner as a principal bundle frame resolution and a dual pair of canonical forms. The role of Levi-Civita connection is naturally generalised to connections with vanishing tors

Xin-Min Hua

Comptonization is the process in which photon spectrum changes due to multiple Compton scatterings in the electronic plasma. It plays an important role in the spectral formation of astrophysical X-ray and gamma-ray sources. There are several intrinsic limitations for the analytical method in dealing with the Comptonization problem and Monte Carlo simulation

G. N. Throumoulopoulos

The equilibrium of a resistive axisymmetric plasma with purely toroidal flow surrounded by a conductor is investigated within the framework of the nonlinear magnetohydrodynamic theory. It is proved that a) the poloidal current density vanishes and b) apart from an idealized case the pressure profile should vanish on the plasma boundary. For the cases of isot

Daniel S. Koltun

Conventional theories of nuclear interactions predict a net increase in the distribution of virtual pions in nuclei relative to free nucleons. Analysis of data from several nuclear experiments has led to claims of evidence against such a pion excess. These conclusions are usually based on a collective theory (RPA) of the pions, which may be inadequate. The i

W. Cassing, Z. Rudy, L. Jarczyk, B. Kamys

We study the production of $Λ$ hyperons in $p + A$ reactions on the basis of a BUU transport approach from 1.1 to 1.9 GeV and evaluate the properties of the hypernuclei produced in particular with respect to their momentum distribution in the laboratory frame. Due to elastic $ΛN$ scattering large cross sections for the production of heavy hypernuclei in the

LSND Collaboration, C. Athanassopoulos, L. B. Auerbach, R. L. Burman

A search for nu_mu -> nu_e oscillations has been conducted with the LSND apparatus at the Los Alamos Meson Physics Facility. Using nu_mu from pi^+ decay in flight, the nu_e appearance is detected via the charged-current reaction C(nu_e,e^-)X. Two independent analyses observe a total of 40 beam-on high-energy electron events (60 < E_e < 200 MeV) consistent wi

Jasper Scholten

By the Mordell-Weil theorem the group of Q(z)-rational points of an elliptic curve is finitely generated. It is not known whether the rank of this group can get arbitrary large as the curve varies. Mestre and Nagao have constructed examples of elliptic curves E with rank at least 13. In this paper a method is explained for finding a 14th independent point on

Ramzi R. Khuri

We discuss the role of string solitons in duality and examine the feature of compositeness, which allows for the interpretation of general solutions as bound states of supersymmetric fundamental constituents. This feature lies at the heart of the recent success of string theory in reproducing the Bekenstein-Hawking black hole entropy formula. Talk given at 1

Esko Keski-Vakkuri, Per Kraus

We propose a formula for the effective action of Matrix Theory which succesfully reproduces a large class of Born-Infeld type D-brane probe actions. The formula is motivated by demanding consistency with known results, and is tested by comparing with a wide range of source-probe calculations in supergravity. In the case of D0-brane sources and Dp-brane probe

Valeri V. Dvoeglazov

On the basis of the first principles we argue that self/anti-self charge conjugate states of the (1/2,0)+(0,1/2) representation can possess the axial charge. Finally, we briefly discuss recent claims of the \sim \vec σ\cdot [ \vec A \times \vec A^\ast ] interaction term for the particles of this representation.

Valeri V. Dvoeglazov

Gauge transformations of type-II spinors are considered in the Majorana-Ahluwalia construct for self/anti-self charge conjugate states. Some speculations on the relations of this model with the earlier ones are given.

A. A. Bytsenko, A. E. Goncalves, F. L. Williams

We compute the one-loop effective action and the conformal anomaly associated with the product $\bigotimes_p{\cal L}_p$ of the Laplace type operators ${\cal L}_p, p=1,2$, acting in irreducible rank 1 symmetric spaces of non-compact type. The explicit form of the zeta functions and the conformal anomaly of the stress-energy momentum tensor is derived.

Ofer Aharony, Micha Berkooz, Shamit Kachru, Eva Silverstein

We propose descriptions of interacting (1,0) supersymmetric theories without gravity in six dimensions in the infinite momentum frame. They are based on the large N limit of quantum mechanics or 1+1 dimensional field theories with SO(N) gauge group and four supercharges. We argue that this formulation allows for a concrete description of the chirality-changi

J. F. Beacom, A. B. Balantekin

Much use has been made of the techniques of supersymmetric quantum mechanics (SUSY QM) for studying bound-state problems characterized by a superpotential $\phi(x)$. Under the analytic continuation $\phi(x) \to i\phi(x)$, a pair of superpartner bound-state problems is transformed into a two-state level-crossing problem in the continuum. The description of ma

Michael Engelhardt, Hugo Reinhardt

The Polyakov loop variable serves as an order parameter to characterize the confined and deconfined phases of Yang-Mills theory. By integrating out the vector fields in the SU(2) Yang-Mills partition function in one-loop approximation, an effective action is obtained for the Polyakov loop to second order in a derivative expansion. The resulting effective pot

M. Li, E. Martinec

We review recent progress in understanding black hole structure and dynamics via matrix theory.

L. Andrianopoli, R. D&#39;Auria, S. Ferrara

We report on some general results on the physics of extremal BPS black holes in four and five dimensions. The duality-invariant entropy-formula for all $N>2$ extended supergravities is derived. Its relation with the fixed-scalar condition for the black-hole ``potential energy&#39;&#39; wich extremizes the BPS mass is obtained. BPS black holes preserving diff

Vadim V. Varlamov

Electromagnetic field is considered in the framework of Clifford algebra $\C_2$ over a field of complex numbers. It is shown here that a modulo 2 periodicity of complex Clifford algebras may be connected with electromagnetic field.

L. Maiani, M. Testa

We show how the state of an unstable particle can be defined in terms of stable asymptotic states. This general definition is used to discuss and to solve some old problems connected with the short-time and large-time behaviour of the non-decay amplitude.

O. G. Miranda, V. Semikoz, J. W. F. Valle

Low-energy high-resolution neutrino-electron scattering experiments may play an important role in testing the gauge structure of the electroweak interaction. We propose the use of radioactive neutrino sources (e.g. $^{51}$Cr) in underground experiments such as BOREXINO and HELLAZ as a probe of the weak neutral current structure. As an illustration, we displa

K. -P. O. Diener, B. A. Kniehl, A. Pilaftsis

We study quantum effects of exotic heavy leptons on the production of two vector bosons in e^+e^- annihilation. We present closed analytic expressions for vector-boson self-couplings and differential cross sections, within the framework of two favourable new-physics scenarios: (i) the fourth-generation Majorana-neutrino model and (ii) an E_6-inspired model w

S. V. Goloskokov

Spin effects in diffractive $pp$ and $lp$ reactions are analyzed. It is shown that the structure of the pomeron coupling can be studied in future polarized experiments.

P. Nason, C. Oleari

We use a recent O(alpha_s^2) calculation of the differential cross section for the production of heavy quarks in e+e- annihilation to compute a few moments of the heavy quark single-inclusive production cross section. We verify that, contrary to some recent claims, the leading and next-to-leading logarithmic terms in this cross section are correctly given by

S. Willenbrock

I discuss two aspects of top-quark physics: V_tb and the top-quark mass. The similarities and differences with bottom and charm physics are emphasized.

J. Cox, W. Franzki, J. Jersak, C. B. Lang

We investigate the scaling behaviour of gauge-ball masses and static potential in the pure U(1) lattice gauge theory on toroidal lattices. An extended gauge field action $-\sum_P(β\cosΘ_P + γ\cos2Θ_P)$ is used with $γ= -0.2$ and -0.5. Gauge-ball correlation functions with all possible lattice quantum numbers are calculated. Most gauge-ball masses scale with

T. DeGrand

I describe studies of quenched spectroscopy, using crude approximations to fixed point actions for fermions interacting with SU(3) gauge fields. These actions have a hypercubic kinetic term and a complicated lattice anomalous magnetic moment term. They show improved scaling compared to the conventional Wilson action.

M Foster, C Michael

The bound states of fermions in the adjoint representation are of interest in supersymmetric models. We investigate the energy spectrum of the simplest -- the gluino-gluon bound states -- on several lattices in the quenched approximation. We use a static approximation for the gluino propagator. We find continuum limits of the splitting between the few lowest

P. Sawicki

We investigate recently proposed method for locating critical temperatures and introduce some modifications which allow to formulate exact criterion for any self-dual model. We apply the modified method for the Ashkin-Teller model and show that the exact result for a critical temperature is reproduced. We test also a two-layer Ising model for the presence of

Petrus Pennanen, Janne Peisa

In order to help the user in choosing the right action a performance comparison is done for seven improved actions. Six of them are Symanzik improved, one at tree-level and two at one-loop, all with or without tadpole improvement. The seventh is an approximate fixed point action. Observables are static on- and off-axis two-body potentials and four-body bindi

Tom Bielefeld, Simon Hands, John D. Stack, Roy J. Wensley

We present results suggesting that magnetic monopoles can account for chiral symmetry breaking in abelian gauge theory. Full U(1) configurations from a lattice simulation are factorized into magnetic monopole and photon contributions. The expectation <psibarpsi> is computed using the monopole configurations and compared to results for the full U(1) configura

Chris R. Allton, Stefano Capitani

We study the work of Leinweber by applying the Continuum Model of QCD Sum Rules (QCDSR) to the analysis of (quenched) lattice correlation functions. We expand upon his work in several areas and find that, while the QCDSR Continuum Model very adequately fits lattice data, it does so only for non-physical values of its parameters. The non-relativistic model is

P. Schmidt with E. Laermann

We present recent results for meson screening masses with quenched Wilson fermions above and below the confinement- deconfinement phase transition. The action used in the simulation is the Sheikholeslami Wohlert action. The quark masses are chosen to be in a range going from light quarks up to the mass of the charm quark. These results are compared with zero

M. Testa

A general review is presented on the problem of non perturbative computation of the $K\toππ$ transition amplitude.

C. Adloff

The transition between photoproduction and deep-inelastic scattering is investigated in jet production at the HERA ep collider, using data collected by the H1 experiment. Measurements of the differential inclusive jet cross-sections dsigep/dEt* and dsigmep/deta*, where Et* and eta* are the transverse energy and the pseudorapidity of the jets in the virtual p

CDF Collaboration

We present a study of events with W bosons and hadronic jets produced in pbar p collisions at a center of mass energy of 1.8 TeV. The data consist of 51400 W^+/- -> e^+/- nu decay candidates from 108 pb^-1 of integrated luminosity collected with the CDF detector at the Tevatron Collider. The cross sections and jet production properties have been measured for

J. Cvach

New experimental results from photoproduction of hadrons at HERA are reviewed.

Carlo Baccigalupi, Luca Amendola, Pierluigi Fortini, Franco Occhionero

We consider true vacuum bubbles generated in a first order phase transition occurring during the slow rolling era of a two field inflation: it is known that gravitational waves are produced by the collision of such bubbles. We find that the epoch of the phase transition strongly affects the characteristic peak frequency of the gravitational waves, causing an

G. Kunstatter, R. Petryk, S. Shelemy

We consider the Hamiltonian mechanics and thermodynamics of an eternal black hole in a box of fixed radius and temperature in generic 2-D dilaton gravity. Imposing boundary conditions analoguous to those used by Louko and Whiting for spherically symmetric gravity, we find that the reduced Hamiltonian generically takes the form: $$ H(M,ϕ_+) = σ_0 E(M,ϕ_+) -{N

Osamu Iguchi, Akio Hosoya, Tatsuhiko Koike

The renormalization group method has been adapted to the analysis of the long-time behavior of non-linear partial differential equation and has demonstrated its power in the study of critical phenomena of gravitational collapse. In the present work we apply the renormalization group to the Einstein equation in cosmology and carry out detailed analysis of ren

Elena Cuoco, Giuseppe Curci, Matteo Beccaria

The aim of this work is to show how it is possible to build an on line whitening filter in an adaptive way. We have modeled the VIRGO noise spectrum as an autoregressive stochastic process, after a pre-filtering of the theoretical curve which flattens the low frequency part of the spectrum. We have tested some very popular adaptive algorithms, based on the g

Shinji Mukohyama

The Wheeler-DeWitt equation is investigated and used to examine a state after a quantum tunneling with gravity. To make arguments definite we treat a discretized version of the Wheeler-DeWitt equation and adopt the WKB method. We expand an Euclidean wave function around an instanton, by using a deviation equation of a vector field tangent to a congruence of

Chunli Zhang, Eric Jeckelmann, Steven R. White

We present a density matrix approach for treating systems with a large or infinite number of degrees of freedom per site with exact diagonalization or the density matrix renormalization group. The method is demonstrated on the 1D Holstein model of electrons coupled to Einstein phonons. In this system, two or three optimized phonon modes per site give results

Sergey N. Rashkeev, Walter R. L. Lambrecht, Benjamin Segall

A LMTO implementation of Aversa and Sipe&#39;s length-gauge formalism for calculating the full frequency dependent second-harmonic generation in the independent particle approximation is presented. It is applied to GaAs, GaP, 3C-SiC, c-BN and wurtzite and zincblende GaN and AlN. The use of the scissor&#39;s operator for correcting LDA errors is discussed and

Peter V. Coveney, Andrew N. Emerton, Bruce M. Boghosian

We simulate self-reproducing micellar systems using a recently introduced lattice-gas automaton. This dynamical model correctly describes the equilibrium and non-equilibrium properties of mixtures of oil, water and surfactants. The simulations reported here mimic the experiments of Luisi et al. in which caprylate micelles are formed by alkaline hydrolysis of

Andrew N. Emerton, Florian W. J. Weig, Peter V. Coveney, Bruce M. Boghosian

Although shear-induced isotropic-to-lamellar transitions in ternary systems of oil, water and surfactant have been observed experimentally and predicted theoretically by simple models for some time now, their numerical simulation has not been achieved so far. In this work we demonstrate that a recently introduced hydrodynamic lattice-gas model of amphiphilic

V. S. U. Fazio, L. Komitov, S. T. Lagerwall

Mono-layers of stearic and behenic acids and mixtures of them in different proportions, deposited with the Langmuir-Blodgett technique, were used to study the alignment and the alignment dynamics in nematic liquid crystal cells. A relaxation process from a splay-bend flow induced metastable orientation to the homeotropic one occurs. The lifetime of the metas

V. L. Aksenov, V. V. Kabanov

We propose a microscopic theory of interaction of long wave molecular phonons with electrons in fullerides in the presence of disorder. Phonon relaxation rate and frequency renormalization are discussed. Finite electronic bandwidth reduces phonon relaxation rate at $q=0$. Electron-phonon coupling constants with molecular modes in fullerides are estimated. Th

S. S. Banerjee

The effect of disorder on flux line lattice (FLL) melting is studied via the Peak Effect phenomenon. On the upper branch of the Peak Effect curve, where this effect is more robust, we observe a stepwise disordering of the FLL, suggesting two first order transition spanning the Peak Effect region. The lower part of the curve is found to be strongly affected b

Holger Stark

In nematic liquid crystals light is strongly scattered from director fluctuations. We are interested in the limit where the incoming light wave is scattered many times. Then, the light transport can be described by a diffusion equation for the energy density of light with diffusion constants $D_{\|}$ and $D_{\perp}$, respectively, parallel and perpendicular

Andreas Mielke

It is shown that one can obtain quantitatively accurate values for the superconducting critical temperature within a Hamiltonian framework. This is possible if one uses a renormalized Hamiltonian that contains an attractive electron-electron interaction and renormalized single particle energies. It can be obtained by similarity renormalization or using flow

C. Lavalle, S. Sorella, A. Parola

We study the low energy spectrum of the nearest neighbor Heisenberg model on a square lattice as a function of the total spin S. By quantum Monte Carlo simulation we compute this spectrum for the s=1/2, s=1 and s=3/2 Heisenberg models. We conclude that the nonlinear sigma model prediction for the low energy spectrum is always verified for large enough system

Masanori Kohno, Minoru Takahashi, Masayuki Hagiwara

We investigate the low-temperature properties of the spin-1 antiferromagnetic Heisenberg chain with bond-alternation by the quantum Monte Carlo method (loop algorithm). The strength of bond-alternation at the gapless point is estimated as $δ_{c}=0.2595\pm0.0005$. We confirm numerically that the low-temperature properties at the gapless point are consistent w

Henryk Arodz, Joachim Stelzer

The director configuration of disclination lines in nematic liquid crystals in the presence of an external magnetic field is evaluated. Our method is a combination of a polynomial expansion for the director and of further analytical approximations which are tested against a numerical shooting method. The results are particularly simple when the elastic const

Elliott H. Lieb, Heinz Siedentop, Jan Philip Solovej

Stability of matter with Coulomb forces has been proved for non-relativistic dynamics, including arbitrarily large magnetic fields, and for relativistic dynamics without magnetic fields. In both cases stability requires that the fine structure constant alpha be not too large. It was unclear what would happen for both relativistic dynamics and magnetic fields

S. Capponi, D. Poilblanc, E. Arrigoni

The single-particle hopping between two chains is investigated by exact-diagonalizations techniques supplemented by finite-size scaling analysis. In the case of two coupled strongly-correlated chains of spinless fermions, the Taylor expansion of the expectation value of the single-particle interchain hopping operator of an electron at momentum k_F in powers

Palle Moller, Stephen J. Warren, Johan U. Fynbo

We present spectroscopic observations of the damped Ly-alpha absorber at redshift z=1.9342 seen in the spectrum of the quasar Q0151+048A. The redshift of the absorber is greater than the redshift of the quasar, so the system resembles the z(abs) ~ z(em) damped absorber at z=2.81 towards the quasar PKS0528-250. We have previously reported the detection of Ly-

Pedro N. Safier

Current magnetic-accretion models for classical T-Tauri stars rely on a strong, dipolar magnetic field of stellar origin to funnel the disk material onto the star, and assume a steady-state. In this paper, I critically examine the physical basis of these models in light of the observational evidence and our knowledge of magnetic fields in low-mass stars, and

E. V. Gotthelf, S. R. Kulkarni

We report the discovery of an unusual X-ray burst from the direction of the Globular Cluster M28 using data acquired with the ASCA Observatory. The burst was recorded by all four ASCA telescopes and displays a fast (~ 70 ms) rise followed by an exponential decay (t = 7.5 s) and a steady afterglow which lasts between 800 - 3250 s. The image of the burst is co

I. V. Igumenshchev, M. A. Abramowicz, I. D. Novikov

We numerically construct slim, global, vertically integrated models of optically thin, transonic accretion discs around black holes, assuming a regularity condition at the sonic radius and boundary conditions at the outer radius of the disc and near the black hole. In agreement with several previous studies, we find two branches of shock-free solutions, in w

L. Amendola, S. Savaglio

We estimate the 1--D power spectrum and the integral density of neighbors in 14 QSO lines of sight. We discuss their variation with respect to redshift and column density and compare the results with standard CDM models.

S. Savaglio

We present a detailed analysis of the ionisation state and heavy element abundances in the Intergalactic Medium (IGM). The CIV doublet is shown by 30 % of the 182 selected optically thin \lya clouds in 10 QSO lines of sight. Direct metallicity calculations have been performed on individual systems with detected CIV and SiIV (10% of the sample) varying the UV

Jordi Jose, Margarita Hernanz

Detailed nucleosynthesis in the ejecta of classical novae has been determined for a grid of hydrodynamic nova models. The reported 14 evolutionary sequences, followed from the onset of accretion up to the explosion and ejection stages, span a range of CO and ONe white dwarf masses (0.8-1.35 $M_o$) and mixing levels between the accreted envelope and the under

Shigehiro Nagataki, Tetsuya Shimizu, Katsuhiko Sato

Growth of Rayleigh-Taylor (R-T) instabilities under the axisymmetric explosion are investigated by two-dimensional hydrodynamical calculations. The degree of the axisymmetric explosion and amplitude of the initial perturbation are varied parametrically to find the most favorable parameter for reproducing the observed line profile of heavy elements. It is fou

Frank van der Hooft, Martin Heemskerk, Frank Alberts, Jan van Paradijs

We report on extensive V, R, and i band photometry of the black-hole candidate Nova Sco 1994 (GRO J1655-40) obtained during March 1996, when the source was close to its quiescent pre-outburst optical brightness (V=17.3). From our observations and data taken from the literature we derive a refined ephemeris for inferior conjunction of the secondary star: HJD

O. Puyoo, L. Ben-Jaffel

We report a quantitative study of the escape of Lyman-alpha photons from an inhomogeneous optically thick medium that mimics the structure of damped Lyman-alpha absorbers. Modeling the optically thick disk with 3 components (massive stars and HII regions, dust, and neutral hydrogen), we study the resulting emission line profile that may arise near the extend