June 1999 arXiv papers — page 21

Songyun Qi, C. M. McCallum

A dynamical lattice model is used to study the viscosity and the velocity-velocity autocorrelation function in a microemulsion phase. We find evidence of anomalous viscosities in these phases (relative to water-rich and/or oil-rich phases), in qualitative agreement with other results. We also investigate the dynamic relaxation in the microemulsion phase. It

Lisa M. Germany, David J. Reiss, Elaine M. Sadler, Brian P. Schmidt

We present observations of SN1997cy, a supernova discovered as part of the Mount Stromlo Abell Cluster SN Search, which does not easily fit into the traditional classification scheme for supernovae. This object's extraordinary optical properties and coincidence with GRB970514, a short duration gamma ray burst, suggest a second case, after SN1998bw/GRB980

Albrecht Klemm, Eric Zaslow

We discuss local mirror symmetry for higher-genus curves. Specifically, we consider the topological string partition function of higher-genus curves contained in a Fano surface within a Calabi-Yau. Our main example is the local P^2 case. The Kodaira-Spencer theory of gravity, tailored to this local geometry, can be solved to compute this partition function.

Alexey A. Petrov, Tibor Torma

At existing and planned neutrino factories (high energy and high intensity neutrino beam facilities) precision studies of QCD in neutrino-nucleon interactions are a realistic opportunity. We investigate charmonium production in fixed target neutrino experiments. We find that $J/ψ$ production in neutrino-nucleon collision is dominated by the color octet $^3S_

Jonathan P. Dowling, Colin P. Williams, J. D. Franson

We discuss the Maxwell electromagnetic duality relations between the Aharonov-Bohm, Aharonov-Casher, and He-McKellar-Wilkens topological phases, which allows a unified description of all three phenomena. We also elucidate Lorentz transformations that allow these effects to be understood in an intuitive fashion in the rest frame of the moving quantum particle

S. L. Dubovsky, P. G. Tinyakov

We show that the deep expected in the diffuse photon spectrum above the threshold of e+e- pair production, i.e., at energies 10^15 - 10^17 eV, may be absent due to the synchrotron radiation by the electron component of the extragalactic Ultra-High Energy Cosmic Rays (UHE CR) in the Galactic magnetic filed. The mechanism we propose requires small (less than 2

M. V. Polyakov

The leading twist parametrization of dipion mass distribution in hard exclusive reactions is proposed. Its parameters are related to quark distributions (usual and skewed) in the pion and to distributions amplitudes of mesons ($π$, $ρ$, etc.). We show that measurements of the shape of dipion mass distribution in hard exclusie reactions can give important inf

Roberto Emparan

The horizon of a static black hole in Anti-deSitter space can be spherical, planar, or hyperbolic. The microscopic dynamics of the first two classes of black holes have been extensively discussed recently within the context of the AdS/CFT correspondence. We argue that hyperbolic black holes introduce new and fruitful features in this respect, allowing for mo

Luca Amendola

I analyze the density perturbations in a cosmological model with a scalar field coupled to ordinary matter, such as one obtains in string theory and in conformally transformed scalar-tensor theories. The spectrum of multipoles on the last scattering surface and the power spectrum at the present are compared with observations to derive bounds on the coupling

I. Antoniadis, C. Bachas, E. Dudas

We compute threshold effects to gauge couplings in four-dimensional $Z_N$ orientifold models of type I strings with ${\cal N}=2$ and ${\cal N}=1$ supersymmetry, and study their dependence on the geometric moduli. We also compute the tree-level (disk) couplings of the open sector gauge fields to the twisted closed string moduli of the orbifold in various mode

A. Gabrielov, W. I. Newman, D. L. Turcotte

We show how clustering as a general hierarchical dynamical process proceeds via a sequence of inverse cascades to produce self-similar scaling, as an intermediate asymptotic, which then truncates at the largest spatial scales. We show how this model can provide a general explanation for the behavior of several models that has been described as ``self-organiz

Q. Zhao, J. -P. Didelez, M. Guidal, B. Saghai

The process $γp \to ϕp$ close to threshold is investigated focusing on the role played by the {\it s}- and {\it u}-channel nucleonic resonances. For this purpose, a recent quark model approach, based on the $SU(6)\otimes O(3)$ symmetry with an effective Lagrangian, is extended to the $ϕ$ meson photoproduction. Another non-diffractive process, the {\it t}-cha

Tao Jiang, Ming Li, Paul Vitanyi

We prove a general lower bound on the average-case complexity of Shellsort: the average number of data-movements (and comparisons) made by a $p$-pass Shellsort for any incremental sequence is $Ω(pn^{1 + 1/p})$ for every $p$. The proof method is an incompressibility argument based on Kolmogorov complexity. Using similar techniques, the average-case complexity

Arne Brataas, Yu. V. Nazarov, Gerrit E. W. Bauer

We formulate a theory of spin dependent transport of an electronic circuit involving ferromagnetic elements with non-collinear magnetizations which is based on the conservation of spin and charge current. The theory considerably simplifies the calculation of the transport properties of complicated ferromagnet-normal metal systems. We illustrate the theory by

Marco Bertola, Vittorio Gorini, Ugo Moschella, Richard Schaeffer

In this letter we show that the ``preferred'' Klein-Gordon Quantum Field Theories (QFT's) on a d-dimensional de Sitter spacetime can be obtained from a Klein-Gordon QFT on a (d+1)-dimensional ``ambient'' Minkowski spacetime satisfying the spectral condition and, conversely, that a Klein-Gordon QFT on a (d+1)-dimensional ``ambient'&#39

Eduardo Fradkin, Steven A. Kivelson, Efstratios Manousakis, Kwangsik Nho

The two dimensional electron gas (2DEG) in moderate magnetic fields in ultra-clean AlAs-GaAs heterojunctions exhibits transport anomalies suggestive of a compressible, anisotropic metallic state. Using scaling arguments and Monte Carlo simulations, we develop an order parameter theory of an electron nematic phase. The observed temperature dependence of the r

Urs Achim Wiedemann, Miklos Gyulassy

We study the transverse momentum dependence of the Landau-Pomeranchuk-Migdal effect in QED, starting from the high energy expansion of the solution of the Dirac equation in the presence of an external field. The angular integrated energy loss formula differs from an earlier expression of Zakharov by taking finite kinematical boundaries into account. In an ex

Paul Fendley

We show that two-dimensional sigma models are equivalent to certain perturbed conformal field theories. When the fields in the sigma model take values in a space G/H for a group G and a maximal subgroup H, the corresponding conformal field theory is the $k\to\infty$ limit of the coset model $(G/H)_k$, and the perturbation is related to the current of G. This

A. Carrington, I. J. Bonalde, R. Prozorov, R. W. Giannetta

We present high precision measurements of the penetration depth λof single crystals of κ-(ET)_2Cu[N(CN)2]Br and κ-(ET)_2Cu(NCS)_2 at temperature down to 0.4 K. We find that, at low temperatures, the in-plane penetration depth varies as a fractional power law, λ\sim T^1.5. W hilst this may be taken as evidence for novel bose excitation processes, we show that

S. Codoban, D. I. Kazakov

We present simple analytical formulae which describe solutions of the RG equations for Yukawa couplings in SUSY gauge theories with the accuracy of a few per cent. Performing the Grassmannian expansion in these solutions one finds those for all the soft couplings and masses. The solutions clearly exhibit the fixed point behaviour which can be calculated anal

G. Cvetic, C. S. Kim

Possibilities for detecting heavy Majorana neutrinos ($N$'s) at future $eμ$ colliders are investigated. In contrast to the $e^-e^+$ colliders (LEP200 and NLC), the center-of-mass (CMS) energies achieved at $eμ$ colliders can be much higher and the $Z$-mediated $s$ channel is excluded automatically. This opens the attractive possibility of having high pro

Surajit Sengupta, Peter Nielaba, Madan Rao, K. Binder

Fluctuations of the instantaneous local Lagrangian strain $ε_{ij}(\bf{r},t)$, measured with respect to a static ``reference'' lattice, are used to obtain accurate estimates of the elastic constants of model solids from atomistic computer simulations. The measured strains are systematically coarse- grained by averaging them within subsystems (of size

Thomas Buchert

For general relativistic spacetimes filled with irrotational `dust' a generalized form of Friedmann's equations for an `effective' expansion factor $a_D (t)$ of inhomogeneous cosmologies is derived. Contrary to the standard Friedmann equations, which hold for homogeneous-isotropic cosmologies, the new equations include the `backreaction effect&#3

Anastasios Petkou, Kostas Skenderis

We provide a non-renormalization theorem for the coefficients of the conformal anomaly associated with operators with vanishing anomalous dimensions. Such operators include conserved currents and chiral operators in superconformal field theories. We illustrate the theorem by computing the conformal anomaly of 2-point functions both by a computation in the co

A. M. Khvedelidze, D. M. Mladenov

The relation between SU(2) Yang-Mills mechanics, originated from the 4-dimensional SU(2) Yang-Mills theory under the supposition of spatial homogeneity of the gauge fields, and the Euler-Calogero-Moser model is discussed in the framework of Hamiltonian reduction. Two kinds of reductions of the degrees of freedom are considered: due to the gauge invariance an

Dmitri Antonov

In the London limit of the Ginzburg-Landau theory (Abelian Higgs model), vortex dipoles (small vortex loops) are treated as a grand canonical ensemble in the dilute gas approximation. The summation over these objects with the most general rotation- and translation invariant measure of integration over their shapes leads to effective sine-Gordon theories of t

S. J. Hatton

Recent results from a number of redshift surveys suggest that the Universe is well described by an inhomogeneous, fractal distribution on the largest scales probed. This distribution has been found to have fractal dimension, D, approximately equal to 2.1, in contrast to a homogeneous distribution in which the dimension should approach the value 3 as the scal

Enrico Carlon, Christophe Chatelain, Bertrand Berche

We study the critical behavior of the random q-state Potts quantum chain by density matrix renormalization techniques. Critical exponents are calculated by scaling analysis of finite lattice data of short chains ($L \leq 16$) averaging over all possible realizations of disorder configurations chosen according to a binary distribution. Our numerical results s

Daniel E. Reichart

At the time of its discovery, the optical and X-ray afterglow of GRB 970228 appeared to be a ringing endorsement of the previously untried relativistic fireball model of gamma-ray burst (GRB) afterglows, but now that nearly a dozen optical afterglows to GRBs have been observed, the wavering light curve and reddening spectrum of this afterglow make it perhaps

Igor Bray

Application of the convergent close-coupling (CCC) method to electron-impact ionization of the ground state of atomic hydrogen is considered at incident energies of 15.6, 17.6, 20, 25, 27.2, 30, 54.4, 150 and 250 eV. Total through to fully differential cross sections are presented. Following the analysis of Stelbovics [submitted to Phys. Rev. Lett. (physics/

Yi Liao, Xiaoyuan Li

We study the light quark and the neutron electric dipole moments (EDMs) under the assumptions that the CP source is still in the usual CKM matrix and that there is a small mixing of right-handed charged currents in the quark sector. We find that the EDMs arise already at two loop order that are much larger than the standard model (SM) result even for a small

Yi Li, D. H. Sattinger

Numerical experiments involving the interaction of two solitary waves of the ion acoustic plasma equations are described. An exact 2-soliton solution of the relevant KdV equation was fitted to the initial data, and good agreement was maintained throughout the entire interaction. The data demonstrates that the soliton interactions are virtually elastic

Richard Beals, D. H. Sattinger, J. Szmigielski

Classical results of Stieltjes are used to obtain explicit formulas for the peakon-antipeakon solutions of the Camassa-Holm equation. The closed form solution is expressed in terms of the orthogonal polynomials of the related classical moment problem. It is shown that collisions occur only in peakon-antipeakon pairs, and the details of the collisions are ana

A. M. Akulshin S. Barreiro A. Lezama

Steep dispersion of opposite signs in driven degenerate two-level atomic transitions have been predicted and observed on the D2 line of 87Rb in an optically thin vapor cell. The intensity dependence of the anomalous dispersion has been studied. The maximum observed value of anomalous dispersion [dn/dnu ~= -6x10^{-11}Hz^{-1}] corresponds to anegative group ve

S. N. Molotkov, S. S. Nazin

The measurement procedures used in quantum teleportation are analyzed from the viewpoint of the general theory of quantum-mechanical measurements. It is shown that to find the teleported state one should only know the identity resolution (positive operator-valued measure) generated by the corresponding instrument (quantum operation describing the system stat

Jonathan P. Dowling

I consider an exact model of atomic spontaneous dipole emission and classical dipole radiation in a finite photonic band-gap structure. The full 3D or 2D problem is reduced to a finite 1D model, and then this is solved for analytically using algebraic matrix transfer techniques. The results give insight to the electromagnetic emission process in periodic die

David Deutsch

The probabilistic predictions of quantum theory are conventionally obtained from a special probabilistic axiom. But that is unnecessary because all the practical consequences of such predictions follow from the remaining, non-probabilistic, axioms of quantum theory, together with the non-probabilistic part of classical decision theory.

David Deutsch, Patrick Hayden

All information in quantum systems is, notwithstanding Bell's theorem, localised. Measuring or otherwise interacting with a quantum system S has no effect on distant systems from which S is dynamically isolated, even if they are entangled with S. Using the Heisenberg picture to analyse quantum information processing makes this locality explicit, and reve

S N Sandhya

We study resonance flourescence in a four level ladder system and illustrate some novel features due to quantum interference and atomic coherence effects. We find that under three photon resonant conditions, in some region of the parameter space of the rabi frequencies $Ω_1,Ω_2,Ω_3$, emission is dominantly by the level 4 at the line center even though there

Hongbo Hu, Jason Nielsen

The interpretation of new particle search results involves a confidence level calculation on either the discovery hypothesis or the background-only ("null") hypothesis. A typical approach uses toy Monte Carlo experiments to build an expected experiment estimator distribution against which an observed experiment's estimator may be compared. In thi

S. Jones, A. T. Stelbovics

Although the convergent close-coupling (CCC) method has achieved unprecedented success in obtaining accurate theoretical cross sections for electron-atom scattering, it generally fails to yield converged energy distributions for ionization. Here we report converged energy distributions for ionization of H(1s) by numerically integrating Schroedinger's equ

Dmitry V. Skryabin, William J. Firth

Numerical studies together with asymptotic and spectral analysis establish regimes where soliton pairs in degenerate optical parametric oscillators fuse, repel, or form bound states. A novel bound state stabilized by coupled internal oscillations is predicted.

P. G. Blunden, M. Burkardt, G. A. Miller

A light-front treatment for finite nuclei is developed from a relativistic effective Lagrangian (QHD1) involving nucleons, scalar mesons and vector mesons. We show that the necessary variational principle is a constrained one which fixes the expectation value of the total momentum operator $P^+$ to be the same as that for $P^-$. This is the same as minimizin

Sidney A. Coon

In these lectures, I examine the effect of the meson factory $π$N data on the current algebra/PCAC program which describes chiral symmetry breaking in this system. After historical remarks on the current algebra/PCAC versus chiral Lagrangians approaches to chiral symmetry, and description of the need for $π$N amplitudes with virtual (off-mass-shell) pions in

V. Yu. Ponomarev, J. Bryssinck, L. Govor, F. Bauwens

Results of nuclear resonance fluorescence experiments on $^{117}$Sn are reported. More than 50 $γ$ transitions with $E_γ < 4$ MeV were detected indicating a strong fragmentation of the electromagnetic excitation strength. For the first time microscopic calculations making use of a complete configuration space for low-lying states are performed in heavy odd-m

Renat Zhdanov, Alexander Zhalij

We consider the problem of separation of variables in the Kramers equation admitting a non-trivial symmetry group. Provided the external potential $V(x)$ is at most quadratic, a complete solution of the problem of separation of variables is obtained. Furthermore, we construct solutions of the Kramers equation with separated variables in explicit form.

R. Z. Zhdanov, V. I. Lahno

We suggest a systematic procedure for classifying partial differential equations invariant with respect to low dimensional Lie algebras. This procedure is a proper synthesis of the infinitesimal Lie&#39;s method, technique of equivalence transformations and theory of classification of abstract low dimensional Lie algebras. As an application, we consider the

Helen Au-Yang, Jacques H. H. Perk

In this paper we study the large-N limits of the integrable N-state chiral Potts model. Three chiral solutions of the star-triangle equations are derived, with states taken from all integers, or from a finite or infinite real interval. These solutions are expected to be chiral-field lattice deformations of parafermionic conformal field theories. A new two-si

Yi-Zhi Huang, Wenhua Zhao

Semi-infinite forms on the moduli spaces of genus-zero Riemann surfaces with punctures and local coordinates are introduced. A partial operad for semi-infinite forms is constructed. Using semi-infinite forms and motivated by a partial suboperad of the partial operad for semi-infinite forms, topological vertex partial operads of type $k<0$ and strong topologi

V. Sahakian

This is a thesis/review article that combines some of the results of hep-th/9809061, hep-th/9810224 and hep-th/9901135 with a short discussion of introductory background material; an attempt has been made to present the work in a self-contained manner. The first chapter mostly targets readers who are vaguely familiar with traditional and contemporary string

H. O. Girotti

The duality symmetric but not manifestly covariant action proposed by Schwarz-Sen is canonically quantized in the Coulomb gauge. The resulting theory turns out to be, nevertheless, relativistically invariant. It is shown, afterwards, that the Schwarz-Sen model naturally emerges when duality is implemented as a local symmetry of sourceless electrodynamics. Th

Igor Bandos, Wolfgang Kummer

A supersymmetric action functional describing the interaction of the fundamental superstring with the D=10, type IIB Dirichlet super-9-brane is presented. A set of supersymmetric equations for the coupled system is obtained from the action principle. It is found that the interaction of the string endpoints with the super-D9-brane gauge field requires some re

Tom Banks, Willy Fischler

We present a model for high energy two body scattering in a quantum theory of gravity. The model is applicable for center of mass energies higher than the relevant Planck scale. At impact parameters smaller than the Schwarzchild radius appropriate to the center of mass energy and total charge of the initial state, the cross section is dominated by an inelast

Jerzy A. Przeszowski

The canonical quantization is performed at a light-front surface for the SU(N) Yang-Mills theory. The Weyl gauge is imposed as a gauge condition. The suitable parameterization is chosen for the transverse gauge field components in order to have Dirac brackets independent of interactions. The generating functional is defined for the perturbation theory and it

Manuel Reenders

The mechanism of dynamical chiral symmetry breaking is studied in the Abelian version of the gauged Nambu-Jona-Lasinio model in four dimensions. The most interesting feature of the gauged Nambu-Jona-Lasinio model is the appearance of relevant (renormalizable) four-fermion interactions near a critical curve separating a chiral symmetric and a dynamically chir

Bo Feng, Amihay Hanany, Yang-Hui He

An example of a non-Abelian Brane Box Model, namely one corresponding to a $Z_k \times D_{k'}$ orbifold singularity of $\C^3$, is constructed. Its self-consistency and hence equivalence to geometrical methods are subsequently shown. It is demonstrated how a group-theoretic twist of the non-Abelian group circumvents the problem of inconsistency that arise fro

F. Csikor, Z. Fodor, P. Hegedüs, A. Piróth

We present a one-loop calculation of the static potential in the SU(2)-Higgs model. The connection to the coupling constant definition used in lattice simulations is clarified. The consequences in comparing lattice simulations and perturbative results for finite temperature applications are explored.

Guy D. Moore, Kari Rummukainen

We measure the sphaleron rate for hot, classical Yang-Mills theory on the lattice, in order to study its dependence on lattice spacing. By using a topological definition of Chern-Simons number and going to extremely fine lattices (up to beta=32, or lattice spacing a = 1 / (8 g^2 T)) we demonstrate nontrivial scaling. The topological susceptibility, converted

A. Peshier, B. Kaempfer

An effective quasiparticle description of deconfined QCD thermodynamics compatible with both finite temperature nonperturbative lattice data and the asymptotic limit is generalized to finite chemical potential. Implications for the N_f = 4 flavor lattice data extended to mu \neq 0 as well as for deconfined matter with realistic quark masses are considered.

J. A. Grifols, Eduard Masso, Subhendra Mohanty, K. V. Shajesh

We calculate the rate for pair production of light pseudoscalars by strong inhomogeneous and static electric (magnetic) fields. We show that, in the case of axions, the stability of atoms over cosmic lifetimes is jeopardised unless the Peccei-Quinn symmetry breaking scale $f_a$ is larger than ${\cal O} (10^{10} GeV)$.

Takashi Nasuno

The object of this thesis is to study the spin-spin correlations for top quark productions and their decay at polarized e^+e^- linear colliders. For the analyses of the spin-spin correlations in top quark production, we introduce a generic spin basis and show which spin basis is the most optimal. We discuss the spin-angular correlations for the top quark dec

Jie-Jie Zhu

We derive the explicit expressions of the canonical and helicity wave functions for massive particles with arbitrary spins. Properties of these wave functions are discussed.

V. E. Markushin, M. P. Locher

The analysis of the poles of the $ππ$ scattering amplitude is shown to favour a dynamical origin of the sigma meson: it is created by a strongly attractive $ππ$ interaction in the $J^{PC}=0^{++}I=0$ channel. In the limit $N_c\to\infty$, the $σ$ meson disappears, contrary to the case of conventional $q\bar{q}$ states. Implications for the search of the scalar

B. Kämpfer, O. P. Pavlenko

The polarization of a surrounding QCD medium modifies the induced gluon radiation spectrum of a high-energy parton at small transverse momenta for a single interaction and for multiple scatterings as well. This effect is an analogue of the Ter-Mikaelian effect in QED, superimposed to the Landau--Pomeranchuk effect, however it appears in QCD in a different ph

A. M. Badalian, V. L. Morgunov, B. L. G. Bakker

It is shown that the fine structure splittings of the $2 ^3P_J$ and $3 ^3P_J$ excited states in charmonium are as large as those of the $1^3P_J$ state if the same $α_s(μ)\approx 0.36$ is used. The predicted mass $M(2 ^3P_0)=3.84$ GeV appears to be 120 MeV lower that the center of gravity of the $2 ^3P_J$ multiplet and lies below the $D\bar D^*$ threshold. Ou

M. B. Hecht, B. H. J. McKellar

We note that off the quark mass shell the operators $(p_i+p_f)_μγ_5$ and $iσ_{μν}(p_i -p_f)^νγ_5$, both of which reduce to $-\vecσ\cdot\vec{E}$ in the non-relativistic limit, are no longer identical. In this paper we explore the effects of this difference in the contribution of these quark electric moments to hadronic electric moments.

Peter Fisher, Boris Kayser, Kevin S. McFarland

The question of neutrino mass is one of the major riddles in particle physics. Recently, strong evidence that neutrinos have nonzero masses has been found. While tiny, these masses could be large enough to contribute significantly to the mass density of the universe. The evidence for nonvanishing neutrino masses is based on the apparent observation of neutri

A. A. Darmohval, V. K. Petrov, G. M. Zinovjev

The potential between sources in arbitrary representations of the gauge group is studied on an anisotropic lattice in a spherical model approximation. It is shown analytically that for half-integer $j$ and $j&#39;$ in the confinement phase the potential rises linearly, whereas for integer $j$ and half-integer $j&#39;$ it rises infinitely which means a strong

M. A. Vasiliev, M. E. Beddo, C. N. Brown, T. A. Carey

A precise measurement of the ratios of the Drell-Yan cross section per nucleon for an 800 GeV/c proton beam incident on Be, Fe and W targets is reported. The behavior of the Drell-Yan ratios at small target parton momentum fraction is well described by an existing fit to the shadowing observed in deep-inelastic scattering. The cross section ratios as a funct

John Krane

Several sources, both experimental and theoretical, subject inclusive jet cross section measurements to large uncertainties. On the experimental side, the energy scale contributes between 10% and 30% uncertainties. On the theoretical side, choice of parton distribution function introduces a 20% variation in the prediction; freedom in renormalization scale pr

Angèle Tripet

Preliminary spin cross section asymmetries for exclusive $ρ^{0}$ lepto-production, $\vecμ + \vec{N} \to μ&#39; + N + ρ^{0} (ρ^{0} \to π^{+} π^{-})$, are reported. These asymmetries have been determined for the first time by the Spin Muon Collaboration (SMC) at low Q^2 (photoproduction) and at large Q^2 (DIS) for different $p_T^2$ intervals in the kinematic r

C. Leonidopoulos, C. Lu, A. J. Schwartz

We have developed a straw tube chamber with pickup-pad readout. The mechanism for signal pickup, the size of the pickup signal, and the distribution of signals among neighboring pads are discussed. We have tested a prototype chamber in a beamtest at Brookhaven National laboratory and have measured chamber efficiencies in excess of 99%.

David Garfinkle

Numerical simulations are performed of the approach to the singularity in Gowdy spacetimes on S2XS1XR. The behavior is similar to that of Gowdy spacetimes on T3XR. In particular, the singularity is asymptotically velocity term dominated, except at isolated points where spiky features develop.

G. Dautcourt

We study in a Brill-Hartle type of approximation the back reaction of a superposition of linear gravitational waves on the mean gravitational field up to second order in the wave amplitudes. The background field is taken as an Einstein-deSitter geometry. In order to follow inflationary scenarios, the wavelengths are allowed to exceed the temporary Hubble dis

Marco Bruni, Sebastiano Sonego

We discuss the issue of observables in general-relativistic perturbation theory, adopting the view that any observable in general relativity is represented by a scalar field on spacetime. In the context of perturbation theory, an observable is therefore a scalar field on the perturbed spacetime, and as such is gauge invariant in an exact sense (to all orders

Cristovao Correia da Silva, Ruth M. Williams

The computation of the simplicial minisuperspace wavefunction in the case of anisotropic universes with a scalar matter field predicts the existence of a large classical Lorentzian universe like our own at late times

Joost Engelfriet, Hendrik Jan Hoogeboom

String transductions that are definable in monadic second-order (mso) logic (without the use of parameters) are exactly those realized by deterministic two-way finite state transducers. Nondeterministic mso definable string transductions (i.e., those definable with the use of parameters) correspond to compositions of two nondeterministic two-way finite state

K. D. Fisher, D. Stroud, L. Janin

We study dynamical phase transitions at temperature T = 0 in a fully frustrated square Josephson junction array subject to a driving current density which has nonzero components parallel to both axes of the lattice. Our numerical results show clear evidence for three dynamical phases: a pinned vortex lattice characterized by zero time-averaged voltages, a ``

Gábor Palágyi, Christophe Chatelain, Bertrand Berche, Ferenc Iglói

We consider random q-state Potts models for $3\le q \le 8$ on the square lattice where the ferromagnetic couplings take two values $J_1>J_2$ with equal probabilities. For any q the model exhibits a continuous phase transition both in the bulk and at the boundary. Using Monte Carlo techniques the surface and the bulk magnetizations are studied close to the cr

A. Buldum, Jian Ping Lu

A carbon nanotube is an ideal object for understanding the atomic scale aspects of interface interaction and friction. Using molecular statics and dynamics methods different types of motion of nanotubes on a graphite surface are investigated. We found that each nanotube has unique equilibrium orientations with sharp potential energy minima. This leads to ato

Holger Adam, Manfred Winterstetter, Milena Grifoni, Ulrich Weiss

A symmetric dissipative two-state system is asymptotically completely delocalized independent of the initial state. We show that driving-induced localization at long times can take place when both the bias and tunneling coupling energy are harmonically modulated. Dynamical symmetry breaking on average occurs when the driving frequencies are odd multiples of

G. Lang, E. Paladino, U. Weiss

We study nonadiabatic electron transfer within the biased spin-boson model. We calculate the incoherent transfer rate in analytic form at all temperatures for a power law form of the spectral density of the solvent coupling. In the Ohmic case, we present the exact low temperature corrections to the zero temperature rate for arbitrarily large bias energies be

J. S. Langer, Alexander E. Lobkovsky

We show that a simple rate-and-state theory accounts for most features of both time-independent and time-dependent plasticity in a spatially inhomogeneous situation, specifically, a circular hole in a large stressed plate. Those features include linear viscoelastic flow at small applied stresses, strain hardening at larger stresses, and a dynamic transition

S. V. Dordevic, N. R. Dilley, E. D. Bauer, D. N. Basov

Infrared reflectance spectroscopy measurements were made on four members of the MFe_4P_12 family of filled skutterudites, with M=La, Th, Ce and U. In progressing from M=La to U the system undergoes a metal-insulator transition. It is shown that, although the filling atom induces such dramatic changes in the transport properties of the system, it has only a s

Paul L. McEuen, Marc Bockrath, David H. Cobden, Young-Gui Yoon

We address the effects of disorder on the conducting properties of metal and semiconducting carbon nanotubes. Experimentally, the mean free path is found to be much larger in metallic tubes than in doped semiconducting tubes. We show that this result can be understood theoretically if the disorder potential is long-ranged. The effects of a pseudospin index t

Kurt Gloos, Frithjof Anders

The RCSJ model of resistively and capacitively shunted Josephson junctions is used to describe superconducting point contacts over a wide range of resistances up to the metallic -- tunneling transition. Their small dynamic capacitance of order $C = 0.1 $fF due to the point-contact geometry results in a huge plasma frequency. The critical current is then stro

M. Promberger

We show that the canonical finite size scaling of the specific heat emerges naturally - and in some sense trivially - from the assumption that the microcanonical specific entropy exhibits no substantial system size dependence.

N. Abarenkova, J. -Ch. Anglès d&#39;Auriac, S. Boukraa, S. Hassani

We consider a family of birational transformations of two variables, depending on one parameter, for which simple rational expressions with integer coefficients, for the exact expression of the dynamical zeta function, have been conjectured. together with an equality between the asymptotic of the Arnold complexity and the exponential of the topological entro

Brad K. Gibson, Darren S. Madgwick, Lewis A. Jones, Gary S. Da Costa

High signal-to-noise integrated spectra of the metal-rich globular cluster 47 Tuc, spanning the H-gamma(HR) and Fe4668 line indices, have been obtained. The combination of these indices has been suggested (Jones & Worthey 1995, ApJ, 446, L31) as the best available mechanism for cleanly separating the age-metallicity degeneracy which hampers the dating of dis

G. Dautcourt

We discuss the question to what degree the geometrical structure and the matter content of the universe at scales exceeding the present Hubble horizon is constrained by cosmological observations, in particular by measurements of the cosmic microwave background radiation. For an answer, a simple formalism is described, which goes back to a paper by Kristian a

Richard A. Battye, Joao Magueijo, Jochen Weller

Quantum fluctuations created during inflation can account for the observed matter distribution in the linear regime if the universe has two components of dark matter, one which is cold and collisionless, and the other which is hot and free streams on small scales. However, this free streaming property of the hot component prevents early structure formation,

Miller, Bureau, Verlome, de Zeeuw

We present the first results from a new and unique integral-field spectrograph, SAURON. Based upon the TIGER concept, SAURON uses a lens array to obtain two-dimensional spectroscopy with complete spatial coverage over a field of 33&#34;x41&#34; in low-resolution mode (0.94&#34; lenslets) and of 9&#34;x11&#34; in high-resolution mode (0.26&#34; lenslets). The

V. I. Slysh, S. V. Kalenskii, I. E. Val&#39;tts, V. V. Golubev

We observed 14 methanol transitions near lambda=2 mm in Galactic star-forming regions. Broad, quasi-thermal J(0)-J(-1)E methanol lines near 157 GHz were detected toward 73 sources. Together with the 6(-1)-5(0)E and 5(-2)-6(-1)E lines at 133 GHz and the 7(1)-7(0)E line at 165 GHz, they were used to study the methanol excitation. In the majority of the observe

Coel Hellier

I review the observational properties of SW Sex stars. I show that they can be explained by an accretion stream overflowing the disc, combined with an accretion disc wind. I suggest that SW Sex behaviour is caused by episodes of very high mass transfer, which are balanced by VY Scl low states.

Claudia Maraston, Laura Greggio, Daniel Thomas

The study of line strengths in the spectra of early-type galaxies has proven to be a powerful tool for investigating the age and the metallicity of these systems. When computing models for spectrophotometric narrow-band indices, index calibrations as functions of the relevant stellar parameters (e.g. temperature, gravity and metal content) are used. Thus syn

The Utah Seven Telescope Array collaboration

Historical TeV gamma-ray flares from Markarian 501 was observed using Utah Seven Telescope Array (7TA) from the end of March to the end of July of 1997. The Rossi X-ray Timing Explorer All Sky Monitor (RXTE ASM) has been observing X rays from Mrk 501 since Jan. 5, 1996. We find evidence for periodicities of $23.9^{+2.3}_{-2.0}$ days and $23.9^{+1.6}_{-2.9}$

D. Dal Fiume, M. Orlandini, S. Del Sordo, F. Frontera

The X-ray telescopes on board BeppoSAX are an optimal set of instruments to observe bright galactic binary pulsars. These sources emit very hard and quite complex X-ray spectra that can be accurately measured with BeppoSAX between 0.1 and 200 keV. A prototype of this complexity, the source Her X-1, shows at least seven different components in its spectrum. A

I. Murakami, A. Babul

We have carried out 2D hydrodynamical simulations in order to study the interaction between supernova-powered gas outflows from low-mass galaxies and the local intergalactic medium (IGM). We are specifically interested in investigating whether a high pressure IGM, such as that in clusters of galaxies, can prevent the gas from escaping from the galaxy. The in

Walter Dehnen

Distribution functions (DFs) for dynamically warm thin stellar disks residing in arbitrary axisymmetric potentials are presented which approximately reproduce pre-described surface-density and velocity-dispersion profiles. The functional form of the DFs is obtained by `warming-up&#39; a model made entirely of circular orbits. This can be done in various ways

Walter Dehnen

Already slightly eccentric orbits, such as those occupied by many old stars in the Galactic disk, are not well approximated by Lindblad&#39;s epicycle theory. Here, alternative approximations for flat orbits in axisymmetric stellar systems are derived and compared to results from numeric integrations. All of these approximations are more accurate than Lindbl