July 2003 arXiv papers — page 12

Jessica Sidman

We give explicit generators for ideals of two classes of subspace arrangements embedded in certain reflection arrangements, generalizing results of Li-Li and Kleitman-Lovasz. We also give minimal generators for the ideals of arrangements that arise in a natural way from the p-skeleton of an n-dimensional cube and discuss conditions under which the generators

Tetsuji Kimura, Kentaroh Yoshida

We calculate the spectrum of the linearized supergravity around the maximally supersymmetric pp-wave background in eleven dimensions. The resulting spectrum agrees with that of zero-mode Hamiltonian of a supermembrane theory on the pp-wave background. We also discuss the connection with the Kaluza-Klein zero modes of AdS_4 x S^7 background.

V. N. Pervushin, V. V. Skokov, A. V. Reichel, S. A. Smolyansky

The oscillator representation is used for the non-perturbative description of vacuum particle creation in a strong time-dependent electric field in the framework of scalar QED. It is shown that the method can be more effective for the derivation of the quantum kinetic equation (KE) in comparison with the Bogoliubov method of time-dependent canonical transfor

A. Foerster, F. Uhlig, I. Boettcher, M. Debowski

Differential production cross sections of K- and K+ mesons have been measured in Ni+Ni and Au+Au collisions at a beam energy of 1.5 AGeV. The K-/K+ ratio is found to be nearly constant as a function of the collision centrality and system size. The spectral slopes and the polar emission pattern differ for K- and K+ mesons. These observations indicate that K+

Bryan Kelleher

The configuration space of general relativity is superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms. However, it has been argued that the configuration space for gravity should be conformal superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms and conformal transformations. Recently a manifestly 3-dimensional theory

Nobuyuki Sakai

Many authors claimed that a large initial inhomogeneity prevents the onset of inflation and therefore inflation takes place only if the scalar field is homogeneous or appropriately chosen over the horizon scale. We show that those arguments do not apply to topological inflation. The core of a defect starts inflation even if it has much smaller size than the

Peter S Conti, Paul A. Crowther

We conduct a Galactic census of Giant HII regions, based on the all sky 6cm dataset of Kuchar & Clark, plus the kinematic distances obtained by Russeil. From an inspection of mid-IR Mid-course Space Experiment (MSX) and far-IR IRAS Sky Survey Atlas images we identify a total of 56 GHII regions in the Milky Way, of which 15% (65%) can be seen at optical (near

David G. Cerdeno, Anke Knauf, Jan Louis

We compare the glueball mass spectrum of an effective N=1 pure super Yang-Mills theory formulated in terms of a three-form supermultiplet with the available lattice data. These confirm the presence of four scalars and two Majorana fermions but the detailed mass spectrum is difficult to reconcile with the effective supersymmetric theory. By imposing supersymm

Young-June Kim, J. P. Hill, H. Benthien, F. H. L. Essler

We report a resonant inelastic x-ray scattering study of charge excitations in the quasi-one-dimensional Mott insulator SrCuO2. We observe a continuum of low-energy excitations, in which a highly dispersive feature with a large sinusoidal dispersion (~1.1 eV) resides. We have also measured the optical conductivity, and studied the dynamic response of the ext

Mohammad R. Garousi

We propose that there is a unique expansion for the string theory S-matrix elements of tachyons that corresponds to non-abelian tachyon action. For those S-matrix elements which, in their expansion, there are the Feynman amplitudes resulting from the non-abelian kinetic term, we give a prescription on how to find the expansion. The gauge invariant action is

G. Arutyunov, S. Frolov, J. Russo, A. A. Tseytlin

We show that solitonic solutions of the classical string action on the AdS_5 x S^5 background that carry charges (spins) of the Cartan subalgebra of the global symmetry group can be classified in terms of periodic solutions of the Neumann integrable system. We derive equations which determine the energy of these solitons as a function of spins. In the limit

E. Lopez

It was shown in hep-th/0301099 that the leading UV/IR mixing effects in noncommutative gauge theories on D-branes are able to capture information about the closed string spectrum of the parent string theory. The analysis was carried out for D-branes on nonsupersymmetric C^3/Z_N orbifolds of Type IIB. In this paper we consider D-branes on twisted circles comp

Jyoti Prasad Saha, Anirban Kundu

We perform a systematic reevaluation of the constraints on the flavor-changing neutral current (FCNC) parameters in R-parity conserving and R-parity violating supersymmetric models. As a typical process, we study the constraints coming from the measurements on the B0-\bar{B0} system on the supersymmetric $δ^d_{13}$ parameters, as well as on the products of t

Yong Zhou

We have investigated the present renormalization prescriptions of the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix. Based on one prescription which is formulated by comparing with the fictitious case of no mixing of quark generations, we propose a new prescription which can make the physical amplitude involving quark's mixing gauge independent and

Jeremy Goodman, Jonathan C. Tan

We propose that supermassive stars may form in quasar accretion disks, and we discuss possible observational consequences. The structure and stability of very massive stars are reviewed. Because of high accretion rates, quasar disks are massive and the fringes of their optically luminous parts are prone to fragmentation. Starting from a few hundred solar mas

L. M. Nieto, A. A. Pecheritsin, Boris F. Samsonov

The technique of differential intertwining operators (or Darboux transformation operators) is systematically applied to the one-dimensional Dirac equation. The following aspects are investigated: factorization of a polynomial of Dirac Hamiltonians, quadratic supersymmetry, closed extension of transformation operators, chains of transformations, and finally p

Marcos Curty, Maciej Lewenstein, Norbert Lütkenhaus

We demonstrate that a necessary precondition for unconditionally secure quantum key distribution is that sender and receiver can use the available measurement results to prove the presence of entanglement in a quantum state that is effectively distributed between them. One can thus systematically search for entanglement using the class of entanglement witnes

Michael J. Bremner, Jennifer L. Dodd, Michael A. Nielsen, Dave Bacon

What interactions are sufficient to simulate arbitrary quantum dynamics in a composite quantum system? It has been shown that all two-body Hamiltonian evolutions can be simulated using \emph{any} fixed two-body entangling $n$-qubit Hamiltonian and fast local unitaries. By \emph{entangling} we mean that every qubit is coupled to every other qubit, if not dire

B F Samsonov, M L Glasser, J Negro, L M Nieto

The potentials for a one dimensional Schroedinger equation that are displaced along the x axis under second order Darboux transformations, called 2-SUSY invariant, are characterized in terms of a differential-difference equation. The solutions of the Schroedinger equation with such potentials are given analytically for any value of the energy. The method is

Dirk Witthaut, Michael Fleischhauer

We discuss the relation between discrete and continuous linear teleportation, i.e. teleportation schemes that use only linear optical elements and photodetectors. For this the existing qubit protocols are generalized to qudits with a discrete and finite spectrum but with an arbitrary number of states or alternatively to continuous variables. Correspondingly

M. Akbari, M. T. Darvishi

In this paper, we prove that two different observers don't equally measure the distance between two points A and B. For this, we introduce some postulates and obtain a new formula to show distance between A and B. In this formula, radius of universe, n, is entered such that if n tends to infinity the ordinary distance is obtained.

V. Lindenstruth, C. Loizides, D. Roehrich, B. Skaali

The ALICE High Level Trigger has to process data online, in order to select interesting (sub)events, or to compress data efficiently by modeling techniques.Focusing on the main data source, the Time Projection Chamber (TPC), we present two pattern recognition methods under investigation: a sequential approach "cluster finder" and "track follower&

A. Kozlov, C. Aidala, B. Azmoun, Z. Fraenkel

A Hadron Blind Detector (HBD) is proposed as upgrade of the PHENIX detector at RHIC, BNL. The HBD will allow the measurement of low-mass e+e- pairs from the decay of the light vector mesons rho, omega, phi and the low-mass continuum in Au-Au collisions at energies up to sqrt{s_{NN}}= 200 GeV. From MC simulations and general considerations, the HBD has to ide

D. Schurig, D. R. Smith

We find that the function that describes the surface of spherical aberration free lenses can be used for both positive and negative refractive index media. With the inclusion of negative index, this function assumes the form of all the conic sections and expands the theory of aplanatic optical surfaces. There are two different symmetry centers with respect t

Tino Weber, Jens Herbig, Michael Mark, Hanns-Christoph Naegerl

We study three-body recombination in an optically trapped ultracold gas of cesium atoms with precise magnetic control of the s-wave scattering length a. At large positive values of a, we measure the dependence of the rate coefficient on a and confirm the theoretically predicted scaling proportional to a^4. Evidence of recombination heating indicates the form

M. S. Hussein, M. Ueda, A. J. Sargeant, M. P. Pato

We present an approximate analytic expression for thermonuclear reaction rate of charged particles when the cross section contains a single narrow or wide resonance described by a Breit-Wigner shape. The resulting expression is uniformly valid as the effective energy and resonance energy coalesce. We use our expressions to calculate the reaction rate for $^{

M. S. Hussein, A. J. Sargeant, M. P. Pato, M. Ueda

We present analytic formulae for the energy average and variance of the intraband decay intensity of a superdeformed band.

N. Tsoneva, H. Lenske, Ch. Stoyanov

Dipole excitations in neutron-rich nuclei below the neutron threshold are investigated. The method is based on Hartree-Fock-Bogoliubov (HFB) and Quasiparticle-Phonon Model (QPM) theory. Of our special interest are the properties of the low-lying 1- Pygmy Resonance and the two-phonon quadrupole-octupole 1- states in Sn-isotopes including exploratory investiga

A. Boyarsky, P. Gora

We present a simple dynamical systems model for the effect of invisible space dimensions on the visible ones. There are three premises. A: Orbits consist of flows of probabilities [P].which is the case in the setting of quantum mechanics. B: The orbits of probabilities are induced by (continuous time) differential or partial differential equations. C: Observ

A. Bäcker, S. Fürstberger, R. Schubert

For the representation of eigenstates on a Poincaré section at the boundary of a billiard different variants have been proposed. We compare these Poincaré Husimi functions, discuss their properties and based on this select one particularly suited definition. For the mean behaviour of these Poincaré Husimi functions an asymptotic expression is derived, includ

V. Gurarie

This paper studies the 1D pressureless turbulence (the Burgers equation). It shows that reliable numerics in this problem is very easy to produce if one properly discretizes the Burgers equation. The numerics it presents confirms the 7/2 power law proposed for probability of observing large negative velocity gradients in this problem. It also suggests that t

N. G. Marchuk, S. E. Martynova

We show how the matrix algebra notions of determinant, spectrum, and Hermitian conjugation transfer to the Clifford algebra and to differential forms on parallelisable manifolds.

N. G. Marchuk

We present a so called Dirac-type tensor equation (DTTE). This equation is written in coordinateless form with the aid of differential operators $d$ and $δ$. A wave function of DTTE belongs to a minimal left ideal of the algebra of exterior forms with respect to the Clifford product. We show that a coordinate form of DTTE is identical to the Dirac equation i

J. Guerrero, J. L. Jaramillo, V. Aldaya

``Pseudo-cohomology'', as a refinement of Lie group cohomology, is soundly studied aiming at classifying of the symplectic manifolds associated with Lie groups. In this study, the framework of symplectic cohomology provides fundamental new insight, which enriches the analysis previously developed in the setting of Cartan-Eilenberg $H^2(G,U(1))$ cohom

Jon Warren, Shinzo Watanabe

We study the noise, in the sense of Tsirelson, generated by Harris flows. A criterion is given for the noise to be non-white, and in this case we study the associated spectral sets.

Lars Andersson

An energy estimate is proved for the Bel--Robinson energy along a constant mean curvature foliation in a spatially compact vacuum spacetime, assuming an $L^{\infty}$ bound on the second fundamental form, and a bound on a spacetime version of Bel--Robinson energy.

William McCune, Ranganathan Padmanabhan, Robert Veroff

In this note we show that the equational theory of all lattices is defined by a single absorption law. The identity of length 29 with 8 variables is shorter than previously known such equations defining lattices.

Ulrich Oertel

We prove results showing that the existence of essential maps of surfaces in a manifold M' obtained from a 3-manifold M by Dehn filling implies the existence of essential maps of surfaces in M.

Anthony Iarrobino

Let R be the polynomial ring in r variables over a field k, with maximal ideal M and let V denote a vector subspace of the space of degree-j homogeneous elements of R. We study three related algebras determined by V. The first is the ``ancestor algebra'' whose defining ideal is the largest graded ideal whose intersection with M^j is the ideal (V). Th

Werner Georg Nowak

Let Q(u,v) be a positive definite binary quadratic form with arbitrary real coefficients. For large real x, one may ask for the number B(x) of primitive lattice points (integer points (m,n) with gcd(m,n) = 1) in the ellipse disc Q(u,v) < x, in particular, for the remainder term R(x) in the asymptotics for B(x). While upper bounds for R(x) depend on zero-free

P. T. Chrusciel, R. Bartnik

We prove regularity for a class of boundary value problems for first order elliptic systems, with boundary conditions determined by spectral decompositions, under coefficient differentiability conditions weaker than previously known. We establish Fredholm properties for Dirac-type equations with these boundary conditions. Our results include sharp solvabilit

Philippe Bonneau, Daniel Sternheimer

After a presentation of the context and a brief reminder of deformation quantization, we indicate how the introduction of natural topological vector space topologies on Hopf algebras associated with Poisson Lie groups, Lie bialgebras and their doubles explains their dualities and provides a comprehensive framework. Relations with deformation quantization and

Ulrich Oertel, Jacek Swiatkowski

A contamination in a 3-manifold is an object interpolating between the contact structure and the lamination. Contaminations seem to provide a link between 3-dimensional contact geometry and the classical topology of 3-manifolds, as described in a separate paper. In this paper we deal with contaminations carried by branched surfaces, giving a sufficient condi

Lei Ni

In this paper, we derive a new monotonicity formula for the plurisuhbarmonic functions on complete Kähler manifolds with nonnegative bisectional curvature. As applications we derive the sharp estimates for the dimension of the spaces of holomorphic functions (sections) with polynomial growth, which in particular, partially solve a conjecture of Yau.

Craig A. Tracy, Harold Widom

To each partition $λ$ with distinct parts we assign the probability $Q_λ(x) P_λ(y)/Z$ where $Q_λ$ and $P_λ$ are the Schur $Q$-functions and $Z$ is a normalization constant. This measure, which we call the shifted Schur measure, is analogous to the much-studied Schur measure. For the specialization of the first $m$ coordinates of $x$ and the first $n$ coordin

Martin Rubey

We show that the h-vector of a ladder determinantal ring cogenerated by M=[u_1|v_1] is log-concave. Thus we prove an instance of a conjecture of Stanley, resp. Conca and Herzog

S. Mignemi

We discuss entropy bounds for a class of two-dimensional gravity models. While the Bekenstein bound can be proved to hold in general for weakly gravitating matter, the analogous of the holographic bound is not universal, but depends on the specific model considered

C. Kristjansen

We review how the identification of gauge theory operators representing string states in the pp-wave/BMN correspondence and their associated anomalous dimension reduces to the determination of the eigenvectors and the eigenvalues of a simple quantum mechanical Hamiltonian and analyze the properties of this Hamiltonian. Furthermore, we discuss the role of ran

Charles B. Thorn, Tuan A. Tran

We identify the strong coupling fishnet diagram with a certain Ising spin configuration in the lightcone worldsheet description of planar TrΦ^3 field theory. Then, using a mean field formalism, we take the remaining planar diagrams into account in an average way. The fishnet spin configuration requires two mean fields ϕ,ϕ&#39; where the fishnet diagram is th

Jurgen Baacke, George Lavrelashvili

We evaluate the one-loop prefactor in the false vacuum decay rate in a theory of a self interacting scalar field in 3+1 dimensions. We use a numerical method, established some time ago, which is based on a well-known theorem on functional determinants. The proper handling of zero modes and of renormalization is discussed. The numerical results in particular

Michael Forger, Hartmann Römer

We give a comprehensive review of various methods to define currents and the energy-momentum tensor in classical field theory, with emphasis on a geometric point of view. The necessity of ``improving&#39;&#39; the expressions provided by the canonical Noether procedure is addressed and given an adequate geometric framework. The main new ingredient is the exp

K. Landsteiner, C. I. Lazaroiu, Radu Tatar

We study a chiral N=1, U(N) field theory in the context of the Dijkgraaf-Vafa correspondence. Our model contains one adjoint, one conjugate symmetric and one antisymmetric chiral multiplet, as well as eight fundamentals. We compute the generalized Konishi anomalies and compare the chiral ring relations they induce with the loop equations of the (intrinsicall

A. Kurylov, M. J. Ramsey-Musolf, S. Su

We compute the supersymmetric (SUSY) corrections to the parity-violating, deep inelastic electron-deuteron asymmetry. Working with the Minimal Supersymmetric Standard Model (MSSM) we consider two cases: R parity conserving and R parity-violating. Under these scenarios, we compare the SUSY effects with those entering other parity-violating observables. For bo

L. Perivolaropoulos

We study analytically and numerically the core structure of global vortices forming on topologically deformed brane-worlds with a single toroidally compact extra dimension. It is shown that for an extra dimension size larger than the scale of symmetry breaking the magnitude of the complex scalar field at the vortex center can dynamically remain non-zero. Sin

A. H. Mueller

An overview of DIS 2003 is given with a focus on small-x physics and the interrelationship between deep inelastic scattering and heavy ion physics which furnishes much of the basic information for understanding high-density QCD matter. In addition to small-x physics, topics covered include single spin asymmeteries, light-cone gauge choices, strange quarks in

T. E. Clark, S. T. Love

The electron and muon number violating muonium-antimuonium oscillation process can proceed provided neutrinos have non-zero masses and mix among the various generations. Modifying the Standard Model only by the inclusion of singlet right handed neutrino fields and allowing for general neutrino masses and mixings, the leading order matrix element contributing

Paul Hoyer

Rescattering of the struck quark in Deep Inelastic Scattering implies that measured parton distributions are not directly related to the Fock state probabilities of the target wave function. The production amplitudes acquire dynamical phases, which gives rise to shadowing and diffraction in DIS. I review the kinematics and dynamics of DIS as seen in various

A. D. Martin, R. G. Roberts, W. J. Stirling, R. S. Thorne

We discuss uncertainties in the extraction of parton distributions from global analyses of DIS and related data. We present conservative sets of partons, at both NLO and NNLO, which are stable to x,Q^2,W^2 cuts on the data. We give the corresponding values of alpha(M_Z^2) and the cross sections for W production at the Tevatron.

Stephane Peigne

Several properties of high energy hadronic collisions are illustrated by comparing DIS and the Drell-Yan process within a scalar QED model. Diffraction and transverse momentum broadening within the target system are found to be non-universal. Here these effects are simply due to the Coulomb phase shift in the Drell-Yan production amplitude.

E. N. Saridakis, N. G. Antoniou, F. K. Diakonos, N. Tetradis

Within the context of the linear $\s$-model for two flavours, we investigate non-equilibrium phenomena that may occur during the QCD chiral phase transition in heavy-ion collisions. We assume that the chiral symmetry breaking is followed by a rapid quench so that the system falls out of thermal equilibrium. We study the mechanism for the amplification of the

D. Pocanic

We report interim results of the PIBETA experiment analysis for the pion beta decay and pion radiative decay. The former is in excellent agreement with the SM predictions at the 1% accuracy level.

Cecilia Lunardini

I review the effects of flavor conversion of neutrinos from stellar collapse due to masses and mixing, and discuss the motivations for their study. I consider in detail the sensitivity of certain observables (characteristics of the energy spectra of nu_e and antinu_e events) to the 13-mixing (sin^2θ_13) and to the type of mass hierarchy/ordering (sign[Delta

A. V. Belitsky

We discuss the possibility of measuring generalized parton distributions in exclusive electroproduction of mesons off the nucleon and estimate the uncertainty from perturbatively induced higher-twist corrections. We find that, while the magnitude of the cross section changes significantly taking into account twist-four contributions modeled via renormalons,

B G Wybourne

The group classification of exotic pentaquarks involving four standard quarks and a single antiquark to produce pentaquarks of strangeness +1 is outlined.

Subhendra Mohanty

The low energy component of the antineutrino spectrum observed in the recent Kamland experiment has significant contribution from the radioactive decay of $^{238}U$ and $^{232}Th$ in the crust and mantle of the earth. By taking the ratio of the antineutrino events obeserved in two different energy ranges we can determine the present value $[Th/U]$ independen

Jonathan Hays

As the integrated luminosity of the Run II Tevatron increases, the sensitivity to new physics is approaching and in some cases surpassing that previously attained in Run I. Presented below are a selection of new results from searches for physics beyond the Standard Model at the CDF and D0 experiments.

Michael A. Ivanov

It is shown that screening the background of super-strong interacting gravitons ensures the Newtonian attraction, if a part of single gravitons is pairing and graviton pairs are destructed by collisions with a body. If the considered quantum mechanism of classical gravity is realized in the nature, than an existence of black holes contradicts to the equivale

Lili Ma, YangQuan Chen, Kevin L. Moore

The common approach to radial distortion is by the means of polynomial approximation, which introduces distortion-specific parameters into the camera model and requires estimation of these distortion parameters. The task of estimating radial distortion is to find a radial distortion model that allows easy undistortion as well as satisfactory accuracy. This p

Amar Isli

We define a ternary Relation Algebra (RA) of relative position relations on two-dimensional directed lines (d-lines for short). A d-line has two degrees of freedom (DFs): a rotational DF (RDF), and a translational DF (TDF). The representation of the RDF of a d-line will be handled by an RA of 2D orientations, CYC_t, known in the literature. A second algebra,

Vincent Guirardel

We give a simple proof of the finite presentation of Sela&#39;s limit groups by using free actions on $\bbR^n$-trees. We first prove that Sela&#39;s limit groups do have a free action on an $\bbR^n$-tree. We then prove that a finitely generated group having a free action on an $\bbR^n$-tree can be obtained from free abelian groups and surface groups by a fin

J. Strand, B. D. Schultz, A. F. Isakovic, X. Lou

We report the observation of nuclear magnetic resonance (NMR) in a ferromagnet-semiconductor heterostructure in the presence of a spin-polarized current. Spin-polarized electrons injected from a metallic ferromagnet generate a large nuclear spin population in a GaAs quantum well by dynamic polarization. The characteristic time for the polarization process is

N. N. Kovaleva, A. V. Boris, D. Munzar, T. Holden

We present results of a systematic study of the c axis lattice dynamics in single layer Bi2Sr2CuO6 (Bi2201), bilayer Bi2Sr2CaCu2O8 (Bi2212) and trilayer Bi2Sr2Ca2Cu3O10 (Bi2223) cuprate superconductors. Our study is based on both experimental data obtained by spectral ellipsometry on single crystals and theoretical calculations. The calculations are carried

Patrick A. Lee

I shall argue that the high Tc problem is the problem of doping into a Mott insulator. Furthermore, the well documented pseudo-gap phenomenon in underdoped cuprates holds the key to understanding this physics. Phase fluctuation alone cannot explain this phenomenon, but there is a clear need to identify a competing state which lives in the vortex core. The st

David L. Mobley, Christopher R. Pike, Joseph E. Davies, Daniel L. Cox

We develop a phenomenological model to study magnetic hysteresis in two samples designed as possible perpendicular recording media. A stochastic cellular automata model captures cooperative behavior in the nucleation of magnetic domains. We show how this simple model turns broad hysteresis loops into loops with sharp drops like those observed in these sample

Wei-Guo Yin, C. -G. Duan, W. N. Mei, J. Liu

We present molecular dynamics simulations of solid NaNO$_2$ using pair potentials with the rigid-ion model. The crystal potential surface is calculated by using an \emph{a priori} method which integrates the \emph{ab initio} calculations with the Gordon-Kim electron gas theory. This approach is carefully examined by using different population analysis method

A. Killinger, R. Höllinger, U. Krey

We study the dynamics of flat circular permalloy nanomagnets for 1.) magnetic vortex and 2.) single-domain configurations, using micromagnetic simulation. Dynamical studies for isolated vortex structures show that both the vorticity and the central polarity of the out-of-plane component can be switched fast (50-100 ps) and independently. Micromagnetic simula

P. Lemmens, K. Y. Choi, G. Caimi, L. Degiorgi

We report infrared and Raman spectroscopy results of the spin-1/2 quantum magnet TiOCl. Giant anomalies are found in the temperature dependence of the phonon spectrum, which hint to unusual coupling of the electronic degrees of freedom to the lattice. These anomalies develop over a broad temperature interval, suggesting the presence of an extended fluctuatio

X. J. Chen, H. -U. Habermeier, C. C. Almasan

We report an experimental study of the time dependence of resistivity of a La$_{0.9}$Sr$_{0.1}$MnO$_{3}$ ultrathin film in order to elucidate the underlying mechanism for metal-insulator transition and colossal magnetoresistance CMR effect. There is a clear change of sign in the resistive relaxation rate across the metal-insulator transition driven by temper

D. Bolle, J. Busquets Blanco, T. Verbeiren

Using the generating functional analysis an exact recursion relation is derived for the time evolution of the effective local field of the fully connected Little-Hopfield model. It is shown that, by leaving out the feedback correlations arising from earlier times in this effective dynamics, one precisely finds the recursion relations usually employed in the

Peter Talkner, Jerzy Luczka

The reduction of a continuous Markov process with multiple metastable states to a discrete rate process is investigated in the presence of slow time dependent parameters such as periodic external forces or slowly fluctuating barrier heights. A quantitative criterion is provided under which condition a kinetic description with time dependent frozen rates appl

Valentin V. Sokolov

Effect of a complicated many-body environment is analyzed on the chaotic motion of a quantum particle in a mesoscopic ballistic structure. The dephasing and absorption phenomena are treated on the same footing in the framework of a model which is free of the ambiguities inherent to earlier models. The single-particle doorway resonance states excited via an e

Lars Oberbeck, Neil J. Curson, Toby Hallam, Michelle Y. Simmons

In order to fabricate precise atomic-scale devices in silicon using a combination of scanning tunnelling microscopy (STM) and molecular beam epitaxy it is necessary to minimize the segregation/diffusion of dopant atoms during silicon encapsulation. We characterize the surface segregation/diffusion of phosphorus atoms from a $δ$-doped layer in silicon after e

U. K. Roessler, A. N. Bogdanov

Equilibrium spin configurations and their stability limits have been calculated for models of magnetic superlattices with a finite number of thin ferromagnetic layers coupled antiferromagnetically through (non-magnetic) spacers as Fe/Cr and Co/Ru multilayers. Depending on values of applied magnetic field and unaxial anisotropy, the system assumes collinear(a

J. Boronat, J. Casulleras, V. Grau, E. Krotscheck

We use structural information from diffusion Monte Carlo calculations for two--dimensional 3He to calculate the effective mass. Static effective interactions are constructed from the density-- and spin structure functions using sumrules. We find that both spin-- and density-- fluctuations contribute about equally to the effective mass. Our results show, in a

V. Ravi Chandra, Diptiman Sen, N. B. Ivanov, J. Richter

We study the low-energy properties of a sawtooth chain with spin-1&#39;s at the bases of the triangles and spin-1/2&#39;s at the vertices of the triangles. The spins have Heisenberg antiferromagnetic interactions between nearest neighbors, with a coupling J_2 between a spin-1 and a spin-1/2, and a coupling J_1 = 1 between two spin-1&#39;s. Analysis of the ex

Y. S. Badyal, U. Bafile, K. Miyazaki, I. M. de Schepper

We present inelastic neutron scattering measurements on liquid mercury at room temperature for wave numbers $q$ in the range 0.3 $< q <$ 7.0 Å$^{-1}$. We find that the energy halfwidth of the incoherent part of the dynamic structure factor $S(q,E)$ is determinded by a self-diffusion process. The halfwidth of the coherent part of $S(q, E)$ shows the character

Damien Challet

We use the Minority Game and some of its variants to show how efficiency depends on learning in models of agents competing for limited resources. Exact results from statistical physics give a clear understanding of the phenomenology, and opens the way to the study of reverse problems. What agents can optimize and how well is discussed in details.

Katherine E. McGowan, Phil A. Charles, Darragh O&#39;Donoghue, Alan P. Smale

We have obtained high time resolution (seconds) photometry of LMC X-2 in December 1997, simultaneously with the Rossi X-ray Timing Explorer (RXTE), in order to search for correlated X-ray and optical variability on timescales from seconds to hours. We find that the optical and X-ray data are correlated only when the source is in a high, active X-ray state. O

Cheongho Han, Kyongae Chang

An extrasolar planet can be detected via microlensing from the perturbation it makes in the smooth lensing light curve of the primary. In addition to the conventional photometric microlensing, astrometric observation of the center-of-light motion of the source star image provides a new channel of detecting and characterizing extrasolar planets. It was known

David E. Johnston, Gordon T. Richards, Joshua A. Frieman, Charles R. Keeton

We report the discovery of a new gravitationally lensed quasar from the Sloan Digital Sky Survey, SDSS J090334.92+502819.2. This object was targeted for SDSS spectroscopy as a Luminous Red Galaxy (LRG), but manual examination of the spectrum showed the presence of a quasar at z= 3.6 in addition to a red galaxy at z=0.388, and the SDSS image showed a second p

D. S. Davis, N. A. Miller, R. F. Mushotzky

In our search for ``hidden&#39;&#39; AGN we present results from a Chandra observation of the nearby cluster Abell 2255. Eight cluster galaxies are associated with point-like X-ray emission, and we classify these galaxies based on their X-ray, radio, and optical properties. At least three are associated with active galactic nuclei (AGN) with no optical signa

M. Brusa, A. Comastri, M. Mignoli, F. Fiore

We present extensive optical, radio and infrared follow-up observations of a sample of 35 hard X-ray (2-10 keV) selected sources discovered serendipitously in the PV XMM-Newton observation of the radio-loud quasar PKS 0312-77 field, for which also an archival Chandra observation is available. The observations have been carried out as part of the HELLAS2XMM s

Paola Marziani, Radoslav K. Zamanov, Jack W. Sulentic, Massimo Calvani

[Abridged] We compute the virial mass of the central black hole (M) and the luminosity-to-mass (L/M) ratio of ~ 300 low-z quasars and luminous Seyfert 1 nuclei. We analyze: (1) whether radio-quiet and radio-loud objects show systematic differences in terms of M and L/M; (2) the influence of M and L/M on the shape of the H-beta broad component line profile; (

I. S. Glass, M. Schultheis

A large and complete sample of stars with K < 9.75 in the NGC6522 Baade&#39;s Window is examined using light curves from MACHO and IJK from DENIS. All 4 of the sequences ABCD in the K vs logP diagram of the LMC are seen in the Bulge. The Bulge sequences however show some differences from the Magellanic Clouds. The sequences may be useful as distance indicato

Nicola Loaring, M. J. Page, G. Ramsay

We present results from XMM-Newton observations of the obscured QSO 1SAX J1218.9+2958. We find that the previously reported optical and soft X-ray counterpart positions are incorrect. However we confirm the spectroscopic redshift of 0.176. The optical counterpart has a K magnitude of 13.5 and an R-K colour of 5.0 and is therefore a bright extremely red objec

G. Bernardi, E. Carretti, S. Cortiglioni, R. J. Sault

We present the first observation of the diffuse polarized synchrotron radiation of a patch ($\sim 3^\circ \times 3^\circ$) in the BOOMERanG field, one of the areas with the lowest CMB foreground emission. The work has been carried out with the Australia Telescope Compact Array at 1.4 GHz with 3.4 arcmin resolution and sensitivity of $\sim 0.18$ mJy beam$^{-1

Carlos Barcelo, Stefano Liberati, Matt Visser

Bose-Einstein condensates (BEC) have recently been the subject of considerable study as possible analogue models of general relativity. In particular it was shown that the propagation of phase perturbations in a BEC can, under certain conditions, closely mimic the dynamics of scalar quantum fields in curved spacetimes. In two previous articles [gr-qc/0110036

C. A. R. Herdeiro

By applying a set of Hassan-Sen transformations and string dualities to the Kerr-Godel solution of minimal D=5 supergravity we derive a four parameter family of five dimensional solutions in type II string theory. They describe rotating, charged black holes in a rotating background. For zero background rotation, the solution is D=5 Kerr-Newman; for zero char

Stephan Narison

We study the dynamics of the the spin zero open charm and beauty mesons using QCD spectral sum rules (QSSR), where we observe the important rôle of the chiral condensate <\bar ψψ> in the mass-splittings between the scalar-pseudoscalar mesons. Fixing the sum rule parameters for reproducing the well-known D(0-) and Ds(0-) masses, we re-obtain the running charm

F. Wu, R. X. Xu, Janusz Gil

Using the method proposed in a previous paper, we calculate pulsar braking indices in the models with torque contributions from both inner and outer accelerating regions, assuming that the interaction between them is negligible. We suggest that it is likely that the inverse Compton scattering induced polar vacuum gap and the outer gap coexist in the pulsar m