September 1999 arXiv papers — page 2

Frank C. van den Bosch

New models for the formation of disk galaxies are presented. I discuss the contraints on galaxy formation that follow from fitting the model to the near-infrared Tully-Fisher (TF) relation, with an emphasis on reproducing the small amount of scatter observed. Once the parameters that describe the supernova feedback are tuned to fit the slope of the observed

H. Garcia-Compean, J. F. Plebanski, M. Przanowski, F. J. Turrubiates

We study the deformation quantization of scalar and abelian gauge classical free fields. Stratonovich-Weyl quantizer, star-products and Wigner functionals are obtained in field and oscillator variables. Abelian gauge theory is particularly intriguing since Wigner functional is factorized into a physical part and other one containing the constraints only. Som

Kenneth Intriligator

It is emphasized that compactified little string theories have compact moduli spaces of vacua, which globally probe compact string geometry. Compactifying various little string theories on T^3 leads to 3d theories with exact, quantum Coulomb branch given by: an arbitrary T^4 of volume M_s^2, an arbitrary K3 of volume M_s^2, and moduli spaces of G=SU(N), SO(2

G. C. McLaughlin, J. N. Ng

Theories involving extra dimensions, a low (TeV) string scale and bulk singlet neutrinos will produce an effective neutrino magnetic moment which may be large (< 10^{-11} mu_B). The effective magnetic moment increases with neutrino energy, and therefore high energy reactions are most useful for limiting the allowed number of extra dimensions. We examine cons

B. Kayser, D. London

The first measurements of CP violation in the $B$ system will likely probe $\sin 2α$, $\sin 2β$ and $\cos 2γ$. Assuming that the CP angles $α$, $β$ and $γ$ are the interior angles of the unitarity triangle, these measurements determine the angle set $(α,β,γ)$ except for a twofold discrete ambiguity. If one allows for the possibility of new physics, the prese

S. Carlip

The observed absence of gravitational aberration requires that ``Newtonian&#39;&#39; gravity propagate at a speed $c_g>2\times10^{10}c$. By evaluating the gravitational effect of an accelerating mass, I show that aberration in general relativity is almost exactly canceled by velocity-dependent interactions, permitting $c_g=c$. This cancellation is dictated b

Conor Houghton, Kimyeong Lee

The mass of 1/4-BPS dyonic configurations in N=4 D=4 supersymmetric Yang-Mills theories is calculated within the Nahm formulation. The SU(3) example, with two massive monopoles and one massless monopole, is considered in detail. In this case, the massless monopole is attracted to the massive monopoles by a linear potential.

A. Chamblin, S. W. Hawking, H. S. Reall

Gravitational collapse of matter trapped on a brane will produce a black hole on the brane. We discuss such black holes in the models of Randall and Sundrum where our universe is viewed as a domain wall in five dimensional anti-de Sitter space. We present evidence that a non-rotating uncharged black hole on the domain wall is described by a ``black cigar&#39

Mohsen Alishahiha, Yaron Oz, M. M. Sheikh-Jabbari

We consider systems of Dp branes in the presence of a nonzero B field. We study the corresponding supergravity solutions in the limit where the branes worldvolume theories decouple from gravity. These provide dual descriptions of large N noncommutative field theories. We analyse the phase structure of the theories and the validity of the different descriptio

Matt Mackie, Ryan Kowalski, Juha Javanainen

We analyze coherent two-color photoassociation of a Bose-Einstein condensate, focusing on stimulated Raman adiabatic passage (STIRAP) in free-bound-bound transitions from atoms to molecules. This problem is of particular interest since STIRAP is predicted to be necessarily absent in the nondegenerate case [Javanainen and Mackie, Phys. Rev. A 58, R789 (1998)]

Mohammad R. Garousi

By integrating the Seiberg-Witten differential equation in a special path, we write ordinary gauge fields in terms of their non-commutative counterparts up to three non-commutative gauge fields. We then use this change of variables to write ordinary abelian Dirac-Born-Infeld action in terms of non-commutative fields. The resulting action is then compared wit

G. E. Volovik

The energy levels of the fermions bound to the vortex core are considered for the general case of chiral superconductors. There are two classes of chiral superconductivity: in the superconducting state of class I the axisymmetric singly quantized vortex has the same energy spectrum of bound states as in s-wave superconductor: E=(n+1/2)ω_0 with integral n. In

Vincent Buonomano

We analyze a conceivable type of local realistic theory, which we call a co-operative phenomena type local realistic theory. In an experimental apparatus to measure second or fourth order interference effects, it images that their exists a stable global pattern or mode in a hypothesized medium that is at least the size of the coherence volume of all the invo

L. Mornas, K. Morawetz

We reexamine the derivation of relativistic transport equations for fermions when conserving the most general spinor structure of the interaction and Green function. Such an extension of the formalism is needed when dealing with {\it e.g.} spin-polarized nuclear matter or non-parity conserving interactions. It is shown that some earlier derivations can lead

Jens Reinbach, Hermann Schulz

The gluon transverse self-energy of the pure Yang-Mills system at high-temperature is analysed in the static limit and at fourth order in the coupling. Possible contributions to this function are collected, seen to be gauge-fixing independent subsets and shown to vanish all, except those which are either regulators or constituents of the self-energy of Eukli

V. Ch. Zhukovsky, V. V. Khudyakov

Gluon and quark contributions to the thermodynamic potential (free energy) of a (2+1)-dimensional QCD model at finite temperature in the background of a constant homogeneous chromomagnetic field H combined with A_0 condensate are calculated. The role of the tachyonic mode in the gluon energy spectrum is discussed. A possibility of the free energy global mini

Dmitri Antonov

Recent progress achieved in the solution of the problem of confinement in various (non-)Abelian gauge theories by virtue of a derivation of their string representation is reviewed. The theories under study include QCD within the so-called Method of Field Correlators, QCD-inspired Abelian-projected theories, and compact QED in three and four space-time dimens

H. V. Klapdor-Kleingrothaus, St. Kolb, V. A. Kuzmin

Recent results of neutrino oscillation experiments point to a nonvanishing neutrino mass. Neutrino mass models favour Majorana-type neutrinos. In such circumstances it is natural that the supersymmetric counterpart of the neutrino, the sneutrino, bears also lepton number violating properties. On the other hand, the fact that the universe exhibits an asymmetr

Johan van de Leur

We obtain the collection of symmetric and symplectic matrix integrals and the collection of Pfaffian tau-functions, recently described by Peng and Adler and van Moerbeke, as specific elements in the Spin-group orbit of the vacuum vector of a fermionic Fock space. This fermionic Fock space is the same space as one constructs to obtain the KP and 1-Toda lattic

A. Aradian, E. Raphael, P. G. de Gennes

We consider a porous solid covered with a water film (or with a drop) in situations where the liquid is pumped in, either spontaneously (if the porous medium is hydrophilic) or mechanically (by an external pump). The dynamics of dewetting is then strongly modified. We analyse a few major examples: a) horizontal films, which break at a certain critical thickn

Giulio Biroli

The Thouless, Anderson, Palmer (TAP) approach to thermodynamics of mean field spin-glasses is generalised to dynamics. A method to compute the dynamical TAP equations is developed and applied to the p-spin spherical model. In this context we show to what extent the dynamics can be represented as an evolution in the free energy landscape. In particular the re

Y. P. Jing, Yasushi Suto

We perform a series of high-resolution N-body simulations designed to examine the density profiles of dark matter halos. From 12 simulated halos ranging the mass of $2\times10^{12}\sim 5\times10^{14} h^{-1}{\rm M_\odot}$ (represented by $\sim 1$ million particles within the virial radius), we find a clear systematic correlation between the halo mass and the

P. J. Forrester, E. M. Rains

We consider the following problem: When do alternate eigenvalues taken from a matrix ensemble themselves form a matrix ensemble? More precisely, we classify all weight functions for which alternate eigenvalues from the corresponding orthogonal ensemble form a symplectic ensemble, and similarly classify those weights for which alternate eigenvalues from a uni

E. DelRe, B. Crosignani, P. Di Porto

We address the issue of totally teleporting the quantum state of an external particle, as opposed to studies on partial teleportation of external single-particle states, total teleportation of coherent states and encoded single-particle states, and intramolecular teleportation of nuclear spin states. We find a set of commuting observables whose measurement d

Georgios M. Nikolopoulos, Søren Bay, P. Lambropoulos

We present a method for dealing with quantum systems coupled to a structured reservoir with any density of modes and with more than one excitation. We apply the method to a two-level atom coupled to the edge of a photonic band gap and a defect mode. Results pertaining to this system, provide the solution to the problem of two photons in the reservoir and pos

R. A. Carrigan, D. Chen, G. Jackson, N. Mokhov

Luminosity-driven channeling extraction has been observed for the first time in a 900 GeV study at the Fermilab Tevatron. This experiment, Fermilab E853, demonstrated that useful TeV level beams can be extracted from a superconducting accelerator during high luminosity collider operations without unduly affecting the background at the collider detectors. Mul

Jean Delsarte

Seminal result of Delsarte is archived here

Jaakko Akola, Matti Manninen, Hannu Hakkinen, Uzi Landman

Photoelectron (PES) spectra from aluminum cluster anions (from 12 to 15 atoms) at various temperature regimes, were studied using ab-initio molecular dynamics simulations and experimentally. The calculated PES spectra, obtained via shifting of the simulated electronic densities of states by the self-consistently determined values of the asymptotic exchange-c

Leonid Il&#39;ichov

Using the concept of the so-called quantum relaxation, we build a semiphenomenological model for orto-para conversion of nuclear spin isomers of hydrogen-type molecules.

A. M. Shalagin, L. V. Il&#39;ichov

We report on a new phenomenon of molecular nuclear spin isomers conversion in the field of resonant laser radiation. It is based on the isomer-selective optical excitation and the difference of conversion rates for excited and unexcited molecules. We expect the considerable magnitude of the effect for all molecules which absorb the radiation of existing lase

Axel G. Rossberg, Nandor Eber, Agnes Buka, Lorenz Kramer

We present the first quantitative verification of an amplitude description for systems with (nearly) spontaneously broken isotropy, in particular for the recently discovered abnormal-roll states. We also obtain a conclusive picture of the 3d director configuration in a spatial period doubling phenomenon involving disclination loops (CRAZY rolls). The first o

Ts. Dankova, G. Rosensteel

A rotating system, such as a star, liquid drop, or atomic nucleus, may rotate as an oblate spheroid about its symmetry axis or, if the angular velocity is greater than a critical value, as a triaxial ellipsoid about a principal axis. The oblate and triaxial equilibrium configurations minimize the total energy, a sum of the rotational kinetic energy plus the

Ts. Dankova, G. Rosensteel

Mean field theory has an unexpected group theoretic mathematical foundation. Instead of representation theory which applies to most group theoretic quantum models, Hartree-Fock and Hartree-Fock-Bogoliubov have been formulated in terms of coadjoint orbits for the groups U(n) and O(2n). The general theory of mean fields is formulated for any arbitrary Lie alge

J. Troupe, G. Rosensteel

Finite-dimensional Lie algebras of vector fields determine geometrical collective models in quantum and classical physics. Every set of vector fields on Euclidean space that generates the Lie algebra sl(3, R) and contains the angular momentum algebra so(3) is determined. The subset of divergence-free sl(3, R) vector fields is proven to be indexed by a real n

G. Rosensteel, Ts. Dankova

Given a vector space of microscopic quantum observables, density functional theory is formulated on its dual space. A generalized Hohenberg-Kohn theorem and the existence of the universal energy functional in the dual space are proven. In this context ordinary density functional theory corresponds to the space of one-body multiplication operators. When the o

A. Yu. Loginov, D. M. Nikolenko, A. V. Osipov, I. A. Rachek

Recently, we have performed the experiment on studying the pion electroproduction at photon point on the internal polarized deuterium target at the VEPP-3 storage ring. For the more complete treatment of the reaction d(e,pp)X we investigate the reaction channel with an additional neutral pion production as background to the leading reaction of the single neg

James Lepowsky

We announce a new type of &#34;Jacobi identity&#34; for vertex operator algebras, incorporating values of the Riemann zeta function at negative integers. Using this we &#34;explain&#34; and generalize some recent work of S. Bloch&#39;s relating values of the zeta function with the commutators of certain operators and Lie algebras of differential operators.

Günter M. Ziegler

These lectures on the combinatorics and geometry of 0/1-polytopes are meant as an \emph{introduction} and \emph{invitation}. Rather than heading for an extensive survey on 0/1-polytopes I present some interesting aspects of these objects; all of them are related to some quite recent work and progress. 0/1-polytopes have a very simple definition and explicit

Anton Alekseev, Yvette Kosmann-Schwarzbach

A Lie group G in a group pair (D,G), integrating a Lie algebra g in a Manin pair (d,g) has a quasi-Poisson structure. We define the quasi-Poisson actions of such Lie groups G, that generalize the Poisson actions of Poisson Lie groups. We define and study the moment maps for those quasi-Poisson actions which are quasi-hamiltonian. These moment maps take value

K. Oguiso, J. Sakurai

First, we classify Calabi-Yau threefolds with infinite fundamental group by means of their minimal splitting coverings introduced by Beauville, and deduce that the nef cone is a rational simplicial cone and any rational nef divisor is semi-ample if the second Chern class is identically zero. We also derive a sufficient condition for the fundamental group to

Janusz Grabowski, Pawel Urbanski

A notion of an algebroid - a generalization of a Lie algebroid structure is introduced. We show that many objects of the differential calculus on a manifold M associated with the canonical Lie algebroid structure on T^M can be obtained in the framework of a general algebroid. Also a compatibility condition which leads, in general, to a concept of a bialgebro

Ulrich Betke, Martin Henk

Based on Minkowski&#39;s work on critical lattices of 3-dimensional convex bodies we present an efficient algorithm for computing the density of a densest lattice packing of an arbitrary 3-polytope. As an application we calculate densest lattice packings of all regular and Archimedean polytopes.

Ezra Getzler

We calculate the Euler characteristics of the local systems S^k(V) \otimes S^l\Wedge^2(V) on the moduli space M_2 of curves of genus 2, where V is the rank 4 local system R^1π_*C.

Michael Joswig

A well-known theorem of Blind and Mani says that every simple polytope is uniquely determined by its graph. Kalai gave a very short and elegant proof of this result using the concept of acyclic orientations. As it turns out, Kalai&#39;s proof can be suitably generalized without much effort. We apply our results to a special class of cubical polytopes.

C. R. Hagen

It is shown that there exists a soluble four parameter model in (1+1) dimensions all of whose propagators can be determined in terms of the corresponding known propagators of the vector coupling theory. Unlike the latter case, however, the limit of zero bare mass is nonsingular and yields a nontrivial theory with a rigorously unbroken gauge invariance.

Patrick Dorey, Ingo Runkel, Roberto Tateo, Gerard Watts

The g-function was introduced by Affleck and Ludwig as a measure of the ground state degeneracy of a conformal boundary condition. We consider this function for perturbations of the conformal Yang-Lee model by bulk and boundary fields using conformal perturbation theory, the truncated conformal space approach and the thermodynamic Bethe Ansatz (TBA). We find

I. Antoniadis

I review the relations between mass scales in various string theories and in M-theory. I discuss physical motivations and possible consistent realizations of large volume compactifications and low string scale. Large longitudinal dimensions, seen by Standard Model particles, imply in general that string theory is strongly coupled unless its tension is close

Cécile Martin

Applying the time-dependent variational principle of Balian and Vénéroni, we derive variational approximations for multi-time correlation functions in $Φ^4$ field theory. We assume first that the initial state is given and characterized by a density operator equal to a Gaussian density matrix. Then, we study the more realistic situation where only a few expe

Kei-Ichi Kondo

We outline a derivation of area law of the Wilson loop in SU(N) Yang-Mills theory in the maximal Abelian gauge. This is based on a new version of non-Abelian Stokes theorem and the novel reformulation of the Yang-Mills theory. Abelian dominance and monopole dominance of the string tension in SU(N) QCD are immediate consequences of this derivation.

H. Lu, C. N. Pope, T. A. Tran

We construct the complete and explicit non-linear Kaluza-Klein ansatz for deriving the bosonic sector of N=4 SU(2)\times U(1) gauged five-dimensional supergravity from the reduction of type IIB supergravity on S^5. This provides the first complete example of such an S^5 reduction that includes non-abelian gauge fields, and it allows any bosonic solution of t

Mary K. Gaillard, Brent D. Nelson

We study the phenomenology of a class of models describing modular invariant gaugino condensation in the hidden sector of a low-energy effective theory derived from the heterotic string. Placing simple demands on the resulting observable sector, such as a supersymmetry-breaking scale of approximately 1 TeV, a vacuum with properly broken electroweak symmetry,

Xiao-Gang He, Hitoshi Murayama, Sandip Pakvasa, G. Valencia

It was pointed out recently that supersymmetry can generate flavor-changing gluonic dipole operators with sufficiently large coefficients to dominate the observed value of epsilon&#39;/epsilon. We point out that the same operators contribute to direct CP violation in hyperon decay and can generate a CP violating asymmetry A(Λ^0_-) in the range probed by the

B. Kayser, D. London

We (re)examine CP violation in the decays B_d -> D K_s, where D represents D^0, D(bar), or one of their excited states. The quantity $\sin^2(2β+ γ)$ can be extracted from the time-dependent rates for $B_d(t) -> {\bar D}^{**0} K_s$ and $B_d(t) -> D^{**0} K_s$, where the $D^{**0}$ decays to $D^{(*)+}π^-$. If one considers a non-CP-eigenstate hadronic final sta

A. Pich, J. Prades

The recent ALEPH measurements of the inclusive Cabibbo--suppressed decay width of the $τ$ and several moments of its invariant mass distribution are used to determine the value of the strange quark mass. We obtain, in the $\bar{\rm MS}$ scheme, $m_s(M_τ^2) = (119\pm 24)$ MeV, which corresponds to $ m_s(1 {\rm GeV}^2) = (164 \pm 33) {\rm MeV}, m_s(4 {\rm GeV}

N. N. Nikolaev, J. Speth, B. G. Zakharov

We study medium modifications of the dilepton mass spectrum in coherent photo- and electroproduction of the Rho(1S)- and Rhoprim(2S)-meson resonances on nuclear targets. The analysis is performed within the coupled Rho, Rhoprim... channel formalism in which nuclear modifications derive from the off-diagonal rescatterings. We find that the effect of off-diago

J. R. Pelaez, J. A. Oller, E. Oset

By means of a coupled channel non-perturbative unitary approach, it is possible to extend the strong constrains of Chiral Perturbation Theory to higher energies. In particular, it is possible to reproduce the lowest lying resonances in meson-meson scattering up to 1.2 GeV using the parameters of the O(p^2) and O(p^4) Chiral Lagrangian. We report on an update

Junji Hisano, Nobuchika Okada

The five dimensional theory compactified on $S^1$ with two ``branes&#39;&#39; (two domain walls) embedded in it is constructed, based on the field-theoretic mechanism to generate the ``brane&#39;&#39;. Some light states localized in the ``brane&#39;&#39; appear in the theory. One is the Nambu-Goldstone boson, which corresponds to the breaking of the translat

Alan Kostelecky

Experimental signals for indirect CPT violation in the neutral-meson systems are studied in the context of a general CPT- and Lorentz-violating standard-model extension. In this explicit theory, some CPT observables depend on the meson momentum and exhibit diurnal variations. The consequences for CPT tests vary significantly with the specific experimental sc

Soon-Tae Hong

The strange form factors of baryon octet are evaluated, in the chiral models with the general chiral SU(3) group structure, to yield the theoretical predictions comparable to the recent experimental data of SAMPLE Collaboration and to study the spin symmetries. Other model predictions are also briefly reviewed to compare with our results and then the strange

A. Piroth

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.

Vladimir Skalozub, Vadim Demchik

The electroweak phase transition in a constant hypermagnetic field=A0 is studied in the Standard Model. The symmetry behaviour is investigated within the consistent effective potential of the scalar and magnetic fields at finite temperature. It includes the one-loop and ring diagram contributions. All fundamental fermions and bosons are taken into considerat

G. Ricco, M. Anghinolfi, M. Ripani, M. Taiuti

The occurrence of the Bloom-Gilman duality in the nucleon structure function is investigated by analyzing the Q**2-behavior of low-order moments, both including and excluding the contribution arising from the nucleon elastic peak. The Natchmann definition of the moments has been adopted in order to cancel out target-mass effects. It is shown that the onset o

Peter Csizmadia, Peter Levai

We investigate the production of the Phi meson and the Omega baryon which interact weakly with hot hadronic matter, and thus their spectra reflect the early stage of the heavy ion collisions. Our analysis shows that the hadronization temperature, T_had, and the transverse flow, v_T, of the initial deconfined phase are strongly correlated: T_had + a * (v_T)**

G. Stoll

A model-independent way of computing the mass corrections of vector-meson distribution amplitudes is given. The method is based on resummation of (next-to-)leading twist local operator.

J. P. Ma

In the NRQCD factorization for productions and decays of a quakonium the difference between the quarkonium mass and the twice of the heavy quark mass is neglected at the leading order of the small velocity expansion. The effect of this difference is included in the relativistic correction. We attempt to define the difference in terms of NRQCD matrix elements

G. Burgio, F. Di Renzo, L. Scorzato, M. Pepe

Several Wilson loops on several lattice sizes are computed in Perturbation Theory via a stochastic method. Applications include: Renormalons, the Mass Term in Heavy Quark Effective Theory and (possibly) the beta-function.

F. Di Renzo, L. Scorzato

Concerning Numerical Stochastic Perturbation Theory, we discuss the convergence of the stochastic process (idea of the proof, features of the limit distribution, rate of convergence to equilibrium). Then we also discuss the expected fluctuations in the observables and give some idea to reduce them. In the end we show that also computation of quantities at fi

S. Capitani, M. Goeckeler, R. Horsley, P. E. L. Rakow

We discuss the improvement of bilinear fermionic operators for Ginsparg-Wilson fermions. We present explicit formulae for improved Green&#39;s functions, which apply both on-shell and off-shell.

H. Arisue

The large-q expansions of the exponential correlation length and the second moment correlation length for the q-state Potts model in two dimensions are calculated at the first order phase transition point both in the ordered and disordered phases. The expansion coefficients in the ordered and disordered phases coincide in lower orders for both of the two typ

K. J. Juge, J. Kuti, C. J. Morningstar

The spectrum of heavy-quark hybrids is studied in the leading Born-Oppenheimer (LBO) approximation and using leading-order NRQCD simulations with an improved gluon action on anisotropic lattices. The masses of four hybrid states are obtained from our simulations for lattice spacings 0.1 fm and 0.2 fm and are compared to the LBO predictions obtained using pre

F. Knechtli

We present results for the ground state and first excited state static potentials in the confinement &#34;phase&#34; of the SU(2) Higgs model. String breaking and the crossing of the energy levels are clearly visible. We address the question of the cut-off effects in our results and observe a remarkable scaling of the static potentials.

Andrea Shindler

We define, within the Schrödinger functional (SF) scheme, the matrix elements of the twist-2 operators corresponding to the first two moments of non-singlet parton density, and the first moment of singlet parton densities. We perform a lattice one-loop calculation that fixes the relation between the SF scheme and other common schemes and shows the main sourc

Z. Fodor

Recent developments on the four dimensional (4d) lattice studies of the finite temperature electroweak phase transition (EWPT) are summarized. The phase diagram is given in the continuum limit. The finite temperature SU(2)-Higgs phase transition is of first order for Higgs-boson masses m_H<66.5 +/- 1.4 GeV. Above this endpoint only a rapid cross-over can be

B. A. Schumm

Over the last decade, precise LEP and SLC measurements of electroweak coupling parameters at the Z0 pole have lead to tests of the Standard Model to unprecedented precision. This report presents a comprehensive review of these studies, including a review of relevant Z0 pole physics issues, facilities, instrumentation, and the measurements made. Global fits f

The OPAL Collaboration, G. Abbiendi

A selection of di-lepton events with significant missing transverse momentum has been performed using a total data sample of 237.4 pb-1 at e+e- centre-of-mass energies of 183 GeV and 189 GeV. The observed numbers of events - 78 at 183 GeV and 301 at 189 GeV - are consistent with the numbers expected from Standard Model processes, which arise predominantly fr

The OPAL Collaboration, G. Abbiendi

A search for charginos and neutralinos, predicted by supersymmetric theories, is performed using a data sample of 182.1 pb-1 taken at a centre-of-mass energy of 189 GeV with the OPAL detector at LEP. No evidence for chargino or neutralino production is found. Upper limits on chargino and neutralino pair production cross-sections are obtained as a function of

Marc Mars

Silent universes are studied using a ``3+1&#39;&#39; decomposition of the field equations in order to make progress in proving a recent conjecture that the only silent universes of Petrov type I are spatially homogeneous Bianchi I models. The infinite set of constraints are written in a geometrically clear form as an infinite set of Codacci tensors on the in

I. Brevik, A. G. Frøseth

The classical electromagnetic modes outside a long, straight, superconducting cosmic string are calculated, assuming the string to be surrounded by a superconducting cylindric surface of radius R. Thereafter, by use of a Bogoliubov-type argument, the electromagnetic energy W produced per unit length in the lowest two modes is calculated when the string is fo

Eugene Goremychkin, Ray Osborn, Brian Rainford, Amir Murani

We have performed an inelastic neutron scattering study of the low energy spin dynamics of the heavy fermion compound Ce0.8La0.2Al3 as a function of temperature and external pressure up to 5 kbar. At temperatures below 3 K, the magnetic response transforms from a quasi-elastic form, common to many heavy fermion systems, to a single well-defined inelastic pea

N. Bulut

The effects of nonmagnetic impurities on the Q=(pi,pi) spin-fluctuation spectral weight Im chi(Q,omega) are studied within the framework of the two-dimensional Hubbard model using the random phase approximation. In the first part of the paper, the effects of the nonmagnetic impurities on the magnetic susceptibility of the noninteracting (U=0) system, chi_0(Q

A. R. Lima, Cristian F. Moukarzel, I. Grosse, T. J. P. Penna

With the purpose of explaining recent experimental findings, we study the distribution $A(λ)$ of distances $λ$ traversed by a block that slides on an inclined plane and stops due to friction. A simple model in which the friction coefficient $μ$ is a random function of position is considered. The problem of finding $A(λ)$ is equivalent to a First-Passage-Time

Arianna Montorsi, Vittorio Penna

We propose a scheme for investigating the quantum dynamics of interacting electron models by means of time-dependent variational principle and spin coherent states of space lattice operators. We apply such a scheme to the one-dimensional hubbard model, and solve the resulting equations in different regimes. In particular, we find that at low densities the dy

J. Shumway, D. M. Ceperley

We review the path integral method wherein quantum systems are mapped with Feynman&#39;s path integrals onto a classical system of &#34;ring-polymers&#34; and then simulated with the Monte Carlo technique. Bose or Fermi statistics correspond to possible &#34;cross-linking&#34; of polymers. As proposed by Feynman, superfluidity and Bose condensation result fr

A. Liebsch, A. Liechtenstein

Multi-band quasi-particle calculations based on perturbation theory and dynamical mean field methods show that the creation of a photoemission hole state in Sr$_2$RuO$_4$ is associated with a highly anisotropic self-energy. Since the narrow Ru-derived $d_{xz,yz}$ bands are more strongly distorted by Coulomb correlations than the wide $d_{xy}$ band, charge is

J. Ambjorn, D. Karakhanyan, M. Mirumyan, A. Sedrakyan

The spin-1 Uimin-Lai-Sutherland (ULS) isotropic chain model is expressed in terms of fermions and the equivalence of the fermionic representation to the supersymmetric t-J model is established directly at the level of Hamiltonians.The spin-S ULS model is fermionized and the Hamiltonian of the corresponding generalisation of the t-J model is written down.

D. A. Ivanov, Patrick A. Lee, Xiao-Gang Wen

We report staggered vorticity correlations of current in the d-wave variational wave function for the lightly-doped t-J model. Such correlations are explained from the SU(2) symmetry relating d-wave and staggered-flux mean-field phases. The correlation functions computed by the variational Monte Carlo method suggest that pairs are formed of holes circulating

A. Mourachkine

The symmetries and origins of the order parameters (OPs) for pairing and long-range phase coherence in hole-doped cuprates are discussed. By analyzing tunneling, inelastic neutron scattering and torque measurements we conclude that the Cooper pairs in cuprates consist of spinons, and the pairing OP has an anisotropic s-wave symmetry, whereas the OP for long-

Staffan Grundberg, Jørgen Rammer

The effect of the Hall force on the pinning of vortices in type II superconductors is considered. A field theoretic formulation of the pinning problem allows a non-perturbative treatment of the influence of quenched disorder. A self-consistent theory is constructed using the diagrammatic functional method for the effective action, and an expression for the p

A. C. C. Coolen, D. Saad

We apply a general theory describing the dynamics of supervised learning in layered neural networks in the regime where the size p of the training set is proportional to the number of inputs N, as developed in a previous paper, to several choices of learning rules. In the case of (on-line and batch) Hebbian learning, where a direct exact solution is possible

Nikolai Laskin

A new stochastic theory of a foreign exchange markets dynamics is developed. As a result we have the new probability distribution which well describes statistical and scaling dependencies &#39;&#39;experimentally&#39;&#39; observed in foreign exchange markets in recent years. The developed dynamic theory is compared with well-known phenomenological Levy dist

P. Strehlow, M. Wohlfahrt, A. G. M. Janssen, R. Haueisen

We report on experiments giving evidence for quantum effects of electromagnetic flux in barium alumosilicate glass. In contrast to expectation, below 100 mK the dielectric response becomes sensitive to magnetic fields. The experimental findings include both, the complete lifting of the dielectric saturation by weak magnetic fields and oscillations of the die

Horacio Ceva

We find that the existence of self-organization of the members of a recently proposed minority game, depends on the type of update rules used. The resulting resource distribution is studied in some detail, and a related strategy scheme is considered, as a tool to improve the understanding of the model

Ingibjorg Magnusdottir, Vidar Gudmundsson

We calculate the magnetization of quantum dots deviating from circular symmetry for noninteracting electrons or electrons interacting according to the Hartree approximation. For few electrons the magnetization is found to depend on their number, and the shape of the dot. The magnetization is an ideal probe into the many-electron state of a quantum dot.

B. Gumhalter, A. Siber, J. P. Toennies

Nonperturbative expressions are derived for the angular resolved energy transfer spectra in the quantum regime of multiphonon scattering of inert gas atoms from surfaces. Application to He atom scattering from a prototype heatbath Xe/Cu(111) shows good agreement with experiments. This enables a full quantum calculation of the total energy transfer $μ$ and th

A. Siber, B. Gumhalter, J. P. Toennies

Recently developed quantum mechanical theory of inelastic He atom scattering (HAS) from solid surfaces is employed to analyze the energy transfer between projectile particles (thermal energy He-atoms) and vibrational degrees of freedom (phonons) characteristic of a variety of experimentally studied surfaces. We have first calculated the angular resolved ener

E. Trizac, J-L Raimbault

Within the framework of a Modified Poisson-Boltzmann theory accounting for steric effects of microions, we prove analytically that the effective pair interactions between like-charge colloids immersed in a confined electrolyte are repulsive. Our approach encompasses and extends previously known results to the case of complete confinement, and further incorpo

A. Siber, B. Gumhalter

In the original paper Althoff et al. (see ibid., vol.79, p.4429 (1997)) reported a study of scattering of thermal Ne, Ar, and Kr atoms from a Cu(111) surface in which they assessed the corresponding Debye-Waller factor (DWF) as a function of the particle mass m in a wide range of substrate temperature T. The experiments were interpreted by the semiclassical

P. Durganandini, Sumathi Rao

We study coherent charge tunneling through a one-dimensional interacting ring with a one-dimensional quantum dot embedded in one of its arms through bosonisation. The symmetries of the effective action explain many of the features such as phase change between resonances, in-phase successive resonances and phase-locking, which have been observed in experiment

M. Krech

The current knowledge about fluctuation - induced long - ranged forces is summarized. Reference is made in particular to fluids near critical points, for which some new insight has been obtained recently. Where appropiate, results of analytic theory are compared with computer simulations and experiments.

J. -W. van der Horst, P. A. Bobbert, M. A. J. Michels, G. Brocks

We present an calculation of the electronic and optical excitations of an isolated polythiophene chain as well as of bulk polythiophene. We use the GW approximation for the electronic self-energy and include excitonic effects by solving the electron-hole Bethe-Salpeter equation. The inclusion of interchain screening in the case of bulk polythiophene drastica