November 1998 arXiv papers — page 11

A. Kabakcioglu, A. N. Berker

In view of the recently seen dramatic effect of quenched random bonds on tricritical systems, we have conducted a renormalization-group study on the effect of quenched random fields on the tricritical phase diagram of the spin-1 Ising model in $d=3$. We find that random fields convert first-order phase transitions into second-order, in fact more effectively

G. Migliorini, A. N. Berker

The finite-temperature phase diagram of the Hubbard model in $d=3$ is obtained from renormalization-group analysis. It exhibits, around half filling, an antiferromagnetic phase and, between 30%--40% electron or hole doping from half filling, a new $τ$ phase in which the electron hopping strength $t$ asymptotically becomes infinite under repeated rescalings.

C. A. Bustamante, M. I. Molina

We study the robustness of the selftrapping phenomenon exhibited by the Discrete Nonlinear Schrodinger (DNLS) equation against the effects of nonadiabaticity and quantum fluctuations in a two-site system (dimer). To test for nonadiabatic effects (in a semiclassical context), we consider the dynamics of an electron (or excitation) in a dimer system and couple

Robert G. Crittenden

Upcoming microwave background experiments will see an incredible increase in the volume of data to be analyzed, which makes the choice of how it is discretized on the sky a crucial issue. I discuss criteria for evaluating different pixelizations and the advantages of using an exactly azimuthal or `igloo' pixelization of the sky. Talk given at ``The CMB a

Yu. M. Toropin, O. D. Toropina, M. M. Romanova, V. V. Savelyev

Quasi-spherical supersonic (Bondi-type) accretion to a star with a dipole magnetic field is investigated using resistive magnetohydrodynamic simulations. A systematic study is made of accretion to a non-rotating star, while sample results for a rotating star are also presented. A new stationary subsonic accretion flow is found with a steady rate of accretion

S. L. Tufte, R. J. Reynolds, L. M. Haffner

Optical emission lines provide an important new window on the HVCs. Recent studies of the H-alpha line reveal that ionized gas is pervasively associated with the neutral hydrogen in HVCs. The Wisconsin H-Alpha Mapper (WHAM) instrument has so far detected H-alpha from high-velocity clouds in the M, A, and C complexes. We find a close spatial correspondence be

Penny D. Sackett

The fields of occultation and microlensing are linked historically. Early this century, occultation of the Sun by the Moon allowed the apparent positions of background stars projected near the limb of the Sun to be measured and compared with their positions six months later when the Sun no longer influenced the light path to Earth. The measured shift in the

V. Berezinsky

Ultra High Energy Cosmic Rays (UHECR) can be a signal from very early (post-inflationary) Universe. At this cosmological epoch Topological Defects (TD) and long-lived suprheavy (SH) particles are expected to be naturally and effectively produced. Both of these relics can produce now the particles, such as protons and photons, with energies in a great excess

B. Boroson, T. Kallman, R. McCray, S. D. Vrtilek

We show that the orbital variation in the UV P Cygni lines of the X-ray binary LMC X-4 results when X-rays photoionize nearly the entire region outside of the X-ray shadow of the normal star. We fit models to HST GHRS observations of N V and C IV P Cygni line profiles. Analytic methods assuming a spherically symmetric wind show that the wind velocity law is

Jorg P. Rachen, P. Meszaros

We review the hypothesis that the acceleration of protons at internal shocks in Gamma Ray Bursts (GRB) could be the origin of the ultra-high energy cosmic rays (UHECR) observed at earth, E_max > 10^19 eV. We find that, even though protons may be accelerated to such energies, their ejection into the interstellar/intergalactic medium is problematic because it

D. R. Goncalves, A. C. S. Friaca

Could the discrepancies found in the determination of mass in clusters of galaxies, from gravitational lensing data and from X-rays observations, be consequence of the standard description of the ICM, in which it is assumed hydrostatic equilibrium maintained by thermal pressure? In analogy to the interstellar medium of the Galaxy, it is expected a non-therma

Debiprosad Duari, Isabelle Cherchneff, Karen Willacy

The gas-phase non-equilibrium chemistry of the inner wind of the oxygen-rich Mira variable IK Tau (NML Tau) is investigated using a physio-chemical model describing the periodically shocked gas close to the stellar photosphere. We predict the formation in large amounts of a few carbon species in the inner envelope, in particular CO$_2$, which has been recent

Mariano Mendez, Michiel van der Klis, Eric C. Ford, Rudy Wijnands

We present new results based on observations carried out with the Rossi X-ray Timing Explorer during the decay of an outburst of the low-mass X-ray binary (LMXB) and atoll source 4U 1608-52. Our results appear to resolve, at least in 4U 1608-52, one of the long-standing issues about the phenomenology of the kilohertz quasi-periodic oscillations (kHz QPOs), n

M. D. Roberts, S. A. Dazeley, P. G. Edwards, T. Hara

Observational and theoretical results indicate that low-redshift BL Lacertae objects are the most likely extragalactic sources to be detectable at TeV energies. In this paper we present the results of observations of 4 BL Lacertae objects (PKS0521-365, EXO0423.4-0840, PKS2005-489 and PKS2316-423) made between 1993 and 1996 with the CANGAROO 3.8m imaging Cher

A. Kercek, W. Hillebrandt, J. W. Truran

We present first results of three-dimensional (3D-) calculations of turbulent and degenerate hydrogen-burning on top of a C+O white dwarf of one solar mass. The simulations are carried out by means of a code which solves Euler's equation for an arbitrary equation of state together with a nuclear reaction network and the energy input from nuclear reaction

A. Brizola, O. A. Battistel, Marcos Sampaio, M. C. Nemes

We propose an implicit regularisation scheme. The main advantage is that since no explicit use of a regulator is made, one can in principle avoid undesirable symmetry violations related to its choice. The divergent amplitudes are split into basic divergent integrals which depend only on the loop momenta and finite integrals. The former can be absorbed by a r

Joseph A. Minahan

We derive WKB expressions for glueball masses of various finite temperature supergravity models. The results are very close to recent numerical computations. We argue that the spectra has some universality that depends only on the dimension of the AdS space and the singularity structure of the horizon. This explains the stability of the $0^{++}$ glueball mas

Tao Han, Joseph D. Lykken, Ren-Jie Zhang

We consider the novel Kaluza-Klein (KK) scenario where gravity propagates in the $4+n$ dimensional bulk of spacetime, while gauge and matter fields are confined to the 3+1 dimensional world-volume of a brane configuration. For simplicity we assume compactification of the extra $n$ dimensions on a torus with a common scale $R$, and identify the massive KK sta

Francisco Gonzalez-Rey, Inyong Park, Koenraad Schalm

We find that the first-order correction to the free-field result for the four-point function of the conformal operator $\tr(ϕ^iϕ^j)$ is nonvanishing and survives in the limit $N_c \rar \infty$.

G. Cleaver, M. Cvetic, J. R. Espinosa, L. Everett

We continue the investigation of the physics implications of a class of flat directions for a prototype quasi-realistic free fermionic string model (CHL5), building upon the results of the previous paper in which the complete mass spectrum and effective trilinear couplings of the observable sector were calculated to all orders in the superpotential. We intro

Jaume Garriga, Xavier Montes, Misao Sasaki, Takahiro Tanaka

The spectrum of cosmological perturbations in the context of the one-bubble open inflation model is discussed, taking into account fluctuations of the metric. We find that, quite generically,thin wall single field models have no supercurvature modes. However, single field models with supercurvature modes do exist. In these models the density parameter $Ω$ be

Chia-Hung V. Chang, Darwin Chang, Wai-Yee Keung

We study the $B$ meson radiative decay $B \to X_s γ$ in the vector quark model. Deviation from the Standard Model arises from the non-unitarity of the charged current KM matrix and related new FCNC interactions. We establish the relation between the non-unitarity of charged current mixing matrix and the mixing among the vector quark and the ordinary quarks.

Hong Liu

We develop a formalism to evaluate generic scalar exchange diagrams in AdS_{d+1} relevant for the calculation of four-point functions in AdS/CFT correspondence. The result may be written as an infinite power series of functions of cross-ratios. Logarithmic singularities appear in all orders whenever the dimensions of involved operators satisfy certain relati

David M. Goldberg, David N. Spergel

Gravitational fluctuations along the line-of-sight from the surface of last scatter to the observer distort the microwave background in several related ways: The fluctuations deflect the photon path (gravitational lensing), the decay of the gravitational potential produces additional fluctuations (ISW effect) and scattering off of hot gas in clusters produce

David N. Spergel, David M. Goldberg

In this paper, we discuss the potential importance of measuring the CMB anisotropy bispectrum. We develop a formalism for computing the bispectrum and for measuring it from microwave background maps. As an example, we compute the bispectrum resulting from the 2nd order Rees-Sciama effect, and find that is undetectable with current and upcoming missions.

U. D'Alesio, A. Metz, H. J. Pirner

We study inclusive electroproduction on the proton at low $x$ and low $Q^2$ using a soft and a hard Pomeron. The contribution of the soft Pomeron is based on the Stochastic Vacuum Model, in which a nonperturbative dipole-dipole cross section can be calculated by means of a gauge invariant gluon field strength correlator. To model the hard Pomeron exchange we

Brian Heltsley

Selected results on hadronic decays of the tau lepton from the TAU98 Workshop are reviewed. A comprehensive picture emerges for strange particle branching fractions, and exploration of resonant substructure of both strange and non-strange decays is seen to have matured substantially.

R. L. Workman

We consider the masses used in recent studies involving the nonstrange sector of the l=1 baryons. The use of T-matrix and K-matrix poles versus the conventional Breit-Wigner masses is discussed within the context of a large-Nc fitting scheme.

Angelo Bassi, GianCarlo Ghirardi

We discuss some features of the Decoherent Histories approach. We consider four assumptions, the first three being in our opinion necessary for a sound interpretation of the theory, while the fourth one is accepted by the supporters of the DH approach, and we prove that they lead to a logical contradiction. We discuss the consequences of relaxing any one of

D. Bazeia

We follow recent work and study the relativistic d-brane system in (d+1,1) dimensions and its connection with a Galileo invariant system in (d,1) dimensions. In particular, we solve d-brane systems in (2,1), (3,1) and (4,1) dimensions and show that their solutions solve the corresponding Galileo invariant systems in (1,1), (2,1), and (3,1) dimensions. The re

Pavol Severa

We study a connection between duality and topological field theories. First, 2d Kramers-Wannier duality is formulated as a simple 3d topological claim (more or less Poincaré duality), and a similar formulation is given for higher-dimensional cases. In this form they lead to simple TFTs with boundary coloured in two colours. Classical models (Poisson-Lie T-du

A. Krzywicki, J. Serreau

We estimate the probability that a disoriented chiral condensate forms during the spherical expansion of a hot medium described by the linear sigma model.

G. G. Pavlov, V. E Zavlin, J. Truemper

There are several supernova remnants which contain unresolved X-ray sources close to their centers, presumably radio-quiet neutron stars. To prove that these objects are indeed neutron stars, to understand the origin of their X-ray radiation, and to explain why they are radio-quiet, one should know their periods and period derivatives. We searched for pulsat

Sergiu I. Vacaru

In this paper we analyze the conditions when the Einstein equations with cosmological constant and matter describe (2+1)-dimensional generic locally anisotropic (la) spacetimes of generalized Finsler type. New classes of solutions for such la-spacetimes are constructed. There are investigated black la-holes with the induced from general relativity la-curvatu

A. Fujii, R. Kemmoku, S. Mizoguchi

We study the Kaluza-Klein spectrum of D=5 simple supergravity on $S^2$ with special interest in the relation to a two-dimensional N=4 superconformal field theory. The spectrum is obtained around the maximally supersymmetric Freund-Rubin-like background $AdS_3\times S^2$ by closely following the well-known techniques developed in D=11 supergravity. All the ve

Tom Adawi, Martin Cederwall, Ulf Gran, Bengt E. W. Nilsson

In the context of brane solutions of supergravity, we discuss a general method to introduce collective modes of any spin by exploiting a particular way of breaking symmetries. The method is applied to the D3, M2 and M5 branes and we derive explicit expressions for how the zero-modes enter the target space fields, verify normalisability in the transverse dire

M. Lassig

We analyze the field theory of fully developed Burgers turbulence. Its key elements are shock fields, which characterize the singularity statistics of the velocity field. The shock fields enter an operator product expansion describing intermittency. The latter is found to be constrained by dynamical anomalies expressing finite dissipation in the inviscid lim

J. Kolacek, P. Vasek

The Hall voltage sign reversal is consistently explained by the model in which vortices with the superconducting and normal state charge carriers are regarded as three subsystems mutually connected by interactions. The equations of motion for these three subsystems are solved simultaneously and a new formula for the Hall resistivity is obtained. It is shown

J. Kolacek, E. Kawate

The vortex lattice with the superconducting and normal state charge carriers fractions may be regarded as three independent subsystems mutually connected by interactions. The equation of motion for these three subsystems must be solved simultaneously. In this way a new consistent theory of the vortex dynamics is obtained and the magnetoconductivity calculate

S. Conti, G. Vignale

The zero temperature response of an interacting electron liquid to a time-dependent vector potential of wave vector q and frequency w such that q << q_F, qv_F<< w << E_F/hbar (where q_F, v_F and E_F are the Fermi wavevector, velocity and energy respectively) is equivalent to that of a continuous elastic medium with nonvanishing shear modulus mu, bulk modulus

M. Sakaguchi

We present a geometric formulation of $(p,q)$-strings in which the $Sl(2;Z)$-doublet of the two-form gauge potentials is constructed as second order in the supersymmetric currents. The currents are constructed using a supergroup manifold corresponding to the $(p,q)$-string superalgebra, which contains fermionic generators in addition to the supercharges and

Nemanja Kaloper, Andrei Linde

We consider some aspects of inflation in models with large internal dimensions. If inflation occurs on a 3D wall after the stabilization of internal dimensions in the models with low unification scale (M ~ 1 TeV), the inflaton field must be extremely light. This problem may disappear In models with intermediate (M ~10^{11} GeV) to high (M ~ 10^{16} GeV) unif

Chun-Woo Lee

Eigenphase shifts and eigentime delays near a resonance for a system of one discrete state and two continua are shown to be functionals of the Beutler- Fano formulas using appropriate dimensionless energy units and line profile indices. Parameters responsible for the avoided crossing of eigenphase shifts and eigentime delays are identified. Similarly, parame

Pilar Garcia Estevez

Painleve analysis and the singular manifold method are the tools used in this paper to perform a complete study of an equation in 2+1 dimensions. This procedure has allowed us to obtain the Lax pair, Darboux transformation and tau functions in such a way that a plethora of different solutions with solitonic behavior can be constructed iteratively

Guido Bacciagaluppi

In de Broglie and Bohm&#39;s pilot-wave theory, as is well known, it is possible to consider alternative particle dynamics while still preserving the quantum distribution. I present the analogous result for Nelson&#39;s stochastic theory, thus characterising the most general diffusion processes that preserve the quantum equilibrium distribution, and discuss

S. N. Molotkov

A quantum cryptosystem is proposed using single-photon states with different frequency spectra as information carriers. A possible experimental implementation of the cryptosystem is discussed.

Brian K. Davis

Molecular evidence regarding the genetic code has been examined and the findings on the nature of the early events responsible for the amino acid distribution in the code are reported.

Oscar Bolina, J. A. da Silva Neto

We present an elementary discussion of two basic properties of angular displacements, namely, the anticommutation of finite rotations and the commutation of infinitesimal rotations, and show how commutation is achieved as the angular displacements get smaller and smaller.

Daniel Ferenc, Dario Hrupec, Eckart Lorenz

A general solution to the positive ion feedback problem in Hybrid Photon Detectors (HPD), photo multipliers (PM) and other similar detectors was found in the insertion of a permanent electrostatic potential barrier which prevents drift of positive ions from the anode, or the first dynode, towards the photocathode. In this paper we present the method as appli

C. Prodan, E. Prodan

In the limit of small concentrations and weak applied electric fields, the dielectric permittivity of suspensions of arbitrarily shaped, shelled and charged particles is calculated. It is proved that the dielectric behavior at low frequencies is dominated by the effects of the diffusion of the free charges on the shell surfaces. Our theoretical formula is va

Arbab I. Arbab

The possibility of an increasing gravitational constant $G$ and its implication on the Earth&#39;s history are discussed. The model is consistent with geophysical and astronomical data. The number of days in early epochs predicted by the model is in agreement with those obtained from fossil corals. The model predicts that the Earth was initially cold and is

C. Wagner, H. W. Mueller, K. Knorr

We investigate Faraday waves on a viscoelastic liquid. Onset measurements and a nonlinear phase diagram for the selected patterns are presented. By virtue of the elasticity of the material a surface resonance synchronous to the external drive competes with the usual subharmonic Faraday instability. Close to the bicriticality the nonlinear wave interaction gi

M. Moscani, B. Mosconi, P. Ricci

We analyze the parity-violating (PV) components of the analyzing power in elastic electron-proton scattering and discuss their sensitivity to the strange quark contributions to the proton weak form factors. We point out that the component of the analyzing power along the momentum transfer is independent of the electric weak form factor and thus compares favo

Toshitaka Tatsumi, Masatomi Yasuhira

A new formulation is presented to treat thermal fluctuations around the kaon condensate, based on chiral symmetry. Separating the zero mode from the beginning we perform the imaginary-time path integral to the one loop to get the thermodynamic potential at finite temperature. The role of the Goldstone mode in the kaon condensed phase is elucidated in relatio

Piotr G. Grinevich, Roman G. Novikov

We study the scattering problem, the Sturm-Liouville problem and the spectral problem with periodic or skew-periodic boundary conditions for the one-dimensional Schrödinger equation with an $n$-cell (finite periodic) potential. We give explicit upper and lower bounds for the distribution functions of discrete spectrum for these problems. For the scattering p

Y. S. Kim

It is possible to construct representations of the Lorentz group using four-dimensional harmonic oscillators. This allows us to construct three-dimensional wave functions with the usual rotational symmetry for space-like coordinates and one-dimensional wave function for time-like coordinate. It is then possible to construct a representation of the Poincaré g

Lubomir Alexandrov

The objective of this paper is to introduce an approach to the study of the nonasymptotic distribution of prime numbers. The natural numbers are represented by theorem 1 in the matrix form ^2N. The first column of the infinite matrix ^2N starts with the unit and contains all composite numbers in ascending order.The infinite rows of this matrix except for the

O. A. Battistel, M. C. Nemes

In this work we revisit questions recently raised in the literature associated to relevant but divergent amplitudes in the gauged NJL model. The questions raised involve ambiguities and symmetry violations which concern the model&#39;s predictive power at one loop level. Our study shows by means of an alternative prescription to handle divergent amplitudes,

Manoelito M. de Souza

A discrete field formalism exposes the physical meaning and the origins of gauge fields and of their symmetries and singularities.

Yuri Kubyshin, Rui Neves, Robertus Potting

We investigate a $Z_2$-symmetric scalar field theory in two dimensions using the Polchinski exact renormalization group equation expanded to second order in the derivative expansion. We find preliminary evidence that the Polchinski equation is able to describe the non-perturbative infinite set of fixed points in the theory space, corresponding to the minimal

D. Anselmi

We investigate the quantum conformal algebras of N=2 and N=1 supersymmetric gauge theories. Phenomena occurring at strong coupling are analysed using the Nachtmann theorem and very general, model-independent, arguments. The results lead us to introduce a novel class of conformal field theories, identified by a closed quantum conformal algebra. We conjecture

V. P. Frolov, A. L. Larsen, M. Christensen

We study a simple system that comprises all main features of critical gravitational collapse, originally discovered by Choptuik and discussed in many subsequent publications. These features include universality of phenomena, mass-scaling relations, self-similarity, symmetry between super-critical and sub-critical solutions, etc. The system we consider is a s

L. Chekhov

The AdS/CFT correspondence is established for the case of AdS$_3$ space compactified on a filled rectangular torus with the CFT field on the boundary.

R. Parthasarathy, K. S. Viswanathan

From the Dirac action on the world sheet, an effective action is obtained by integrating over the 4-dimensional fermion fields pulled back to the world sheet. This action consists of the Nambu-Goto area term with right dimensionful constant in front, extrinsic curvature action and the topological Euler characteristic term.

E. Sezgin

We give a brief history of the passage from strings to branes and we review some aspects of the following topics in M-theory: (a) an extended brane scan, (b) superembedding approach to the dynamics of superbranes and (c) supermembranes in anti de Sitter space, singletons and massless higher spin field theories.

Nima Arkani-Hamed, Savas Dimopoulos

The recently proposed theories with TeV-scale quantum gravity remove the usual ultraviolet desert between $\sim 10^{3} - 10^{19}$ GeV where effective field theory ideas apply. Consequently, the success of the desert in explaining approximate symmetries is lost, and theories of flavor, neutrino masses, proton longevity or supersymmetry breaking, lose their us

J. Bluemlein, W. L. van Neerven

We have calculated the first and second order corrections to several deep inelastic sum rules which are due to heavy flavour contributions. A comparison is made with the existing perturbation series which has been computed up to third order for massless quarks only. In general it turns out that the effects of heavy quarks are very small except when $Q \sim m

Philip G. Ratcliffe

I discuss the present situation with regard to a variety of theoretical topics in hadronic spin physics: (a) global analysis of the g1 data---positivity at leading and next-to-leading order, renormalisation-scheme dependence, parametrisation, and hyperon beta-decays; (b) items from the realm of transverse spin---twist-three effects, single-spin asymmetries,

J. Berges, D. -U. Jungnickel, C. Wetterich

We investigate the QCD chiral phase transition at high baryon number density within the linear quark meson model for two flavors. The method we employ is based on an exact renormalization group equation for the free energy. Truncated nonperturbative flow equations are derived at nonzero chemical potential and temperature. Whereas the renormalization group fl

A. Bialas, H. Navelet, R. Peschanski

Using the QCD dipole picture of BFKL dynamics, the quasi elastic component of the diffractive gamma*-dipole cross-section, dominating at small M^2/Q^2, is calculated.

Ana M. Mourao, Anna Rossi

We have studied the effect of a non-vanishing neutrino magnetic moment \ ($μ_ν$) on the $ν_{\rm x}$ ({x=$e,μ,τ$}) elastic scattering off electrons for the Super-Kamiokande detector. The bounds on the $μ_ν$ we have obtained are comparable to that extracted from laboratory experiments. Furthemore, we outline the potential of the Borexino experiment which may b

M. Drees, O. J. P. Eboli, J. K. Mizukoshi

We analyze several signals at HERA and the Tevatron of a light $U(1)_B$ gauge boson ($γ_B$) coupling to baryon number. We show that the study of the production of $b \bar{b}$ pairs at the (upgraded) Tevatron can exclude $γ_B$ with masses ($m_B$) in the range $40 \lesssim m_B \lesssim 300$ GeV for $γ_B$ couplings ($α_B$) greater than $2 \times 10^{-2}$ ($3 \t

M. Steinhauser

The computation of higher order processes very often involves a large number of diagrams. In addition, it is in general not possible to solve the occurring integrals explicitly and expansions in small quantities have to be performed. This makes it necessary to automate the calculations as much as possible. A program package will be described which generates

J. Louis, I. Brunner, S. Huber

This set of lectures introduces at an elementary level the supersymmetric Standard Model and discusses some of its phenomenological properties. (Lectures given by J. Louis at the summer school ``Grundlagen und neue Methoden der theoretischen Physik&#39;&#39;, Saalburg, 1996.)

D. Falcone

We study the implications of having a similarity between quark and lepton mixing in the Dirac sector of the Standard Model plus the right-handed neutrino. This enable us to describe all masses and mixings in the Dirac sector in terms of only five parameters: three mass scales $m_b$, $m_τ$ and $m_t$, one parameter $λ$ describing all the mixings, and a CP viol

Gideon Alexander, Iuliana Cohen

This report summarises the recent studies of the Bose-Einstein Correlations (BEC) carried out by the four LEP experiments using hadronic Z$^0$ decay events and $e^+ e^-$ reactions leading to the WW decay final states. The three identical charged pion systems $π^{\pm} π^{\pm} π^{\pm}$ have been studied by OPAL with $4 \times 10^6$ hadronic Z$^0$ decays events

Fyodor V. Tkachov

The difficulties of perturbation theory associated with unstable fundamental fields (such as the lack of exact gauge invariance in each order) are cured if one constructs perturbative expansion directly for probabilities interpreted as distributions in kinematic variables. Such an expansion is made possible by the powerful method of non-Euclidean asymptotic

J. Kuti

Recent developments in Quantum Chromodynamics (QCD) are reviewed on three major topics where nonperturbative gluon excitations of the QCD vacuum and the physical properties of the confining flux play a central role: (1) New lattice results on the spectrum and wave functions of heavy quark-antiquark molecules, known as heavy hybrids, will be discussed. (2) Re

M. Artuso

We have observed four fully reconstructed B0 -> D*+D*- candidates in 5.8 million Upsilon(4S) -> BBbar decays recorded with the CLEO detector. The background is estimated to be 0.31 +- 0.10 events. The probability that the background could produce four or more signal candidates with the observed distribution among D*+ and D*- decay modes is 1.1 X 10^{-4}. The

The OPAL Collaboration, G. Abbiendi et al

The data collected by the OPAL experiment at sqrts=183 GeV were used to search for Higgs bosons which are predicted by the Standard Model and various extensions, such as general models with two Higgs field doublets and the Minimal Supersymmetric Standard Model (MSSM). The data correspond to an integrated luminosity of approximately 54pb-1. None of the search

V. Faraoni, R. M. Dumse

An explanation is proposed for the fact that pp-waves superpose linearly when they propagate parallely, while they interact nonlinearly, scatter and form singularities or Cauchy horizons if they are antiparallel. Parallel pp-waves do interact, but a generalized gravitoelectric force is exactly cancelled by a gravitomagnetic force. In an analogy, the interact

A. D. Rendall, K. P. Tod

The dynamics of a class of cosmological models with collisionless matter and four Killing vectors is studied in detail and compared with that of corresponding perfect fluid models. In many cases it is possible to identify asymptotic states of the spacetimes near the singularity or in a phase of unlimited expansion. Bianchi type II models show oscillatory beh

Vladimir Skalsky

According to observations, in our Universe for gravitational phenomena in a Newtonian approximation the Newtonian non-modified relations are valid. The Friedmann equations of universe dynamics describe infinite number of relativistic universe models in Newtonian approximation, but only in one of them the Newtonian non-modified relations are valid. From these

Ilja Schmelzer

We define a metric theory of gravity with preferred Newtonian frame (X^i(x),T(x)) by L = L_{GR} + Ξg^{mn}δ_{ij}X^i_{,m}X^j_{,n} - Υg^{mn}T_{,m}T_{,n} It allows a condensed matter interpretation which generalizes LET to gravity. The Ξ-term influences the age of the universe. Υ>0 allows to avoid big bang singularity and black hole horizon formation. This solve

Akira Fujii, Andreas Kluemper

We derive the non-linear integral equations determining the free energy of the three-state pure bosonic Uimin-Sutherland model. In order to find a complete set of auxiliary functions, the anti-symmetric fusion procedure is utilized. We solve the non-linear integral equations numerically and see that the low-temperature behavior coincides with that predicted

M. P. Blencowe, M. N. Wybourne

We show that substantial quantum squeezing of mechanical motion can be achieved for micron-sized cantilever devices fabricated using available techniques. A method is also described for measuring the cantilever fluctuation magnitudes in the squeezing regime.

H. C. Rae, P. Sollich, A. C. C. Coolen

We solve the dynamics of on-line Hebbian learning in large perceptrons exactly, for the regime where the size of the training set scales linearly with the number of inputs. We consider both noiseless and noisy teachers. Our calculation cannot be extended to non-Hebbian rules, but the solution provides a convenient and welcome benchmark with which to test mor

Holger Stark

We study the director field around a spherical particle immersed in a uniformly aligned nematic liquid crystal and assume that the molecules prefer a homeotropic orientation at the surface of the particle. Three structures are possible: a dipole, a Saturn-ring, and a surface-ring configuration, which we investigate by numerically minimizing the Frank free en

M. E. Pierce, E. Manousakis

In order to resolve the controversy about the low density region of the phase diagram of the 4He monolayer on graphite, we have undertaken a path integral Monte Carlo study of the system. We provide direct evidence that the low density monolayer possesses solid clusters and a low density vapor as opposed to the most recent proposal that the system is in a su

Neil F. Johnson, Michael Hart, Pak Ming Hui

We present analytic and numerical results for two models, namely the minority model and the bar-attendance model, which offer simple paradigms for a competitive marketplace. Both models feature heterogeneous agents with bounded rationality who act using inductive reasoning. We find that the effects of crowding are crucial to the understanding of the macrosco

A. Amici, P. Thalmeier, P. Fulde

Borocarbide compounds with the formula RNi2B2C show interesting superconducting and magnetic properties and the coexistence of the two phenomena. BCS theory is extended to systems with underlying commensurate magnetic order. In the case of helical phases the technique may be extended to any Q-vector and there exists a well defined limit for incommensurate va

Rolf Olsen, Terence Hwa, Michael Lassig

Mutual correlation between segments of DNA or protein sequences can be detected by Smith-Waterman local alignments. We present a statistical analysis of alignment of such sequences, based on a recent scaling theory. A new fidelity measure is introduced and shown to capture the significance of the local alignment, i.e., the extent to which the correlated subs

W. Apel, Yu. A. Bychkov

We study the spin relaxation in an interacting two--dimensional electron gas in a strong magnetic field for the case that the electron density is close to filling just one Landau sub--level of one spin projection, i.e., for filling factor near one. Assuming the relaxation to be caused by scattering with phonons, we derive the kinetic equations for the electr

Yukitoshi Motome, Hiroki Nakano, Masatoshi Imada

We discuss Mott insulating and metallic phases of a model with $e_g$ orbital degeneracy to understand physics of Mn perovskite compounds. Quantum Monte Carlo and Lanczos diagonalization results are discussed in this model. To reproduce experimental results on charge gap and Jahn-Teller distortions, we show that a synergy between the strong correlation effect

Joel. L. Lebowitz, Herbert Spohn

We extend the work of Kurchan on the Gallavotti-Cohen fluctuation theorem, which yields a symmetry property of the large deviation function, to general Markov processes. These include jump processes describing the evolution of stochastic lattice gases driven in the bulk or through particle reservoirs, general diffusive processes in physical and/or velocity s

Herbert Spohn, Wilhelm Zwerger

Using Griffiths and Lieb-Simon type inequalities, it is shown that the two-point function of ferromagnetic spin models with N components in one dimension decays like the interaction provided that N=1,2,3,4 and T > T_c.

G. Jug, K. Ziegler

The dynamical transport properties near the integer quantum Hall transition are investigated at zero temperature by means of the Dirac fermion approach. These properties have been studied experimentally at low frequency omega and low temperature near the nu=1 filling factor Hall transition, with the observation of an anusual broadening and an overall increas

Rosario Fazio, F. W. J. Hekking, A. A. Odintsov, R. Raimondi

In this paper we review some recent results concerning the physics of superconductor - Luttinger liquid proximity systems. We discuss both equilibrium (the pair amplitude, Josephson current, and the local density of states) and nonequilibrium (the subgap current) properties.

R. Seviour, C. J. Lambert, A. F. Volkov

We have calculated the temperature dependence of the conductance variation ($δS(T)$) of mesoscopic superconductor normal metal(S/N) structures, in the diffusive regime, analysing both weak and strong proximity effects. We show that in the case of a weak proximity effect there are two peaks in the dependence of $δS(T)$ on temperature. One of them (known from

Leonid Didukh, Vasyl Hankevych

In the present paper metal-insulator transition is studied in a generalized Hubbard model with correlated hopping at half-filling and zero temperature. Single-particle Green function and energy spectrum of electron system are calculated. The expressions for energy gap width and the concentration of polar states (holes or doublons) are obtained. The condition