March 1999 arXiv papers — page 21

J. Lleweilun Smith, Qimiao Si

We further develop an extended dynamical mean field approach introduced earlier. It goes beyond the standard $D=\infty$ dynamical mean field theory by incorporating quantum fluctuations associated with intersite (RKKY-like) interactions. This is achieved by scaling the intersite interactions to the same power in 1/D as that for the kinetic terms. In this app

Roland Stumpf, Clarence Tracy

Using first principles electronic structure calculations we screen nine elements for their potential to retard oxygen diffusion through poly-crystalline Pt (p-Pt) films. We determine that O diffuses preferentially as interstitial along Pt grain boundaries (GBs). The calculated barriers are compatible with experimental estimates. We find that Be controls O di

M. V. Tokarchuk, I. P. Omelyan, A. E. Kobryn

A statistical approach to a self-consistent description of kinetic and hydrodynamic processes in systems of interacting particles is formulated on the basis of the nonequilibrium statistical operator method by D.N.Zubarev. It is shown how to obtain the kinetic equation of the revised Enskog theory for a hard sphere model, the kinetic equations for multistep

A. Malinowski, A. Krickser, Marta Z. Cieplak, S. Guha

The effect of zinc doping on the anomalous temperature dependence of the magnetoresistance and the Hall effect in the normal state was studied in a series of La{1.85}Sr{0.15}Cu{1-y}Zn{y}O{4} films, with values of y between zero and 0.12. The orbital magnetoresistance at high temperatures is found to be proportional to the square of the tangent of the Hall an

C. Busshaus, H. Rieger

We present a new microscopic stochastic model for an ensemble of interacting investors that buy and sell stocks in discrete time steps via limit orders based on individual forecasts about the price of the stock. These orders determine the supply and demand fixing after each round (time step) the new price of the stock according to which the limited buy and s

Rolf Wittmann

It is shown that the covering approach with a single decagonal prototile can be transformed into a hexagon, boat and star tiling. Particularly, the atomic decoration recently proposed by Cockayne and Widom (Phys. Rev. Lett. 81, 598 (1998)) as a structure model for the decagonal phase is investigated. There, conflicts with the prototile approach arise which a

Stefan Bornholdt

We introduce a dynamical annealing schedule for population-based optimization algorithms with mutation. On the basis of a statistical mechanics formulation of the population dynamics, the mutation rate adapts to a value maximizing expected rewards at each time step. Thereby, the mutation rate is eliminated as a free parameter from the algorithm.

Stefan Bornholdt

The genetic algorithm is an optimization procedure motivated by biological evolution and is successfully applied to optimization problems in different areas. A statistical mechanics model for its dynamics is proposed based on the parent-child fitness correlation of the genetic operators, making it applicable to general fitness landscapes. It is compared to a

M. J. Graf, R. J. Keizer, A. de Visser, A. A. Menovsky

The suppression of superconductivity by substitution effects has been measured in high quality single crystals of U(Pt_{1-x} Pd_x)_3 with 0 <= x <= 0.002. While the superconducting transition temperature T_c varies linearly with residual resistivity r_0, consistent with pair-breaking by impurity potential scattering, the rate of suppression of T_c with r_0 i

Uwe Grimm, Dieter Joseph

Understanding the growth of quasicrystals poses a challenging problem, not the least because the quasiperiodic order present in idealized mathematical models of quasicrystals prohibit simple local growth algorithms. This can only be circumvented by allowing for some degree of disorder, which of course is always present in real quasicrystalline samples. In th

S. E. Krasavin, V. A. Osipov

The problem of both electron and phonon scattering by wedge disclination dipoles (WDD) is studied in the framework of the deformation potential approach. The exact analytical results for the mean free path are obtained within the Born approximation. The WDD-induced contribution to the residual resistivity in nanocrystalline metals is estimated. Using the WDD

A. S. Alexandrov, V. V. Kabanov

A parameter-free expression for the superconducting critical temperature of layered cuprates is derived which allows us to express Tc in terms of experimentally measured parameters. It yields Tc values observed in about 30 lanthanum, yttrium and mercury-based samples for different levels of doping. This remarkable agreement with the experiment as well as the

Erik Koch, Olle Gunnarsson, Richard M. Martin

Gutzwiller functions are popular variational wavefunctions for correlated electrons in Hubbard models. Following the variational principle, we are interested in the Gutzwiller parameters that minimize e.g. the expectation value of the energy. Rewriting the expectation value as a rational function in the Gutzwiller parameters, we find a very efficient way for

Nathan Argaman

Mesoscopic superconducting-normal-metal-superconducting (S-N-S) junctions with a large separation between the superconducting electrodes (i.e. wide junctions) exhibit nonequilibrium supercurrents, even at temperatures for which the equilibrium Josephson effect is exponentially small. The second harmonic of the Josephson frequency dominates these currents, as

Yasuhiro Higashiyama, Akira Shimizu

We study nonequilibrium properties of small and chaotic quantum systems, i.e., non-integrable systems whose size is small in the sense that the separations of energy levels are non-negligible as compared with other relevant energy scales. The energy change $ΔE$ induced by a slowly-varying external field $λ(t)$ is evaluated when the range of the variation $Δλ

Robert Lupton, Jim Gunn, Alex Szalay

We describe a modification of the usual definition of astronomical magnitudes, replacing the usual logarithm with an inverse hyperbolic sine function; we call these modified magnitudes `asinh magnitudes&#39;. For objects detected at signal-to-noise ratios of greater than about five, our modified definition is essentially identical to the traditional one; for

Yang Chen, Ming Sun, Zhen-Ru Wang, Q. F. Yin

The ASCA SIS and the ROSAT PSPC spectral data of the SNR 3C397 are analysed with a two-component non-equilibrium ionization model. Besides, the ASCA SIS0 and SIS1 spectra are also fitted simultaneously in an equilibrium case. The resulting values of the hydrogen column density yield a distance of $\sim8\kpc$ to 3C397. It is found that the hard X-ray emission

A. Ferrara, S. Bianchi, A. Cimatti, C. Giovanardi

We present an extensive study of the radiative transfer in dusty galaxies based on Monte Carlo simulations. The main output of these simulations are the attenuation curves ${\cal A}_λ$ (i.e. the ratio between the observed, dust extinguished, total intensity to the intrinsic unextinguished one of the galaxy as a function of wavelength). We have explored the d

H. Hirashita

We consider evolution of interstellar clouds in Local Group dwarf spheroidal galaxies (dSphs) in the context of their observed star formation histories. The Local Group dSphs generally experienced initial bursts of star formations in their formation epochs ($\sim 15$ Gyr ago), when hot gas originating from the supernovae can make the cold interstellar clouds

Herve Dole, Guilaine Lagache, Jean-Loup Puget, Richard Gispert

FIRBACK is one of the deepest cosmological surveys performed in the far infrared, using ISOPHOT. We describe this survey, its data reduction and analysis. We present the maps of fields at 175 microns. We point out some first results: source identifications with radio and mid infrared, and source counts at 175 microns. These two results suggest that half of t

Jonathan A. D. Wattis, Peter V. Coveney

The aims of this paper are to propose, construct and analyse microscopic kinetic models for the emergence of long chains of RNA from monomeric beta-D-ribonucleotide precursors in prebiotic circumstances. Our theory starts out from similar but more general chemical assumptions to those of Eigen, namely that catalytic replication can lead to a large population

V. K. Horvath, J. R. Cressman, W. I. Goldburg, X. L. Wu

Hysteresis has been observed in a study of the transition between laminar flow and vortex shedding in a quasi-two dimensional system. The system is a vertical, rapidly flowing soap film which is penetrated by a rod oriented perpendicular to the film plane. Our experiments show that the transition from laminar flow to a periodic Kármán vortex street can be hy

R. Shankar

The Lowest Landau Level (LLL), long distance theory of Composite Fermions (CF) developed by Murthy and myself is minimally extended to all distances, guided by very general principles. The resulting theory is mathematically consistent, and physically appealing: we clearly see the electron and the vortices binding to form the CF. The meaning of the constraint

Z. Maassarani

Integrable multistate or multiflavor/color models were recently introduced. They are generalizations of models corresponding to the defining representations of the U_q(sl(m)) quantum algebras. Here I show that a similar generalization is possible for all higher dimensional representations. The R-matrices and the Hamiltonians of these models are constructed b

O. Panella, C. Carimalo, Y. N. Srivastava

The production of Like-Sign-Di-leptons (LSD), in the high energy lepton number violating ($ΔL = +2$) reaction, p p --> 2jets + l+l+ (l=e,μ,τ) of interest for the experiments to be performed at the forthcoming Large Hadron Collider (LHC), is investigated in detail, taking up a composite model scenario in which the exchanged virtual composite neutrino is assum

Tommy Ohlsson, Hakan Snellman

Global fits to all data of candidates for neutrino oscillations are presented in the framework of a three-flavor model. The analysis excludes mass regions where the MSW effect is important for the solar neutrino problem. The best fit gives $θ_1 \approx 28.9^\circ, θ_2 \approx 4.2^\circ, θ_3 \approx 45.0^\circ, m_2^2 - m_1^2 \approx 2.87 \cdot 10^{-4} eV^2$,

J. C. Montero, C. A. de S. Pires, V. Pleitez

In a 331 model in which the lepton masses arise from a scalar sextet it is possible to break spontaneously a global symmetry implying in a pseudoscalar majoron-like Goldstone boson. This majoron does not mix with any other scalar fields and for this reason it does not couple, at the tree level, neither to the charged leptons nor to the quarks. Moreover, its

I. I. Mazin

I review the principal experimental findings about superconductivity, suppression thereof, and related properties of RE_{1-x}Pr_xBa_2Cu3O7 in a decision-tree manner, eliminating the models substantially incompatible with established experimental facts, eventually focussing on the pfσhybridization models and listing on a verbal level the interpretations of th

Chris Simpson, Peter Eisenhardt

We investigate the ability of the Space Infrared Telescope Facility&#39;s Infrared Array Camera to detect distant (z ~ 3)galaxies and measure their photometric redshifts. Our analysis shows that changing the original long wavelength filter specifications provides significant improvements in performance in this and other areas.

C. Adam, B. Muratori, C. Nash

We investigate zero modes of the Dirac operator coupled to an Abelian gauge field in three dimensions. We find that the existence of a certain class of zero modes is related to a specific topological property precisely when the requirement of finite Chern--Simons action is imposed.

A. Loewy

We construct SUGRA solutions of brane configurations of intersecting Dp and NS branes. These solutions are semi-localized in the sense that one of the intersecting branes is smeared along the world volume of the other, while the second is localized. We examine the gauge theory that lives on the localized brane, and the various descriptions possible via T and

F. Lefloch, C. Hoffmann, O. Demolliens

We have studied the superconducting behavior of 100 nm Titanium Nitride (TiN) thin film in a perpendicular magnetic field. We found a zero field transition temperature of 4.6 K and a slope in the H-T plane of -0.745 T/K. At 4.2 K, we have performed careful transport measurements by measuring both the differential resistivity and voltage as a function of a DC

Yutaka Sakamura

The upper bound on the mass of the lightest Higgs boson is provided in the supersymmetric standard model with multi-Higgs doublets, up to two-loop order. Relatively large corrections are expected from the experimentally unconstrained extra Yukawa couplings. We calculate it including the two-loop leading-log contributions as a function of the scale $Λ$, below

Yuri V. Kovchegov, Larry McLerran

We derive an expression for diffractive F_2 structure function which should be valid at small x for quasi-elastic scattering on a hadron and for quasi-elastic scattering on a large nucleus. This expression includes multiple rescatterings of the quark-antiquark pair produced by the virtual photon off the sources of color charge in a quasi-classical approximat

Xiao-Gang He

Recently KTev collaboration has measured $Re(ε&#39;/ε) = (28\pm 4.1) \times 10^{-4}$ which is in agreement with early measurement from NA31. The Standard Model prediction for $ε&#39;/ε$ is on the lower end of the experimentally allowed range depending on models for hadronic matrix elements. In this paper we study the contributions from anomalous gauge coupli

O. Újsághy, A. Zawadowski

Recently, for spin $S=5/2$ impurities quite different size dependence of the Kondo contribution to the resistivity was found experimentally than for S=2. Therefore previous calculation about the effect of the spin-orbit-induced magnetic anisotropy on the Kondo amplitude of the resistivity is extended to the case of $S=5/2$ impurity spin which differs from th

A. Burinskii

Non-trivial supergeneralization of the Kerr-Newman solution is considered as representing a combined model of the Kerr-Newman spinning particle and superparticle. We show that the old problem of obtaining non-trivial super black hole solutions can be resolved in supergravity broken by Goldstone fermion. Non-linear realization of broken N=2 supersymmetry spec

Xiao-Guang Wang, Hong-Chen Fu

We show that the well-known negative binomial states of the radiation field and their excitations are nonlinear coherent states. Excited nonlinear coherent state are still nonlinear coherent states with different nonlinear functions. We finally give exponential form of the nonlinear coherent states and remark that the binomial states are not nonlinear cohere

Shin&#39;ichi Nojiri, Sergei D. Odintsov

We follow to Witten proposal in the calculation of conformal anomaly from d+1-dimensional higher derivative gravity via AdS/CFT correspondence. It is assumed that some d-dimensional conformal field theories have a description in terms of above d+1-dimensional higher derivative gravity which includes not only Einstein term and cosmological constant but also c

Nima Arkani-Hamed, Savas Dimopoulos, Nemanja Kaloper, John March-Russell

We discuss early cosmology in theories where the fundamental Planck mass is close to the TeV scale. In such theories the standard model fields are localized to a (3+1)-dimensional wall with n new transverse sub-millimeter sized spatial dimensions. The topic touched upon include: early inflation that occurs while the size of the new dimensions are still small

E. L. Bratkovskaya, W. Cassing, M. Effenberger, U. Mosel

We have performed a detailed study of dilepton production from pp collisions including the subthreshold $ρ$ production via baryonic resonances (N(1520), N(1700)) in addition to the conventional dilepton sources as $π^0, η, ω$ and $Δ$ Dalitz decays and direct decays of vector mesons ($ρ, ω$). The role of baryonic resonances in $ρ$ production from nucleon-nucl

Joseph D. Lykken, Konstantin T. Matchev

We study the supersymmetry reach of the Tevatron in channels containing both isolated leptons and identified tau jets. In the most challenging case, where the branching ratios of gauginos to taus dominate, we find that searches for two leptons, a tau jet and a large amount of missing transverse energy have a much better reach than the classic trilepton signa

S. M. H. Wong

In the last years, the need of the colour octet state in inclusive P-wave charmonium decay has been firmly established. However, the implications of this in the corresponding exclusive reactions have not been fully recognized. We argue for the necessity of the colour octet in P- and higher-wave quarkonium decay. Using a set of phenomenologically constructed

Dumitru Baleanu, Nugzar Makhaldiani

In this paper we introduce a system of nonlinear ordinary differential equations which in a particular case reduces to Volterra&#39;s system. We found in two simplest cases the complete sets of the integrals of motion using Nambu--Poisson reformulation of the Hamiltonian dynamics. In these cases we have solved the systems by quadratures.

M. Lewenstein, J. I. Cirac, S. Karnas

We show that all density operators of 2$\times N$--dimensional quantum systems that remain invariant after partial transposition with respect to the first system are separable. Based on this criterion, we derive a sufficient separability condition for general density operators in such quantum systems. We also give a simple proof of the separability criterion

R. B. Breslav, G. N. Parfionov, R. R. Zapatrin

An idealised experiment estimating the spacetime topology is considered in both classical and quantum frameworks. The latter is described in terms of histories approach to quantum theory. A procedure creating combinatorial models of topology is suggested. The correspondence between these models and discretised spacetime models is established.

R. A. Melikian, D. P. Barber

The exact solution of the Dirac equation and the spectrum of electron quasi-energies in a superposition of the field of a circularly polarized electromagnetic wave and a homogeneous magnetic field parallel to the direction of wave propagation, are found taking into account the anomalous magnetic moment. It is found that taking account of the anomalous magnet

D. Xenakis, N. E. Karapanagioti, D. Charalambidis, H. Bachau

The multiphoton ionization and photoelectron spectra of magnesium were studied at laser intensities of up to 6x10^{13} Wcm^{-2} using 150 fs laser pulses of a wavelength of 400 nm. The results indicated that a variety of different ionization mechanisms played a role in both types of spectra. A theoretical model describing the processes is presented and the r

F. J. Vanhecke

The product of two real spectral triples {A1,H1,D1,J1,gamma1} and {A2,H2,D2,J2(,gamma2)}, the first of which is necessarily even, was defined by A.Connes as {A,H,D,J(,gamma)} given by A=A1 x A2,H=H1 x H2, D=D1 x I2 + gamma1 x D2, J=J1 x J2 and by, in the even-even case, gamma=gamma1 x gamma2. Generically it is assumed that the real structure J obeys the rela

Janusz Gwoździewicz

Sergey Pinchuk found a polynomial map from the real plane to itself which is a local diffeomorphism but is not one-to-one. The aim of this paper is to give a geometric description of Pinchuk&#39;s map.

Hitoshi Murakami

We construct a hyperbolic three-manifold with trivial finite type invariants up to a given degree.

Finnur Larusson

Let Y be an infinite covering space of a projective manifold M in P^N of dimension n geq 2. Let C be the intersection with M of at most n-1 generic hypersurfaces of degree d in P^N. The preimage X of C in Y is a connected submanifold. Let phi be the smoothed distance from a fixed point in Y in a metric pulled up from M. Let O_phi(X) be the Hilbert space of h

Tsukasa Tada, Asato Tsuchiya

We propose a unitary matrix formulation of type IIB matrix model. One-loop effective action of the model exhibits supersymmetry for BPS background in the large N limit.

Davide Fabbri, Pietro Fre`, Leonardo Gualtieri, Piet Termonia

We reconsider the Kaluza Klein compactifications of D=11 supergravity on AdS_4x(G/H)_7 manifolds that were classified in the eighties, in the modern perspective of AdS_4/CFT_3 correspondence. We focus on one of the three N=2 cases: (G/H)_7=M^{111}=SU(3)xSU(2)xU(1)/SU(2)xU(1)&#39;xU(1)&#39;&#39;. Relying on the systematic use of the harmonic analysis techniqu

J. Bijtebier

We compare two opposite ways of performing a 3D reduction of the two-fermion Bethe-Salpeter equation beyond the instantaneous approximation and Salpeter&#39;s equation. The more usual method consists in performing an expansion around an instantaneous approximation of the product of the free propagators (propagator-approximated reduction). The second method s

A. I. Nikishov

Several energy-momentum &#34;tensors&#34; of gravitational field are considered and compared in the lowest approximation. Each of them together with energy-momentum tensor of point-like particles satisfies the conservation laws when equation of motion of particles are the same as in general relativity. It is shown that in Newtonian approximation the consider

V. Barger

Our knowledge of the neutrino sector of the Standard Model has recently undergone a revolution. Deficits of the atmospheric muon neutrino flux and the solar electron neutrino flux compared to their predicted values can be understood in terms of neutrino oscillations and we can therefore infer that neutrinos have non-degenerate masses. Additional but somewhat

P. Gambino, A. Sirlin, G. Weiglein

In order to test the accuracy of the Heavy Top-mass Expansion (HTE) employed in recent two-loop calculations of MW and sin^2theta_eff, we consider their contributions to subtracted quantities of the form MW_sub=MW(mh)-MW(mh0), where mh0 is a reference point. The results are compared with those obtained by a precise numerical evaluation of all the two-loop co

B. Badelek, J. Kwiecinski, A. Stasto

The parametrisation of the photon structure function in the low Q^2 region is formulated. It includes the VMD contribution and the QCD improved parton model component suitably extrapolated to the low Q^2 region. The parametrisation describes reasonably well existing experimental data on sigma_{γγ} for real photons and the low Q^2 data on sigma_{γ^* γ}. Predi

F. de Campos, M. A. Diaz, O. J. P. Eboli, M. B. Magro

We study unconventional decays of the top-quark and the top-squark in the framework of SUSY models with broken R-parity. The model under study is the MSSM with an additional bilinear term that breaks R-parity. In this model the top-squark behaves similar to a third generation leptoquark. We demonstrate that existing Tevatron data on the top give rise to rest

A. Capella, A. Kaidalov, J. Tran Thanh Van

Gribov approach to high-energy interactions of hadrons and nuclei is reviewed and applied to calculation of particle production in heavy-ions collisions. It is pointed out that the AGK (Abramovsky, Gribov, Kancheli) cutting rules is a powerful tool to investigate particle spectra in these processes. It leads, in the Glauber approximation, to a simple formula

Liu Lianshou, Fu Jinghua, Wu Yuanfang

It is shown using Monte Carlo simulation that for low multiplicity events the single-event factorial moments are saturated by the statistical fluctuations. The diverse of the event-space moments $C_{p,q}$ of single-event moments with the diminishing of phase space scale, called ``erraticity&#39;&#39;, observed in experiment can readily be reproduced by a fla

L. Favart

Brief review of the diffractive physics at HERA, stressing QCD aspects.

Gianluca Oderda

By defining dijet rapidity gap events according to interjet energy flow, we treat the photoproduction cross section of two high transverse momentum jets with a large intermediate rapidity region as a factorizable quantity in perturbative QCD. We show that logarithms of soft gluon energy in the interjet region can be resummed to all orders in perturbation the

Edmond L. Berger, Brian Harris, Michael Klasen, Tim Tait

We summarize the status of next-to-leading order perturbative quantum chromodynamics (pQCD) calculations of the cross sections for the production of squarks, gluinos, neutralinos, charginos, and sleptons as a function of the produced sparticle masses in proton-antiproton collisions at the hadronic center-of-mass energy 2 TeV.

J. P. Ma

We study gluon propagator in Landau gauge with lattice QCD, where we use an improved lattice action. The calculation of gluon propagator is performed on lattices with the lattice spacing from 0.40 fm to 0.24 fm and with the lattice volume from $(2.40 fm)^4$ to $(4.0 fm)^4$. We try to fit our results by two different ways, in the first one we interpret the ca

Taku Izubuchi, Jun Nishimura

We point out that a fermion determinant of a chiral gauge theory on a 2D torus has a phase ambiguity proportional to the Polyakov loops along the boundaries, which can be reproduced by the overlap formalism. We show that the requirement on the fermion determinant that a singularity in the gauge field can be absorbed by a change of the boundary condition for

Luis M. A. Bettencourt, Salman Habib, Grant Lythe

Stochastic evolutions of classical field theories have recently become popular in the study of problems such as determination of the rates of topological transitions and the statistical mechanics of nonlinear coherent structures. To obtain high precision results from numerical calculations, a careful accounting of spacetime discreteness effects is essential,

Alicia M. Sintes, Bernard F. Schutz

We describe a procedure to identify and remove a class of non-stationary and non-harmonic interference lines from gravitational wave interferometer data. These lines appear to be associated with the external electricity main supply, but their amplitudes are non-stationary and they do not appear at harmonics of the fundamental supply frequency. We find an emp

Jean-Luc Brylinski, Bin Zhang

We compute the equivariant $K$-theory $K_G^*(G)$ for a simply connected Lie group $G$ (acting on itself by conjugation). We prove that $K_G^*(G)$ is isomorphic to the algebra of Grothendieck differentials on the representation ring. We also study a special example of a non-simply connected Lie group $G$, namely PSU(3), and compute the corresponding equivaria

P. V. Komissinski, G. A. Ovsyannikov, N. A. Tulina, V. V. Ryazanov

We present the experimental results for Nb/Au/YBaCuO structures, in which the current flows along (001) direction of YBaCuO film. The theoretical evaluations show, that at the experimental values of the Au/YBaCuO interface transparency, determined from the interface resistance D~10^-6, the critical current of the structure is of the fluctuation order of magn

Veit Elser

When the charge density in a crystal or a quasicrystal is reconstructed from its Fourier modes, the global minimum value of the density is sensitively dependent on the relative phases of the modes. The set of phases that maximizes the value of the global minimum, corresponds, by positivity of the density, to the charge density having the minimum total charge

V. Brouet, H. Alloul, F. Quere, G. Baumgartner

We present a 13C and 133Cs NMR investigation of the CsC60 cubic quenched phase. Previous ESR measurements suggest that this phase is metallic, but NMR reveals contrasting electronic behavior on the local scale. The 13C spin-lattice relaxation time (T1) exhibits a typical metallic behavior down to 50 K, but indicates that a partial spin-gap opens for T<50 K.

Y. L. Lee, Y. W. Lee, C. -Y. Mou, Z. Y. Weng

Two-leg t-J ladders are investigated in the framework of a combination of the phase string formulation and bond-operator representation. We develope a mean-field theory in the strong rung interaction regime, i.e. $J_{\perp}\gg J, t$, which provides a unified description of the undoped insulating phase and the low doping phase --- the so-called C1S0 phase. Bo

W. Pan, D. C. Tsui, B. L. Draper

We wish to report in this paper a study of the effective mass (m^*) in thin-oxide Si-metal-oxide-semiconductor field-effect-transistors, using the temperature dependence of the Shubnikov-de Haas (SdH) effect and following the methodology developed by J.L. Smith and P.J. Stiles, Phys. Rev. Lett. {\bf 29}, 102 (1972). We find that in the thin oxide limit, when

Roland Assaraf, Patrick Azaria, Michel Caffarel, Philippe Lecheminant

We investigate the metal-insulator transition of the one-dimensional SU(N) Hubbard model for repulsive interaction. Using the bosonization approach a Mott transition in the charge sector at half-filling (k_F=π/Na_0) is conjectured for N > 2. Expressions for the charge and spin velocities as well as for the Luttinger liquid parameters and some correlation fun

Stefan Mueller

Based on a recently established formalism (U. Ebert, J. Stat. Phys. 82, 183 (1996)) we analyze the diffusive motion of a long polymer in a quenched random medium. The medium is modeled by a frozen semidilute polymer system. In the framework of standard renormalization group (RG) theory we present a systematic perturbative approach to handle such a many chain

F. de los Santos, Miguel A. Munoz

We use field theoretic renormalization group methods to study the critical behavior of a recently proposed Langevin equation for driven lattice gases under infinitely fast drive. We perform an expansion around the upper critical dimension, d_c=4, and obtain the critical exponents to one loop order. The main features of the two loop calculation are then outli

Jayajit Das, Madan Rao

We study the dynamics of ordering of the nonconserved and conserved Heisenberg magnet. The dynamics consists of two parts - an irreversible dissipation into a heat bath and a reversible precession induced by a torque due to the local molecular field. For quenches both to T=0 and T=T_c, we show that the torque is irrelevant when the dynamics is nonconserved b

Baowen Li, Jie Liu, Yan Gu, Bambi Hu

We study quantum chaos in a non-KAM system, i.e. a kicked particle in a one-dimensional infinite square potential well. Within the perturbative regime the classical phase space displays stochastic web structures, and the diffusion coefficient D in the regime increases with the perturbative strength K giving a scaling $D \propto K^{2.5}$, and in the large K r

K. R. Anantharamaiah, Nimisha G. Kantharia

We report observations of carbon recombination lines near 34.5 MHz (qunatum number n=578) and 325 MHz (n=272) made towards Cas A, the Galactic centre and about ten other directions in the galactic plane. Constraints on the physical conditions in the line forming regions are derived from these and other existing observations. The CII regions that produce the

Thomas Hertog, Neil Turok

We perform a first principles computation of the spectrum of gravity waves produced in open inflationary universes. The background spacetime is taken to be the continuation of an instanton saddle point of the Euclidean no boundary path integral. The two-point tensor correlator is computed directly from the path integral and is shown to be unique and well beh

Thaisa Storchi-Bergmann

I discuss some recent observational results in the research of nearby active galactic nuclei (AGN). These results cover three main topics: (i) evidences for the current paradigm for AGN&#39;s, which include a nuclear supermassive blackhole (SMBH) fed via an accretion disk; (ii) evidence that this paradigm may also apply to LINER&#39;s, the lowest luminous AG

M. Machacek, G. Bryan, P. Anninos, A. Meiksin

The comparison of quasar absorption spectra with numerically simulated spectra from hierarchical cosmological models of structure formation promises to be a valuable tool to discriminate among these models. We present simulation results for the column density, Doppler b parameter, and optical depth probability distributions for five popular cosmological mode

K. R. Anantharamaiah, A. Pedlar, W. M. Goss

Radio recombination lines at a wavelength of 20 cm reveals the presence of an extended component of ionized gas of lower density in the Sgr A complex. This component extends well beyond the thermal `mini-spiral&#39; SgrA-West, which seem to be embedded in it. The low-density component is present over the entire extent of SgrA East and possibly beyond and it

Jay A. Frogel

Observations of the stellar content of the Milky Way&#39;s bulge helps to understand the stellar content and evolution of distant galaxies. In this brief overview I will first highlight some recent work directed towards measuring the history of star formation and the chemical composition of the central few parsecs of the Galaxy. High resolution spectroscopic

Robert F. Coker, Fulvio Melia, Heino Falcke

In the first paper of this series, using analytic tools, we examined how the evolution and structure of a massive accretion disk may be influenced by the deposition of mass and angular momentum by an infalling Bondi-Hoyle wind. Such a mass influx impacts the long-term behavior of the disk by providing additional sources of viscosity and heating. Here, we mak

Tereasa G. Brainerd, Candace Oaxaca Wright, David M. Goldberg, Jens Verner Villumsen

High-resolution N-body simulations are used to investigate systematic trends in the mass profiles and total masses of clusters as derived from 3 simple estimators: (1) the weak gravitational lensing shear field under the assumption of an isothermal cluster potential, (2) the dynamical mass obtained from the measured velocity dispersion under the assumption o

K. R. Anantharamaiah, C. C. Lang, N. E. Kassim, T. J. W. Lazio

We report the discovery of a new filamentary structure, G358.85+0.47, consisting of at least three mutually parallel but bent `strands&#39;, located about 1.5 degrees SW of the Sgr A complex. Unlike all the other known Galactic center filaments, G358.85+0.47 is oriented parallel to the galactic plane. This orientation of the filament may have implications fo

E. Vazquez-Semadeni, E. C. Ostriker, T. Passot, C. F. Gammie

We review recent results from numerical simulations and related models of MHD turbulence in the interstellar medium (ISM) and in molecular clouds. We discuss the implications of turbulence for the processes of cloud formation and evolution, and the determination of clouds&#39; physical properties. Numerical simulations of the turbulent ISM to date have inclu

Kenneth J. Mighell, Christopher J. Burke

We present our analysis of archival Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) observations in F555W (~V) and F814W (~I) of the central region of the Ursa Minor dwarf spheroidal galaxy. The V versus V-I color-magnitude diagram features a sparsely populated blue horizontal branch, a steep thin red giant branch, and a narrow subgiant branch.

Ben Moore, George Lake, Joachim Stadel, Thomas Quinn

We follow the evolution of disk galaxies within a cluster that forms hierarchically in a standard cold dark matter N-body simulation. At a redshift z=0.5 we select several dark matter halos that have quiet merger histories and are about to enter the newly forming cluster environment. The halos are replaced with equilibrium high resolution model spirals that

Sara L. Ellison, Geraint F. Lewis, Max Pettini, Wallace L. W. Sargent

We present high S/N echelle spectra of the recently discovered ultraluminous QSO APM 08279+5255 and use these data to re-examine the abundance of Carbon in Ly alpha forest clouds. In agreement with previous work, we find that approximately half of the Ly alpha clouds whose hydrogen column densities log N(HI) > 14.5 have associated weak CIV absorption with lo

Tod E. Strohmayer, Craig B. Markwardt

We investigate the time dependence of the frequency of X-ray brightness oscillations during thermonuclear bursts from several neutron star low mass X-ray binaries. We find that the oscillation frequencies in the cooling tails of X-ray bursts from 4U 1702-429 and 4U 1728-34 are well described by an exponential &#34;chirp&#34; model. With this model we demonst

M. Bureau, E. Athanassoula

We develop diagnostics to detect the presence and orientation of a bar in an edge-on disk, using its kinematical signature in the position-velocity diagram (PVD) of a spiral galaxy observed edge-on. Using a well-studied barred spiral galaxy mass model, we briefly review the orbital properties of two-dimensional non-axisymmetric disks and identify the main fa

A. Gil de Paz, J. Zamorano, J. Gallego

We have studied the velocity field of the Blue Compact Dwarf galaxy Mrk86 (NGC2537) using data provided by 14 long-slit optical spectra. This kinematical information is complemented with narrow-band ([OIII]5007A and Halpha) and broad-band (B, V, Gunn-r and K) imaging. The analysis of the galaxy global velocity field suggests that the ionized gas could be dis

Sean G. Ryan, John E. Norris, Timothy C. Beers

We have studied 23 very metal-poor field turnoff stars, specifically chosen to enable a precise measurement of the dispersion in the lithium abundance of the Spite Li plateau. We concentrated on stars having a narrow range of effective temperature and very low metallicities ([Fe/H] < -2.5) to reduce the effects of systematic errors, and have made particular

Gabriel W. Pratt, B. J. M. Hassall, T. Naylor, Janet H. Wood

We present a phase-resolved ROSAT HRI X-ray light curve of the dwarf nova OY Car in quiescence. The X-ray flux is eclipsed at the same time as the optical eclipse of the primary, and the region of X -ray emission is comparable in size to the white dwarf. We use subsequent optical observations to update the orbital ephemeris of the system.

C. S. Crawford, S. W. Allen, H. Ebeling, A. C. Edge

We present new spectra of dominant galaxies in X-ray selected clusters, which combine with our previously published spectra to form a sample of 256 dominant galaxies in 215 clusters; 177 of these are members of the ROSAT Brightest Cluster Sample. 27% of the central dominant galaxies have emission-line spectra, all but 5 with line intensity ratios typical of

L. Ciotti

In this paper I present three new results of astronomical interest concerning the theory of Abel inversion. 1) I show that in the case of a spatial emissivity that is constant on toroidal surfaces and projected along the symmetry axis perpendicular to the torus&#39; equatorial plane, it is possible to invert the projection integral. From the surface (i.e. pr