October 1998 arXiv papers — page 4

Paweł Preś, Kenneth J. H. Phillips

Several coronal bright points identified in a quiet region of the Sun from SOHO/EIT Fe XII images are found to have a time evolution from birth to decay which is extremely well correlated with the rise and fall of magnetic flux as determined from photospheric magnetograms made with the SOHO/MDI instrument. Radiative losses of the bright points are found to b

P. Grandi, M. Guainazzi, F. Haardt, L. Maraschi

A BeppoSAX observation of the BLRG 3C390.3 is reported. For the first time, both the 6.4 keV iron line and a strong reflection hump, produced by the illumination of the primary X-ray emission on cold matter, are detected in this source. The 0.1-100 keV continuum is modeled by an absorbed power law (Γ~ 1.8) reflected at high energies by material with a fairly

S. Gottloeber, A. A. Klypin, A. V. Kravtsov

We study the formation and evolution of the dark matter halos in a LCDM model. The dynamics of 16.8 million DM particles is followed numerically in a box of 60 Mpc/h with the dynamic range of 32,000 in spatial resolution. The high resolution of the simulation allows us to examine evolution of both isolated and satellite halos in a representative volume. We p

Gordon Walker, Scott Chapman, Georgi Mandushev, Rene Racine

We have searched, so far in vain, for brown dwarfs or giant planets in the vicinity of several nearby stars using cameras built at Universite de Montreal attached to the CFHT Adaptive Optics system. Here, we show how pairs of images taken simultaneously through separate filters on, and off, the 1.6 micron methane absorption band, can be used to completely de

Delphine Porquet, Anne-Marie Dumont, Suzy Collin, Martine Mouchet

We present results of the photoionization code IRIS, which calculates the spectrum emitted by the Warm Absorber (WA) in Seyfert 1 galaxies for a large grid of parameters (density, column density, ionization parameter...). We show that in Seyfert 1s, coronal lines Fe X, Fe XI, Fe XIV...), whose emission region shares common characteristics with the WA, could

Zoltan Haiman, Kristen Menou

We consider a class of models for the redshift evolution (between $0\lsim z \lsim 4$) of the observed optical and X-ray quasar luminosity functions (LFs), with the following assumptions: (i) the mass-function of dark matter halos follows the Press-Schechter theory, (ii) the black hole (BH) mass scales linearly with the halo mass, (iii) quasars have a constan

Jonathan L. Feng, Christopher Kolda, Nir Polonsky

The supersymmetric flavor problem may be solved if the first and second generation scalars are heavy (with multi-TeV masses) and scalars with large Higgs couplings are light (with sub-TeV masses). We show that such an inverted spectrum may be generated radiatively; that is, from initial conditions where all scalar masses are multi-TeV at some high scale, tho

Steven S. Gubser

Spinning black three-branes in type IIB supergravity are thermodynamically stable up to a critical value of the angular momentum density. Inside the region of thermodynamic stability, the free energy from supergravity is roughly reproduced by a naive model based on free N=4 super-Yang-Mills theory on the world-volume. The field theory model correctly predict

P. John

We present a general numerical approach to solve the equations for bubble wall profiles in models with more than one scalar field and CP violating phases. We discuss the algorithm as well as several problems associated with it and show some profiles for demonstration found with our method.

A. F. Martini, M. J. Menon, J. T. S. Paes, M. J. Silva Neto

We discuss the evaluation of the real part of the elementary amplitudes in the context of a multiple diffraction model for $pp$ elastic scattering earlier developed. The framework is based on the concepts of analyticity and polynomial boundedness, and the techniques of dispersion relations. Novel results concern the use of derivative dispersion relations at

T. E. Coan

We report the results of a search for the rare baryonic decay modes B -> Lambda Lambdabar, B -> Lambdabar p, B -> Lambdabar p pi, and B -> p pbar using 5.8M BBbar pairs collected with the CLEO detector. We see no statistically significant signals in any of these modes and set 90% confidence level upper limits on their branching fractions, B(B -> Lambda Lambd

V. Sahakian, E. Martinec

The complete phase diagram of objects in M-theory compactified on tori $T^p$, $p=1,2,3$, is elaborated. Phase transitions occur when the object localizes on cycle(s) (the Gregory-Laflamme transition), or when the area of the localized part of the horizon becomes one in string units (the Horowitz-Polchinski correspondence point). The low-energy, near-horizon

J. Malek, S. Flach, K. Kladko

A generalization of Faddeev's approach of the 3-body problem to the many-body problem leads to the method of increments. This method was recently applied to account for the ground state properties of Hubbard-Peierls chains (JETP Letters 67 (1998) 1052). Here we generalize this approach to two-dimensional square lattices and explicitely treat the incremen

K. Scharnhorst

QED vacua under the influence of external conditions (background fields, finite temperature, boundary conditions) can be considered as dispersive media whose complex behaviour can no longer be described in terms of a single universal vacuum velocity of light c. Beginning in the early 1950's (J.S. Toll), quantum field theoretic investigations have led to

G. De Filippis, V. Cataudella, G. Iadonisi

A simple approach to the many-polaron problem for both weak and intermediate electron-phonon coupling and valid for densities much smaller than those typical of metals is presented. Within the model the total energy, the collective modes and the single-particle properties are studied and compared with the available theories. It is shown the occurrence of a c

Anjan Kundu

A novel algebra underlying integrable systems is shown to generate and unify a large class of quantum integrable models with given $R$-matrix, through reductions of an ancestor Lax operator and its different realizations. Along with known discrete and field models a new class of inhomogeneous and impurity models are obtained.

C. Hofman, E. Verlinde

In this paper, we describe non-abelian gauge bundles with magnetic and electric fluxes on higher dimensional noncommutative tori. We give an explicit construction of a large class of bundles with nonzero magnetic 't Hooft fluxes. We discuss Morita equivalence between these bundles. The action of the duality is worked out in detail for the four-torus. As

S. Jain

The Glauber dynamics of the pure and weakly disordered random-bond 2d Ising model is studied at zero-temperature. A single characteristic length scale, $L(t)$, is extracted from the equal time correlation function. In the pure case, the persistence probability decreases algebraically with the coarsening length scale. In the disordered case, three distinct re

J. R. Cudell, A. Le Yaouanc, C. Pittori

We analyse the Structure Function collaboration data on the quark pseudoscalar vertex and extract the Goldstone boson pole contribution, in 1/p2. The strength of the pole is found to be quite large at presently accessible scales. We draw the important consequences of this finding for the various definitions of quark masses, and point out potential problems w

A. A. Penin, A. A. Pivovarov

The total cross section of the top quark-antiquark pair production near threshold in $γγ$ collision is computed analytically up to the next-to-leading order in perturbative and nonrelativistic expansion for general photon helicity. The approximation includes the first order corrections in the strong coupling constant and the heavy quark velocity to the nonre

A. Sibirtsev, K. Tsushima, W. Cassing, A. W. Thomas

Using the resonance model, which was successfully applied for the study of the $pp{\to}p{\Lambda}K^+$ reaction, we investigate $NN{\to}N{\Sigma}K$ reactions that should provide cleaner information about resonance excitations and meson exchange contributions. For this purpose we demonstrate that the invariant mass distribution for the ${\Sigma}K$ system, as w

G. De Franceschi, F. Palumbo

We present a new perturbative approach to QCD based on the use of quark composites with hadronic quantum numbers as fundamental variables. We apply it to the case of the nucleons by performing a nonlinear change of variables in the Berezin integral which defines the partition function of QCD. The nucleon composites are thereby assumed as new integration vari

Achim Geiser

The current case for atmospheric $ν_μ$ oscillations into active or sterile neutrinos is reviewed. It is argued that neither the study of neutral current events at Super-Kamiokande, nor the information obtained from future long baseline experiments might be sufficient to unambigously decide between these two scenarios. However, a combination of these results

Lorenz Bartosch, Peter Kopietz

We develop a non-perturbative method to calculate the density of states (DOS) of the fluctuating gap model describing the low-energy physics of electrons on a disordered Peierls chain. For real order parameter field we calculate the DOS at the Fermi energy exactly as a functional of the disorder for a chain of finite length L. Averaging rho (0) with respect

T. Hotta, T. Tamae, T. Miura, H. Miyase

The triple differential cross sections for the 6Li(e,e'p) reaction have been measured in the excitation energy region from 27 to 46 MeV in a search for evidence of the giant dipole resonance (GDR) in 6Li. The cross sections have no distinct structures in this energy region, and decrease smoothly with the energy transfer. Angular distributions are differe

Yue-Liang Wu

Based on the SO(3) gauge symmetry for three family leptons and general see-saw mechanism, we present a simple scheme that allows three nearly degenerate Majorana neutrino masses needed for hot dark matter. The vacuum structure of the spontaneous SO(3) symmetry breaking can automatically lead to a maximal CP-violating phase. Thus the current neutrino data on

Igor Bray

The convergent close-coupling method is applied to the calculation of fully differential cross sections for ionization of atomic hydrogen by 15.6 eV electrons. We find that even at this low energy the method is able to yield predictive results with small uncertainty. As a consequence we suspect that the experimental normalization at this energy is approximat

M. S. Miesch, J. M. Scalo, J. Bally

The probability density functions (pdfs) of molecular line centroid velocity fluctuations and fluctuation differences at different spatial lags are estimated for several nearby molecular clouds with active internal star formation. The data consist of over 75,000 $^{13}$CO line profiles divided among twelve spatially and/or kinematically distinct regions. Alt

Alexei Razoumov, Douglas Scott

A numerical scheme is proposed for the solution of the three-dimensional radiative transfer equation with variable optical depth. We show that time-dependent ray tracing is an attractive choice for simulations of astrophysical ionization fronts, particularly when one is interested in covering a wide range of optical depths within a 3D clumpy medium. Our appr

N. Kamran, R. Milson

In this article, we study and settle several structural questions concerning the exact solvability of the Olshanetsky-Perelomov quantum Hamiltonians corresponding to an arbitrary root system. We show that these operators can be written as linear combinations of certain basic operators admitting infinite flags of invariant subspaces, namely the Laplacian and

Luigi Palatella, Paolo Grigolini

We study the thermodynamical properties of the quantum kicked rotator, coarsened by an external fluctuation with a weak intensity D, by means of the Tsallis entropy with a changing entropic index q. The genuine entropic index, corresponding to given values of D and $\hbar$ is that making the Tsallis entropy increase linearly in time, and it is proved to beco

Seth Lloyd, Samuel L. Braunstein

This paper provides necessary and sufficient conditions for constructing a universal quantum computer over continuous variables. As an example, it is shown how a universal quantum computer for the amplitudes of the electromagnetic field might be constructed using simple linear devices such as beam-splitters and phase shifters, together with squeezers and non

A. F. Kracklauer

An error in the proof of Bell's Theorem is identified and a semiclassical model of the EPRB experiment is presented

C. H. Mak, R. Egger

We propose a novel approach toward the general solution of the sign problem in real-time path-integral simulations. Using a recursive multilevel blocking strategy, this method circumvents the sign problem by synthesizing the phase cancellations arising from interfering quantum paths on multiple timescales. A number of numerical examples with one or a few exp

Jurij Darewych

Integral identities that hold between ``desired'' and ``comparison'' solutions of the radial Dirac equations for scattering precesses are considered. Applications of these identities are discussed, particularly the determination of bounds to variational calculations of $K$-matrix elements.

Luca Falconi, Marco Maccarini, Giuseppe Briganti, Giovanni D'Arrigo

By means of density, dielectric spectroscopy and sound velocity measurements we perform a systematic study on the polyoxyethylene $C_{12}E_{6}$ nonionic surfactant solutions as a function of temperature and concentration. Both density and sound velocity data, at about $34^{\circ}C$, coincide with the value obtained for pure water. Above this temperature the

M. Daoud, M. Kibler

We present some recent progress achieved in the application of symmetry adaptation techniques to n-photon absorption spectroscopy of rare earth ions in finite symmetry. More specifically, this work is concerned with the determination of the intensity of n-photon transitions between Stark levels (rather than J levels) of an ion in an environment with a given

Ulrich H. E. Hansmann, Frank Eisenmenger, Yuko Okamoto

We develop a formulation for molecular dynamics, Langevin, and hybrid Monte Carlo algorithms in the recently proposed generalized ensemble that is based on a physically motivated realisation of Tsallis weights. The effectiveness of the methods are tested with an energy function for a protein system. Simulations in this generalized ensemble by the three metho

W. Schadow, W. Sandhas, J. Haidenbauer, A. Nogga

The quality of two different separable expansion methods ({\sl W} matrix and Ernst-Shakin-Thaler) is investigated. We compare the triton binding energies and components of the triton wave functions obtained in this way with the results of a direct two-dimensional treatment. The Paris, Bonn {\sl A} and Bonn {\sl B} potentials are employed as underlying two-bo

C. Barbero, F. Krmpotić, A. Mariano, D. Tadić

We have extended the formalism for the two-neutrino double beta decay by including the weak-magnetism term, as well as other second-forbidden corrections. The weak magnetism diminishes the calculated half-lives in $\sim 10%$, independently of the nuclear structure. Numerical computations were performed within the pn-QRPA, for $^{76}Ge$, $^{82}Se$, $^{100} Mo

T. Gross-Boelting, C. Fuchs, Amand Faessler

We investigate nuclear matter properties in the relativistic Brueckner approach. The in-medium on-shell T-matrix is represented covariantly by five Lorentz invariant amplitudes from which we deduce directly the nucleon self-energy. We discuss the ambiguities of this approach and the failure of previously used covariant representations in reproducing the nucl

David P. Roberts

In this paper we construct number fields ramified at 2 and 3 only, with various moderate-sized non-solvable Galois groups. We construct these fields by specializing three point covers, some from the literature and some new here. The specialization points come from solutions to a generalized Fermat equation. We conclude with a specific suggestion for further

Emmanuel Kowalski, Philippe Michel

We provide, on the Birch and Swinnerton-Dyer conjecture, an explicit upper bound for the rank of the Mordell-Weil group of the Jacobian of the modular curve X_0(q) for q prime large enough, namely rank J_0(q)< 6.5 dim J_0(q). The file j0q-pari.dvi contains the .dvi version of the commented listing of the Pari/GP program used for the computations of the paper

John R. Parker, Jouni Parkkonen

We consider complex Fenchel-Nielsen coordinates on the quasi-Fuchsian space of punctured tori. These coordinates arise from a generalisation of Kra&#39;s plumbing construction and are related to earthquakes on Teichmueller space. They also allow us to interpolate between two coordinate systems on Teichmueller space, namely the classical Fuchsian space with F

Graham A. Niblo, Daniel T. Wise

We show that there are Haken 3-manifolds whose fundamental groups do not satisfy the engulfing property. In particular one can construct a pi_1-injective immersion of a surface into a graph manifold which does not factor through any proper finite cover of the 3-manifold.

H. R. Morton, H. J. Ryder

Details of quantum knot invariant calculations using a specific SU(3)_q-module are given which distinguish the Conway and Kinoshita-Teresaka pair of mutant knots. Features of Kuperberg&#39;s skein-theoretic techniques for SU(3)_q invariants in the context of mutant knots are also discussed.

Albert Marden

Let M^3 be a compact, oriented, irreducible, and boundary incompressible 3-manifold. Assume that its fundamental group is without rank two abelian subgroups and its boundary is non-empty. We will show that every homomorphism from pi_1(M) to PSL(2,C) which is not `boundary elementary&#39; is induced by a possibly branched complex projective structure on the b

Christos Kourouniotis

We examine the dependence of the deformation obtained by bending quasi-Fuchsian structures on the bending lamination. We show that when we consider bending quasi-Fuchsian structures on a closed surface, the conditions obtained by Epstein and Marden to relate weak convergence of arbitrary laminations to the convergence of bending cocycles are not necessary. B

Yohei Komori, Caroline Series

In [4]: `The Riley slice of Schottky space&#39;, (Proc. London Math. Soc. 69 (1994), 72-90), Keen and Series analysed the theory of pleating coordinates in the context of the Riley slice of Schottky space R, the deformation space of a genus two handlebody generated by two parabolics. This theory aims to give a complete description of the deformation space of

M. Izquierdo, D. Singerman

Macbeath gave a formula for the number of fixed points for each non-identity element of a cyclic group of automorphisms of a compact Riemann surface in terms of the universal covering transformation group of the cyclic group. We observe that this formula generalizes to determine the fixed-point set of each non-identity element of a cyclic group of automorphi

Xianzhe Dai, Guofang Wei

In this note we give a heat kernel lower bound in term of integral Ricci curvature, extending Cheeger-Yau&#39;s estimate.

Ross Geoghegan, Andrew Nicas

We define a &#34;circle Euler characteristic&#34; of a circle action on a compact manifold or finite complex X. It lies in the first Hochschild homology group of ZG where G is the fundamental group of X. It is analogous in many ways to the ordinary Euler characteristic. One application is an intuitively satisfying formula for the Euler class (integer coeffic

Alexander Sergeev

The symmetric group S_n possesses a nontrivial central extension, whose irreducible representations, different from the irreducible representations of S_n itself, coincide with the irreducible representations of a certain algebra A_n. Recently M.~Nazarov realized irreducible representations of A_n and Young symmetrizers by means of the Howe duality between t

Walter D. Neumann

This paper is an expansion of my lecture for David Epstein&#39;s birthday, which traced a logical progression from ideas of Euclid on subdividing polygons to some recent research on invariants of hyperbolic 3-manifolds. This `logical progression&#39; makes a good story but distorts history a bit: the ultimate aims of the characters in the story were often fa

Matthew J. Strassler

As in two and four dimensions, supersymmetric conformal field theories in three dimensions can have exactly marginal operators. These are illustrated in a number of examples with N=4 and N=2 supersymmetry. The N=2 theory of three chiral multiplets X,Y,Z and superpotential W=XYZ has an exactly marginal operator; N=2 U(1) with one electron, which is mirror to

Mu-In Park, Young-Jai Park, Sean J. Yoon

We apply an improved version of Batalin-Fradkin-Tyutin (BFT) Hamiltonian method to the a=1 chiral Schwinger Model, which is much more nontrivial than the a>1.$ one. Furthermore, through the path integral quantization, we newly resolve the problem of the non-trivial $δ$ function as well as that of the unwanted Fourier parameter $ξ$ in the measure. As a result

Choonkyu Lee, Q-Han Park

An exact one monopole solution in a uniform self-dual background field is obtained in the BPS limit of the SU(2) Yang-Mills-Higgs theory by using the inverse scattering method.

Dimitra Karabali

Using a gauge-invariant matrix parametrization of the gauge fields, we present an analysis of how the mass gap arises in (2+1)-dimensional Yang-Mills theory. We further derive an analytical continuum expression for the vacuum wavefunction and based on this we calculate the string tension which is in excellent agreement with Monte Carlo simulations of the cor

M. Chizhov, M. Maris, S. T. Petcov

Assuming two-neutrino mixing takes place in vacuum, we study in detail the conditions under which the $ν_2 \to ν_{e}$ and $ν_μ \to ν_{e}$ ($ν_e \to ν_{μ(τ)}$) transitions in the Earth are strongly enhanced by the neutrino oscillation length resonance when the neutrinos cross the Earth core. We show, in particular, that the neutrino oscillation length resonan

M. A. Ivanov, V. E. Lyubovitskij, E. Z. Lipartia, A. G. Rusetsky

The relativistic perturbative approach based on the Bethe-Salpeter (BS) equation is developed for the study of the characteristics of the hadronic pi+ pi- atom. The general expression for the atom lifetime is derived. Lowest-order corrections to the relativistic Deser-type formula for the atom lifetime are evaluated within the Chiral Perturbation Theory. The

Sergey Troshin, Nikolai Tyurin

New mode in the hadron scattering is predicted to appear at the energies beyond $\sqrt{s}\simeq 2$ TeV: the antishadow scattering mode and the experiments at LHC and VLHC in hadronic reactions will be able to reveal it. The appearance of the antishadow scattering mode at these energies is considered on the basis of unitarity and geometrical notions of hadron

M. K. Parida

In the context of a viable, supersymmetric,preon model,it has been shown by Babu and Pati that the unity of forces can well occur at the level of preons near the Planck scale.This preonic approach to unification is explored further in this note with the inclusion of threshold effects which arise due to spreading of masses near the scale of suppersymmetry ($M

K. Fialkowski, R. Wit

We briefly review various methods of implementing the Bose - Einstein effect into Monte Carlo generators. The weight methods are discussed in more detail; in particular, our method employing a clustering algorithm is applies for the process e^+e^- -> W^+W^-. New results for the multiplicity distributions are presented.

Zenro Hioki, Kazumasa Ohkuma

We calculate the CP-violating polarization asymmetry of tt-bar, delta =[ sigma(ee-bar --> t(-)t-bar(-))-sigma(ee-bar --> t(+)t-bar(+)) ]/ sigma(ee-bar --> tt-bar), for the most general tt-bar gamma/Z couplings without dropping any non-standard contribution. We find that one term which is usually neglected increases with s and will eventually become non-negli

Hsiang-nan Li

We review the perturbative QCD formalism for exclusive heavy meson decays, concentrating on the three-scale factorization theorem for nonleptonic processes. The formalism is then extended to the radiative decay $B\to K^*γ$, which occurs through penguin diagrams. It is observed that the contributions from the operators other than the penguin one $b\to sγ$ are

Jean Letessier, Johann Rafelski

The hadronic particle production data from relativistic nuclear Pb--Pb 158 A GeV collisions are successfully described within the chemical non-equilibrium model, provided that the analysis treats Omega and anti-Omega abundances with care. We further show that there is a subtle influence of the Coulomb potential on strange quarks in quark matter which is also

P. H. Damgaard, U. M. Heller, A. Krasnitz

Measurements of the lowest-lying eigenvalues of the staggered fermion Dirac operator are made on ensembles of equilibrium gauge field configurations in quenched SU(3) lattice gauge theory. The results are compared with exact analytical predictions in the microscopic finite-volume scaling regime.

Matthew J. Strassler

Supersymmetric gauge theories in four dimensions have taught us many important physics lessons. These can both inform and be informed by future work on the lattice. I focus on three issues: the properties of supersymmetric Yang-Mills theory and its relation to the non-supersymmetric case; the properties of gauge theories with matter and their relation to rea

TARO Collaboration, Ph. de Forcrand, M. Garcia Perez, T. Hashimoto

We study the effects of the chemical potential on the $ρ$ meson mass at finite temperature. Our preliminary results show that some effects are seen in the vicinity of the phase transition point. Although the signal is still too noisy to obtain conclusive physical results within limited statistics, the mass susceptibility is consistent with zero.

S. Hashimoto, A. X. El-Khadra, A. S. Kronfeld, P. B. Mackenzie

The zero recoil limit of the B -> D l nu form factors is calculated on the lattice, which provides a model-independent determination of |Vcb|. Considering a ratio of form factors, in which the bulk of statistical and systematic errors cancel, we obtain a precise result both for h_+(1) and for h_-(1).

L. E. Sinclair

In the ZEUS experiment at HERA, photoproduction processes have been studied for photon-proton centre-of-mass energies in the range 100 < W_gamma p < 300 GeV and jet transverse energies extending to E_T^jet ~ 70 GeV. The data contribute to our understanding of QCD dynamics, and also provide new constraints on the photon&#39;s parton density.

E. Tournefier

The determination of the Z lineshape parameters at LEP1 is presented and the value of $\alsmz$ is derived from these measurements. The constraint on the Higgs mass obtained from a global fit to LEP1 and SLC data is also given.

Matthew Wing

Advances in knowledge of the structure of the photon and tests of perturbative QCD have been made using the increased luminosity with the ZEUS detector at HERA. Events with a low photon virtuality and two high transverse energy jets have been studied. Measurements of inclusive dijet and multijet production are herein compared to Next-to-Leading-Order calcula

Pedro F Gonzalez-Diaz

Starting with a study of the cosmological solution to the Einstein equations for the internal spacetime of an extreme supermassive cosmic string kink, and by evaluating the probability measure for the formation of such a kink in semiclassical approximation using a minisuperspace with the appropriate symmetry, we have found a set of arguments in favor of the

Mirco Calura, Enrico Montanari

We present the exact solution to the linearized Maxwell equations in space-time slightly curved by a gravitational wave. We show that in general, even dealing with a first-order theory in the strength of the gravitational field, the solution can not be written as the sum of the flat space-time one and a weak perturbation due to the external field. Such an im

Kengo Maeda, Takashi Torii, Makoto Narita

A new mechanism for causing naked singularities is found in an effective superstring theory. We investigate the gravitational collapse in a spherically symmetric Einstein-Maxwell-dilaton system in the presence of a pure cosmological constant &#34;potential&#34;, where the system has no static black hole solution. We show that once gravitational collapse occu

J. Fabian, S. Das Sarma

Relaxation of electronic spins in metals is significantly enhanced whenever a Fermi surface crosses Brillouin zone boundaries, special symmetry points, or lines of accidental degeneracy. A realistic calculation shows that if aluminum had one valence electron, its spin relaxation would be slower by nearly two orders of magnitude. This not only solves a longst

S. Das Sarma, E. H. Hwang

We calculate the collective charge density excitation dispersion and spectral weight in bilayer semiconductor structures {\it including effects of interlayer tunneling}. The out-of-phase plasmon mode (the ``acoustic&#39;&#39; plasmon) develops a long wavelength gap in the presence of tunneling with the gap being proportional to the square root (linear power)

S. Melinte, E. Grivei, V. Bayot, M. Shayegan

Measurements on a multilayer two-dimensional electron system (2DES) near Landau level filling $ν$=1 reveal the disappearance of the nuclear spin contribution to the heat capacity as the ratio $\tilde{g}$ between the Zeeman and Coulomb energies exceeds a critical value $\tilde{g}_c \approx$0.04. This disappearance suggests the vanishing of the Skyrmion-mediat

Takaaki Kawaguchi, Hiroshi Matsukawa

Pinning phenomena in an incommensurate two-chain model of friction are studied numerically. The pinning effect due to the breaking of analyticity exists in the present model. The pinning behavior is, however, quite different from that for the breaking of analyticity state of the Frenkel-Kontorova model. When the elasticity of chains or the strength of interc

L. S. Borkowski, C. A. R. Sa de Melo

The evolution from BCS to BEC superconductivity in the s-wave and d-wave channels is analyzed at zero temperature for a two-dimensional superconductor. Spectroscopic quantities for s-wave and d-wave systems present fundamental differences when particle density and attraction strength are varied. A detailed analysis of single quasiparticle properties (excitat

Carl M. Bender, Gerald V. Dunne, Peter N. Meisinger

This paper demonstrates that complex PT-symmetric periodic potentials possess real band spectra. However, there are significant qualitative differences in the band structure for these potentials when compared with conventional real periodic potentials. For example, while the potentials V(x)=i\sin^{2N+1}(x), (N=0, 1, 2, ...), have infinitely many gaps, at the

Dmitrii S. Golubev, Andrei D. Zaikin

In a recent paper \cite{EH} Eriksen and Hedegard (EH) claimed that they ``clarified&#39;&#39; our path integral calculation \cite{GZ1} and found an error in our analysis. Here we will demonstrate that this claim is based on mathematically incorrect and physically meaningless procedure invented by the authors \cite{EH}. The main problem in the EH analysis is

Thorsten Emig, Thomas Nattermann

We reply to the recent comment cond-mat/9810097 on our original Letter `Roughening Transition of Interfaces in Disordered Systems&#39;, Phys. Rev. Lett. 81, 1469 (1998).

S. G. Magalhaes, Alba Theumann

We have examined the role of the BCS pairing mechanism in the formation of the magnetic moment and henceforth a spin glass (SG) phase by studying a fermionic Sherrington-Kirkpatrick model with a local BCS coupling between the fermions. This model is obtained by using perturbation theory to trace out the conduction electrons degrees of freedom in conventional

S. D. Baranovskii, I. S. Shlimak

To interpret recent experimental observations of the phononless hopping conduction, we suggest a novel transport mechanism according to which the current-carrying single electrons move via quantum resonant tunneling between localized states brought into resonance by fast electron hops in their environment.

B. Andraka, R. Pietri, S. G. Thomas, G. R. Stewart

UPt_(5-x)Au_x alloys form in a single crystal structure, cubic AuBe_5-type, over a wide range of concentrations from x = 0 to at least x = 2.5. All investigated alloys, with an exception for x = 2.5, were non-magnetic. Their electronic specific heat coefficient $γ$ varies from about 60 (x = 2) to about 700 mJ/mol K^2 (x = 1). The electrical resistivity for a

Z. Toroczkai, T. J. Newman, S. Das Sarma

We apply the recently introduced distribution of sign-times (DST) to non-equilibrium interface growth dynamics. We are able to treat within a unified picture the persistence properties of a large class of relaxational and noisy linear growth processes, and prove the existence of a non-trivial scaling relation. A new critical dimension is found, relating to t

U. H. E. Hansmann, Y. Okamoto

We report results from multicanonical simulations of poly-alanine. Homopolymers of up to 30 amino acids were considered and various thermodynamic quantities as a function of temperature calculated. We study the nature of the observed helix-coil transition and present estimates for critical exponents.

J. S. Thakur, Lerwen Liu, D. Neilson

We calculate self-consistently the mutual dependence of electron correlations and electron-defect scattering for a two dimensional electron gas at finite temperature. We employ an STLS approach to calculate the electron correlations while the electron scattering rate off Coulombic impurities and surface roughness is calculated using self-consistent current-r

J. Christopher Howk, Blair D. Savage

We present interstellar absorption line measurements of the ions S III and Al III towards six stars using archival Goddard High Resolution Spectrograph data. The ions Al III and S III trace heavily depleted and non-depleted elements, respectively, in ionized gas. We use the photoionization code CLOUDY to derive the ionization correction relating N(Al III)/N(

Michelle B. Larson, Bennett Link

The recent temperature measurements of the two older isolated neutron stars PSR 1929+10 and PSR 0950+08 (ages of $3\times 10^6$ and $2\times 10^7$ yr, respectively) indicate that these objects are heated. A promising candidate heat source is friction between the neutron star crust and the superfluid it is thought to contain. We study the effects of superflui

R. Benton Metcalf

The weak gravitational lensing of high redshift type Ia supernovae has the potential of probing the structure of matter on galaxy halo scales. This is complementary to the weak lensing of galaxies which probes structure of larger scales. There are already several organized searches for these supernovae being carried out for the purposes of cosmological param

P. P. Avelino, E. P. S. Shellard, J. H. P. Wu, B. Allen

We investigate the contribution made by small loops from a cosmic string network as seeds for large-scale structure formation. We show that cosmic string loops are highly correlated with the long-string network on large scales and therefore contribute significantly to the power spectrum of density perturbations if the average loop lifetime is comparable to o

J. Christopher Howk, Blair D. Savage

We present high-resolution (<0.7&#34;) ground-based images of the edge-on spiral galaxies NGC 891 (D=9.5 Mpc) and NGC 4013 (D=17 Mpc) acquired with the WIYN 3.5-m telescope. These BVI + H-alpha images reveal complex webs of dusty interstellar material far above the midplanes of both galaxies (0.5 < |z| < 2 kpc) as discussed previously by Howk & Savage (1997)

Vadim Burwitz, Klaus Reinsch, Klaus Beuermann, Hans-Christoph Thomas

RXJ 0501.7-0359 is a new V ~ 17 mag eclipsing polar discovered during the ROSAT all-sky survey (RASS). Extensive follow-up observations at X-ray (pointed ROSAT PSPC and HRI observations) and optical (time-resolved photometry and spectroscopy) wavelengths were obtained which allowed us to determine a very precise orbital period and to provide constraints for

Johann Albers

Based on previously published alternative reflections on gravitation, additional conclusions concerning anomalous gravitational effects in the universe are derived. For systems with spherical mass distribution and high central density of the luminous matter, abnormal increases in the gravitational potential towards the centers of these systems are derived. T

A. Del Popolo, M. Gambera, x

In this paper we extend Chandrasekhar and von Neumann&#39;s analysis of the statistics of the gravitational field to systems in which particles (e.g. stars, galaxies) are not homogeneously distributed. We derive a distribution function W({F},dF/dt) giving the joint probability that a test particle is subject to a force F and an associated rate of change of F

T. Oka, G. J. White, T. Hasegawa, F. Sato

We report the detection of a peculiar molecular cloud, CO 0.02-0.02, lying about 5&#39; Galactic-east from the center of the Galaxy. (12)CO images taken with NRO 45 m telescope showed that it is relatively compact (about 3x4 pc^2) as well as having a very large velocity width (DV>=100 km s(-1)). The cloud has a virial mass about one order of magnitude larger

R. Braun, W. B. Burton

We have identified a class of high-velocity clouds which are compact and apparently isolated. The clouds are compact in that they have angular sizes less than 2 degrees FWHM. They are isolated in that they are separated from neighboring emission by expanses where no emission is seen to the detection limit of the available data. Candidates for inclusion in th