August 1997 arXiv papers — page 5

C. Fradin, A. Braslau, D. Luzet, M. Alba

Grazing incidence x-ray surface scattering has been used to investigate liquid surfaces down to the molecular scale. The free surface of water is well described by the capillary wave model (<z(q)z(-q)> ~ q-2 spectrum) up to wavevectors > 10^8 m^-1. At larger wavevectors near-surface acoustic waves must be taken into account. When the interface is bounded by

C. Fradin, J. Daillant, A. Braslau, D. Luzet

The linear compressibility of two-dimensional fatty acid mesophases has determined by grazing incidence x-ray diffraction. Surface pressure vs molecular area isotherms were reconstructed from these measurements, and the linear compressibility (relative distortion along a given direction for isotropic applied stress) was determined both in the sample plane an

M. J. Omero, M. Dzierzawa, M. Marsili, Y. -C. Zhang

We study the optimization of the stable marriage problem. All individuals attempt to optimize their own satisfaction, subject to mutually conflicting constraints. We find that the stable solutions are generally not the globally best solution, but reasonably close to it. All the stable solutions form a special sub-set of the meta-stable states, obeying intere

Matthias Vojta, Klaus W. Becker

The motion of a single hole in an arbitrary magnetic background is investigated for the 2D t-J model. The wavefunction of the hole is described within a generalized string picture which leads to a modified concept of spin polarons. We calculate the one-hole spectral function using a large string basis for the limits of a Neel ordered and a completely disorde

B. E. Baaquie

The Black-Scholes formula for pricing options on stocks and other securities has been generalized by Merton and Garman to the case when stock volatility is stochastic. The derivation of the price of a security derivative with stochastic volatility is reviewed starting from the first principles of finance. The equation of Merton and Garman is then recast usin

Shiping Feng, Yun Song

A mean-field theory which satisfying the electron on-site local constraint in the relevant regime of density for the high temperature superconductors is developed. Within this approach, the electron spectral function, the electron dispersion, and the electron density of states of copper oxide materials are discussed, and the results are qualitative consisten

Shiping Feng, Yun Song, Zhongbing Huang

Within the $t$-$J$ model, we study the doping dependence of antiferromagnetism in the copper oxide materials by considering quantum fluctuations of spinons in the random-phase-approximation. The staggered magnetization vanishes around doping $δ=5%$ for a reasonable parameter value $t/J=5$, which is in agreement with the experiments on copper oxide materials.

Valerii M. Vinokur, Thomas Nattermann

We investigate the depinning transition in a dirty periodic medium considering a model of layered charge density waves as a prototype system. We find that depinning from strong disorder occurs via a two stage process, where, first, the pinned system experiences a continuous transition into a plastically sliding state and undergoes a second sharp hysteretic t

Doron Cohen, Harel Primack, Uzy Smilansky

We consider Hamiltonian systems which can be described both classically and quantum mechanically. Trace formulas establish links between the energy spectra of the quantum description and the spectrum of actions of periodic orbits in the classical description. This duality is investigated in the present paper. The duality holds for chaotic as well as for inte

C. Adami, A. Mazure, F. Durret, C. Lobo

We present here results from a deep spectroscopic survey of the Coma cluster of galaxies (29 galaxies between 18.98<m_R<21.5). Only 1 of these galaxies is within Coma compared to an expected 6.7 galaxies computed from nearby control fields. This discrepancy potentially indicates that Coma&#39;s faint end luminosity function has been grossly overestimated and

Aaron J. Romanowsky, Christopher S. Kochanek

We investigate X-ray isophote twists created by triaxiality differences between the luminous stellar distributions and the dark halos in elliptical galaxies. For a typically oblate luminous galaxy embedded in a more prolate halo formed by dissipationless collapse, the triaxiality difference of ΔT = ~0.7 leads to typical isophote twists of <Δψ_X> = ~16 deg +/

W. N. Brandt, M. J. Ward, A. C. Fabian, P. W. Hodge

We report on pointed X-ray observations of IC 10, NGC 147 and NGC 185 made with the ROSAT High Resolution Imager (HRI). These are three Local Group galaxies that have never been previously studied in detail in the X-ray regime. IC 10 is the closest starburst galaxy to our own Galaxy, and NGC 147 and NGC 185 are companions to M31. We have discovered a variabl

Francesco R. Ferraro, Barbara Paltrinieri, Flavio Fusi Pecci, Ben Dorman

We report on HST/WFPC2 U,V and far-ultraviolet observations of two Galactic Globular Clusters (GGCs), NGC 6205 = M13 and NGC 6093 = M80. Both of these clusters have horizontal-branch (HB) tails that extend to the helium-burning main sequence, with the hottest stars reaching theoretical effective temperatures above 35,000 K. In both clusters, groups of stars

B. Fuchs, H. Jahreiss

We have searched the Forth Catalogue of Nearby Stars for halo stars and identified 15 subdwarfs and a high velocity white dwarf in the solar neighbourhood. This search was motivated mainly by the recent determinations of MACHO masses of about 0.5 M_sun, which are typical for halo dwarfs. The local mass density of the stars is 1.5 10^{-4} M_sun pc^{-3}, which

E. M. Puchnarewicz, K. O. Mason

We discuss the properties of X-ray selected `red&#39; AGN from the RIXOS sample. These are Seyfert 1 galaxies and quasars whose optical continua are relatively soft, ie. with an energy index, alpha_opt>2. There are 14 objects in the RIXOS sample which satisfy this criterion and they cover a range in redshift from z=0.08 to 1.27. Of these, two have characteri

Coryn A. L. Bailer-Jones, Mike Irwin, Gerard Gilmore, Ted von Hippel

We present a technique which employs artificial neural networks to produce physical parameters for stellar spectra. A neural network is trained on a set of synthetic optical stellar spectra to give physical parameters (e.g. T_eff, log g, [M/H]). The network is then used to produce physical parameters for real, observed spectra. Our neural networks are traine

Sperello di Serego Alighieri, Andrea Cimatti, R. A. E. Fosbury, Ronald Hes

We present the results of spectropolarimetry of a sample of 7 powerful radio galaxies and 2 quasars with $0.07<z<0.35$ obtained to detect possible anisotropies in the [OIII] line emission, which could explain the higher [OIII] luminosity of quasars than that of radio galaxies within the framework of the Unified Model of radio-loud AGN. We detect polarized [O

Andrea Cimatti, Wolfram Freudling, Huub Roettgering, Rob Ivison

We present continuum observations of a small sample of high-redshift, radio-loud AGN (radio galaxies and quasars) aimed at the detection of thermal emission from dust. Seven AGN were observed with IRAM and SEST at 1.25mm; two of them, the radio galaxies 1243+036 ($z \sim 3.6$) and MG1019+0535 ($z \sim 2.8$) were also observed at 0.8mm with the JCMT submillim

Ken Ganga, Bharat Ratra, Mark A. Lim, Naoshi Sugiyama

We account for experimental and observational uncertainties in likelihood analyses of cosmic microwave background (CMB) anisotropy data from the MAX 4 and MAX 5 experiments. These analyses use CMB anisotropy spectra predicted in open and spatially-flat Lambda cold dark matter cosmogonies. Amongst the models considered, the combined MAX data set is most consi

Gunnar Floystad

Let $S_d$ be the vector space of monomials of degree $d$ in the variables $x_1, ..., x_s$. For a subspace $V \sus S_d$ which is in general coordinates, consider the subspace $\gin V \sus S_d$ generated by initial monomials of polynomials in $V$ for the revlex order. We address the question of what properties of $V$ may be deduced from $\gin V$. % This is an

Alexander A. Voronov

We show that for g > 2k+2 the k-rational homotopy type of the moduli space M_{g,n} of algebraic curves of genus g with n punctures is independent of g, and the space M_{g,n} is k-formal. This implies the existence of a limiting rational homotopy type of M_{g,n} as g goes to infinity and the formality of it.

Kenneth Intriligator

We present several classes of new 6d string theories which arise via branes at orbifold singularities. They have compact moduli spaces, associated with tensor multiplets, given by Weyl alcoves of non-Abelian groups. We discuss T-duality and Matrix model applications upon compactification.

Patricia R. Levstein, Gonzalo Usaj, Horacio M. Pastawski

The reversal of the time evolution of the local polarization in an interacting spin system involves a sign change of the effective dipolar Hamiltonian which refocuses the &#39;spin diffusion&#39; process generating a polarization echo. Here, the attenuation of these echo amplitudes as a function of evolution time is presented for cymantrene and ferrocene pol

L. R. Baboukhadia, V. Elias, M. D. Scadron

Linkage is demonstrated between the quark mass, quark condensate and coupling strength in the infrared limit of QCD and in the quark-level linear sigma model.

F. M. Steffens

Quark mass effects are included in the calculation of polarized structure functions. In particular, the validity of fixed order perturbation theory and of massless evolution is studied in the framework of heavy quarks structure functions. The polarized version of the ACOT and MRRS interpolating schemes for the evolution of massive quarks distributions is als

D. J. Dean, M. T. Ressell, M. Hjorth-Jensen, S. E. Koonin

We demonstrate the feasibility of realistic Shell-Model Monte Carlo (SMMC) calculations spanning multiple major shells, using a realistic interaction whose bad saturation and shell properties have been corrected by a newly developed general prescription. Particular attention is paid to the approximate restoration of translational invariance. The model space

G. Papadopoulos, A. Teschendorff

We interpret a class of 4k-dimensional instanton solutions found by Ward, Corrigan, Goddard and Kent as four-dimensional instantons at angles. The superposition of each pair of four-dimensional instantons is associated with four angles which depend on some of the ADHM parameters. All these solutions are associated with the group $Sp(k)$ and are examples of H

S. Dalley

Massless Majorana fermions in the adjoint representation of SU(N_c) are expected to screen gauge interactions in 1+1 dimensions, analogous to a similar Higgs phenomena known for 1+1-dimensional U(1) gauge theory with massless fundamental fermions (Schwinger model). Using the light-cone formalism and large-N_c limit, a non-abelian analogue of the Schwinger bo

Graham Vincent, Nuno D. Antunes, Mark Hindmarsh

We present the results of a field theory simulation of networks of strings in the Abelian Higgs model. Starting from a random initial configuration we show that the resulting vortex tangle approaches a self-similar regime in which the length density of lines of zeros of $ϕ$ reduces as $t^{-2}$. We demonstrate that the network loses energy directly into scala

I T Drummond, R R Horgan, P V Landshoff, A Rebhan

We show that large-$N$ $ϕ^4$ theory is not trivial if one accepts the presence of a tachyon with a truly huge mass, and that it allows exact calculation. We use it to illustrate how to calculate the exact resummed pressure at finite temperature and verify that it is infrared and ultraviolet finite even in the zero-mass case. In 3 dimensions a residual effect

Bastian Bergerhoff, Christof Wetterich

We compute the momentum dependence of the effective four quark interaction in QCD after integrating out the gluons. Our method is based on a truncation of exact renormalization group equations which should give reasonable results for momenta above the confinement scale. The difference between the four quark interaction and the heavy quark potential can be mi

V. C. de Andrade, J. G. Pereira

In the framework of the teleparallel equivalent of general relativity, we study the dynamics of a gravitationally coupled electromagnetic field. It is shown that the electromagnetic field is able not only to couple to torsion, but also, through its energy-momentum tensor, to produce torsion. Furthermore, it is shown that the coupling of the electromagnetic f

Shiping Feng, Zhongbing Huang

The charge dynamics of the copper oxide materials in the underdoped and optimal doped regimes is studied within the framework of the fermion-spin theory. The conductivity spectrum shows the non-Drude behavior at low energies and unusual midinfrared peak, and the resistivity exhibits a linear behavior in the temperature, which are consistent with experiments

Dan Kiselman

The possibility of significant systematic errors due to the use of 1D homogeneous atmospheres in lithium-abundance determinations of cool stars motivates a study of non-local-thermodynamic-equilibrium (NLTE) effects on Li I line formation in a 3D solar-granulation simulation snapshot. The NLTE effect on the equivalent width of the 671 nm resonance line is sm

F. Igloi, L. Turban, D. Karevski, F. Szalma

We consider the Ising model and the directed walk on two-dimensional layered lattices and show that the two problems are inherently related: The zero-field thermodynamical properties of the Ising model are contained in the spectrum of the transfer matrix of the directed walk. The critical properties of the two models are connected to the scaling behavior of

Klaus Hecker, Helmut Hegger, Alexander Altland, Klaus Fiegle

We study the magnetoconductance fluctuations of mesoscopic normal-metal/superconductor (NS) samples consisting of a gold-wire in contact with a niobium film. The magnetic field strength is varied over a wide range, including values that are larger than the upper critical field B_c2 of niobium. In agreement with recent theoretical predictions we find that in

Feng-Li Lin, Chopin Soo

Boundary conditions and the corresponding states of a quantum field theory depend on how the horizons are taken into account. There is ambiguity as to which method is appropriate because different ways of incorporating the horizons lead to different results. We propose that a natural way of including the horizons is to first consider the Kruskal extension an

Jiang Yi, Ma Wen-gan, Han Liang, Han Meng

The production of charged Higgs boson pairs from gluon-gluon fusion is studied in the minimal supersymmetric model(MSSM) at proton-proton colliders. We find that the contribution of the scalar quark loops to the subprocess production rate is substantial and consequently the production rate in proton-proton colliders is enhanced in the MSSM if there exist sca

A. Marchewka, Z. Schuss

We propose a formulation of an absorbing boundary for a quantum particle. The formulation is based on a Feynman-type integral over trajectories that are confined to the non-absorbing region. Trajectories that reach the absorbing wall are discounted from the population of the surviving trajectories with a certain weighting factor. Under the assumption that ab

S. Majid

We introduce anyonic Lie algebras in terms of structure constants. We provide the simplest examples and formulate some open problems.

Ieke Moerdijk, Dorette A Pronk

For any orbifold M, we explicitly construct a simplicial complex S(M) from a given triangulation of the `coarse&#39; underlying space together with the local isotropy groups of M. We prove that, for any local system on M, this complex S(M) has the same cohomology as M. The use of S(M) in explicit calculations is illustrated in the example of the `teardrop&#3

A. Y. Potekhin

Analytical approximations are constructed for binding energies of hydrogen atoms arbitrarily moving in magnetic fields 7\times10^{11} G to 2\times10^{13} G, typical of magnetic neutron stars.

Yu. Shibata, E. G. Bessonov

Some considerations of long wavelength and broadband radiation sources based on the emission of the coherent radiation by a train of short relativistic electron bunches moving in an open resonator along an arc-like or undulator trajectories and some new versions of the transition radiation sources and long wavelength sources based on storage rings are presen

John David Crawford, Edgar Knobloch

We consider the simplest instabilities involving multiple unstable electrostatic plasma waves corresponding to four-dimensional systems of mode amplitude equations. In each case the coupled amplitude equations are derived up to third order terms. The nonlinear coefficients are singular in the limit in which the linear growth rates vanish together. These sing

R. J. Furnstahl, John J. Rusnak

Recent studies have shown that concepts of effective field theory such as naturalness can be profitably applied to relativistic mean-field models of nuclei. Here the analysis by Friar, Madland, and Lynn of naturalness in a relativistic point-coupling model is extended. Fits to experimental nuclear data support naive dimensional analysis as a useful principle

David J. Grabiner

Let $n$ particles move in standard Brownian motion in one dimension, with the process terminating if two particles collide. This is a specific case of Brownian motion constrained to stay inside a Weyl chamber; the Weyl group for this chamber is $A_{n-1}$, the symmetric group. For any starting positions, we compute a determinant formula for the density functi

Anjan Kundu

An overview of the quantum integrable systems (QIS) is presented. Basic concepts of the theory are highlighted stressing on the unifying algebraic properties, which not only helps to generate systematically the representative Lax operators of different models, but also solves the related eigenvalue problem in an almost model independent way. Difference betwe

Francesco Sannino, Joseph Schechter

We propose a toy model to illustrate how the effective Lagrangian for super QCD might go over to the one for ordinary QCD by a mechanism whereby the gluinos and squarks in the fundamental theory decouple below a given supersymmetry breaking scale $m$. The implementation of this approach involves a suitable choice of possible supersymmetry breaking terms. An

Alon E. Faraggi

The realistic free fermionic models have had remarkable success in providing plausible explanations for various properties of the Standard Model which include the natural appearance of three generations, the explanation of the heavy top quark mass and the qualitative structure of the fermion mass spectrum in general, the stability of the proton and more. The

Yoav Achiman

The recent GUT (x SUSY) models which can predict the neutrino properties are reviewed.

Vladimir Gribov

The formulation of QCD which contains no divergences and no renormalization procedure is presented. It contains both perturbative and non-perturbative phenomena. It is shown that, due to its asymptotically free nature, the theory is not defined uniquely. The chiral symmetry breaking and the nature of the octet of pseudo-scalar particles as quasi-Goldstone st

V. A. Smirnov

A brief review of recent results on asymptotic expansions of Feynman integrals on the mass shell in momenta and masses and their application to 2-loop calculations is presented.

A. Shuvaev

Multiple soft pion production in the baryon scattering reactions is considered in the framework of chiral nonlinear sigma model neglecting the pion mass. Treating baryons in the eikonal approximation as classical sources, a set of analytical solutions for the pion field is found. A tree S-matrix is constructed on the basis of these solutions describing the e

Guenter Sigl

A cubic kilometer scale experiment has been proposed to detect cosmic neutrinos of energy from tens of GeV up to the highest energies observed for cosmic rays, around 10**20 eV, or possibly even beyond. Detection efficiencies depend crucially on the neutrino-nucleon cross section at these energies at which radiative corrections beyond the lowest order approx

S. Aoki, G. Boyd, R. Burkhalter, S. Hashimoto

A status report is made of an on-going full QCD study on the CP-PACS aiming at a comparative analysis of the effects of improving gauge and quark actions on hadronic quantities and static quark potential. Simulations are made for four action combinations, the plaquette or an RG-improved action for gluons and the Wilson or SW-clover action for quarks, at $a^{

G. R. Blackett, K. Danyo, T. Handler, M. Pisharody

We report on a study of the reaction, $γp \to p π^+π^+π^-π^-π^0$, at an incident photon energy of 19.3 GeV. The most significant feature of this reaction is $Δ^{++}$ production which occurs with a cross section of $0.6\pm 0.1 μ$b. An upper limit is set for the cross section for the reaction, $γp \to Δ^{++}b_1^-(1235)$, and a search is made for resonances dec

Eduardo Guéron, P. S. Letelier

Newtonian theory is used to study the gravitational effects of a texture, in particular the formation of massive structures.

Beverly K. Berger, David Garfinkle, Vincent Moncrief

A standard and reasonable definition of asymptotic velocity term dominance (AVTD) shows that the numerical study by Hern and Stewart (gr-qc/9708038) confirms previous results that generic Gowdy cosmologies on $T^3 \times R$ have an AVTD singularity.

Andreas Heuer, Peter Neu

Simulations on a Lennard-Jones computer glass are performed to study effects arising from defects in glasses at low temperatures. The numerical analysis reveals that already a low concentration of defects may dramatically change the low temperature properties by giving rise to extrinsic double-well potentials (DWP&#39;s). The main characteristics of these ex

Peter Neu, Robert J. Silbey, Stephan J. Zilker, Dietrich Haarer

A quantitative theory is developed, which accounts for heating artifacts in three-pulse photon echo (3PE) experiments. The heat diffusion equation is solved and the average value of the temperature in the focal volume of the laser is determined as a function of the 3PE waiting time. This temperature is used in the framework of nonequilibrium spectral diffusi

J. K. Burton,, C. L. Henley

We define a four-state Potts model ensemble on the square lattice, with the constraints that neighboring spins must have different values, and that no plaquette may contain all four states. The spin configurations may be mapped into those of a 2-dimensional interface in a 2+5 dimensional space. If this interface is in a Gaussian rough phase (as is the case f

A. G. Huibers, M. Switkes, C. M. Marcus, K. Campman

Shape-averaged magnetoconductance (weak localization) is used for the first time to obtain the electron phase coherence time $τ_ϕ$ in open ballistic GaAs quantum dots. Values for $τ_ϕ$ in the range of temperature T from 0.335 to 4 K are found to be independent of dot area, and are not consistent with the $τ_ϕ \propto T^{-2}$ behavior expected for isolated do

Thomas R. Powers, Dengfu Zhang, Raymond E. Goldstein, Howard A. Stone

The Rayleigh capillary instability of a cylindrical interface between two immiscible fluids is one of the most fundamental in fluid dynamics. As Plateau observed from energetic considerations and Rayleigh clarified through hydrodynamics, such an interface is linearly unstable to fission due to surface tension. In traditional descriptions of this instability

K. P. Li, Dragana Popovic, S. Washburn

Measurements of conductance $G$ on short, wide, high-mobility Si-MOSFETs reveal both a two-dimensional metal-insulator transition (MIT) at moderate temperatures (1 $<~ T <$ 4~K) and mesoscopic fluctuations of the conductance at low temperatures ($T~ <$ 1~K). Both were studied as a function of chemical potential (carrier concentration $n_s$) controlled by gat

E. V. Tsiper, A. L. Efros

We consider a one-dimensional lattice model with the nearest-neighbor interaction $V_1$ and the next-nearest neighbor interaction $V_2$ with filling factor 1/2 at zero temperature. The particles are assumed to be spinless fermions or hard-core bosons. Using very simple assumptions we are able to predict the basic structure of the insulator-metal phase diagra

Dragana Popovic, A. B. Fowler, S. Washburn

We have varied the disorder in a two-dimensional electron system in silicon by applying substrate bias. When the disorder becomes sufficiently low, we observe the emergence of the metallic phase, and find evidence for a metal-insulator transition (MIT): the single-parameter scaling of conductivity with temperature near a critical electron density. We obtain

A. Levy Yeyati, A. Martín-Rodero, F. Flores

The electronic and transport properties of atomic-size contacts are analyzed theoretically using a self-consistent tight-binding model. Our results show that, for s-like metals, a sufficiently narrow contact exhibits well defined resonant states at the Fermi energy, spatially localized in the neck region. These states are robust with respect to disorder and

Sergei Skorik

Fendley, Ludwig and Saleur [Phys. Rev. B52 (1995) 8934] have obtained an expression for the non-equilibrium current through a constriction in the quantum Hall bar based on the Bethe ansatz technique and the Bolzmann equation. In this Comment we draw attention to a serious flaw in their derivation. We argue that their result is correct in the linear response

Th. M. Nieuwenhuizen

For the dynamical glassy transition in the $p$-spin mean field spin glass model a thermodynamic description is given. The often considered marginal states are not the relevant ones for this purpose. This leads to consider a cooling experiment on exponential timescales, where lower states are accessed. The very slow configurational modes are at quasi-equilibr

J. van den Brink, O. P. Sushkov

We consider the single hole dynamics in a modified $t-J$ model at finite temperature. The modified model includes a next nearest ($t&#39;$) and next-next nearest ($t&#39;&#39;$) hopping. The model has been considered before in the zero temperature limit to explain angle resolved photo-emission measurements. We extend this consideration to the case of finite

J. David Moroz, Philip Nelson

DNA and other biopolymers differ from classical polymers due to their torsional stiffness. This property changes the statistical character of their conformations under tension from a classical random walk to a problem we call the `torsional directed walk&#39;. Motivated by a recent experiment on single lambda-DNA molecules [Strick et al., Science 271 (1996)

Margarita Voitikova

The time delayed cytotoxic T-lymphocyte response on the tumor growth has been developed on the basis of discrete approximation (2-dimensional map). The growth kinetic has been described by logistic law with growth rate being the bifurcation parameter. Increase in the growth rate results in instability of the tumor state and causes period-doubling bifurcation

A. C. Marti, F. Sagues, J. M. Sancho

A study of a stable front propagating in a turbulent medium is presented. The front is generated through a reaction-diffusion equation, and the turbulent medium is statistically modeled using a Langevin equation. Numerical simulations indicate the presence of two different dynamical regimes. These regimes appear when the turbulent flow either wrinkles a stil

Martin Sieber, Henning Schomerus

We derive a uniform approximation for semiclassical contributions of periodic orbits to the spectral density which is valid for generic period-quadrupling bifurcations in systems with a mixed phase space. These bifurcations involve three periodic orbits which coalesce at the bifurcation. In the vicinity of the bifurcation the three orbits give a collective c

R. Dykstra, M. Y. Li, N. R. Heckenberg

The route to chaos as the pump power is raised in the Lorenz-like ammonia laser is studied using transients and compared with the route which is expected in the Lorenz Haken equations. The differences between the routes to chaos, as normally displayed by the experimental system and the Lorenz Haken equations, is described in terms of the bifurcations experie

Steven M. Matz

The orbital dynamics of Cyg X-3 are a key to understanding this enigmatic X-ray binary. Recent observations by the RXTE ASM and the OSSE instrument on GRO enable us to extend the baseline of arrival time measurements and test earlier models of orbital period evolution. We derive new quadratic and cubic ephemerides from the soft X-ray data (including ASM). We

Robin Ciardullo, George Jacoby, John Feldmeier, Roger Bartlett

We present the results of a wide-field [O III] $λ5007$ survey for planetary nebulae (PN) in M87 and its surrounding halo. We show that the planetary nebula luminosity function (PNLF) of M87&#39;s halo is unlike any PNLF observed to date, with a shape that differs from that of the empirical law at the 99.9% confidence level. In addition, we find that the PNLF

E. M. Puchnarewicz, K. O. Mason, F. J. Carrera, W. N. Brandt

We present the optical and UV emission line properties of 160 X-ray selected AGN taken from the RIXOS survey (including Halpha, Hbeta, [OIII]5007, MgII2798 and CIII]1909). This sample is believed to contain a mixture of absorbed and unabsorbed objects, with column densities up to 4e21 cm-2. Although the distribution of the [OIII] EW for the RIXOS AGN is typi

Andrea Cimatti, Simone Bianchi, Andrea Ferrara, Carlo Giovanardi

We present the preliminary results of Monte Carlo simulations aimed to investigate the effects of realistic dust extinction (absorption + scattering) on the colours of high-z galaxies. In this paper, we concentrate on the case of spheroidal galaxies, and we obtain attenuation curves in the range 0.1-1.2$μ$m for different dust spatial distributions, and for a

Silvia Mollerach

We study the effect of a stochastic background of gravitational waves on the gravitational lensing of the Cosmic Microwave Background (CMB) radiation. It has been shown that matter density inhomogeneities produce a smoothing of the acoustic peaks in the angular power spectrum of the CMB anisotropies. A gravitational wave background gives rise to an additiona

A. Retter, E. M. Leibowitz, O. Kovo-Kariti

Continuous CCD photometry of Nova Aquilae 1995 was performed through the standard B,V,R and I filters during three nights in 1995 and with the I filter during 18 nights in 1996. The power spectrum of the 1996 data reveals three periodicities in the light curve: 0.2558 d, 0.06005 d and 0.079 d, with peak-to-peak amplitudes of about 0.012, 0.014 and 0.007 mag.

A. Retter, E. M. Leibowitz

It was believed, with little theoretical basis, that the accretion disk (AD) is destroyed in nova outbursts, and recovers only a few decades later. In my thesis I tried to find observational signature for the presence of ADs in young novae. I will discuss two cases: 1. Nova V1974 Cyg 1992 - we found permanent superhumps about 2.5 years after the nova eruptio

Robert W. Nelson, Lars Bildsten, Deepto Chakrabarty, Mark H. Finger

Dramatic torque reversals between spin up and spin down have been observed in half of the persistent X-ray pulsars monitored by the BATSE all-sky monitor on CGRO. Theoretical models developed to explain early pulsar timing data can explain spin down torques via a disk-magnetosphere interaction if the star nearly corotates with the inner accretion disk. To pr

L. H. Li, Q. L. Cheng, Q. H. Peng, H. Q. Zhang

We relate the MSW effect to the efective absorption of the electronic collective motion energy by retaining the imaginary part of the index of refraction associated with the charged-current scattering and show that the small angle MSW solution to the solar neutrino anomaly can be used as a probe of the physical conditions of the solar interior if it is corre

Anatoly Klypin, Stefan Gottloeber, Andrey Kravtsov, Alexei Khokhlov

We present analysis of the evolution of dark matter halos in dense environments of groups and clusters in dissipationless cosmological simulations. The premature destruction of halos in such environments, known as the overmerging, reduces the predictive power of N-body simulations and makes difficult any comparison between models and observations. We analyze

JoAnne L. Hewett, Thomas G. Rizzo

We discuss the general framework for the construction of new models containing a single, fermion number zero scalar leptoquark of mass $\simeq 200-220$ GeV which can both satisfy the D0/CDF search constraints as well as low energy data, and can lead to both neutral and charged current-like final states at HERA. The class of models of this kind necessarily co

Gentil O. Pires

The Renormalization Group Flow Equations of the Scalar-QED model near Planck&#39;s scale are computed within the framework of the average effective action. Exact Flow Equations, corrected by Einstein Gravity, for the running self-interacting scalar coupling parameter and for the running v.e.v. of $ϕ^* ϕ$, are computed taking into account threshold effects. A

The MACHO Collaboration, C. Alcock, R. A. Allsman, D. Alves

We report the first discovery of a gravitational microlensing candidate towards a new population of source stars, the Small Magellanic Cloud (SMC). The candidate event&#39;s light curve shows no variation for 3 years before an upward excursion lasting $ \sim 217$ days that peaks around January 11, 1997 at a magnification of $ \sim 2.1$. Microlensing events t

Qijin Chen, Zhangda Lin

Nucleation and its mechanism of diamond on titanium substrates under very low pressure was studied using hot-filament chemical vapor deposition. Very high nucleation rates and densities (10^8-10^{10} cm^{-2}) were obtained under 1 torr, which were 1-3 orders of magnitude higher than the counterpart (10^7 cm^{-2}) under conventionally low pressure (tens of to

H. Lu, C. N. Pope, K. S. Stelle

There exist simple single-charge and multi-charge BPS p-brane solutions in the D-dimensional maximal supergravities. From these, one can fill out orbits in the charge vector space by acting with the global symmetry groups. We give a classification of these orbits, and the associated cosets that parameterise them.

Gordon Chalmers, Warren Siegel

We use analyticity arguments to conjecture a one-loop gravity scattering amplitude with an arbitrary number of external legs possessing the same helicity. This result also gives the complete perturbative S-matrix of self-dual gravity.

E787 Collaboration, S. Adler

An event consistent with the signature expected for the rare kaon decay K+ --> pi+ nu anti-nu has been observed. In the pion momentum region examined, 211<P<230 MeV/c, the backgrounds are estimated to contribute 0.08 +/- 0.03 events. If the event is due to K+ --> pi+ nu anti-nu, the branching ratio is (4.2 +9.7/-3.5) x E-10.

Esteban Calzetta

We derive the formulae of fluctuating hydrodynamics appropiate to a relativistically consistent divergence type theory, obtaining Landau - Lifshitz fluctuating hydrodynamics as a limiting case.

P. Muruganandam, K. Murali, M. Lakshmanan

The circuit recently proposed by Murali, Lakshmanan and Chua (MLC) is one of the simplest non-autonomous nonlinear electronic circuits which shows a variety of dynamical phenomena including various bifurcations, chaos and so on. In this paper we study the spatio-temporal dynamics in one and two dimensional arrays of coupled MLC circuits both in the absence a

Neil Cornish, Paul Shellard

Much of the foundational work on quantum cosmology employs a simple minisuperspace model describing a Friedmann-Robertson-Walker universe containing a massive scalar field. We show that the classical limit of this model exhibits deterministic chaos and explore some of the consequences for the quantum theory. In particular, the breakdown of the WKB approximat

B. -D. Doerfel, St. Meissner

We investigate the anisotropic integrable spin chain consisting of spins $s={1/2}$ and $s=1$ by means of thermodynamic Bethe ansatz for the anisotropy $γ>π/3$, where the analysis of the Takahashi conditions leads to a more complicated string picture. We give the phase diagram with respect to the two real coupling constants $\bar{c}$ and $\tilde{c}$, which co

S. S. Banerjee

The vortex lattice is an ideal system to study the competition and interplay between interaction and disorder. New results on 2H-NbSe_2 (in samples of progressively increasing pinning) elucidate how pinning alters the phase boundary separating the &#34;ordered&#34; and &#34;disordered&#34; states of the flux lines and causes a novel disorder-induced transiti

Ralph A. M. J. Wijers, Joshua S. Bloom, Jasjeet S. Bagla, Priyamvada Natarajan

A gamma-ray burst (GRB) releases an amount of energy similar to that of a supernova explosion, which combined with its rapid variability suggests an origin related to neutron stars or black holes. Since these compact stellar remnants form from the most massive stars not long after their birth, gamma-ray bursts should trace the star formation rate in the Univ

Rachel M. Quick, Sergei G. Sharapov

The existence of a pseudogap above the critical temperature has been widely used to explain the anomalous behaviour of the normal state of high-temperature superconductors. In two dimensions the existence of a pseudogap phase has already been demonstrated in a simple model. It can now be shown that the pseudogap phase persists even for the more realistic cas

Jiin-Chang Shaw, Ming-Hsien Tu

We study the conformal properties of the multi-constraint KP hierarchy and its nonstandard partner by covariantizing their corresponding Lax operators. The associated second Hamiltonian structures turn out to be nonlocal extension of $W_n$ algebra by some integer or half-integer spin fields depending on the order of the Lax operators. In particular, we show