April 1997 arXiv papers — page 2

Wojciech Florkowski

By making decomposition of the Wigner function simultaneously in both the spinor and the isospin spaces we derive a set of kinetic equations for the quark distribution functions and the spin densities. A detailed analysis of the consequences imposed by the chiral invariance on the form of the transport equations is presented.

C. Balazs, C. -P. Yuan

To offer a possible resolution to the apparent discrepancy between the experimental and the theoretical values of the $W + 1$ jet to $W + 0$ jets ratio reported by the \D0 group, we examine the effects of the multiple soft gluon radiation on the $W$ boson production at the Tevatron. Based on the calculation of the $W$ boson transverse momentum ($Q_T$) distri

N. Eicker, U. Glässner, S. Güsken, H. Hoeber

We determine the masses of the light and the strange quarks in the $\bar{MS}$-scheme using our high-statistics lattice simulation of QCD with dynamical Wilson fermions. For the light quark mass we find $m^{light}_{\bar{MS}}(2 GeV) = 2.7(2) MeV$, which is lower than in quenched simulations. For the strange quark, in a sea of two dynamical light quarks, we obt

ZEUS Collaboration, M. Derrick et al

Using the ZEUS detector at the HERA electron-proton collider, we have searched for lepton flavor violation in ep collisions at a center-of-mass energy s^1/2 of 300 GeV. Events of the type e + p -> lepton + X with a final-state lepton (mu or tau) of high transverse momentum, were sought. No evidence was found for lepton flavor violation in the combined 1993 a

Z. Lalak, R. Poppe

Jordan-Brans-Dicke theories with a linearized potential for the scalar field are investigated in the framework of the stochastic approach. The fluctuations of this field are examined and their backreaction on the classical background is described. We compute the mode functions and analyze the time evolution of the variance of the stochastic ensemble correspo

David Hochberg, Matt Visser

Traversable wormholes have traditionally been viewed as intrinsically topological entities in some multiply connected spacetime. Here, we show that topology is too limited a tool to accurately characterize a generic traversable wormhole: in general one needs geometric information to detect the presence of a wormhole, or more precisely to locate the wormhole

Gen Yoneda, Hisaaki Shinkai, Akika Nakamichi

We examine one of the advantages of Ashtekar's formulation of general relativity: a tractability of degenerate points from the point of view of following the dynamics of classical spacetime. Assuming that all dynamical variables are finite, we conclude that an essential trick for such a continuous evolution is in complexifying variables. In order to rest

Johan Kustermans

In this paper, we build a solid framework for KMS-weights on C*-algebras. We use another definition than the one introduced by Combes, but prove that they are equivalent.

T. P. Pareek, Mangal C. Mahato, A. M. Jayannavar

We study the dynamics of a dissipative two-level, system driven by a monochromatic ac field, starting from the usual spin-boson Hamiltonian. The quantum Langevin equations for the spin variables are obtained. The amplitude of the coherent oscillations in the average position of the particle is studied in the high temperature limit. The system exhibits quantu

N. Kumar, T. P. Pareek, A. M. Jayannavar

It is shown that a strong intraplanar incoherent scattering can effectively block the interplanar coherent tunneling between the weakly coupled planes of the highly anisotropic but clean (intrinsic) materials such as the optimally doped high-T_c layered cuprate superconductors. The calculated normal-state C-axis resistivity ρ_c(T) then follows the metal-like

Mangal C. Mahato, A. M. Jayannavar

We calculate, numerically, the residence times (and their distribution) of a Brownian particle in a two-well system under the action of a periodic, saw-tooth type, external field. We define hysteresis in the system. The hysteresis loop area is shown to be a good measure of synchronization of passages from one well to the other. We establish connection betwee

Igor Zutic, Oriol T. Valls

We present a method to compute the magnetic moment of a bulk, finite-size, three-dimensional, anisotropic superconductor. Our numerically implemented perturbative procedure is based on a solution of the nonlinear Maxwell- London equations, where we include the nonlinear relation between current and gauge invariant velocity. The method exploits the small rati

A. C. E. Reid, R. J. Gooding

We present a dynamical theory of a two-dimensional martensitic transition in an elastic solid, connecting a high-temperature phase which is nondegenerate and has triangular symmetry, and a low-temperature phase which is triply degenerate and has oblique symmetry. A global mode-based Galerkin method is employed to integrate the deterministic equation of motio

J. Krug, H. Kallabis, S. N. Majumdar, S. J Cornell

Numerical and analytic results for the exponent θdescribing the decay of the first return probability of an interface to its initial height are obtained for a large class of linear Langevin equations. The models are parametrized by the dynamic roughness exponent β, with 0 < β< 1; for β= 1/2 the time evolution is Markovian. Using simulations of solid-on-solid

J. Boronat, A. Polls, A. Fabrocini

We present variational calculations of the one-body density matrices and momentum distributions for ^3He-^4He mixtures in the zero temperature limit, in the framework of the correlated basis functions theory. The ground-state wave function contains two- and three-body correlations and the matrix elements are computed by (Fermi)Hypernetted Chain techniques. T

Ou-Yang Zhong-can, Zhao-Bin Su, Chui-Lin Wang

To study the shape formation process of carbon nanotubes, a string equation describing the possible existing shapes of the axis-curve of multishell carbon tubes (MCTs) is obtained in the continuum limit by minimizing the shape energy, that is the difference between the MCT energy and the energy of the carbonaceous mesophase (CM). It is shown that there exist

G. Giacomin, J. L. Lebowitz

We present and discuss the derivation of a nonlinear non-local integro-differential equation for the macroscopic time evolution of the conserved order parameter of a binary alloy undergoing phase segregation. Our model is a d-dimensional lattice gas evolving via Kawasaki exchange dynamics, i.e. a (Poisson) nearest-neighbor exchange process, reversible with r

Jerry R. Hobbs, Andrew Kehler

We provide a general account of parallelism in discourse, and apply it to the special case of resolving possible readings for instances of VP ellipsis. We show how several problematic examples are accounted for in a natural and straightforward fashion. The generality of the approach makes it directly applicable to a variety of other types of ellipsis and ref

Piet Hut

The gravitational N-body problem, for $N>2$, is the oldest unsolved problem in mathematical physics. Some of the most ideal examples that can be found in nature are globular star clusters, with $N \sim 10^6$. In this overview, I discuss six types of fundamental sources of unpredictability, each of which poses a different challenge to attempts to determine th

Ch. Einsel, R. Spurzem

The influence of rotation on the dynamical evolution of collisional stellar systems is investigated by solving the orbit-averaged Fokker-Planck equation in (E,J_z)-space. We find that large amounts of initial rotation drive the system into a phase of strong mass loss while it is moderately contracting. The core is rotating even faster than before although an

Howard D. Greyber

Observations have shown the existence of narrow, very long, straight jets emitted by some newly forming stars (1). It is highly likely that stars forming in the plane of a spiral galaxy do so in the presence of an almost uniform magnetic field. In the Strong Magnetic Field model (SMF), gravitational collapse of a highly conducting plasma in the presence of s

Marianne Sodemann, Bjarne Thomsen

We present a thorough investigation of stellar photometry based on HST imaging of crowded fields at 85 and 10 arcsec from the centre of the high-surface brightness elliptical M32. The Principal Investigators of the present archive data have elsewhere presented an impressive colour-magnitude diagram of the field at 85 arcsec. Based on the same data we enlarge

S. Frink, S. Roeser, R. Neuhaeuser, M. F. Sterzik

We present proper motions of 72 T Tauri stars located in the central region of Taurus-Auriga. These proper motions are taken from a new proper motion catalogue called STARNET. Our sample comprises 17 classical T Tauri stars and 55 weak-line T Tauri stars, most of the latter discovered by ROSAT. 53 stars had no proper motion measurement before. Kinematically,

Bodo L. Ziegler, Ralf Bender

We derive absorption indices of ellipticals in clusters at z=0.37 from medium-resolution spectroscopy together with kinematical parameters. These galaxies exhibit a relationship between the Mgb linestrength and their internal velocity dispersion similar to local dynamically hot galaxies. But for any given sigma, Mgb of the distant ellipticals is significantl

B. Dutta, R. N. Mohapatra, S. Nandi

We point out that in extended supersymmetric models such as supersymmetric left-right models, it is possible to have leptoquarks that explain the HERA high $Q^2$ anomaly without giving up R-parity conservation. The leptoquarks belong to vectorlike $(2, 2, \pm{4/3}, 3 or 3^*) $ representations of $SU(2)_L\times SU(2)_R\times U(1)_{B-L}\times SU(3)_c$ (denoted

A. Duncan, Will Loinaz, R. S. Willey

The problem of defining a gauge invariant effective potential with a strict energetic interpretation is examined in the context of spontaneously broken gauge theories. It is shown that such a potential can be defined in terms of a composite gauge invariant order parameter in physical gauges. This effective potential is computed through one loop order in a mo

V. Kartvelishvili, R. Kvatadze, R. Moller

The influence of Bose-Einstein correlations on the determination of the mass of the W boson in e+e- -> WW -> 4jet events at LEP2 energies is studied, using a global event weighting method. We find that it is possible to keep the systematic error on the W mass from this source below 20 MeV, if suitable precautions are taken in the experimental analysis.

V. A. Litvin, F. F. Tikhonin

We calculate the cross-sections for the production of Standard Model Higgs Boson in association with the neutral gauge bosons (photon and Z--boson). For the case of reaction $μ^+ μ^- \to γH^0$, complete and compact analytical expressions for the differential and total cross--sections, applicable also for the case of any (pseudo)scalar particle with mass-coup

M. E. Berbenni-Bitsch, S. Meyer, A. Schäfer, J. J. M. Verbaarschot

Large ensembles of complete spectra of the Euclidean Dirac operator for staggered fermions are calculated for SU(2) lattice gauge theory. The accumulation of eigenvalues near zero is analyzed as a signal of chiral symmetry breaking and compared with parameter-free predictions from chiral random matrix theory. Excellent agreement for the distribution of the s

Martin Goetz

It is shown that the `conservation law&#39; for metric fluctuations with long wavelengths is indeed applicable for growing modes of perturbations, which are of interest in cosmology, in spite of a recent criticism [L. P. Grishchuk, Preprint gr-qc/9511074, now published in N. Sanchez, A. Zichichi (eds.), `String Gravity and Physics at the Planck Scale&#39;, K

Insu Yi, J. Craig Wheeler, Ethan T. Vishniac

Accretion-powered X-ray pulsars 4U 1626-67, GX 1+4, and OAO 1657-415 have recently shown puzzling torque reversals. These reversals are characterized by short time scales, on the order of days, nearly identical spin-up and spin-down rates, and very small changes in X-ray luminosity. We propose that this phenomenon is the result of sudden dynamical changes in

Devis Iellici

The $ζ$ function of a massive scalar field near a cosmic string is computed and then employed to find the vacuum fluctuation of the field. The vacuum expectation value of the energy-momentum tensor is also computed using a point-splitting approach. The obtained results could be useful also for the case of self-interacting scalar fields and for the finite-tem

Martin Mojzis

The elastic pi-N scattering amplitude in the isospin limit is calculated in the framework of heavy baryon chiral perturbation theory, up to the third order. Threshold parameters like scattering lengths, volumes, effective ranges, etc. are compared with data. All relevant low energy constants are fixed from the available pion-nucleon data. A clear improvement

Martin Ulmke

The Hubbard model on fcc-type lattices is studied in the dynamical mean-field theory of infinite spatial dimensions. At intermediate interaction strength finite temperature Quantum Monte Carlo calculations yield a second order phase transition to a highly polarized, metallic ferromagnetic state. The Curie temperatures are calculated as a function of electron

S Schultz, S Panzeri, ET Rolls, A Treves

Advances in techniques for the formal analysis of neural networks have introduced the possibility of detailed quantitative analyses of brain circuitry. This paper applies a method for calculating mutual information to the analysis of the Schaffer collateral connections between regions CA3 and CA1 of the hippocampus. Attention is given to the introduction of

S. Marti i Garcia

Since 1995, LEP has steadily increased the center of mass energy of the colliding beams, from the M_Z resonance to 133, 161 and 172 GeV. New measurements of the strong coupling constant, alpha_s, at these energies have been performed by the LEP experiments, L3, ALEPH, OPAL and DELPHI. In this article, the new results are summarized, and combined with the pre

Ti-Pei Li

Systematic variations of average observational characteristics and correlation properties between different parameters of gamma-ray bursts (GRBs) with time from 1991 April to 1994 September are revealed. It is hard to explain the observed long-term variability by variations of experimental conditions. The variability of GRB properties with the time scale of

James V. Steele, Hidenaga Yamagishi, Ismail Zahed

We extend our recent analysis of the dilepton and photon emission rates to the case of finite temperature and baryon density, within the context of a density expansion. To leading order, the effects of the baryon density are assessed using data (photon emission) or constraints from broken chiral symmetry (dilepton emission). Next to leading order effects are

Matias Zaldarriaga, Uros Seljak, Edmund Bertschinger

We present an efficient method to compute CMB anisotropies in non-flat universes. First we derive the Boltzmann equation for cosmic microwave background temperature and polarization fluctuations produced by scalar perturbations in a general Robertson-Walker universe. We then apply the integral method to solve this equation, writing temperature and polarizati

S. Antoci, D. -E. Liebscher

Quantum mechanics can be formulated in three ways, as Heisenberg, Schrödinger and Feynman did respectively. For the last way, an unknown (i.e. forgotten) forerunner exists, that we have found in a paper by Gregor Wentzel, published before the famous works by Heisenberg and Schrödinger, and contemporary with the fundamental works of L. de Broglie. In that pap

Attila Csoto, B. F. Gibson, G. L. Payne

The importance of n-p radiative capture, utilizing polarized cold neutrons, as a means of measuring the weak pion coupling constant is reviewed. Parity conserving processes of the form k_gamma*[s_n,k_n] can contribute to the s_n*k_gamma photon asymmetry in any such experiment, if the apparatus is not perfectly symmetric. For an incident laboratory neutron en

Dmitry Kozlov

We reprove and generalize in a combinatorial way the result of A. Björner [J.\ Comb.\ Th.\ A {\bf 30}, 1981, pp.~90--100, Theorem 3.3], that order complexes of noncomplemented lattices are contractible, namely by showing that these simplicial complexes are in fact nonevasive, in particular collapsible.

Vladimir Kanovei

We prove the following classification theorem of the ``Glimm -- Effros&#39;&#39; type for Borel order relations: a Borel partial order on the reals either is Borel linearizable or includes a copy of a certain Borel partial order $\meo$ which is not Borel linearizable.

N. Dorey, V. V. Khoze, M. P. Mattis

We calculate multi-instanton effects in a three-dimensional gauge theory with N=8 supersymmetry and gauge group SU(2). The k-instanton contribution to an eight-fermion correlator is found to be proportional to the Gauss-Bonnet-Chern integral of the Gaussian curvature over the centered moduli-space of charge-k BPS monopoles, \tilde{M}_{k}. For k=2 the integra

HoSeong La

The supersymmetric generalization of dilatations in the presence of the dilaton is defined. This is done by defining the supersymmetric dilaton geometry which is motivated by the supersymmetric volume preserving diffeomorphisms. The resulting model is classical superconformal field theory with an additional dilaton-axion supermultiplet coupled to the supersy

Chuan-Tsung Chan

Three symmetry constraints on the CP violations in QCD are discussed in this paper. In order to generate CP violating observables from QCD, these constraints require: (1) spontaneous chiral symmetry breaking, (2) explicit chiral symmetry breaking, e.g., finite quark masses, (3) $U_A(1)$ anomaly, in addition to a nonzero $\thetabar$ parameter. A pictorial ill

George Chiladze

Heavy baryon chiral perturbation theory is extended to include the effects of quenching. In this framework the leading nonanalytic dependence of the heavy baryon masses on the light quark masses is studied. The size of quenching effects is estimated by comparing the results of quenched and ordinary chiral perturbation theories. It is found that in general th

Robert Fleischer, Thomas Mannel

Motivated by recent CLEO measurements of $B\toπK$ modes, we investigate their implications for the CKM angle $γ$ and a consistent description of these decays within the Standard Model. Interestingly it turns out that already the measurement of the combined branching ratios $B^\pm\toπ^\pm K$ and $B_d\toπ^\mp K^\pm$ allows to derive stringent constraints on $γ

H. Walliser

Chiral lagrangians as effective field theories of QCD are most suitable for the study of nucleons in a hot pion gas because they contain pions and also baryons as solitons of the same action. The semiclassical treatment of the soliton solutions must be augmented by pionic fluctuations which requires renormalisation to 1-loop, and finite temperatures do not i

Dmitri Melikhov

Nonperturbative effects in exclusive reactions $B\to K^{(*)}ll$ are discussed. Form factors which describe the main long-distance contribution to the meson transition amplitude are calculated within the dispersion formulation of the quark model: namely, the form factors in the decay region are expressed as relativistic double spectral representations through

Mauro Anselmino, Marc Bertini, Francesco Murgia, Paulo Quintairos

Final state quark-antiquark interactions may give origin to non zero values of the off-diagonal element rho_{1,-1} of the helicity density matrix of vector mesons produced in e+e- annihilations, as confirmed by recent OPAL data on phi and D^*&#39;s. Predictions are given for rho_{1,-1} of several mesons produced at large z and small p_T, i.e. collinear with

W. T. Giele, S. Keller

Methods for measuring the W-boson properties at hadron colliders are discussed. It is demonstrated that the ratio between the W- and Z-boson observables can be reliably calculated using perturbative QCD, even when the individual W- and Z-boson observables are not. Hence, by using a measured Z-boson observable and the perturbative calculation of the ratio of

M. Hayakawa

The basic feature of the measurement of CPT violation in the neutral kaon system is overviewed beginning with noting the physical implication of CPT violation. After describing $K^0-\bar{K}^0$ system at length, how CPT test is possible is illustrated with adding a few remarks on it.

K. Kajantie, M. Laine, K. Rummukainen, M. Shaposhnikov

We study to what extent the three-dimensional SU(N)+adjoint Higgs theory can be used as an effective theory for finite temperature SU(N) gauge theory, with N=2,3. The parameters of the 3d theory are computed in 2-loop perturbation theory in terms of T/Lambda_MSbar,N,N_f. The perturbative effective potential of the 3d theory is computed to two loops for N=2.

Chao-Hsi Chang, Liang Han, Wen-Gan Ma, Zeng-Hui Yu

The complete QCD corrections to the scalar top quark pair production via $γγ$ fusion in parent $e^{+}e^{-}$ collider are calculated in the Supersymmetric Model. The various origins of corrections are discussed. We find that the correction due to gluino exchange is smaller than that due to conventional gluonic contribution, and the contribution due to squark

Kurt Langfeld, Hugo Reinhardt, Oliver Tennert

Renormalization of composite fields is employed to suppress the statistical noise in lattice gauge calculations. We propose a new action which differs from the standard Wilson action by &#39;&#39;irrelevant&#39;&#39; operators, but suppresses the fluctuations of the plaquette. We numerically study the Creutz ratios and find a scaling window. The SU(2) mass g

Jan C. Plefka, Stuart Samuel

A $θ$ term, which couples to topological charge, is added to the two-dimensional lattice CP^3 model and U(1) gauge theory. Monte Carlo simulations are performed and compared to strong-coupling character expansions. In certain instances, a flattening behavior occurs in the free-energy at sufficiently large $θ$, but the effect is an artifact of the simulation

L. Gibbons

The experimental status of the Cabibbo-Kobayashi-Maskawa matrix is reviewed. Measurements discussed include B0_(s)-\bar{B}0_(s) mixing and several rare B and K decays with implications for |V_td| and |V_ts|. Extraction of |V_cb| and |V_ub| from studies of semileptonic B decay is also discussed.

J. Ambjorn, J. Nielsen, J. Rolf, G. Savvidy

We demonstrate by explicit calculation of the DeWitt-like measure in two-dimensional quantum Regge gravity that it is highly non-local and that the average values of link lengths $l, <l^n>$, do not exist for sufficient high powers of $n$. Thus the concept of length has no natural definition in this formalism and a generic manifold degenerates into spikes. Th

V. N. Pervushin, V. I Smirichinski

We consider the possibility of describing the Higgs effect in unified theories without the Higgs potential in the presence of the Einstein gravity with the conformal gravity-scalar coupling under the assumption of homogeneous matter distribution. The scalar field values can be found from the Friedmann equations for the homogeneous Universe. The considered co

Naresh Dadhich, K. Narayan

We propose a geometric ansatz, a restriction on Euclidean / Minkowski distance in the embedding space being propotional to distance in the embedded space, to generate spacetimes with vanishing gravitational mass ($R_{ik} u^i u^k = 0, u_i u^i = 1 $). It turns out that these spacetimes can represent global monopoles and textures. Thus the ansatz is a prescript

Alexander L. Fetter, Daniel Rokhsar

The low-lying hydrodynamic normal modes of a dilute Bose-Einstein gas in an isotropic harmonic trap determine the corresponding Bogoliubov amplitudes. In the Thomas-Fermi limit, these modes have large low-temperature occupation numbers, and they permit an explicit construction of the dynamic structure function $S(q,ω)$. The total noncondensate number $N&#39;

Karlo Penc, Mohammed Serhan

The spectral functions of tJ and tJ_{XY} models in the limit of J/t-> 0 and at finite temperatures T>>t are calculated using the spin-charge factorized wave function. We find that the Luttinger-liquid like scaling behavior for a finite system with L sites is restricted below temperatures of the order T = J/L. We also observe weight redistribution in the phot

M. C. Bonsager, K. Flensberg, B. Y-K. Hu, A. -P. Jauho

A treatment of frictional Coulomb drag between two 2-dimensional electron layers in a strong perpendicular magnetic field, within the independent electron picture, is presented. Assuming fully resolved Landau levels, the linear response theory expression for the transresistivity $ρ_{21}$ is evaluated using diagrammatic techniques. The transresistivity is giv

V. I. Anisimov, A. I. Poteryaev, M. A. Korotin, A. O. Anokhin

A recently developed dynamical mean-field theory in the iterated perturbation theory approximation was used as a basis for construction of the &#34;first principles&#34; calculation scheme for investigating electronic structure of strongly correlated electron systems. This scheme is based on Local Density Approximation (LDA) in the framework of the Linearize

V. F. Yudanov, O. N. Martyanov

For polycrystalline specimens of zeolites treated to thermal oxidation we have revealed and studied the weak spectra of reproducible magnetic microwave absorption fluctuations at a frequency of 9.4 GHz. The investigation was carried out by the ESR method over the 77-500 K temperature range. The fluctuation spectra have features typical of mesoscopic phenomen

Jae Dong Noh, M. den Nijs

The uniaxial structure of Si and Ge (001) facets leads to nontrivial topological properties of steps and hence to interesting equilibrium phase transitions. The disordered flat phase and the preroughening transition can be stabilized without the need for step-step interactions. A model describing this is studied numerically by transfer matrix type finite-siz

N. Shibata, M. Sigrist, E. Heeb

The one-dimensional Kondo lattice model with attractive interaction among the conduction electrons is analyzed in the case of half-filling. It is shown that there are three distinct phases depending on the coupling constants of the model. Two phases have a spin and charge gap. While one shows a clear separation of the spin and charge excitation spectrum the

D. Riveline, Chris H. Wiggins, A. Ott, Raymond E. Goldstein

We probed the bending of actin subject to external forcing and viscous drag. Single actin filaments were moved perpendicular to their long axis in an oscillatory way by means of an optically tweezed latex bead attached to one end of the filaments. Shapes of these polymers were observed by epifluorescence microscopy. They were found to be in agreement with pr

Y. Nakamura, A. N. Korotkov, C. D. Chen, J. S. Tsai

We report the experimental observation of the recently predicted peaks on the I-V curve of the superconducting single-electron transistor at relatively high temperatures. The peaks are due to the matching of singularities in the quasiparticle density of states in two electrodes of a tunnel junction. The energy shift due to Coulomb blockade provides the match

Alexander N. Korotkov

It is shown that quasi-Langevin method can be used for the calculation of the shot noise in correlated single-electron tunneling. We generalize the existing Fokker-Plank-type approach and show its equivalence to quasi-Langevin approach. The advantage of the quasi-Langevin method is a natural possibility to describe simultaneously the high (``quantum&#39;&#39

Javier Ballesteros-Paredes, Enrique Vazquez-Semadeni

We present results from a virial analysis of fully nonlinear two-dimensional (2D) simulations of the ISM. We discuss the Eulerian Virial Theorem in 2D, and describe preliminary results on the virial budget of clouds in the simulations. The clouds are far from a static equilibrium, and the Virial Theorem is dominated by the time-derivative terms, indicating t

Bradley E. Schaefer, Thomas Cline, Kevin Hurley, John Laros

The surest solution of the Gamma Ray Burst (GRB) mystery is to find an unambiguous low-energy quiescent counterpart. However, to date no reasonable candidates have been identified in the x-ray, optical, infrared, or radio ranges. The Hubble Space Telescope (HST) has now allowed for the first deep ultraviolet searches for quiescent counterparts. This paper re

Piet Hut

Recently, special-purpose computers have surpassed general-purpose computers in the speed with which large-scale stellar dynamics simulations can be performed. Speeds up to a Teraflops are now available, for simulations in a variety of fields, such as planetary formation, star cluster dynamics, galactic nuclei, galaxy interactions, galaxy formation, large sc

Piet Hut, Yoko Funato, Eiichiro Kokubo, Junichiro Makino

We present two types of meta-algorithm that can greatly improve the accuracy of existing algorithms for integrating the equations of motion of dynamical systems. The first meta-algorithm takes an integrator that is time-symmetric only for constant time steps, and ensures time-symmetry even in the case of varying time steps. The second meta-algorithm can be a

Maurice Dubin, Robert K. Soberman

Stars accrete near invisible hydrogen dominated agglomerates. This population, the `dark matter,&#39; effects the nature of stars. Measurements show plasma streams impacting Earth, planets, Sun and stars. This mass-energy source contradicts nebula collapse model for stars. The visual derived model, to which later discoveries (e.g., fusion) were appended, is

W. J. G. de Blok, Stacy S. McGaugh

We present mass models of a sample of 19 low surface brightness (LSB) galaxies and compare the properties of their constituent mass components with those of a sample of high surface brightness (HSB) galaxies.We find that LSB galaxies are dark matter dominated. Their halo parameters are only slightly affected by assumptions on stellar mass-to-light ratios. Co

M. van der Klis

I discuss some practical aspects of the analysis of millisecond time variability X-ray data obtained from accreting neutron stars and black holes. First I give an account of the statistical methods that are at present commonly applied in this field. These are mostly based on Fourier techniques. To a large extent these methods work well: they give astronomers

M. van der Klis

In early 1996 a series of discoveries begun with NASA&#39;s Rossi X-ray Timing Explorer of a new, up to then unknown astrophysical phenomenon. It turned out that accreting low magnetic-field neutron stars show quasi-periodic oscillations in their X-ray flux at rates of up to more than a kilohertz. These kHz QPO, now reported from eleven different systems, ar

Insu Yi, Scott J. Kenyon

We analyze the ultraviolet spectrum of the cataclysmic variable GK Per at maximum light. The flat ultraviolet spectrum in this system requires a truncated inner accretion disk and an unusually flat radial temperature profile. This requirement is not satisfied by any non-magnetic steady or non-steady disk model. We consider a magnetized accretion disk model t

Insu Yi, Eric G. Blackman

We study accretion induced collapse of magnetized white dwarfs as an origin of millisecond pulsars. We apply magnetized accretion disk models to the pre-collapse accreting magnetic white dwarfs and calculate the white dwarf spin evolution. If the pulsar magnetic field results solely from the flux-frozen fossil white dwarf field, a typical millisecond pulsar

Jean-Paul Meyer, L. O&#39;C. Drury, Donald C. Ellison

This is the first of a series of papers analysing the Galactic Cosmic Ray composition and origin. We show that the Galactic Cosmic Ray source (GCRS) composition is best described in terms of (i) a general enhancement of the refractory elements relative to the volatile ones, and (ii) among the volatile elements, an enhancement of the heavier elements relative

S. Kuznetsov, M. Gilfanov, E. Churazov, R. Sunyaev

The entire dataset of the GRANAT/SIGMA observations of Cyg X-1 and 1E1740.7-2942 in 1990-1994 was analyzed in order to search for correlations between primary observational characteristics of the hard X-ray (40-200 keV) emission - hard X-ray luminosity, hardness of the spectrum (quantified in terms of the best-fit thermal bremsstrahlung temperature kT) and t

Girish S. Setlur

Based on ideas introduced in a previous preprint cond-mat/9701206 we propose an exactly solvable model of bosons interacting amongst themselves via a Van-der Waal-like repulsive interaction, and compute both the filling fraction and the dynamical structure factor exactly. The novelty of this approach involves introducing, analogous to Fermi sea (or surface)

Steven S. Gubser

The semi-classical cross-sections for arbitrary partial waves of ordinary scalars to fall into certain five-dimensional black holes have a form that seems capable of explanation in terms of the effective string model. The kinematics of these processes is analyzed in detail on the effective string and is shown to reproduce the correct functional form of the s

Sean M. Carroll, George B. Field

Measurements of the polarization angle and orientation of cosmological radio sources may be used to search for unusual effects in the propagation of light through the universe. Recently, Nodland and Ralston (astro-ph/9704196) have claimed to find evidence for a redshift- and direction-dependent rotation effect in existing data. We re-examine these data and a

Igor Halperin, Ariel Zhitnitsky

A theory of the B -> K η&#39; decay is proposed. It is based on the Cabbibo favored b -> \bar{c} c s process followed by a direct materialization of the \bar{c} c pair into the η&#39;. This mechanism works due to a non-valence Zweig rule violating c-quark component of the η&#39;, which is unique to its very special nature. This non-perturbative &#34;intrinsi

Liu Zhao, Bo-Yu Hou

With slight modifications in the zero modes contributions, the positive and negative screening currents for the quantum deformed W-algebra W_{q,p}(g) can be put together to form a single algebra which can be regarded as an elliptic deformation of the universal enveloping algebra of \hat{g}, where g is any classical simply-laced Lie algebra.

Edward A. Baltz, Paolo Gondolo

We constrain the hadronic R-parity violating couplings in extensions to the minimal supersymmetric standard model. These interactions violate baryon and lepton number, and allow the lightest superpartner (LSP) to decay into standard model particles. The observed flux of cosmic ray antiprotons places a strong bound on the lifetime of the LSP in models where t

Pedro G. Ferreira, Joao Magueijo, Joseph Silk

We discuss the requirements of good statistics for quantifying non-Gaussianity in the Cosmic Microwave Background. The importance of rotational invariance and statistical independence is stressed, but we show that these are sometimes incompatible. It is shown that the first of these requirements prefers a real space (or wavelet) formulation, whereas the latt

Masahito Hayashi

The author studies the Cramer-Rao type bound by a linear programming approach. By this approach, he found a necessary and sufficient condition that the Cramer-Rao type bound is attained by a random measurement. In a spin 1/2 system, this condition is satisfied.

A. Ingemarsson, R. Shyam

We investigate the effect of the deuteron breakup on the optical potential for the elastic scattering of 56 MeV deuterons from $^{51}$V. The breakup probabilities calculated within the post-form distorted wave Born-approximation theory of breakup reactions are fitted to derive the contribution to the optical potential from the breakup channels. The breakup p

Denny Fliegner, Martin Reuter, Michael G. Schmidt, Christian Schubert

We clarify a discrepancy between two previous calculations of the two-loop QED Euler-Heisenberg Lagrangian, both performed in proper-time regularization, by calculating this quantity in dimensional regularization.

Rainer Dick

After a review of theoretical motivations to consider theories with direct couplings of scalar fields to Ricci and gauge curvature terms, we consider the dynamics and non-perturbative stabilization of a dilaton in three and in four dimensions. In particular, we derive generalized Coulomb potentials in the presence of a dilaton and discuss a low energy effect

J. F. Gunion, B. Grzadkowski, H. E. Haber, J. Kalinowski

We derive a sum rule which shows how to extend LEP limits on the masses of the lightest CP-even and CP-odd Higgs bosons of a CP-conserving two-Higgs-doublet model to any two Higgs bosons of a general CP-violating two-Higgs-doublet model. We generalize the analysis to a Higgs sector consisting of an arbitrary number of Higgs doublets and singlets, giving expl

Bernard S. Kay

We briefly review the current status of the algebraic approach to quantum field theory on globally hyperbolic spacetimes, both axiomatic -- for general field theories, and constructive -- for a linear Klein-Gordon model. We recall the concept of F-locality, introduced in the latter context in BS Kay: Rev. Math. Phys., Special Issue, 167-195 (1992) and explai

Don Koks, B. L. Hu, Andrew Matacz, Alpan Raval

The stochastic method based on the influence functional formalism introduced in an earlier paper to treat particle creation in near-uniformly accelerated detectors and collapsing masses is applied here to treat thermal and near-thermal radiance in certain types of cosmological expansions. It is indicated how the appearance of thermal radiance in different co

Marco Picco

We have studied the effect of weak randomness on q-state Potts models for q > 4 by measuring the central charges of these models using transfer matrix methods. We obtain a set of new values for the central charges and then show that some of these values are related to one another by a factorization law.

V. Yu. Irkhin, A. A. Katanin

The O(N) model of layered antiferro- and ferromagnets with a weak interlayer coupling and/or easy-axis anisotropy is considered. A renormalization group (RG) analysis in this model is performed, the results for N=3 being expected to agree with those of the 1/M expansion in the CP^{M-1} model at M=2. The quantum and classical cases are considered. A crossover

J. P. Lu

Elastic properties of carbon nanotubes and nanoropes are investigated using an empirical force-constant model. For single and multi-wall nanotubes the elastic moduli are shown to be insensitive to details of the structure such as the helicity, the tube radius and the number of layers. The tensile Young&#39;s modulus and the torsion shear modulus calculated a