November 1998 arXiv papers — page 20

T. R. Kirkpatrick, D. Belitz

These are notes for lectures delivered at the NATO ASI on Dynamics in Leiden, The Netherlands, in July 1998. The quantum kinetic theory for noninteracting electrons in a disordered solid is introduced and discussed. We first use many-body theory to derive the quantum Boltzmann equation that describes transport and time correlation functions in this system. P

S. Fratini, P. Quemerais

On examining the stability of a Wigner crystal in an ionic dielectric, two competitive effects due to the polaron formation are found to be important: (i) the screening of the Coulomb force, which destabilizes the crystal, compensated by (ii) the increase of the carrier mass (polaron mass). The competition between the two effects is carefully studied, and th

Yukito Iba

In this paper, we introduce a dynamical Monte Carlo algorithm for spin models in which the number of the spins fluctuates from zero to a given number by addition and deletion of spins with a probabilistic rule. Such simulations are realized with a variable-system-size ensemble, a mixture of canonical ensembles each of which corresponds to a system with diffe

Rangan Lahiri, Sriram Ramaswamy

We study the liquid-solid transition in a collection of interacting particles moving through a dissipative medium under the action of a constant, spatially uniform external force, e.g. a charge-stabilized suspension in a fluidized bed or a flux-point lattice moving through a thin, current-carrying slab of type II superconductor. The mobility of a given regio

A. V. Nikulov

The concept of the transition of type II superconductor into the Abrikosov state as the appearance of long-range phase coherence is considered. It is shown that this transition should be first order in ideal (without disorder) superconductor. Such transition is indeed observed in bulk superconductors with weak disorder at a field Hc4 < Hc2. No experimental e

R. Folk, Yu. Holovatch, T. Yavors&#39;kii

The leading correction-to-scaling exponent $ω$ for the three-dimensional dilute Ising model is calculated in the framework of the field theoretic renormalization group approach. Both in the minimal subtraction scheme as well as in the massive field theory (resummed four loop expansion) excellent agreement with recent Monte Carlo calculations [Ballesteros H G

H. -Q. Zhou, X. -Y. Ge, M. D. Gould

Integrable Kondo impurities in the one-dimensional supersymmetric U model of strongly correlated electrons are studied by means of the boundary graded quantum inverse scattering method. The boundary K matrices depending on the local magnetic moments of the impurities are presented as nontrivial realizations of the reflection equation algebras in an impurity

H. -Q. Zhou, X. -Y. Ge, M. D. Gould

An integrable Kondo problem in the one-dimensional supersymmetric extended Hubbard model is studied by means of the boundary graded quantum inverse scattering method. The boundary $K$ matrices depending on the local moments of the impurities are presented as a nontrivial realization of the graded reflection equation algebras in a two-dimensional impurity Hil

Eugene Demler, S. Das Sarma

We develop an effective spin theory to describe magnetic properties of the $ν=2$ Quantum Hall bilayer systems. In the absence of disorder this theory gives quantitative agreement with the results of microscopic Hartree-Fock calculations, and for finite disorder it predicts the existence of a novel spin Bose glass phase. The Bose glass is characterized by the

C. -H. Kiang, M. Endo, P. M. Ajayan, G. Dresselhaus

The inter-shell spacing of multi-walled carbon nanotubes was determined by analyzing the high resolution transmission electron microscopy images of these nanotubes. For the nanotubes that were studied, the inter-shell spacing ${\hat{d}_{002}}$ is found to range from 0.34 to 0.39 nm, increasing with decreasing tube diameter. A model based on the results from

Girish S. Setlur

As the title suggests, this is an attempt at bosonizing fermions in any number of dimensions without paying attention to the fact that the Fermi surface is an extended object. One is tempted to introduce the density fluctuation and its conjugate and recast the interacting problem in terms of these canonical Bose fields. However, we find that the attempt is s

B. Q. Wu, P. L. Leath

The failure probabilities or the strength distributions of heterogeneous 1D systems with continuous local strength distribution and local load sharing have been studied using a simple, exact, recursive method. The fracture behavior depends on the local bond-strength distribution, the system size, and the applied stress, and crossovers occur as system size or

Sebastian Eggert, Stefan Rommer

A magnetic impurity in the spin-1/2 chain is a simple realization of the two-channel Kondo problem since the field theoretical descriptions in the spin-sector are identical. The correlation functions near the impurity can be calculated. Using a modified version of the numerical transfer matrix DMRG, we are able to accurately determine local properties close

P. D. Ditlevsen

The effect of extreme hyperviscous damping, $νk_n^p, p=\infty$ is studied numerically in the GOY shell model of turbulence. It has resently been demonstrated [Leveque and She, Phys. Rev. Lett, 75,2690 (1995)] that the inertial range scaling in the GOY model is non-universal and depending on the viscous damping. The present study shows that the deviation from

Kiran M. Kolwankar

The thesis deals with applications of fractional calculus to fractals. It introduces the notion of local fractional derivative (LFD). Fractal and multifractal functions have been studied in the thesis using LFD. New kind of equations are introduced which involve LFD and one example, local fractional Fokker-Planck equation, is studied in detail.

A. S. Szalay, A. J. Connolly, G. P. Szokoly

We present a novel way to detect objects when multiband images are available. Typically, object detection is performed in one of the available bands or on a somewhat arbitrarily co-added image. Our technique provides an almost optimal way to use all the color information available. We build up a composite image of the N passbands where each pixel value corre

Pierluigi Monaco

The Press & Schechter ``numerical recipe&#39;&#39; is briefly reviewed, together with the recently proposed dynamical mass function theory, in which the mass function is constructed by using the powerful Lagrangian perturbation theory. The dynamical mass function is found in good agreement with the recent N-body simulations of Governato et al. (1998), in the

Christian Boily, Christian Einsel, Marc Hemsendorf, Rainer Spurzem

1- Simulations of star clusters and galactic nuclei: rotation and other challenges (R. Spurzem & C. Einsel) 2- Relaxation of elliptical galaxies (C. Boily) 3- Simulations with an Hybrid Nbody-Scf code (M. Hemsendorf) These are three two-page contributions to the Rutgers galaxy dynamics held in august, 1998. Each will be included in the proceedings to be publ

B. Vicini, A. Natta, A. Marconi, L. Testi

This paper presents new near-infrared observations of the planetary nebula NGC 2346. The data include a broad K-band image, an image in the H2 vibrationally excited 1-0S(1) line and K band slit spectra at three positions in the nebula. In the H2 1-0S(1) line, the nebula is characterized by a central, bright torus, surrounded by weaker emission with a typical

Philip R. Maloney, J. Bland-Hawthorn

We review the possible sources of ionizing photons within the Local Group. Throughout most of the LG volume, the cosmic background radiation will dominate, but locally (e.g., within d\sim 100 kpc of the Galactic disk) stellar ionizing photons escaping from galaxies may dominate. The magnitude of the cosmic ionizing background should be determined in the very

R. Plaga

The article gives a brief overview, aimed at nonspecialists, about the goals and selected recent results of the detection of very-high energy gamma-rays (energies above 100 GeV) with ground based detectors. The stress is on the physics questions, especially the origin of Galactic Cosmic Rays and the emission of TeV gamma-radiation from active galaxies. Moreo

E. Covas, R. Tavakol, A. Tworkowski, A. Brandenburg

We study the changes in the dynamical behaviour of axisymmetric spherical mean-field dynamo models produced by changes in their geometry and topology, by considering a two parameter family of models, ranging from a full sphere to spherical shell, torus and disc-like configurations, within a unified framework. We find that the two parameter space of the famil

Klaas S. de Boer

Horizontal-branch stars play an important role in defining the absolute distance scale in the universe. For that one has to know Mv at relevant B-V with well defined [M/H] for each type of horizontal-branch star. The nature of the horizontal-branch stars is reviewed with emphasis on all the open questions regarding evolution and structure, questions which sh

F. Herwig, D. Schoenberner, T. Bloecker

We investigate the validity of the core mass - luminosity relation (CMLR), originally described by Paczynski (1970), for asymptotic giant branch stars under the presence of third dredge-up events. We find, that models with efficient third dredge-up with less massive cores than those associated with hot bottom burning (Bloecker and Schoenberner 1991) do not o

John D. Barrow, Joao Magueijo

If the fine structure constant $α=e^2/(\hbar c)$ were to change, then a number of interpretations would be possible, attributing this change either to variations in the electron charge, the dielectric constant of the vacuum, the speed of light, or Planck&#39;s constant. All these variations should be operationally equivalent and can be related by changes of

A. Vogler, W. Pietsch

We report the results of a deep spatial, spectral, and timing analysis of ROSAT HRI and PSPC observations of the edge-on starburst galaxy NGC 253. In this first paper, point-like X-ray sources detected within the galaxy and in the field are discussed. In total, 73 X-ray sources have been collected in the NGC 253 field, 32 of which are associated with the dis

Eugenio Carretta, Raffaele G. Gratton, Gisella Clementini, Flavio Fusi Pecci

We discuss the different biases affecting the sample of field subdwarfs selected from the Hipparcos Catalogue, and used in the Main Sequence Fitting technique to derive distances to Galactic Globular Clusters. The adopted average corrections significantly affect the derived distance moduli, explaining the differences among various groups using this technique

J. Hwang, H. Noh

We derive the power spectra of the scalar- and tensor-type structures generated in a chaotic-type inflation model based on non-minimally coupled scalar field with a self interaction. By comparing contributions of both-structures to the anisotropy of the cosmic microwave background radiation with the four-year COBE-DMR data on quadrupole anisotropy we derive

Jayaram N Chengalur, Nissim Kanekar

We present Giant Metrewave Radio Telescope (GMRT) observations of redshifted HI 21cm absorption in two low redshift (z=0.2212, z=0.0912) damped Lyman-alpha systems seen towards the gigahertz peaked source OI 363 (z_em = 0.630). The object at z=0.0912 is the lowest redshift damped Lyman-alpha system known to date. Ground based imaging (Rao & Turnshek, 1998) s

R Foot, R R Volkas

The paper &#34;Big Bang Nucleosynthesis and Active-Sterile Neutrino Mixing: Evidence for Maximal $ν_μ\leftrightarrow ν_τ$ Mixing in Super Kamiokande?&#34; by X. Shi and G. M. Fuller (astro-ph/9810075) discusses the cosmological implications of the $ν_μ\to ν_s$ solution to the atmospheric neutrino anomaly. It incorrectly concludes that a lower bound on the $ν

T. E. Clarke, Gabriela Mallen-Ornelas, Marcin Sawicki, Mark Brodwin

We present distance estimates to a set of high-latitude intermediate-velocity HI clouds. We explore some of the physical parameters that can be determined from these results, such as cloud mass, infall velocity and height above the Galactic plane. We also briefly describe some astrophysical applications of these data and explore future work.

Robert A. Benjamin

We explore the hypothesis that clouds detected in quasar absorption line systems are falling at a terminal velocity toward the center of high redshift gaseous galactic halos. Since both the ionization level and terminal velocity of halo clouds increase with increasing distance from the central galaxy, velocity resolved profiles of highly ionized gas are pred

Oleg Y. Gnedin

Recent observations by the Hubble Space Telescope suggest that a strong dynamical and morphological evolution of disk galaxies has occurred in clusters of galaxies. I present the result of the self-consistent high-resolution simulations of galactc dynamics in the three cosmologically formed clusters. The disks of large galaxies survive but thicken by a facto

Jimmy A. Irwin, Joel N. Bregman

We determine the X-ray spectral properties of a sample of low-mass X-ray binaries (LMXBs) which reside in globular clusters of M31, as well as five LMXBs in Galactic globular clusters and in the Large Magellanic Cloud using the ROSAT PSPC. We find a trend in the X-ray properties of the LMXBs as a function of globular cluster metallicity. The spectra of LMXBs

R. Ibata, G. Lewis, J. -P. Beaulieu

It has recently been suggested that the stars in a vertical extension of the red clump feature seen in LMC color-magnitude diagrams could belong to a tidal stream of material located in front of that galaxy. If this claim is correct, this foreground concentration of stars could contribute significantly to the rate of gravitational microlensing events observe

V. V. Gafiychuk, I. A. Lubashevsky, Robert E. Ulanowicz

We consider an ecological system governed by Lotka-Volterra dynamics and an example of an economic system as a mesomarket with perfect competition. We propose a mechanism for cooperative self-regulation that enables the system under consideration to respond properly to changes in the environment. This mechanism is based on (1) active individual behavior of t

I. R. Klebanov, A. A. Tseytlin

We consider the type 0 theories, obtained from the closed NSR string by a diagonal GSO projection which excludes space-time fermions, and study the D-branes into these theories. The low-energy dynamics of N coincident D-branes is governed by a U(N) gauge theory coupled to adjoint scalar fields. It is tempting to look for the type 0 string duals of such boson

Naihuan Jing, Kailash C. Misra, Masato Okado

We use the fusion construction in the twisted quantum affine algebras to obtain a unified method to deform the wedge product for classical Lie algebras. As a byproduct we uniformly realize all non-spin fundamental modules for quantized enveloping algebras of classical types, and show that they admit natural crystal bases as modules for the (derived) twisted

R. de Mello Koch, J. P. Rodrigues

The realization of ${\cal N}=2$ four dimensional super Yang-Mills theories in terms of a single Dirichlet fivebrane in type IIB string theory is considered. A classical brane computation reproduces the full quantum low energy effective action. This result has a simple explanation in terms of mirror symmetry.

R. Bijker, A. Leviatan

Nucleon elastic and transition form factors are analyzed in the framework of a collective model of baryons. Effects of meson cloud couplings and relativistic corrections are considered.

Jan Brinckmann, Patrick A. Lee

The evolution of the so-called `41meV resonance&#39; in the magnetic response of YBCO cuprates is studied with slave-boson theory for the t-t&#39;-J-model. The resonance appears as a collective spin fluctuation in the d-wave superconducting (SC) state. It is undamped at optimal doping due to a threshold in the excitation energies of particle--hole pairs with

S. M. Klishevich

We study the interaction of gauge fields of arbitrary half-integer spins with the homogeneous electromagnetic field. We reduce the problem of obtaining the gauge-invariant Lagrangian and transformations of the half-integer spin fields in the external field to an algebraic problem of search for a set of operators with certain algebraical features using the re

Tal Alexander, Amiel Sternberg

We investigate microlensing amplification of faint stars in the dense stellar cluster in the Galactic Center (GC) by the super-massive black hole (BH). Such events would appear very close to the position of the radio source SgrA*, which is thought to coincide with the BH, and could be observed during the monitoring of stellar motions in the GC. We use the ob

J. Sollfrank, U. Heinz, H. Sorge, N. Xu

Some questions arising in the application of the thermal model to hadron production in heavy ion collisions are studied. We do so by applying the thermal model of hadron production to particle yields calculated by the microscopic transport model RQMD(v2.3). We study the bias of incomplete information about the final hadronic state on the extraction of therma

G. Papadopoulos, A. Teschendorff

We present a geometric construction of a new class of hyper-Kahler manifolds with torsion. This involves the superposition of the four-dimensional hyper-Kahler geometry with torsion associated with the NS-5-brane along quaternionic planes in quaternionic k-space, $\bH^k$. We find the moduli space of these geometries and show that it can be constructed using

A. N. Ivanov, H. Oberhummer, N. I. Troitskaya, M. Faber

The generalized version of the relativistic field theory model of the deuteron (RFMD) is applied to the description of processes of astrophysical interest and low-energy elastic NN scattering. The value of the astrophysical factor S_{pp}(0) = 5.52x10^{-25} MeV b is found to be enhanced by a factor of 1.42 with respect to the classical value S^*_{pp}(0) = 3.8

L. A. Mikaelyan, V. V. Sinev

We show that in a reactor disappearance oscillation experiment the sensitivity to the mixing parameter can be substantially improved for $(1 - 5\cdot10^{-4}) eV^{2}$ mass parameter range which includes both the LSND and the atmospheric neutrino oscillation regions. The objectives are: to search for the sterile neutrinos and to get a better understanding of t

Kurt Langfeld, Mannque Rho

The phase structure of hadronic matter at high density relevant to the physics of compact stars and relativistic heavy-ion collisions is studied in a low-energy effective quark theory. The relevant phases that figure are (1) chiral condensation, (2) diquark color condensation (color superconductivity) and (3) induced Lorentz-symmetry breaking (ISB). For reas

Mu-In Park

I consider the classical Kac-Moody algebra and Virasoro algebra in Chern-Simons theory with boundary within the Dirac&#39;s canonical method and Noether procedure. It is shown that the usual (bulk) Gauss law constraint becomes a second-class constraint because of the boundary effect. From this fact, the Dirac bracket can be constructed explicitly without int

Myeong-Gu Park, Jeremiah P. Ostriker

Spherical and axisymmetric accretion onto black holes is discussed. Physical processes in various families of solutions are explained and their characteristics are summarized. Recently discovered solutions of axisymmetric flow provide us with various radiation efficiency and spectrum, which may successfully model diverse accretion systems. Possible role of p

N. G. Pletnev, A. T. Banin

A simple systematic method for calculating derivative expansions of the one-loop effective action is presented. This method is based on using symbols of operators and well known deformation quantization theory. To demonstrate its advantages we present several examples of application for scalar theory, Yang-Mills theory, and scalar electrodynamics. The supers

Michael Kunzinger, Roland Steinbauer

Impulsive pp-waves are commonly described either by a distributional spacetime metric or, alternatively, by a continuous one. The transformation $T$ relating these forms clearly has to be discontinuous, which causes two basic problems: First, it changes the manifold structure and second, the pullback of the distributional form of the metric under $T$ is not

R. Kuriki, S. Ogushi, A. Sugamoto

We attempt to construct new superstring actions with a $D$-plet of Majorana fermions $ψ^{\cal B}_A$, where ${\cal B}$ is the $D$ dimensional space-time index and $A$ is the two dimensional spinor index, by deforming the Schild action. As a result, we propose three kinds of actions: the first is invariant under N=1 (the world-sheet) supersymmetry transformati

Michael Efroimsky, A. Lazarian

Asteroids and comets dissipate energy when they rotate about the axis different from the axis of the maximal moment of inertia. We show that the most efficient internal relaxation happens at the double frequency of body&#39;s tumbling. Therefore the earlier estimates that ignore double frequency input underestimate the internal relaxation in asteroids and co

F. Wang, H. Sorge

Anisotropic high energy density domains may be formed at early stages of ultrarelativistic heavy ion collisions, e.g. due to phase transition dynamics or non-equilibrium phenomena like (mini-)jets. Here we investigate hadronic observables resulting from an initially created anisotropic high energy density domain. Based on our studies using a transport model

A. Lazarian, E. T. Vishniac

We examine the effect of weak, small scale magnetic field structure on the rate of reconnection in a strongly magnetized plasma. This affects the rate of reconnection by reducing the transverse scale for reconnection flows, and by allowing many independent flux reconnection events to occur simultaneously. Allowing only for the first effect and using Goldreic

Rajiv R. P Singh, Zheng Weihong

We study the spin-half Heisenberg chain with alternating nearest neighbor interactions $J_1(1+δ)$ and $J_1(1-δ)$ and a uniform second neighbor interaction $J_2=y (1-δ)$ by series expansions around the limit of decoupled dimers ($δ=1$). By extrapolating to $δ=0$ and tuning $y$, we study the critical point separating the power-law and spontaneously dimerized p

A. Furusaki

The dc Josephson effect in a superconducting quantum point contact, where supercurrent flows through a small number of channels, is reviewd. The central role of Andreev levels is emphasized which carry the whole supercurrent in short symmetric Josephson junctions including tunnel junctions. A simple intuitive view of the dc Josephson effect in a quantum poin

Petr Horava

The AdS/CFT correspondence of elementary string theory has been recently suggested as a ``microscopic&#39;&#39; approach to QCD string theory in various dimensions. We use the microscopic theory to show that the ultraviolet regime on the string world-sheet is mapped to the ultraviolet effects in QCD. In the case of QCD_2, a world-sheet path integral represen

Inigo L. Egusquiza, Luis J. Garay, Jose M. Raya

We characterize good clocks, which are naturally subject to fluctuations, in statistical terms. We also obtain the master equation that governs the evolution of quantum systems according to these clocks and find its general solution. This master equation is diffusive and produces loss of coherence. Moreover, real clocks can be described in terms of effective

Richard L. Hall, Nasser Saad

The eigenvalue bounds obtained earlier [J. Phys. A: Math. Gen. 31 (1998) 963] for smooth transformations of the form V(x) = g(x^2) + f(1/x^2) are extended to N-dimensions. In particular a simple formula is derived which bounds the eigenvalues for the spiked harmonic oscillator potential V(x) = x^2 + lambda/x^alpha, alpha > 0, lambda > 0, and is valid for all

M. Fleischhauer, R. Unanyan, B. W. Shore, K. Bergmann

We show that the physical mechanism of population transfer in a 3-level system with a closed loop of coherent couplings (loop-STIRAP) is not equivalent to an adiabatic rotation of the dark-state of the Hamiltonian but coresponds to a rotation of a higher-order trapping state in a generalized adiabatic basis. The concept of generalized adiabatic basis sets is

Christof Zalka

This is a short introduction to quantum computers, quantum algorithms and quantum error correcting codes. Familiarity with the principles of quantum theory is assumed. Emphasis is put on a concise presentation of the principles avoiding lengthy discussions.

Harel Primack, Reinhold Blümel

We study the modifications of synchrotron radiation of charges in a storage ring as they are cooled. The pair correlation lengths between the charges are manifest in the synchrotron radiation and coherence effects exist for wavelengths longer than the coherence lengths between the charges. Therefore the synchrotron radiation can be used as a diagnostic tool

Harel Primack, Reinhold Blümel

With respect to a &#34;hot&#34;, non-crystallized beam the synchrotron radiation of a cold crystallized beam is considerably modified. We predict suppression of synchrotron radiation emitted by a crystallized beam in a storage ring. We also propose experiments to detect this effect.

P. V. Vorob&#39;ev, I. N. Nesterenko, A. R. Frolov, T. V. Shaftan

The apparatus description for control of the time parameters of photomultipliers with high time resolution is described. For generation of ultrashort light flashes have been used sonoluminescence effect -- emission of the light flashes which is appearing at the stressed interior of collapsing air microbubble by sound wave in water.

Diptiman Sen

This article briefly reviews the quantum Hall effect and the contributions of the winners of the 1998 Nobel Prize in Physics.

Paolo M. Gensini, Rafael Hurtado, Galileo Violini

Rapidly convergent, unsubtracted dispersion relations have been used to test coupled channel analyses of low-energy S = -1 meson-baryon pi Y --> pi Y&#39; channels. We conclude that the low-energy S = -1 meson-baryon sector is less well known than currently believed, and that it deserves more accurate experiments and analyses.

O. Benhar, S. Fantoni, G. I. Lykasov

The extrapolation of the nuclear spectral function at large nucleon three-momentum and removal energy is suggested.

Daniel R. Phillips

We review a three-dimensional formalism that provides a systematic way to include relativistic effects including relativistic kinematics, the effects of negative-energy states, and the boosts of the two-body system in calculations of two-body bound-states. We then explain how to construct a conserved current within this relativistic three-dimensional approac

David B. A. Epstein, Derek F. Holt

We describe a procedure which verifies that a group given by generators and relators is word-hyperbolic. This procedure always works with a group which is word-hyperbolic, provided there is sufficient memory and time devoted to the problem. If the group is not word-hyperbolic, the procedure continues indefinitely. We also describe a procedure which computes

Krzysztof Ciesielski, Andrzej Roslanowski

We construct, under the assumption that union of less than continuum many meager subsets of R is meager in R, an additive connectivity function f:R-->R with Cantor intermediate value property which is not almost continuous. This gives a partial answer to a question of D. Banaszewski. We also show that every extendable function g:R-->R with a dense graph sati

A. Genestier

Let S(g,N,p) be the Siegel modular variety of principally polarized abelian varieties of dimension g with a Γ_0(p)-level structure and a full N-level structure (where p is a prime not dividing N \geq 3 and Γ_0(p) is the inverse image of a Borel subgroup of Sp(2g,F_p) in Sp(2g,Z)). This variety has a natural integral model over Z[1/N] which is not semi-stable

Robert Bieri, Ross Geoghegan

This is the second of two papers but has been written so as to have minimal dependence on the first paper (which is also on this archive). Let G be a group and let M be a CAT(0) proper metric space (e.g. a simply connected complete Riemannian manifold of non-positive sectional curvature or a locally finite tree). Assume G is of type F_n (type F_1 is finitely

Robert Bieri, Ross Geoghegan

Let G be a group and let M be a CAT(0) proper metric space (e.g. a simply connected complete Riemannian manifold of non-positive sectional curvature or a locally finite tree). Isometric actions of G on M are (by definition) points in the space R := Hom(G, Isom(M)) with the compact open topology. Sample theorems: 1. The cocompact actions form an open subset o

Herbert Clemens, Holger P. Kley

Let X be a (possibly nodal) K-trivial threefold moving in a fixed ambient space P. Suppose X contains a continuous family of curves, all of whose members satisfy certain unobstructedness conditions in P. A formula is given for computing the corresponding virtual number of curves, that is, the number of curves on a generic deformation of X &#34;contributed by

Vijay Balasubramanian, David Kastor, Jennie Traschen, K. Z. Win

The 256 dimensional M2-brane multiplet contains solitons of many different intrinsic spins. Using the broken supersymmetry transformations of the M2-brane, we find supergravity solutions which explicitly display these spins. This amounts to quantizing the fermionic zero modes and computing the back reaction on the metric and gauge potential. These spacetime

I. Gaida, H. R. Hollmann, J. M. Stewart

Non--minimal repulsive singularities (``repulsons&#39;&#39;) in extended supergravity theories are investigated. The short distance antigravity properties of the repulsons are tested at the classical and the quantum level by a scalar test--particle. Using a partial wave expansion it is shown that the particle gets totally reflected at the origin. A high freq

H. Saleur

In this paper I complete the solution of the Bukhvostov Lipatov model by computing the physical excitations and their factorized S matrix. I also explain the paradoxes which led in recent years to the suspicion that the model may not be integrable.

V. P. Nair

Three topics, the self-consistent resummation of the perturbative expansion for thermal Yang-Mills (YM) theory, nonperturbative analysis of Yang-Mills theories in (2+1) dimensions and modification of the Bose distribution for gluons, are discussed. These topics are related to the magnetic mass or magnetic screening in the quark-gluon plasma. The value of the

N. Ano, T. Suzuki

We examine a possibility to introduce a non-trivial classical background metric into the 2-d Liouville gravity theory. The classical background appears as a part of the Weyl factor of the physical metric of 2-d surfaces with some conformal dimension. On the other hand, the rest part of the factor corresponds to the quantum fluctuating sector, having another

Samir D. Mathur, Alec Matusis

We study the absorption of a class of fields in the geometry produced by extremal three-branes. We consider fields that do not mix with the ten-dimensional graviton. For these fields we solve the wave equations and find the absorption probabilities for all partial waves at leading order in the energy. We note that in some of these cases one needs an `interme

A. Quadt

Measurements of the proton structure function $F_2$ in the $Q^2$ range $0.6 - 17 \rm GeV^2$ from ZEUS 1995 shifted vertex data and $Q^2 \simeq 1.5 - 20000 \rm GeV^2$ from 1996 and 1997 ZEUS data are presented. From the former and other ZEUS $F_2$ data the slopes $d F_2 / d \ln Q^2$ at fixed $x$ and $d F_2 / d \ln(1/x)$ at fixed $Q^2$ are derived. $F_2$ data

David Bowser-Chao, Kingman Cheung, Wai-Yee Keung

In a general two-Higgs-doublet model (2HDM), without the {\it ad hoc} discrete symmetries to prevent tree-level flavor-changing-neutral currents, an extra phase angle in the charged-Higgs-fermion coupling is allowed. We show that the charged-Higgs amplitude interferes destructively or constructively with the standard model amplitude depending crucially on th

Shuquan Nie, Marc Sher

In the standard model, the requirements of vacuum stability and the validity of perturbation theory up to the unification scale force the mass of the Higgs boson to be approximately between 130 GeV and 180 GeV. We re-examine these requirements in the (non-supersymmetric) two-Higgs doublet model, in the light of the large top quark mass, and constrain the mas

Berthold Stech

The standard model taken with a momentum space cut-off may be viewed as an effective low energy theory. The structure of it and its known parameters can give us hints for relations between these parameters. In the present investigation the Higgs problem will be discussed, the possible connection of the Higgs meson with the heavy top quark, and the geometric

Chun-Khiang Chua, W-Y. P. Hwang

Allowing leptoquarks to interact with both right-handed and left-handed neutrinos (i.e., ``non-chiral&#39;&#39; leptoquarks), we show that a non-zero neutrino magnetic moment can arise naturally. Although the mass of the non-chiral vector leptoquark that couples to the first generation fermions is constrained severely by universality of the $π^+$ leptonic de

G. C. Gellas, T. R. Hemmert, C. N. Ktorides, G. I. Poulis

The three complex form factors entering the $Δ\to Nγ^\ast$ vertex are calculated to ${\cal O}(ε^3)$ in the framework of a chiral effective theory with explicit $Δ$(1232) degrees of freedom. Furthermore, the role of presently unknown low energy constants that affect the values of EMR and CMR is elucidated.

A. Kirk, O. Villalobos Baillie

The non-Abelian nature of QCD suggests that particles that have a gluon constituent, such as glueballs or hybrids, should exist. Experiments WA76, WA91 and WA102 have performed a dedicated search for these states in central production using the CERN Omega Spectrometer. New results from central production show that there is a kinematical filter which can sele

Patrik Eden

We propose event cuts in deep inelastic scattering, suitable for an examination of quark fragmentation universality. We compare the current hemisphere of the Breit frame with hemispheres in e+e- annihilation events, using Monte Carlo simulations. The agreement between the two processes is improved after the suggested events cuts. A method to study the scale

Wu-Sheng Dai, Xiao-Gang He, Xue-Qian Li, Gang Zhao

The light quarks inside $B$ mesons are usually treated as spectators and do not affect the decay rates which are assumed to be purely due to b quark decays. In this paper we calculate the non-spectator contributions to inclusive charmless $B$ decays due to the spectator effects. We find that the non-spectator contributions to the branching ratio for $\bar B^

Jihn E. Kim, Bumseok Kyae, Jong Dae Park

In R parity violating theories, there does not exist the {\it stable} lightest supersymmetric particle (LSP). The LSP, $χ$, of MSSM decays to lighter ordinary particles with dimension 6 effective R violating interaction terms. Since the lifetime of $χ$ can be sufficiently long for small R-violating couplings, it can affect the standard nucleosynthesis scenar

K. Kajantie, M. Laine, A. Rajantie, K. Rummukainen

We study the phase diagram of the three-dimensional SU(3)+adjoint Higgs theory with lattice Monte Carlo simulations. A critical line consisting of a first order line, a tricritical point and a second order line, divides the phase diagram into two parts distinguished by <Tr A0^3>=0 and /=0. The location and the type of the critical line are determined by meas

J. M. Butterworth, ZEUS Collaboration

Some recent ZEUS results on the photoproduction of open charm and possible implications for photon structure are discussed.

L. C. Garcia de Andrade

The method of Hamilton-Jacobi is used to obtain geodesics around non- Riemannian planar torsional defects.It is shown that by perturbation expansion in the Cartan torsion the geodesics obtained are parabolic curves along the plane x-z when the wall is located at the plane x-y.In the absence of defects the geodesics reduce to straight lines.The family of para

L. C. Garcia de Andrade

On the non-minimal coupling of Riemann-flat Klein-Gordon Fields to Space-time torsion} The energy spectrum of Klein-Gordon particles is obtained via the non-minimal coupling of Klein-Gordon fields to Cartan torsion in the approximation of Riemann-flatness and constant torsion.When the mass squared is proportional to torsion coupling constant it is shown that

Thomas B. Bahder

Coordinate transformations are derived from global Minkowski coordinates to the Fermi coordinates of an observer moving in a circle in Minkowski space-time. The metric for the Fermi coordinates is calculated directly from the tensor transformation rule. The behavior of ideal clocks is examined from the observer&#39;s reference frame using the Fermi coordinat

Bruno Preziosi

It is proved that in experiments on or near the Earth, no anisotropy in the one-way velocity of light may be detected. The very accurate experiments which have been performed to detect such an effect are to be considered significant tests of both special relativity and the equivalence principle

Vladimir S. Mashkevich

We argue that the conventional construction for quantum fields in curved spacetime has a grave drawback: It involves an uncountable set of physical field systems which are nonequivalent with respect to the Bogolubov transformations, and there is, in general, no canonical way for choosing a single system. Thus the construction does not result in a definite th

Dan Roth

We analyze a few of the commonly used statistics based and machine learning algorithms for natural language disambiguation tasks and observe that they can be re-cast as learning linear separators in the feature space. Each of the methods makes a priori assumptions, which it employs, given the data, when searching for its hypothesis. Nevertheless, as we show,