March 2000 arXiv papers — page 23

Stephen Rock, Peter Bosted

We have extracted ratios of cross sections for scattering electrons from high mass targets compared to low mass targets in the region of x ~ 0.02 and Q^2 < 1 (GeV/c)^2 from SLAC experiments performed over the past three decades. Additional analysis was needed for radiative corrections, target end caps and calibration runs. We observe no significant differenc

John L. Pollock

This is a system description for the OSCAR defeasible reasoner.

Burkhard D. Steinmacher-Burow

The Task System and Item Architecture (TSIA) is a model for transparent application execution. In many real-world projects, a TSIA provides a simple application with a transparent reliable, distributed, heterogeneous, adaptive, dynamic, real-time, parallel, secure or other execution. TSIA is suitable for many applications, not just for the simple application

Gabriele Kern-Isberner

The idea of preserving conditional beliefs emerged recently as a new paradigm apt to guide the revision of epistemic states. Conditionals are substantially different from propositional beliefs and need specific treatment. In this paper, we present a new approach to conditionals, capturing particularly well their dynamic part as revision policies. We thorough

Victoria I. Fernández, Carlos M. Naón

We compute the charge-density oscillations in a Tomonaga-Luttinger model with impurities for a short-range electron-electron potential.

Patrik Recher, Eugene V. Sukhorukov, Daniel Loss

We consider a quantum dot in the Coulomb blockade regime weakly coupled to current leads and show that in the presence of a magnetic field the dot acts as an efficient spin-filter (at the single-spin level) which produces a spin-polarized current. Conversely, if the leads are fully spin-polarized the up or down state of the spin on the dot results in a large

Savas Berber, Young-Kyun Kwon, David Tomanek

We use parametrized linear combination of atomic orbitals calculations to determine the stability, optimum geometry and electronic properties of nanometer-sized capped graphitic cones, called ``nano-horns&#39;&#39;. Different nano-horn morphologies are considered, which differ in the relative location of the five terminating pentagons. Simulated scanning tun

Yu. A. Kuznetsov, E. G. Timoshenko

We study the role of topological restrictions for the conformational structure of a nonphantom homopolymer chain in a lattice Monte Carlo model. In the athermal regime we find that the standard Metropolis algorithm violates the detailed balance condition if both local monomer and global reptational moves are included. However, if about 1 reptation is perform

S. Pilla, J. A. Hamida, N. S. Sullivan

A high resolution non-adiabatic method for measuring the heat capacity ($C_v$) of bulk samples of condensable gases in the range 7.5-70 K is described. In this method $C_v$ is evaluated by directly comparing the heating and cooling rates of the sample temperature for two algebraically independent heat pulse sequences without explicit use of the thermal condu

Antonio H. Castro Neto, Barbara A. Jones

In this paper we provide the theoretical basis for the problem of Griffiths-McCoy singularities close to the quantum critical point for magnetic ordering in U and Ce intermetallics. We show that the competition between Kondo effect and RKKY interaction can be expressed in Hamiltonian form and the dilution effect due to alloying leads to a quantum percolation

Peter Sollich, Patrick B Warren, Michael E Cates

A polydisperse system contains particles with at least one attribute $σ$ (such as particle size in colloids or chain length in polymers) which takes values in a continuous range. It therefore has an infinite number of conserved densities, described by a density {\em distribution} $ρ(σ)$. The free energy depends on all details of $ρ(σ)$, making the analysis o

C. M. Newman, D. L. Stein

We rigorously rule out the appearance of multiple domain walls between ground states in 2D Edwards-Anderson Ising spin glasses (with periodic boundary conditions and, e.g., Gaussian couplings). This supports the conjecture that there is only a single pair of ground states in these models.

S. Viefers, T. H. Hansson, S. M. Reimann

We exploit the analogy with the Quantum Hall (QH) system to study weakly interacting bosons in a harmonic trap. For a $δ$-function interaction potential the ``yrast&#39;&#39; states with $L\ge N(N-1)$ are degenerate, and we show how this can be understood in terms of Haldane exclusion statistics. We present spectra for 4 and 8 particles obtained by numerical

M. Mambrini, F. Mila

{Extensive calculations in the short-range RVB (Resonating valence bond) subspace on both the trimerized and the regular (non-trimerized) Heisenberg model on the kagome lattice show that short-range dimer singlets capture the specific low-energy features of both models. In the trimerized case the singlet spectrum splits into bands in which the average number

Jose M. Sancho, Angel Sanchez

We study the dynamics of fronts when both inertial effects and external fluctuations are taken into account. Stochastic fluctuations are introduced as multiplicative noise arising from a control parameter of the system. Contrary to the non-inertial (overdamped) case, we find that important features of the system, such as the velocity selection picture, are n

Sergio Ciuchi, Jose Lorenzana, Carlo Pierleoni

Within the path integral formalism, we derive exact expressions for correlation functions measuring the lattice charge induced by an electron and associated polarization in Frohlich polaron problem. We prove that a sum rule for the total induced charge, already obtained within approximated approaches is indeed exact. As a consequence the total induced charge

P. Manca, G. Calestani, A. Migliori, R. De Renzi

The oxygen-order dependent emergence of superconductivity in YBa2Cu3O6+x is studied, for the first time in a comparative way, on pair samples having the same oxygen content and thermal history, but different Cu(1)Ox chain arrangements deriving from their intercalated and deintercalated nature. Structural and electronic non-equivalence of pairs samples is det

Gerhard Muller, Michael Karbach

The investigation of the dynamics of quantum many-body systems is a concerted effort involving computational studies of mathematical models and experimental studies of material samples. Some commonalities of the two tracks of investigation are discussed in the context of the quantum spin dynamics of low-dimensional magnetic systems, in particular spin chains

Jizhong Lou, Jianhui Dai, Shaojin Qin, Zhaobin Su

We analyze the logarithmic corrections due to ferromagnetic impurity ending bonds of open spin 1/2 antiferromagnetic chains, using the density matrix renormalization group technique. A universal finite size scaling $\sim {\frac 1 {L \log L}}$ for impurity contributions in the quasi-degenerate ground state energy is demonstrated for a zigzag spin 1/2 chain at

Janos Torok, Supriya Krishnamurthy, Janos Kertesz, Stephane Roux

We introduce a mesoscopic model for the formation and evolution of shear bands in loose granular media. Numerical simulations reveal that the system undergoes a non-trivial self-organization process which is governed by the motion of the shear band and the consequent restructuring of the material along it. High density regions are built up, progressively con

K. Takahata, Y. Iguchi, D. Tanaka, T. Itoh

The thermal conductivity of polycrystalline samples of (Na,Ca)Co_2O_4 is found to be unusually low, 20 mW/cmK at 280 K. On the assumption of the Wiedemann-Franz law, the lattice thermal conductivity is estimated to be 18 mW/cmK at 280 K, and it does not change appreciably with the substitution of Ca for Na. A quantitative analysis has revealed that the phono

Xiao Hu, Masashi Tachiki

A critical value in the product of the anisotropy parameter and the magnetic field is observed in interlayer Josephson-vortex systems by extensive Monte Carlo simulations. Below/above this critical value the thermodynamic phase transition between the normal and the superconducting states upon temperature sweeping is first/second order. The origin is the intr

E. T. Seppala, M. J. Alava

We discuss the zero-temperature susceptibility of elastic manifolds with quenched randomness. It diverges with system size due to low-lying local minima. The distribution of energy gaps is deduced to be constant in the limit of vanishing gaps by comparing numerics with a probabilistic argument. The typical manifold response arises from a level-crossing pheno

Manabu Takahashi, Jun-ichi Igarashi, Peter Fulde

We study the pre-K-edge structure of the resonant X-ray scattering for forbidden reflections (anomalous scattering) in LaMnO3, using the band calculation based on the local density approximation. We find a two-peak structure with an intensity approximately 1/100 of that of the main peak. This originates from a mixing of 4p states of Mn to 3d states of neighb

B. M. Caradoc-Davies, R. J. Ballagh, P. B. Blakie

We simulate in the mean-field limit the effects of rotationally stirring a three-dimensional trapped Bose-Einstein condensate with a Gaussian laser beam. A single vortex cycling regime is found for a range of trap geometries, and is well described as coherent cycling between the ground and the first excited vortex states. The critical angular speed of stirri

H. Xin, D. E. Oates, S. Sridhar, G. Dresselhaus

The response of YBCO bicrystal grain-boundary junctions to small dc magnetic fields (0 - 10 Oe) has been probed with a low-power microwave (rf) signal of 4.4 GHz in a microwave-resonator setup. Peaks in the microwave loss at certain dc magnetic fields are observed that result from individual Josephson vortices penetrating into the grain-boundary junctions un

Pierre-Gilles de Gennes

Solid state actuators (piezoelectric, ferroelectric, ...) deform under an external field, and have found many applications. They respond fast, but their mechanical deformations are very small. There is a need for soft actuators, giving larger responses, but necessarily less fast. This paper describes the early attempts by Katchalsky and others, and the probl

J. Froehlich, B. Pedrini, C. Schweigert, J. Walcher

Incompressible Quantum Hall fluids (QHF&#39;s) can be described in the scaling limit by three-dimensional topological field theories. Thanks to the correspondence between three-dimensional topological field theories and two dimensional chiral conformal field theories (CCFT&#39;s), we propose to study QHF&#39;s from the point of view of CCFT&#39;s. We derive

H. van Beijeren, R. van Zon, J. R. Dorfman

The kinetic theory of gases provides methods for calculating Lyapunov exponents and other quantities, such as Kolmogorov-Sinai entropies, that characterize the chaotic behavior of hard-ball gases. Here we illustrate the use of these methods for calculating the Kolmogorov-Sinai entropy, and the largest positive Lyapunov exponent, for dilute hard-ball gases in

Laura Grego, John E. Carlstrom, Marshall K. Joy, Erik D. Reese

We present interferometric measurements of the Sunyaev-Zel&#39;dovich (SZ) effect towards the galaxy cluster Abell 370. These measurements, which directly probe the pressure of the cluster&#39;s gas, show the gas distribution to be strongly aspherical, as do the x-ray and gravitational lensing observations. We calculate the cluster&#39;s gas mass fraction in

Nino Panagia

The properties of supernovae (SNe) are reviewed. It is shown that the observed characteristics of the morphological classes of SNe (types Ia, Ib/c, II) can be explained in terms of two basic explosion mechanisms, i.e. core collapse of massive stars and thermonuclear explosion of low/moderate mass stars. The study of SNe can provide valuable insight in the la

U. D. J. Gieseler, T. W. Jones

Numerical results for particle acceleration at multiple oblique shocks are presented. We calculate the steady state spectral slope of test particles accelerated by the first order Fermi process. The results are compared to analytical treatments, for parameters, where the diffusion approximation does apply. Effects of injection and finite shock extend are inc

Canadian Galactic Plane Survey, :, Jayanne English, A. Russ Taylor

The Dominion Radio Astrophysical Observatory&#39;s Synthesis Telescope provides the highest resolution data (1 arcmin and 0.82 km/s) to date of an HI worm candidate. Observed as part of the Canadian Galactic Plane Survey, mushroom-shaped GW 123.4-1.5 extends only a few hundred parsecs, contains ~10^5 solar masses of neutral hydrogen, and appears unrelated to

James Reeves, Martin Turner

The results from an X-ray spectral analysis of a large sample of quasars, observed with ASCA, are presented. Data reduction leaves 62 quasars, 35 radio-loud and 27 radio-quiet, suitable for spectral analysis. Differences are found between the radio-quiet quasars (RQQs) and the radio-loud quasars (RLQs), in agreement with previous studies. A correlation betwe

Todd M. Fuller, H. M. P. Couchman

We have included the chemical rate network responsible for the formation of molecular Hydrogen in the N-body hydrodynamic code, Hydra, in order to study the formation of the first cosmological at redshifts between 10 and 50. We have tested our implementation of the chemical and cooling processes by comparing N-body top hat simulations with theoretical predic

Sergei A. Levshakov, Irina I. Agafonova, Wilhelm H. Kegel

A new method, based on the simulated annealing algorithm and aimed at the inverse problem in the analysis of intergalactic (interstellar) complex spectra of hydrogen and metal lines, is presented. We consider the process of line formation in clumpy stochastic media accounting for fluctuating velocity and density fields (mesoturbulence). This approach general

W. Junor, F. Mantovani, R. Morganti, L. Padrielli

Multi-wavelength VLA observations of two extended radio galaxies, 0235-197 and 1203+043 are presented. There is some evidence from earlier studies that these two sources exhibit low frequency (<1 GHz) variability. This work shows that both sources have linear polarizations, if any, below the detection limits at 320 MHz, so we cannot explain the variability a

R. Cayrel, M. Steffen

Based on detailed 2D radiation hydrodynamics (RHD) simulations, we have investigated the effects of photospheric temperature inhomogeneities induced by convection on spectroscopic determinations of the lithium abundance. Computations have been performed both for the solar case and for a metal-poor dwarf. NLTE effects are taken into account, using a five-leve

Matthias Steffen

The dynamics and thermal structure of the surface layers of stars with outer convection zones can be studied in some detail by means of numerical simulations of time-dependent compressible convection. In an effort to investigate the properties of ``stellar granulation&#39;&#39; as a function of spectral type, we have carried out elaborate 2-dimensional radia

M. A. Garrett

In this paper I outline a new strategy for the routine detection and imaging of faint (sub-mJy and microJy) radio sources with VLBI and SVLBI. The strategy relies on a combination of in-beam phase-referencing, wide-field VLBI imaging and simultaneous correlation of multiple field centres. A combination of these techniques, together with the steeply rising ra

Coryn A. L. Bailer-Jones, Peter Bizenberger, Clemens Storz

The ongoing development of large infrared array detectors has enabled wide field, deep surveys to be undertaken. There are, however, a number of challenges in building an infrared instrument which has both excellent optical quality and high sensitivity over a wide field. We discuss these problems in the context of building a wide field imaging camera for the

A G Lyne, S H Mankelow, J F Bell, R N Manchester

We report on searches of the globular cluster Terzan 5 for low luminosity and accelerated radio pulsars using the 64-m Parkes radio telescope. One new millisecond pulsar, designated PSR J1748-2446C, was discovered, having a period of 8.44ms. Timing measurements using the 76-m Lovell radio telescope at Jodrell Bank show that it is a solitary pulsar and lies c

Robert L. Kurucz

WE do not know how to make realistic model atmospheres; understand convection; consider the variation in microturbulent velocity; understand spectroscopy; have good spectra of the sun or any other star; have energy distributions for the sun or any other star; know how to determine abundances; know the abundances of the sun or any other star; have good atomic

J. Martin-Pintado, P. de Vicente, N. J. Rodriguez-Fernandez, A. Fuente

In this letter we present a map of the GC in the 1-0 line of SiO covering the same region than the ASCA observations of the Fe 6.4 keV line. The SiO emission is restricted to molecular clouds with radial velocity between 10 and 60 km/s in the Sgr A and Sgr B complexes. We find a correlation between the SiO morphology and the spatial distribution of the Fe 6.

S. Nagataki, K. Kohri

In this study we present two indicators that will reflect the difference between collapsars and normal collapse-driven supernovae. They are products of explosive nucleosynthesis and neutrino emission. In the collapsar model, it is natural to consider that the product of explosive nucleosynthesis depends on the zenith angle because the system becomes highly a

Pierre-Yves Gaillard

If M is a riemannian manifold, then the inclusion of the complex of coclosed harmonic forms into the de Rham complex induces a linear isomorphism in cohomology. If M has at most countably many connected components, this linear isomorphism is a Frechet isomorphism.

X. X. Yi, D. L. Zhou, C. P. Sun, W. M. Zheng

We derive and discuss the temperature dependance of the condensate and noncondensate density profile of a Bose-Einstein condensate gas with Feshbach resonance in a parabolic trap. These quantities are calculated self-consistently using the generalized Hartree-Fock-Bogoliubov (HFB) equations within the Bogoliubov approximation. At zero temperature, the HFB eq

A. Dreischuh, D. Neshev, G. G. Paulus, H. Walther

In this work we report the first realization of odd dark beams of finite length under controllable initial conditions. The mixed edge-screw phase dislocations are obtained by reproducing binary computer-generated holograms. Two effective ways to control the steering of the beams are analyzed experimentally and compared with numerical simulations.

Joseph E. Avron, Lorenzo Sadun

We describe the generic behavior of Fredholm indices in the space of Toeplitz operators. We relate this behavior to certain conjectures and open problems that arise in the context of the Quantum Hall Effect.

Se-Goo Kim

Kirby and Lickorish showed that every knot in the 3-sphere is concordant to a prime knot, equivalently, every concordance class contains a prime knot. We prove here that their result can be strengthened: Every knot in the 3-sphere is invertibly concordant to a prime knot. A consequence is that every double concordance class contains a prime knot.

Gregory G. Smith, Bernd Sturmfels

This tutorial illustrates how to use Grayson and Stillman&#39;s computer algebra system, Macaulay2, to study schemes. The examples are taken from the homework for an algebraic geometry class given at the University of California, Berkeley in the fall of 1999. This graduate course was taught by the second author with assistance for the first author. Our choic

Anatole Katok, Svetlana Katok, Klaus Schmidt

We show that for certain classes of actions of Z^d, d >= 2, by automorphisms of the torus any measurable conjugacy has to be affine, hence measurable conjugacy implies algebraic conjugacy; similarly any measurable factor is algebraic, and algebraic and affine centralizers provide invariants of measurable conjugacy. Using the algebraic machinery of dual modul

Grigori Olshanski, Amitai Regev, Anatoly Vershik

We introduce and study a family of inhomogeneous symmetric functions which we call the Frobenius-Schur functions. These functions are indexed by partitions and differ from the conventional Schur functions in lower terms only. Our interest in these new functions comes from the fact that they provide an explicit expression for the dimension of a skew Young dia

Anton Dzhamay

In this paper we present a construction of a new class of explicit solutions to the WDVV (or associativity) equations. Our construction is based on a relationship between the WDVV equations and Whitham (or modulation) equations. Whitham equations appear in the perturbation theory of exact algebro-geometric solutions of soliton equations and are defined on th

Ehab Malkawi, E. I. Lashin, Hatem Widyan

A scenario based on the TopFlavor model is presented to explain the origin of a light sterile neutrino as indicated by all combined neutrino oscillation experiments. The model is phenomenologically well motivated and compatible with all available low-energy data. The derived nuetrino mass matrix can qualitatively explain the observed hierarchy in the neutrin

Michael Krämer, Fredrick I. Olness, Davison E. Soper

We investigate a simplified version of the ACOT prescription for calculating deeply inelastic scattering from Q^2 values near the squared mass M_H^2 of a heavy quark to Q^2 much larger than M_H^2.

Mitesh Patel, George M. Fuller

Taken at face value, current experimental data indicate the existence of a new particle, the sterile neutrino, which must be a singlet under the Standard Model gauge group. Although they are not detectable through traditional means, such particles have interesting observable consequences for particle astrophysics and cosmology. Here we examine these implicat

Bahram Mashhoon

The theory of measurement is employed to elucidate the physical basis of general relativity. For measurements involving phenomena with intrinsic length or time scales, such scales must in general be negligible compared to the (translational and rotational) scales characteristic of the motion of the observer. Thus general relativity is a consistent theory of

Ken Satoh

This paper presents a method of computing a revision of a function-free normal logic program. If an added rule is inconsistent with a program, that is, if it leads to a situation such that no stable model exists for a new program, then deletion and addition of rules are performed to avoid inconsistency. We specify a revision by translating a normal logic pro

Ken Satoh, Hidenori Okamoto

In this paper, we consider a method of computing minimal models in circumscription using integer programming in propositional logic and first-order logic with domain closure axioms and unique name axioms. This kind of treatment is very important since this enable to apply various technique developed in operations research to nonmonotonic reasoning. Nerode et

Vladimir Privman

Selected theoretical developments in modeling of deposition of submicrometer size (submicron) particles on solid surfaces, with and without surface diffusion, of interest in colloid, polymer, and certain biological systems, are surveyed. We review deposition processes involving extended objects, with jamming and its interplay with in-surface diffusion yieldi

L. Solimany

Classical transport properties of an electron, moving in plain, in an array of magnetic antidot has been calculated. The homogeneous magnetic field in z-direction fills the whole space except of cylinders of radius r_0. The magnetoresistance shows additional peak and minimum according to pinned orbits at antidots and to propagating orbits in transport direct

S. S. Safonov, S. H. Roshko, A. K. Savchenko, A. G. Pogosov

The resistance R of the 2DEG on the vicinal Si surface shows an unusual behaviour, which is very different from that in the (100) Si MOSFET where an unconventional metal to insulator transition has been reported. The crossover from the insulator with dR/dT<0 to the metal with dR/dT>0 occurs at a low resistance of R_{\Box}^c \sim 0.04h/e^2. At the low-tempera

Rosa M. Gonzalez Delgado, Enrique Perez

The ultraviolet resonance wind stellar lines, the nebular optical emission lines and the higher order terms of the Balmer series and HeI absorption lines detected in the spectra of NGC 604 are interpreted using evolutionary models optimized for young star forming regions. The evolutionary state and the massive stellar content of the region is derived in a se

Zakir F. Seidov, P. I. Skvirsky

The relation between the gravitational potential energy, W, the central potential, U, and the mass, M: W/U/M is considered for various homogeneous and inhomogeneous self-gravitating bodies.

Mitesh Patel, George M. Fuller

Phase transitions in the early universe are prime settings for the production of primordial black holes, since they can break the relatively quiescent homogeneity and isotropy of Friedmann-Robertson-Walker (FRW) cosmologies. These epochs of &#34;symmetry breaking,&#34; moreover, can affect the subsequent development of spacetime by changing the evolution of

Eduardo Eyras, Sudhakar Panda

We investigate the classical geometry generated by a stable non-BPS D-particle. We consider the boundary state of a stable non-BPS D-particle in the covariant formalism in the type IIB theory orbifolded by (-1)^{F_L} I_4. We calculate the scattering amplitude between two D-particles in the non-compact and compact orbifold and analyse the short and long dista

J. Dyks, B. Rudak

The separation $\del$ between two peaks in the gamma-ray pulse profile is calculated as a function of energy for several polar cap models with curvature-radiation-induced cascades. The Monte Carlo results are interpreted with the help of analytical approximations and discussed in view of the recent data analysis for the Vela pulsar (Kanbach 1999). We find th

Aya Bamba, Jun Yokogawa, Masaaki Sakano, Katsuji Koyama

We present the results of deep ASCA observations of two shell-like radio supernova remnants (SNRs) located in the direction to the Galactic center (GC) region. Unlike the radio morphology, G359.1-0.5 shows center-filled X-rays with prominent K-alpha lines of He-like silicon and H-like sulfur. The plasma requires at least two temperature components: a silicon

Makoto Narita, Takashi Torii, Kengo Maeda

We study $T^{3}$ Gowdy spacetimes in the Einstein-Maxwell-dilaton-axion system and show by the Fuchsian algorithm that they have in general asymptotically velocity-term dominated singularities. The families of the corresponding solutions depend on the maximum number of arbitrary functions. Although coupling of the dilaton field with the Maxwell and/or the ax

Rob Clifton

In a recent article, Dieks has proposed a way to implement the modal interpretation of (nonrelativistic) quantum theory in relativistic quantum field theory. We show that his proposal fails to yield a well-defined prescription for which observables in a local spacetime region possess definite values. On the other hand, we demonstrate that there is a well-def

Andrei Khrennikov

We analyse the proof of Bell&#39;s inequality and demonstrate that this inequality is related to one particular model of probability theory, namely Kolmogorov measure-theoretical axiomatics, 1933. We found a (numerical) statistical correction to Bell&#39;s inequality. Such an additional term in the right hand side of Bell&#39;s inequality can be considered a

Andrei Khrennikov

We use the system of p-adic numbers for the description of information processes. Basic objects of our models are so called transformers of information, basic processes are information processes, the statistics are information statistics (thus we present a model of information reality). The classical and quantum mechanical formalisms on information p-adic sp

A. Kuzmich, E. S. Polzik

A set of protocols for atomic quantum state teleportation and swapping utilizing Einstein-Podolsky-Rosen light is proposed. The protocols are suitable for collective spin states of a macroscopic sample of atoms, i.e. for continuous atomic variables. Feasibility of experimental realization for teleportation of a gas sample of atoms is analyzed.

B. Aune

The conceptional design of the proposed linear electron-positron collider TESLA is based on 9-cell 1.3 GHz superconducting niobium cavities with an accelerating gradient of Eacc >= 25 MV/m at a quality factor Q0 > 5E+9. The design goal for the cavities of the TESLA Test Facility (TTF) linac was set to the more moderate value of Eacc >= 15 MV/m. In a first se

Jacob Sonnenschein

In these lectures we describe the attempt to extract the expectation values of Wilson loops from the string/gauge correspondence. We start with the original calculation in $AdS_5$. It is then extended to the non-conformal background of $D_p$ in the near horizon limit. We discuss the computation at finite temperature. Supergravity models that admit confinemen

M. Beneke, I. Efthymiopoulos, M. L. Mangano, J. Womersley

We review the prospects for studies of the top quark at the LHC.

Hitoshi Murayama

This is a very pedagogical review of supersymmetry phenomenology, given at ICTP Summer School in 1999, aimed mostly at students who had never studied supersymmetry before. It starts with an analogy that the reason why supersymmetry is needed is similar to the reason why the positron exists. It introduces the construction of supersymmetric Lagrangians in a pr

Saeid Davatolhagh, Bruce R. Patton

We consider the idea of bond ordering as a model for glass transition: a generic covalently bonded liquid may substantially reduce its energy through bond ordering, without undergoing significant structural order. This concept is developed for a model system using quantities such as a bond order parameter and susceptibility which provide new identification f

Takashi Hotta, Andre Luiz Malvezzi, Elbio Dagotto

The main properties of realistic models for manganites are studied using analytic mean-field approximations and computational numerical methods, focusing on the two-orbital model with electrons interacting through Jahn-Teller (JT) phonons and/or Coulombic repulsions. Analyzing the model including both interactions by the combination of the mean-field approxi

Silvano Molendi, Sabrina De Grandi, Roberto Fusco-Femiano

We present results from a spatially resolved spectral analysis of the merging cluster Abell 2256. The long integration time (135 ks) and the good spatial resolution of the MECS onboard BeppoSAX allow us to derive a new and substantially improved measurement of the temperature structure. We find that, within a central region of the cluster, where the effects

Ioulia V. Artemova, Gennadi S. Bisnovatyi-Kogan, Igor V. Igumenshchev, Igor D. Novikov

Global solutions of optically thick advective accretion disks around black holes are constructed. The solutions are obtained by solving numerically a set of ordinary differential equations corresponding to a steady axisymmetric geometrically thin disk. We pay special attention to consistently satisfy the regularity conditions at singular points of the equati

Masashi Shimada, Youichi Ohyama, Shingo Nishiura, Takashi Murayama

In order to investigate the nuclear activity of galaxies residing in compact groups of galaxies, we present results of our optical spectroscopic program made at Okayama Astrophysical Observatory. We have performed optical spectroscopy of 69 galaxies which belong to 31 Hickson Compact Groups (HCGs) of Galaxies. Among them, three galaxies have discordant redsh

Tohru Nagao, Yoshiaki Taniguchi, Takashi Murayama

Recently Murayama & Taniguchi proposed that a significant part of the high-ionization nuclear emission-line region (HINER) in Seyfert nuclei arises from the inner wall of dusty tori because type 1 Seyfert nuclei (S1s) show the excess HINER emission with respect to type 2 Seyfert ones (S2s). This means that the radiation from the HINER has the anisotropic pro

Todd A. Thompson, Adam Burrows, J. E. Horvath

We investigate the rates of production and thermalization of $ν_μ$ and $ν_τ$ neutrinos at temperatures and densities relevant to core-collapse supernovae and protoneutron stars. Included are contributions from electron scattering, electron-positron annihilation, nucleon-nucleon bremsstrahlung, and nucleon scattering. For the scattering processes, in order to

Lev I. Deych, A. A. Lisyansky

The structure of polariton spectrum is analyzed for periodic multiple quantum well structures with periods at or close to Bragg resonance condition at the wavelength of the exciton resonance. The results obtained used to discuss recent reflection and luminescent experiments by M. Hübner et al [Phys. Rev. Lett. {\bf 83}, 2841 (1999)] carried out with long mul

Colin Rourke, Brian Sanderson

This is the second of three papers about the Compression Theorem. We give proofs of Gromov&#39;s theorem on directed embeddings [M Gromov, Partial differential relations, Springer--Verlag (1986); 2.4.5 C&#39;] and of the Normal Deformation Theorem [The compression theorem I; 4.7], arxiv:math.GT/9712235.

Horst G. Kausch

We study two-dimensional conformal field theories generated from a ``symplectic fermion&#39;&#39; - a free two-component fermion field of spin one - and construct the maximal local supersymmetric conformal field theory generated from it. This theory has central charge c=-2 and provides the simplest example of a theory with logarithmic operators. Twisted stat

J. M. Cline

I review recent progress on the electroweak phase transition and baryogenesis, focusing on the minimal supersymmetric standard model as the source of new physics.

HongSheng Zhao, Danny Pronk

While the Hubble constant can be derived from observable time delays between images of lensed quasars, the result is often highly sensitive to assumptions and systematic uncertainties in the lensing model. Unlike most previous authors we explore a broad class of models with non-parametric lens radial profile and allow for non-elliptical lens potentials. The

G. S. Adkins, R. N. Fell, J. Sapirstein

Order α^2 corrections to the decay rate of orthopositronium are calculated in the framework of nonrelativistic QED. The resulting contribution is found to be in significant disagreement with one set of experimental measurements though another experiment is in agreement with theory.

Ph. Boucaud, G. Burgio, F. Di Renzo, J. P. Leroy

We report on very strong evidence of the occurrence of power terms in $\as(p)$, the QCD running coupling constant in the $\widetilde{MOM}$ scheme, by analyzing non-perturbative measurements from the lattice three-gluon vertex between 2.0 and 10.0 GeV at zero flavor. While putting forward the caveat that this definition of the coupling is a gauge dependent on

Lucia Baroni, Roberto Livi, Alessandro Torcini

Spatially extended dynamical systems, namely coupled map lattices, driven by additive spatio-temporal noise are shown to exhibit stochastic synchronization. In analogy with low-dymensional systems, synchronization can be achieved only if the maximum Lyapunov exponent becomes negative for sufficiently large noise amplitude. Moreover, noise can suppress also t

Steen Hannestad, Robert J. Scherrer

It has been shown by many independent studies that the cold dark matter scenario produces singular galactic dark halos, in strong contrast with observations. Possible remedies are that either the dark matter is warm so that it has significant thermal motion or that the dark matter has strong self interactions. We have combined these ideas to calculate the li

Martin C. Bonsager, Yong Baek Kim, A. H. MacDonald

We report on a study of the phonon-mediated frictional drag between two-dimensional electron layers at the Landau level filling factor $ν=1/2$ predicted by Chern-Simons composite-fermion theory. Frictional drag between widely spaced layers is dominated by the phonon-mediated interaction and is altered from its zero-field form because of the large composite-f

A. Rajantie, E. J. Copeland

We show by studying the Abelian Higgs model with numerical lattice simulations that non-thermal phase transitions arising out of preheating after inflation are possible in gauge-Higgs models under rather general circumstances. This may lead to the formation of gauged topological defects and, if the scale at which inflation ends is low enough, to electroweak

Amihay Hanany, Barak Kol

We find some lifts to M theory of orientifold and orbifold planes including the O1, O3 and O5 planes of Type IIB and their transformations under SL(2,Z). The possible discrete torsion variants (or K theory classes) are explored, and are interpreted as arising from brane intersections with planes. We find new variants of the O0 and of an orbifold line (OF1) a

V. Buehner, Chr. Tamm

We experimentally investigate the resonance fluorescence spectrum of single 171Yb and 172Yb ions which are laser cooled to the Lamb-Dicke regime in a radiofrequency trap. While the fluorescence scattering of 172Yb is continuous, the 171Yb fluorescence is interrupted by quantum jumps because a nonvanishing rate of spontaneous transitions leads to electron she

Ralph Blumenhagen, Lars Goerlich, Boris Kors, Dieter Lust

We investigate the D-brane contents of asymmetric orbifolds. Using T-duality we find that the consistent description of open strings in asymmetric orbifolds requires to turn on background gauge fields on the D-branes. We derive the corresponding noncommutative geometry arising on such D-branes with mixed Neumann-Dirichlet boundary conditions directly by appl

A. K. Hartmann, I. A. Campbell

True ground states are evaluated for a 2d Ising model with random near neighbor interactions and ferromagnetic second neighbor interactions (the Randomly Coupled Ferromagnet). The spin glass stiffness exponent is positive when the absolute value of the random interaction is weaker than the ferromagnetic interaction. This result demonstrates that in this para