October 2000 arXiv papers — page 9

Hajime Tsuji

We develop an intersection theory for a singular hemitian line bundle with positive curvature current on a smooth projective variety and irreducible curves on the variety. And we prove the existence of a natural rational fibration structure associated with the singular hermitian line bundle. Also for any pseudoeffective line bundle on a smooth projective var

Valery N. Marachevsky

General formalism of quantum field theory and addition theorem for Bessel functions are applied to derive formula for Casimir-Polder energy of interaction between a polarizable particle and a dilute dielectric ball. The equivalence of dipole-dipole interaction and Casimir energy for dilute homogeneous dielectrics is shown. A novel method is used to derive Ca

Ludwik Turko

The dynamics governing the evolution of a many body system is constrained by a nonabelian local symmetry. We obtain explicit forms of the global macroscopic condition assuring that at the microscopic level the evolution respects the overall symmetry constraint.

A. Bashir, A. Kizilersu, M. R. Pennington

We derive constraints on the non-perturbative 3-point fermion-boson transverse vertex in massless QED3 from its perturbative calculation to order $α$. We also check the transversality condition to two loops and evaluate the fermion propagator to the same order. We compare a conjecture of the non-perturbative vertex by Burden and Tjiang against our results an

Marijan Ribaric, Luka Sustersic

We consider properties of connected diagrams with fermion-photon interaction and such fermion and photon propagators and vertex function that the values of these diagrams are finite. We establish the properties of these propagators and vertex function that imply that these diagrams are invariant under C, P, T, CP, CT, PT, or CPT transformations up to some ph

Brian R. Greene, Koenraad Schalm, Gary Shiu

We study topology change in M theory compactifications on Calabi-Yau three-folds in the presence of G flux (the four form field strength). In particular, we discuss vacuum solutions in strongly coupled heterotic string theory in which the topology change is inevitable within a single spacetime background. For rather generic choices of initial conditions, the

Andrei Mikhailov

We introduce a class of supersymmetric cycles in spacetimes of the form AdS times a sphere or $T^{1,1}$ which can be considered as generalizations of the giant gravitons. Branes wrapped on these cycles preserve $1\over 2$, $1\over 4$ or $1\over 8$ of the supersymmetry. On the CFT side these configurations correspond to superpositions of the large number of B

I. Dymnikova, L. Koziel, M. Khlopov, S. Rubin

We investigated the bubble collisions during the first order phase transitions. Numerical results indicate that within the certain range of parameters the collision of two bubbles leads to formation of separate relatively long-lived quasilumps - configurations filled with scalar field oscillating around the true vacuum state. Energy is perfectly localized, a

Y. S. Myung

The question of whether the Kaluza-Klein (KK) graviphoton $h_{5μ}$ and graviscalar $h_{55}$ are localized or not on the brane is one of the important issues. In this letter, we address this problem in five dimensions. Here we consider the massless (zero-mode) propagations without requiring the Z$_2$-symmetry on $h_{5μ}$. We obtain the graviton $h_{μν}$, grav

Alfredo Aranda, Christopher D. Carone

A topcolor model is presented that contains both composite and fundamental scalar fields. Strong dynamics accounts for most of the top quark mass and part of the electroweak symmetry breaking scale. The fundamental scalar is weakly coupled and transmits its share of electroweak symmetry breaking to the light fermions. The model is allowed by the current expe

Peter John

In order to generate the baryon asymmetry of the Universe sufficiently strong CP violation is needed. It was therefore proposed that at finite temperature there might be spontaneous (transitional) CP violation within the bubble walls at the electroweak phase transition in supersymmetric models. We investigate this question in the MSSM.

M. Laine

Standard theories of electroweak interactions are based on the concept of a gauge symmetry broken by the Higgs mechanism. If they are placed in an environment with a sufficiently high temperature, the symmetry gets restored. It turns out that the characteristics of the symmetry restoring phase transition, such as its order, are important for cosmological app

A. Hebecker, T. Teubner

We show that the diffractive structure function is perturbatively calculable in the domain where the diffractive mass is small but still outside the resonance region. In this domain, which can be characterized by Lambda^2/Q^2 << 1-beta << (Lambda^2/Q^2)^1/2, the structure function represents a new observable, which is highly sensitive to the small-x skewed g

Eugene Levin

This is a talk, given at Diffraction&#39;2000, Sept. 2 - 7, Centraro, Italy. In this talk, we present the arguments, that a new QCD regime - gluon saturation, has been reached at HERA.

Eugene Levin

This is a talk, given at Diffraction&#39;2000, Sept. 2 - 7, Centraro, Italy. This talk is a brief presentation of our view on the Pomeron, as a non-perturbative QCD phenomenon but from sufficiently short distances. Our approach is based on the scale anomaly of QCD and emphasizes the r{ô}le of semi-classical QCD vacuum fields. We show that both the intercept

Xiao-Jun Bi, Yuan-Ben Dai, Xiao-Yuan Qi

The study for lepton flavor violation combined with the neutrino oscillation may provide more information about the lepton flavor structure of the grand unified theory. In this paper, we study two lepton flavor violation processes, $τ\to μγ$ and $Z\to τμ$, in the context of supersymmetric SO(10) grand unified models. We find the two processes are both of phe

Nam-Young Lee, K. Goeke, C. Weiss

The result for the matrix element A(I=2) = -0.14 F_pi^2 appears to be an artifact of an improper ultraviolet regularization. Paper withdrawn pending resolution of this problem.

Dean Lee, Nathan Salwen, Mark Windoloski

We propose a method for eliminating the truncation error associated with any subspace diagonalization calculation. The new method, called stochastic error correction, uses Monte Carlo sampling to compute the contribution of the remaining basis vectors not included in the initial diagonalization. The method is part of a new approach to computational quantum p

K. Jansen

We report on a lattice computation of the second moment of the pion matrix element of the twist-2 non-singlet operator corresponding to the average momentum of parton densities. We apply a fully non-perturbatively evaluated running renormalization constant as well as a careful extrapolation of our results to the continuum limit. Thus the only limitation of o

Bernd A. Berg

For the measurement of $N_s$ signals in $N$ events rigorous confidence bounds on the true signal probability $p_{\rm exact}$ were established in a classical paper by Clopper and Pearson [Biometrica 26, 404 (1934)]. Here, their bounds are generalized to the HEP situation where cuts on the data tag signals with probability $P_s$ and background data with likeli

Akos Csilling

A preliminary update of the previous OPAL measurement of the inclusive production of D* mesons in anti-tagged photon-photon collisions is presented together with the first preliminary OPAL measurement of bottom production in photon-photon collisions.

Paul Halpern

We extend the induced matter model, previously applied to a variety of isotropic cases, to a generalization of Bianchi type-I anisotropic cosmologies. The induced matter model is a 5D Kaluza-Klein approach in which assumptions of compactness are relaxed for the fifth coordinate, leading to extra geometric terms. One interpretation of these extra terms is to

J. Frauendiener, L. B. Szabados

The dimension of the kernels of the edth and edth-prime operators on closed, orientable spacelike 2-surfaces with arbitrary genus is calculated, and some of its mathematical and physical consequences are discussed.

Stephen Fairhurst, Badri Krishnan

We present new solutions to the Einstein-Maxwell equations representing a class of charged distorted black holes. These solutions are static-axisymmetric and are generalizations of the distorted black hole solutions studied by Geroch and Hartle. Physically, they represent a charged black hole distorted by external matter fields. We discuss the zeroth and fir

Karhan Akcoglu, James Aspnes, Bhaskar DasGupta, Ming-Yang Kao

Two general algorithms based on opportunity costs are given for approximating a revenue-maximizing set of bids an auctioneer should accept, in a combinatorial auction in which each bidder offers a price for some subset of the available goods and the auctioneer can only accept non-intersecting bids. Since this problem is difficult even to approximate in gener

D. C. Cabra, M. D. Grynberg, A. Honecker, P. Pujol

This is a short review of recent theoretical work on magnetization plateaux in one-dimensional strongly correlated electron systems, i.e. in spin chains, spin ladders or more generally, Hubbard chains and ladders.

Wolfgang Ketterle, Ananth P. Chikkatur, Chandra Raman

The coherent and collective nature of Bose-Einstein condensate can enhance or suppress physical processes. Bosonic stimulation enhances scattering in already occupied states which leads to atom amplification, and the suppression of dissipation leads to superfluidity. In this paper, we review several experiments where suppression and enhancement have been obs

Jose A. Miranda

We investigate the flow of two immiscible, viscous fluids in a rotating Hele-Shaw cell, when one of the fluids is a ferrofluid and an external magnetic field is applied. The interplay between centrifugal and magnetic forces in determining the instability of the fluid-fluid interface is analyzed. The linear stability analysis of the problem shows that a non-u

Chang-Soo Park, Anupam Garg

We study the points of degeneracy (diabolical points) in magnetic molecules such as Mn_{12}-acetate that have an easy axis of four-fold symmetry. This is done for general magnetic field that need not be oriented along a high-symmetry direction. We develop a perturbative technique that gives the diabolical points as the roots of a small number of polynomials

B. P. Dolan, D. Johnston

It is known that the (exact) renormalization transformations for the one-dimensional Ising model in field can be cast in the form of a logistic map f(x) = 4 x (1 - x) with x a function of the Ising couplings. Remarkably, the line bounding the region of chaotic behaviour in x is precisely that defining the Yang-Lee edge singularity in the Ising model. In this

A. P. Young

This talk describes how techniques developed by Computer Scientists have helped our understanding of certain problems in statistical physics which involve randomness and ``frustration&#39;&#39;. Examples will be given from two problems that have been widely studied: the ``spin glass&#39;&#39; and the ``random field model&#39;&#39;.

Sebastiao Correia, Janos Polonyi, Jean Richert

A simple model is presented for the calculation of the quenched average over impurities which are rendered static by setting their mass equal to infinity. The path integral formalism of the second quantized theory contains annealed averages only. The similarity with the Gaussian quenched potential model is discussed.

German Drazer, Joel Koplik

Tracer diffusion and hydrodynamic dispersion in two-dimensional fractures with self-affine roughness is studied by analytic and numerical methods. Numerical simulations were performed via the lattice-Boltzmann approach, using a new boundary condition for tracer particles that improves the accuracy of the method. The reduction in the diffusive transport, due

Chi-Ok Hwang, James A. Given, Michael Mascagni

We describe two efficient methods of estimating the fluid permeability of standard models of porous media by using the statistics of continuous Brownian motion paths that initiate outside a sample and terminate on contacting the porous sample. The first method associates the &#34;penetration depth&#34; with a specific property of the Brownian paths, then use

Doron Cohen

There are three regimes in the theory of energy absorption: The adiabatic regime, the linear-response (Kubo) regime, and the non-perturbative regime. The mesoscopic Drude formula for electrical conductance, and the wall formula for friction, can be regarded as special cases of the general formulation of the dissipation problem. The overview is based on a res

Doron Cohen

The motion of a particle under the influence of a dynamical disorder is described by the DLD model. One motivation is to understand the motion of an electron inside a metal; Another is to understand quantal Brownian motion. The overview is based on a research report for 1996-1998.

D. Mandrus, J. R. Thompson, R. Gaal, L. Forro

Cd2Os2O7 crystallizes in the pyrochlore structure and undergoes a metal-insulator transition (MIT) near 226 K. We have characterized the MIT in Cd2Os2O7 using X-ray diffraction, resistivity at ambient and high pressure, specific heat, magnetization, thermopower, Hall coefficient, and thermal conductivity. Both single crystals and polycrystalline material wer

M. Annunziato, P. Grigolini, B. J. West

We address the problem of the dynamical foundation of non-canonical equilibrium. We consider, as a source of divergence from ordinary statistical mechanics, the breakdown of the condition of time scale separation between microscopic and macroscopic dynamics. We show that this breakdown has the effect of producing a significant deviation from the canonical pr

M. -H. Julien, A. Campana, A. Rigamonti, P. Carretta

We report on 139La and 63Ccu NMR/NQR measurements in the high-Tc superconductor La1.90Sr0.10CuO4 with Tc=26.5 K. Spin fluctuations probed by 139La spin-lattice relaxation (T1), continuously slow down on cooling through Tc. We argue that spin-freezing and superconductivity are bulk effects in this sample. Thus, both phenomena have to coexist microscopically.

F. Mazzanti, A. Polls, J. Boronat

The high-momentum dynamic structure function of liquid 3He-4He mixtures has been studied introducing final state effects. Corrections to the impulse approximation have been included using a generalized Gersch-Rodriguez theory that properly takes into account the Fermi statistics of 3He atoms. The microscopic inputs, as the momentum distributions and the two-

Massimo Campostrini, Martin Hasenbusch, Andrea Pelissetto, Paolo Rossi

We improve the theoretical estimates of the critical exponents for the three-dimensional XY universality class. We find alpha=-0.0146(8), gamma=1.3177(5), nu=0.67155(27), eta=0.0380(4), beta=0.3485(2), and delta=4.780(2). We observe a discrepancy with the most recent experimental estimate of alpha; this discrepancy calls for further theoretical and experimen

L. Šamaj, B. Jancovici

An ideal conductor electrode in contact with a semi-infinite two-dimensional two-component plasma in an external potential is considered. The model is mapped onto an integrable sine-Gordon theory with Dirichlet boundary conditions. The information gained from the mapping provides an explicit form of the surface tension in the plasma-stability regime.

Zeno Farkas, Tamas Fulop

Motivated by a novel method for granular segregation, we analyze the one dimensional drift-diffusion between two absorbing boundaries. The time evolution of the probability distribution and the rate of absorption are given by explicit formulae, the splitting probability and the mean first passage time are also calculated. Applying the results we find optimal

S. Hørlück, P. Dimon

We have used particle tracking methods to study the dynamics of individual balls comprising a granular flow in a small-angle two-dimensional funnel. We statistically analyze many ball trajectories to examine the mechanisms of shock propagation. In particular, we study the creation of, and interactions between, shock waves. We also investigate the role of gra

Valeria Ferrari, Guillermo Chiappe, Enrique Anda

The system described in this work consists of a quantum dot inserted in a mesoscopic ring threaded by a magnetic flux. Our aim is to present a complete description for this device and to predict the physics of a experiment with these features. We have proposed a model that takes into account the conditions that are usual in experiments with quantum dots and

Shan-Wen Tsai, J. B. Marston

A Hubbard model at half-filling on an anisotropic triangular lattice has been proposed as the minimal model to describe conducting layers of $κ-(BEDT-TTF)_2X$ organic materials. The model interpolates between the square lattice and decoupled chains. The $κ-(BEDT-TTF)_2X$ materials present many similarities with cuprates, such as the presence of unconventiona

R. J. Rivers

The dual &#39;worldline&#39;, or &#39;string&#39;, description of adiabatic Ginzburg-Landau field theory near a phase transition in terms of quasi-Brownian strings and loops is well understood. In reality, the implementation of a transition is intrinsically non-equilibrium. We sketch how time-dependent Ginzburg-Landau theory leads to a modified dual string p

Q. A. Wang, M. Pezeril, L. Nivanen, A. Le Mehaute

The problem of factorization of a nonextensive probability distribution is discussed. It is shown that, in general, the correlation energy between the correlated subsystems in the canonical composite system can not be neglected even in the thermodynamic limit. In consequence, the factorization approximation should be employed carefully according to different

Roberto De Propris, Warrick J. Couch, the 2dFGRS Team

The 2dF Galaxy Redshift Survey has obtained 135,000 redshifts for galaxies in two broad strips. Here we present the first results of a 3-dimensional search for galaxy clusters based on known 2-dimensional compilations. We derive new redshifts and velocity dispersions for clusters, assess the level of contamination in the sample, analyze the accuracy of photo

C. Firmani, E. D&#39;Onghia, G. Chincarini

We investigate the density profiles and evolution of weakly self-interacting cold dark matter haloes using a numerical code based on the collisional Boltzmann equation. This approach is alternative to N-body techniques in following the dynamical evolution of haloes in the cosmological context and taking into account particle self-interaction. The physical ca

Parviz Ghavamian, John Raymond, R. Chris Smith, Patrick Hartigan

We present an observational and theoretical study of the optical emission from nonradiative shocks in three supernova remnants: the Cygnus Loop, RCW 86 and Tycho. The spectra of these shocks are dominated by collisionally excited hydrogen Balmer lines which have both a broad component caused by proton-neutral charge exchange and a narrow component caused by

Axel Brandenburg

Using a periodic box calculation it is shown that, owing to helicity conservation, a large scale field can only develop on a resistive timescale. This behaviour can be reproduced by a mean-field dynamo with alpha and eta_t quenchings that are equally strong and `catastrophic&#39;.

M. Feroci, K. Hurley, R. Duncan, C. Thompson

The giant flare of 1998 August 27 from SGR 1900+14 was extraordinary in many ways: it was the most intense flux of gamma rays ever detected from a source outside our solar system; it was longer than any previously detected burst from a soft gamma repeater (SGR) in our Galaxy by more than an order of magnitude; and it showed a remarkable four-peaked, periodic

Stuart L. Shapiro

Diffferentially rotating stars can support significantly more mass in equilibrium than nonrotating or uniformly rotating stars, according to general relativity. The remnant of a binary neutron star merger may give rise to such a ``hypermassive&#39;&#39; object. While such a star may be dynamically stable against gravitational collapse and bar formation, the

E. Pignatelli, G. Galletta

We present B and I band photometry, gas and star kinematics and 3D modelling of 7 giant spiral galaxies. The stellar systems studied have morphological types spanning from S0/a to Sc and absolute magnitudes from -20.6 to -22.5. The spectra have been collected with the spectrographs Boller & Chivens and EFOSC2 of the 2.2m ESO-MPI telescope. Images have been t

Eurico Covas, Reza Tavakol, David Moss

Recent analyses of the helioseismic observations indicate that the previously observed surface torsional oscillations with periods of about 11 years extend significantly downwards into the solar convective zone. Furthermore, there are indications that the dynamical regimes at the base of the convection zone are different from those observed at the top, havin

J. N. Reeves, M. J. L Turner, K. A. Pounds, P. T. O&#39;Brien

XMM-Newton observations of the low luminosity, radio-quiet quasar Markarian 205 have revealed a unique iron K emission line profile. In marked contrast to the broad and redshifted iron K line commonly seen in ASCA observations of Seyfert 1 galaxies, we find that a substantial amount of the line flux in Mrk 205 occurs above the neutral line energy of 6.4 keV.

David J. Nice, Eric M. Splaver, Ingrid H. Stairs

We report on nine years of timing observations of PSR J2019+2425, a millisecond pulsar in a wide 76.5 day orbit with a white dwarf. We measure a significant change over time of the projected semi-major axis of the orbit, x-dot/x=(1.3+-0.2)x10^-15 s^-1, where x=(a sin i)/c. We attribute this to the proper motion of the binary. This constrains the inclination

Edward F. Guinan, Ignasi Ribas

We have carried out an analysis of about 160 eclipse timings spanning over 30 years of the Hyades eclipsing binary V471 Tauri that shows a long-term quasi-sinusoidal modulation of its observed eclipse arrival times. The O-Cs have been analyzed for the ``light-time&#39;&#39; effect that arises from the gravitational influence of a tertiary companion. The pres

Maarten Reyniers, Hans Van Winckel

We present in this paper a study on the peculiar supergiant HD172481. Its spectral type (F2Ia), high galactic latitude (b=-10.37), circumstellar dust, high radial velocity and moderate metal deficiency ([Fe/H]=-0.55) confirm the post-AGB character of this object. A detailed chemical analysis shows slight but real s-process overabundances, however no CNO-enha

Stefano Bianchi, Giorgio Matt, Kazushi Iwasawa

The ASCA and BeppoSAX spectra of the Circinus Galaxy and NGC 1068 are analysed and compared with photoionization models based on cloudy. In the case of Circinus, a single, mildly ionized reflector can account for the line spectrum, while in NGC 1068 at least three different reflectors (with different ionization states) are needed. We suggest that the reflect

S. Capozziello, G. Iovane

We consider filamentary and planar large scale structures as possible refraction channels for electromagnetic radiation coming from cosmological structures. By this hypothesis, it is possible to explain the quasar luminosity distribution and, in particular, the presence of &#34;twin&#34; and &#34;brother&#34; objects. Method and details of simulation are giv

K. F. Gunn, I. M. McHardy, O. Almaini, T. Shanks

We present multiwaveband photometric and optical spectropolarimetric observations of the R=15.9 narrow emission line galaxy R117_A which lies on the edge of the error circle of the ROSAT X-ray source R117 (from McHardy et al 1998). The overall spectral energy distribution of the galaxy is well modelled by a combination of a normal spiral galaxy and a moderat

R. Morganti, T. A. Oosterloo, C. N. Tadhunter, K. A. Wills

We present a study, done with the Australian LBA, of HI absorption for two compact radio galaxies (PKS 1549-79 and PKS 1814-63). In both the radio galaxies, the HI appears to give us information about the environment in which the radio sources are embedded, the effect that the ISM can have on the observed characteristics and the possible presence of interact

P. G. Perez-Gonzalez, J. Gallego, J. Zamorano, A. Gil de Paz

We present Johnson B surface photometry for the UCM Survey galaxies. One-dimensional bulge-disk decomposition is attempted, discussing on fitting functions and computational procedures. The results from this decomposition, jointly with concentration indices and an asymmetry coefficient, are employed to study the morphological properties of these galaxies. We

P. J. E. Peebles, S. D. Phelps, Edward. J. Shaya, R. Brent Tully

Analysis of the peculiar velocities of galaxies should take account of the uncertainties in both redshifts and distances. We show how this can be done by a numerical application of the action principle. The method is applied to an improved catalog of the galaxies and tight systems of galaxies within 4$h_{75}^{-1}$ Mpc, supplemented with a coarser sample of t

Christian Fendt, Elisabetta Memola

The magnetic flux distribution is determined by the solution of the Grad-Shafranov equation. With differential rotation, i.e. the variation of the iso-rotation parameter, the shape of the light surface must be calculated in an iterative way. For the first time, we have calculated the force-free magnetic structure of truly two-dimensional, relativistic jets,

G. Efstathiou, S. J. Moody

We estimate the two- and three-dimensional power spectra, P_2(K) and P_3(k), of the galaxy distribution by applying a maximum likelihood estimator to pixel maps of the APM Galaxy Survey. The analysis provides optimal estimates of the power spectra and of their covariance matrices if the fluctuations are assumed to be Gaussian. Our estimates of P_2(K) and P_3

Lucio M. Buson, Francesco Bertola, David Burstein, Michele Cappellari

Newly obtained HST/WFPC2 images of the disturbed elliptical galaxy NGC 5018 show that the average amount of internal reddening due to the its complex ``dust web&#39;&#39; is as low as E(B-V)~0.02 within the IUE aperture, thus implying that its observed and intrinsic energy distributions do not differ significantly down to UV wavelengths. This, in turn, is qu

A. Comastri, G. M. Stirpe, C. Vignali, W. N. Brandt

The BeppoSAX observations of the bright Narrow-Line Seyfert 1 galaxy Ark 564 are presented along with a high quality optical spectrum taken at the 1.5m telescope at La Silla. The 0.1-10 keV X-ray spectrum is characterized by a strong soft component which is best described by blackbody-like emission with a temperature of about 160 eV. At higher energies a ste

Eduardo Battaner, Estrella Florido

We review the topic of rotation curves of spiral galaxies emphasizing the standard interpretation as evidence for the existence of dark matter halos. Galaxies other than spirals and late-type dwarfs may also possess great amounts of dark matter, and therefore ellipticals, dwarf spirals, lenticulars and polar ring galaxies are also considered. Furthermore, ot

John Ellis

Cosmic rays may provide opportunities for probing fundamental physics. For example, ultra-high-energy cosmic rays might originate from the decays of metastable heavy particles, and astrophysical gamma rays can be used to test models of quantum gravity. Both scenarios offer ways to avoid the GZK cut-off.

Edvard Mortsell

In this paper we use a generalized version of a method originally proposed by Holz and Wald to investigate the effects from gravitational lensing on Type Ia supernovae measurements. We find that results for different mass distributions in smooth dark matter halos are very similar, making lensing effects predictable for a broad range of density profiles. Also

T. W. Jones, Francesco Miniati, Dongsu Ryu, Hyesung Kang

We review the possible roles of large scale shocks as particle accelerators in clusters of galaxies. Recent observational and theoretical work has suggested that high energy charged particles may constitute a substantial pressure component in clusters. If true that would alter the expected dynamical evolution of clusters and increase the dynamical masses con

Lynne A. Hillenbrand, John M. Carpenter, M. F. Skrutskie

The Becklin-Neugebauer (BN) object in the Orion Nebula Cluster (ONC) is a well-studied optically invisible, infrared-bright young stellar object, thought to be an intermediate-mass protostar. We report here that BN exhibited nearly-sinusoidal periodic variability at the near-infrared H- and Ks-bands during a one month observing campaign in 2000 March/April.

Y. -H. Chu, B. C. Dunne, R. A. Gruendl, W. Brandner

Current searches for extrasolar planets have concentrated on observing the reflex Doppler shift of solar-type stars. Little is known, however, about planetary systems around non-solar-type stars. We suggest a new method to extend planetary searches to hot white dwarfs. Near a hot white dwarf, the atmosphere of a Jovian planet will be photoionized and emit hy

Alejandro Corichi, Daniel Sudarsky

Black hole entropy and its relation to the horizon area are considered. More precisely, the conditions and specifications that are expected to be required for the assignment of entropy, and the consequences that these expectations have when applied to a black hole are explored. In particular, the following questions are addressed: When do we expect to assign

Cedric Deffayet

We discuss the cosmology of a 3-brane embedded in a 5D bulk space-time with a cosmological constant when an intrinsic curvature Ricci scalar is included in the brane action. After deriving the `brane-Friedmann&#39; equations for a Z_2 symmetrical metric, we focus on the case of a Minkowski bulk. We show that there exist two classes of solutions, close to the

Iver Brevik, Kimball A. Milton, Shin&#39;ichi Nojiri, Sergei D. Odintsov

We consider the quantum effects of bulk matter (scalars, spinors) in the Randall-Sundrum AdS$_5$ brane-world at nonzero temperature. The thermodynamic energy (modulus potential) is evaluated at low and high temperatures. This potential has an extremum which could be a minimum in some cases (for example, for a single fermion). That suggests a new dynamical me

Michael Gutperle, Michal Spalinski

The dimensional reduction of eleven dimensional supergravity on a Calabi-Yau manifold gives N=2 supergravity in five dimensions with $h_{1,1}$ vector and $h_{2,1}+1$ hypermultiplets. In this paper instanton solutions are constructed which are responsible for nonperturbtative corrections to the hypermultiplet moduli spaces. These instantons are wrapped Euclid

Y. Chou, J. E. Grindlay, P. F. Bloser

We present the timing analysis results for our observations of the x-ray dip source X1916-053 conducted with RXTE between February and October of 1996. Our goal was to finally measure the binary period - as either the x-ray dip period or ~1% longer optical modulation period, thereby establishing if the binary has a precessing disk (SU UMa model) or a third s

G. Alexanian, A. Pinzul, A. Stern

We construct a star product associated with an arbitrary two dimensional Poisson structure using generalized coherent states on the complex plane. From our approach one easily recovers the star product for the fuzzy torus, and also one for the fuzzy sphere. For the latter we need to define the `fuzzy&#39; stereographic projection to the plane and the fuzzy s

R. J. Furnstahl, H. -W. Hammer, Negussie Tirfessa

The apparent dependence of nuclear matter observables on off-shell properties of the two-nucleon potential is re-examined in the context of the effective field theory (EFT) approach. Finite density (thermodynamic) observables are invariant under field redefinitions, which extends the well-known theorem about the invariance of S-matrix elements. Simple exampl

Andreas Klappenecker, Martin Roetteler

Knill introduced a generalization of stabilizer codes, in this note called Clifford codes. It remained unclear whether or not Clifford codes can be superior to stabilizer codes. We show that Clifford codes are stabilizer codes provided that the abstract error group has an abelian index group. In particular, if the errors are modelled by tensor products of Pa

Andreas Klappenecker, Martin Roetteler

Nice error bases have been introduced by Knill as a generalization of the Pauli basis. These bases are shown to be projective representations of finite groups. We classify all nice error bases of small degree, and all nice error bases with abelian index groups. We show that in general an index group of a nice error basis is necessarily solvable.

Thomas Mehen, Mark B. Wise

Higher order terms in the effective action of noncommutative gauge theories exhibit generalizations of the *-product (e.g. *&#39; and *-3). These terms do not manifestly respect the noncommutative gauge invariance of the tree level action. In U(1) gauge theories, we note that these generalized *-products occur in the expansion of some quantities that are inv

M. Granath, V. Oganesyan, S. A. Kivelson, E. Fradkin

We study the properties of a quasi-one dimensional superconductor which consists of an alternating array of two inequivalent chains. This model is a simple charicature of a locally striped high temperature superconductor, and is more generally a theoretically controllable system in which the superconducting state emerges from a non-Fermi liquid normal state.

Ezequiel Alvarez, Francisco D. Mazzitelli

The effective action for quantum fields on a $d$-dimensional spacetime can be computed using a non local expansion in powers of the curvature. We show explicitly that, for conformal fields and up to quadratic order in the curvature, the non local effective action is equivalent to the $d+1$ action for classical gravity in $AdS_{d+1}$ restricted to a $d-1$-bra

Conall Kennedy, Emil M. Prodanov

We investigate the cosmology of (4+1)-dimensional gravity coupled to a scalar field and a bulk anisotropic fluid within the context of the single-brane Randall-Sundrum scenario. Assuming a separable metric, a static fifth radius and the scalar to depend only on the fifth direction, we find that the warp factor is given as in the papers of Kachru, Schulz and

Luigi Amico, G. Falci, Rosario Fazio

We study the connection between the BCS pairing model and the inhomogeneous vertex model. The two spectral problems coincide in the quasi-classical limit of the off-shell Bethe Ansatz of the disordered six vertex model. The latter problem is transformed into an auxiliary spectral problem which corresponds to the diagonalization of the integrals of motion of

Gerald Dunne, Ian I. Kogan, Alex Kovner, Bayram Tekin

We analyze the finite temperature deconfining phase transition in 2+1 dimensional Georgi-Glashow model. We show explicitly that the transition is due to the restoration of the magnetic $Z_2$ symmetry and that it is in the Ising universality class. We find that neglecting effects of the charged $W$ bosons leads to incorrect predictions for the value of the cr

Paul P. van der Werf, Kirsten Kraiberg Knudsen, Ivo Labbe, Marijn Franx

Can the submillimeter counts and background be produced by applying a locally derived extinction correction to the population of Lyman break galaxies? We investigate the submillimeter emission of two strongly lensed Lyman break galaxies (MS1512+36-cB58 and MS1358+62-G1) and find that the procedure that is used to predict the submillimeter emission of the Lym

D. Klemm, W. A. Sabra

We obtain charged rotating black hole solutions to the theory of Einstein-Maxwell gravity with cosmological constant in five dimensions. Some of the physical properties of these black holes are discussed.

A. Banfi, Yu. L. Dokshitzer, G. Marchesini, G. Zanderighi

We present the results of QCD analysis of out-of-event-plane momentum distribution in 3-jet e+e- annihilation events. We consider the all-order resummed perturbative prediction and the leading power suppressed non-perturbative corrections to the mean value <K_out> and the distribution and explain their non-trivial colour structure. The technique we develop a

Marko Znidaric, Tomaz Prosen

We study a certain type of the celebrated Fermi-Pasta-Ulam particle chain, namely the inverted FPU model, where the inter-particle potential has a form of a quartic double well. Numerical evidence is given in support of a simple symbolic description of dynamics (in the regime of sufficiently high potential barrier between the wells) in terms of an (approxima

I. Prandoni, L. Gregorini, P. Parma, H. R. de Ruiter

This paper is part of a series reporting the results of the ATESP radio survey obtained at 1.4 GHz with the Australia Telescope Compact Array. The survey consists of 16 radio mosaics with ~8&#34;x14&#34; resolution and uniform sensitivity (1sigma noise level ~79 microJy) over the whole area of the ESO Slice Project redshift survey (~26 sq. degrees at decl. =

Suresh Govindarajan, T. Jayaraman

We present a method based on mutations of helices which leads to the construction (in the large volume limit) of exceptional coherent sheaves associated with the $(\sum_al_a=0)$ orbits in Gepner models. This is explicitly verified for a few examples including some cases where the ambient weighted projective space has singularities not inherited by the Calabi

Yan Guo, Gerhard Rein

The present paper completes our earlier results on nonlinear stability of stationary solutions of the Vlasov-Poisson system in the stellar dynamics case. By minimizing the energy under a mass-Casimir constraint we construct a large class of isotropic, spherically symmetric steady states and prove their nonlinear stability against general, i. e., not necessar

S. Boettcher, A. G. Percus

We explore a new general-purpose heuristic for finding high-quality solutions to hard optimization problems. The method, called extremal optimization, is inspired by self-organized criticality, a concept introduced to describe emergent complexity in physical systems. Extremal optimization successively replaces extremely undesirable variables of a single sub-

Julian Lee

I consider the giant gravitons in AdS5 x S5. By numerical simulation, I show a strong indication that there is no instanton solution describing the direct tunneling between the giant graviton in the S5 and its dual counterpart in the AdS5. I argue that it supports the supersymmetry breaking scenario suggested in hep-th/0008015