June 2001 arXiv papers — page 6

Dimitri Debruyne, Jan Ryckebusch

An unfactorized and relativistic framework for calculating A(e,e'p) observables at typical JLAB energies is presented. Results of (e,e'p) model calculations for the target nuclei ^{12}C and ^{16}O are presented and compared to data from SLAC and JLAB.

Yu. G. Zdesenko, O. A. Ponkratenko, V. I. Tretyak

The GEM project is designed for the next generation 2 beta decay experiments with 76-Ge. One ton of ''naked'' HP Ge detectors (natural at the first GEM-I phase and enriched in 76-Ge to 86% at the second GEM-II stage) are operating in super-high purity liquid nitrogen contained in the Cu vacuum cryostat (sphere with diameter 5 m). The latest i

M. V. Fistul, J. B. Page

We give a theoretical study of unusual resistive (dynamic) localized states in anisotropic Josephson junction ladders, driven by a DC current at one edge. These states comprise nonlinearly coupled rotating Josephson phases in adjacent cells, and with increasing current they are found to expand into neighboring cells by a sequence of sudden jumps. We argue th

E. V. Ferapontov

Hydrodynamic surfaces are solutions of hydrodynamic type systems viewed as non-parametrized submanifolds of the hodograph space. We propose an invariant differential-geometric characterization of hydrodynamic surfaces by expressing the curvature form of the characteristic web in terms of the reciprocal invariants.

I. Antoniou, S. A. Shkarin, E. Yarevsky

We study a family of chaotic maps with limit cases the tent map and the cusp map (the cusp family). We discuss the spectral properties of the corresponding Frobenius--Perron operator in different function spaces including spaces of analytic functions. A numerical study of the eigenvalues and eigenfunctions is performed.

A. J. Roberts

I previously used Burgers' equation to introduce a new method of numerical discretisation of \pde{}s. The analysis is based upon centre manifold theory so we are assured that the discretisation accurately models all the processes and their subgrid scale interactions. Here I show how boundaries to the physical domain may be naturally incorporated into the

P. F. Kelly, Terry Pilling

Recently we have introduced a novel characterisation of the distribution of twin primes that consists of three essential elements. These are: that the twins are most naturally viewed as a subsequence of the primes themselves, that the likelihood of a particular prime in sequence being the first element of a twin is akin to a fixed-probability random event, a

Laurent Evain

Let H_{ab} be the equivariant Hilbert scheme parametrizing the 0-dimensional subschemes of the affine plane invariant under the natural action of the one-dimensional torus T_{ab}:={(t^{-b},t^a), t\in k^*}. We compute the irreducible components of H_{ab}: they are in one-one correspondence with a set of Hilbert functions. As a by-product of the proof, we give

Jean Berstel, Laurent Vuillon

We show that the coding of rotation by $α$ on $m$ intervals with rationally independent lengths can be recoded over $m$ Sturmian words of angle $α.$ More precisely, for a given $m$ an universal automaton is constructed such that the edge indexed by the vector of values of the $i$th letter on each Sturmian word gives the value of the $i$th letter of the codin

Shigeru Yamagami

Free products of semisimple tesnor categories are constructed with the help of polygonal presentation. The semisimplicity criterion is obtained for the Bisch-Jones' planar algebras as a byproduct.

Philip Foth

The purpose of this note is to give a simple description of a (complete) family of functions in involution on certain hermitian symmetric spaces. This family, obtained via bi-hamiltonian approach using the Bruhat Poisson structure, is especially simple for the projective spaces, where the formulas in terms of the moment map coordinates are presented. We show

Adel Bilal

After an introduction to N=2 susy Yang-Mills theories, I review in some detail, for the SU(2) gauge group, how the low-energy effective action is obtained using duality and the constraints arising from the supersymmetry. Then I discuss how knowledge of this action, duality and certain discrete symmetries allow us to determine the spectra of stable BPS states

David Langlois, Maria Rodriguez-Martinez

We consider ``cosmologically symmetric'' (i.e. solutions with homogeneity and isotropy along three spatial dimensions) five-dimensional spacetimes with a scalar field and a three-brane representing our universe. We write Einstein's equations in a conformal gauge, using light-cone coordinates. We obtain explicit solutions: a. assuming proportional

B. de Carlos, M. B. Hindmarsh, N. McNair, J. M. Moreno

We study domain walls in two different extensions of super Yang--Mills characterized by the absence of a logarithmic term in their effective superpotential. The models, defined by the usual gaugino condensate and an extra field Y, give different patterns of domain walls despite both leading to the same effective limit for heavy Y, i.e. the Veneziano--Yankiel

David J. Gross, Vipul Periwal

Motivated by noncommutative Chern-Simons theory, we construct an infinite class of field theories that satisfy the axioms of Witten's string field theory. These constructions have no propagating open string degrees of freedom. We demonstrate the existence of non-trivial classical solutions. We find Wilson loop-like observables in these examples.

Renata Kallosh, Lev Kofman, Andrei Linde, Arkady Tseytlin

The possibility to study the M/string theory cosmology via 5d bulk & brane action is investigated. The role of the 4-form field in the theory of BPS branes in 5d is clarified. We describe arguments suggesting that the effective 4d description of the universe in the ekpyrotic scenario (hep-th/0103239) should lead to contraction rather than expansion of the un

P. J. Heslop, P. S. Howe

We discuss composite operators in N=4 super Yang-Mills theory and their realisations as superfields on different superspaces. The superfields that realise various operators on analytic superspace may be different in the free, interacting and quantum theories. In particular, in the quantum theory, there is a restricted class of operators that can be written a

Biswarup Mukhopadhyaya, Soumitra SenGupta, Saurabh Sur

The possibility of parity violation through spacetime torsion has been explored in a scenario containing fields with different spins. Taking the Kalb-Ramond field as the source of torsion, an explicitly parity violating $U(1)_{EM}$ gauge invariant theory has been constructed by extending the KR field with a Chern-Simons term.

M. E. Carrington, Hou Defu, R. Kobes

We study nonlinear response in weakly coupled nonequilibrium $ϕ^4$ theory in the context of both classical transport theory and real time quantum field theory, based on a generalized Kubo formula which we derive. A novel connection between these two approaches is established which provides a diagrammatic interpretation of the Boltzmann equation.

Ernest Ma, G. Rajasekaran

The leptonic Higgs doublet model of neutrino masses is implemented with an A_4 discrete symmetry (the even permutation of 4 objects or equivalently the symmetry of the tetrahedron) which has 4 irreducible representations: 1, 1', 1'', and 3. The resulting spontaneous and soft breaking of A_4 provides a realistic model of charged-lepton masses as w

Carl E. Carlson

This is a summary of perturbative QCD calculations of baryon form factors. For e^+ e^- going to baryon-antibaryon pairs, normalized calculations are available and reported for the entire ground state octet and decuplet, including off-diagonal form factors, and for the S_{11}(1535)-antiS_{11}. (The latter results are new for this report.) We also include some

M. Sullivan

The PEP-N project consists of a small, very low-energy e- storage ring (VLER) located in one of the interaction-straight regions of PEP-II. The small ring is brought into collision with the low-energy (3.1 GeV) e+ beam (LER). The center-of-mass energies from this collision are between the Phi and J/Psi resonances. We achieve a head-on collision through the u

A. D. Martin

We briefly review some of the developments in the study of parton distributions which have occurred since DIS2000, including discussion of uncertainties, shadowing, unintegrated and generalized distributions.

Kenneth Lane

I propose a resolution of the strong CP problem of quarks based on vacuum alignment in theories of dynamically broken electroweak and flavor symmetries. Mixing in the neutral B and K--meson systems is used to restrict the form of quark mass and mixing matrices and to constrain the masses of the topcolor gauge bosons V_8 and Z' to be greater than 5 TeV. T

M. N. Chernodub, E. -M. Ilgenfritz, A. Schiller

The compact Abelian model in three space--time dimensions is studied in the presence of external electromagnetic fields at finite temperatures. We show that the deconfinement phase transition is independent on the strength of the external fields. This result is in agreement with our observation that the external fields create small--size magnetic dipoles fro

UKQCD Collaboration, A. M. Green, J. Koponen, P. Pennanen

In nuclear many-body problems the short-range correlation between two nucleons is well described by the corresponding correlation in the {two}-body problem. Therefore, as a first step in any attempt at an analogous description of many-quark systems, it is necessary to know the two-quark correlation. With this in mind, we study the light quark distribution in

FOCUS Collaboration, Jonathan M. Link

We report on a direct measurement of the mixing parameter y=(3.42+-1.39+-0.74)% in the D0-D0bar system by measuring the lifetime difference between the CP mixed final state K^+pi^- and the CP even state K^+K^-. We also present a study of the decay \ws based on a sample of 149+-31 observed events compared to 36760+-195 events observed in the Cabibbo favored c

E. Pasqualucci

A very preliminary study for a trigger for the PEP-N experiment is presented. Its aim is to show the feasibility of a very efficient trigger for multihadronic events based on energy releases in the electromagnetic calorimeter. Though the efficiency of such a trigger is very high and simple topology requirements can be applied to reduce cosmic background, an

R. J. Taylor

The present status of the measurements of hadronic structure functions of the photon, investigated in deep inelastic electron-photon scattering at LEP, is presented. This article covers the hadronic structure function F_2^gamma of quasi-real photons as well as the structure function of virtual photons. Special emphasis is given to new developments in the ana

S G Ghosh, R V Saraykar, A Beesham

Gravitational collapse of radiation shells in a non self-similar higher dimensional spherically symmetric spacetime is studied. Strong curvature naked singularities form for a highly inhomogeneous collapse, violating the cosmic censorship conjecture. As a special case, self similar models can be constructed.

Mustafa Ozcan

We construct the Hadamard Green's function by using the eigenfunction, which are obtained by solving the wave equation for the massless conformal scalar field on the S^n-1 of a n-dimensional closed, static universe. We also consider the half space case with both the Dirichlet and the Neumann boundary conditions. Solving of eigenfunction and eigenvalues o

Oscar J. C. Dias

It is well known that massive black holes may form through the gravitational collapse of a massive astrophysical body. Less known is the fact that a black hole can be produced by the quantum process of pair creation in external fields. These black holes may have a mass much lower than their astrophysical counterparts. This mass can be of the order of Planck

Ronald J. Adler, Pisin Chen, David I. Santiago

In the current standard viewpoint small black holes are believed to emit radiation as black bodies at the Hawking temperature, at least until they reach Planck size, after which their fate is open to conjecture. A cogent argument against the existence of remnants is that, since no evident quantum number prevents it, black holes should radiate completely away

Valentin D. Gladush

We consider 5D spaces which admit the most symmetric 3D subspaces. 5D vacuum Einstein equations are constructed and 5D analog of the mass function is found. The corresponding conservation law leads to 5D analog of Birkhoff's theorem. Hence the cylinder condition is dynamically implemented for the considered spaces. For some obtained metrics a period of s

Dmitri Soshnikov

The paper discusses the basic principles and the architecture of the software toolkit for constructing knowledge-based systems which can be used cooperatively over computer networks and also embedded into larger software systems in different ways. Presented architecture is based on frame knowledge representation and production rules, which also allows to int

Alexander Serebrenik, Danny De Schreye

We present a new approach to termination analysis of numerical computations in logic programs. Traditional approaches fail to analyse them due to non well-foundedness of the integers. We present a technique that allows to overcome these difficulties. Our approach is based on transforming a program in way that allows integrating and extending techniques origi

Danny De Schreye, Alexander Serebrenik

We present a new approach to termination analysis of logic programs. The essence of the approach is that we make use of general orderings (instead of level mappings), like it is done in transformational approaches to logic program termination analysis, but we apply these orderings directly to the logic program and not to the term-rewrite system obtained thro

S. Sivasubramanian, A. Widom

The physical kinetics of single domain ferroelectric materials are studied using Landau-Khalatnikov equation. The hysteretic curves are obtained numerically. The effective coercive electric field theoretically varies with the driving amplitude and frequency. The effects of thermal noise are explored using the Fokker-Planck kinetic equation. The ferroelectric

M. Eschrig, D. Rainer, J. A. Sauls

We investigate the equilibrium and nonequilibrium properties of the core region of vortices in layered superconductors. We discuss the electronic structure of singly and doubly quantized vortices for both s-wave and d-wave pairing symmetry. We consider the intermediate clean regime, where the vortex-core bound states are broadened into resonances with a widt

Kelly R. Patton, Michael R. Geller

We calculate the vibrational density-of-states in an insulating nanoparticle that is in weak mechanical contact with a semi-infinite substrate. The work is motivated by a recent experiment by Yang et al., where the low-energy phonon density-of-states of Y2O3 nanoparticles doped with Eu was measured. Preliminary results presented here, based on the convention

Denis Bartolo, Imre Derenyi, Armand Ajdari

We analyze the response of molecular adhesion complexes to increasing pulling forces (dynamic force spectroscopy) when dissociation can occur along either one of two alternative trajectories in the underlying multidimensional energy landscape. A great diversity of behaviors (e.g. non-monotonicity) is found for the unbinding force and time as a function of th

Raul Gago, Luis Vazquez, Rodolfo Cuerno, Maria Varela

We report on the production of ordered assemblies of silicon nanostructures by means of irradiation of a Si(100) substrate with 1.2 keV Ar ions at normal incidence. Atomic Force and High-Resolution Transmission Electron microscopies show that the silicon structures are crystalline, display homogeneous height, and spontaneously arrange into short-range hexago

Eugene M. Chudnovsky

Spatial dependence of the magnetic field and the superconducting current in a flux line pinned by a screw dislocation are computed. Interaction of a superconducting vortex with the chiral-symmetry breaking elastic strain of a screw dislocation results in a helical current along the axis of the dislocation. It is argued that screw dislocations make impossible

Jonathan Yedidia, Jean-Philippe Bouchaud

We explain an algorithm that approximately but efficiently assesses particular parity-check error-correcting codes of large, but finite, blocklength. This algorithm is based on the ``renormalization-group'' approach from physics: the idea is to continually replace an error-correcting code with a simpler error-correcting code that has nearly identical

Jean-Philippe Bouchaud, Vincent Dupuis, Jacques Hammannn, Eric Vincent

We summarize the different puzzles raised by aging experiments of spin-glasses and their various interpretations. We try to reconcile the `real space', droplet like pictures with the hierarchical pictures that have been proposed in the past. The basic ingredient is a strong separation of the time scales that govern the dynamics of the system on different

A. Emperador, M. Pi, M. Barranco, E. Lipparini

We present a systematic study of ground state and spectroscopic properties of many-electron nanoscopic quantum rings. Addition energies at zero magnetic field (B) and electro-chemical potentials as a function of $B$ are given for a ring hosting up to 24 electrons. We find discontinuities in the excitation energies of multipole spin and charge density modes,

Z. Y. Zeng, L. D. Zhang, X. H. Yan, J. Q. You

We investigate theoretically the resonant splitting of ballistic conductance peaks in magnetic superlattices. It is found that, for magnetic superlattices with periodically arranged $n$ identical magnetic-barriers, there exists a general $(n-1)$-fold resonant peak splitting rule for ballistic conductance, which is the analogy of the $(n-1)$-fold resonant spl

Byounghak Lee, T. Jungwirth, A. H. MacDonald

We predict that a novel bias-voltage assisted magnetization reversal process will occur in Mn doped II-VI semiconductor quantum wells or heterojunctions with carrier induced ferromagnetism. The effect is due to strong exchange-coupling induced subband mixing that leads to electrically tunable hysteresis loops. Our model calculations are based on the mean-fie

Vadym Vekslerchik, Victor M. Perez-Garcia

We find the explicit solution of a two--mode model used to explain vortex dynamics in multicomponent Bose-Einstein condensates. We prove that all the solutions are constants or periodic functions and give explicit formulae for the time evolution of the populations of the two atomic species present in the condensate.

A. Diaz-Sanchez, Antonio de Candia, Antonio Coniglio

We study the relaxation process in a two-dimensional lattice gas model, where the interactions come from the excluded volume. In this model particles have three arms with an asymmetrical shape, which results in geometrical frustration that inhibits full packing. A dynamical crossover is found at the arm percolation of the particles, from a dynamical behavior

G. Campagnano, D. Giuliano, A. Tagliacozzo

We apply a Gutzwiller-like variational technique to study Josephson conduction across a quantum dot with an odd number of electrons connected to two superconducting leads. We show that, for small values of the superconducting gap, Kondo correlations and superconductivity cooperate to enhance the Josephson current. As the superconducting gap increases, the cu

P. E. Jönsson, S. Felton, P. Svedlindh, P. Nordblad

The effect of applied magnetic fields on the collective nonequilibrium dynamics of a strongly interacting Fe-C nanoparticle system has been investigated. It is experimentally shown that the magnetic aging diminishes to finally disappear for fields of moderate strength. The field needed to remove the observable aging behavior increases with decreasing tempera

S. I. Shevchenko, E. D. Vol

It is shown that in bilayer conducting structures in crossed electric and magnetic fields of a special configuration (the fields should have opposite signs in the adjacent layers) the dependence of the energy of a pair of equally charged carriers on the momentum of the pair has a local minimum. This minimum corresponds to a bound state of the pair. The local

V. Bondah-Jagalu, S. T. Bramwell

The series of magnetic rare earth pyrochlore stannates R2Sn2O7 (R = rare earth, except Ce and Pm) have been investigated by powder susceptibility measurements down to T =1.8 K. The results are compared to results for the analogous titanate series, which are well-known frustrated magnets. Unlike the titanates, the whole series can be formed in the cubic pyroc

K. E. Nagaev

Metal microbridges with a high impurity content and shorter than the energy relaxation length are considered. Their conductance is calculated with allowance made for the Coulomb electron-electron interaction. It is shown that nonequilibrium electrons in the microbridges gives rise to a nonlinear current-voltage characteristic (published in Physics Letters A,

Andrea Pelissetto, Paolo Rossi, Ettore Vicari

We compute the chiral critical exponents for the chiral transition in frustrated two- and three-component spin systems with noncollinear order, such as stacked triangular antiferromagnets (STA). For this purpose, we calculate and analyze the six-loop field-theoretical expansion of the renormalization-group function associated with the chiral operator. The re

M. Kraemer, L. Pitaevskii, S. Stringari, F. Zambelli

Using a semi-analytic model based on the Thomas-Fermi approximation, we investigate the relevance of the quadrupole deformation of a trapped Bose-Einstein condensate for the nucleation of quantized vortices. For sufficiently high angular velocities $Ω$ of the trap, the tendency of the system to exhibit spontaneous deformation is shown to lower the barrier wh

Pietro Caputo, Fabio Martinelli

We consider the anisotropic three dimensional XXZ Heisenberg ferromagnet in a cylinder with axis along the 111 direction and boundary conditions that induce ground states describing an interface orthogonal to the cylinder axis. Let $L$ be the linear size of the basis of the cylinder. Because of the breaking of the continuous symmetry around the $\hat z$ axis

U. Alver, R. G. Goodrich, N. Harrison, Donavan Hall

Measurements of the de Haas-van Alphen effect in CexLa1-xRhIn5 reveal that the Ce 4f electrons remain localized for all x, with the mass enhancement and progressive loss of one spin from the de Haas-van Alphen signal resulting from spin fluctuation effects. This behavior may be typical of antiferromagnetic heavy fermion compounds, inspite of the fact that th

H. Sakai, K. Yoshimura, H. Ohno, H. Kato

We make the first report that a metallic pyrochlore oxide \Cd2Re2O7, exhibits type II superconductivity at 1.1 K. The pyrochlore oxide is known to be a geometrical frustrated system, which includes the tetrahedral network of magnetic ions. A large number of compounds are classified in the family of pyrochlore oxides, and these compounds exhibit a wide variet

D. Sornette, A. Johansen

We clarify the status of log-periodicity associated with speculative bubbles preceding financial crashes. In particular, we address Feigenbaum's [2001] criticism and show how it can be rebuked. Feigenbaum's main result is as follows: ``the hypothesis that the log-periodic component is present in the data cannot be rejected at the 95% confidence level

V. M. Apalkov, Tapash Chakraborty

We consider a system of a incompressible quantum Hall liquid in close proximity to a parabolic quantum dot containing a few electrons. We observe a significant influence of the interacting electrons in the dot on the excitation spectrum of the incompressible state in the electron plane. Our calculated charge density indicates that unlike in the case of an im

N. A. Frederick, Shi Li, M. B. Maple, V. F. Nesterenko

We present electrical transport, magnetization, and specific heat measurements on bulk MgB2 samples (T_{c} = 38.5 K) synthesized under 200 MPa pressure using a process based on hot isostatic pressing with cooling under pressure. The samples are fully dense and display excellent superconducting properties, including a narrow superconducting transition width (

I. M. Suslov

Answer to cond-mat/0106005 and cond-mat/0106006 and additional notes are given concerning to my previous comment (cond-mat/0105324).

I. M. Suslov

Numerical results for Anderson transition are critically discussed. A simple procedure to deal with corrections to scaling is suggested. With real uncertainties taken into account, the raw data are in agreement with a value $ν=1$ for the critical index of the correlation length in three dimensions.

B. M. Gaensler, M. J. Pivovaroff, G. P. Garmire

We present observations with the Chandra X-ray Observatory of the pulsar wind nebula (PWN) within the supernova remnant G0.9+0.1. At Chandra's high resolution, the PWN has a clear axial symmetry; a faint X-ray point source lying along the symmetry axis possibly corresponds to the pulsar itself. We argue that the nebular morphology can be explained in ter

Robert W. O'Connell

M82 is the nearest starburst galaxy. It contains two large systems of super star clusters, one being spawned today in the active starforming core, and one produced by an earlier starburst event which coincided with the last orbital passage of its neighbor, M81. The proximity of M82 makes it uniquely valuable for a wide range of studies of massive young clust

Robert J. Brunner, S. George Djorgovski, Thomas A. Prince, Alex S. Szalay

Astronomy has a long history of acquiring, systematizing, and interpreting large quantities of data. Starting from the earliest sky atlases through the first major photographic sky surveys of the 20th century, this tradition is continuing today, and at an ever increasing rate. Like many other fields, astronomy has become a very data-rich science, driven by t

Bruce Macintosh, Claire Max, Ben Zuckerman, Eric E. Becklin

Adaptive optics (AO) on 8-10 m telescopes is an enormously powerful tool for studying young nearby stars. It is especially useful for searching for companions. Using AO on the 10-m W.M. Keck II telescope we have measured the position of the brown dwarf companion to TWA5 and resolved the primary into an 0.055 arcsecond double. Over the next several years foll

Randall K. Smith, Nancy S. Brickhouse, Duane A. Liedahl, John C. Raymond

New X-ray observatories (Chandra and XMM-Newton) are providing a wealth of high-resolution X-ray spectra in which hydrogen- and helium-like ions are usually strong features. We present results from a new collisional-radiative plasma code, the Astrophysical Plasma Emission Code (APEC), which uses atomic data in the companion Astrophysical Plasma Emission Data

Lesley K. Summers, Ian R. Stevens, David K. Strickland

We present ROSAT HRI X-ray data and optical imaging of the important dwarf starburst Markarian 33. We find an extended, complex, shell-like morphology in the X-ray emission, with an extent of 2.3 x 1.9kpc, coincident with the bright star-forming regions at the centre of the galaxy. The physical extent of this X-ray emission from Mrk 33 is very similar to the

P. R. Wozniak, A. Udalski, M. Szymanski, M. Kubiak

We present a sample of microlensing events discovered in the Difference Image Analysis (DIA) of the OGLE-II images collected during 3 observing seasons, 1997--1999. 4424 light curves pass our criteria on the presence of a brightening episode on top of a constant baseline. Among those, 512 candidate microlensing events were selected visually. We designed an a

Matt J. Jarvis, Steve Rawlings, Chris J. Willott, Katherine M. Blundell

We use three samples (3CRR, 6CE and 6C*) selected at low radio frequency to constrain the cosmic evolution in the radio luminosity function (RLF) for the `most luminous' steep-spectrum radio sources. Although intrinsically rare, such sources give the largest possible baseline in redshift for the complete flux-density-limited samples currently available.

S. L. Dubovsky, P. G. Tinyakov

The observed clustering of ultra-high energy cosmic rays suggests the existence of a neutral component. The models with violation of Lorentz invariance may explain this component by neutrons becoming stable above some threshold energy E_0. The protons, in turn, may become unstable above some energy E_1>E_0. We calculate the dependence of the threshold energi

Stefano Borgani

This Meeting featured the recent advancements in our understanding of galaxy clusters and the distant Universe, achieved by the past and new generation of X-ray satellites. I summarize here the main themes that have been discussed: (a) Clusters of galaxies as probes of cosmological models; (b) The physics of cosmic baryons trapped within the potential wells

C. P. Dullemond, C. Dominik, A. Natta

A model for irradiated dust disks around Herbig Ae stars is proposed. The model is based on the flaring disk model of Chiang & Goldreich (1997), but with the central regions of the disk removed. The inner rim of the disk is puffed up and is much hotter than the rest of the disk, because it is directly exposed to the stellar flux. If located at the dust evapo

Wolfgang Brandner, Dan Potter, Scott S. Sheppard, Andrea Moneti

There is strong evidence that the planets in the solar system evolved from a disk-shaped solar nebula ~4.56 Gyr ago. By studying young stars in various evolutionary stages, one aims at tracing back the early history of the solar system, in particular the timescales for disk dissipation and for the formation of planetary systems. We used the VLT & ISAAC, and

E. Bertone, A. Buzzoni, M. Chavez, L. H. Rodriguez

The fitting atmosphere parameters (Teff, g, and [Fe/H]) for over 300 stars in the Gunn & Striker and Jacoby et al. catalogs have been obtained relying on the Kurucz (1992) ATLAS9 and Hauschildt et al (1999) NextGen5 synthesis models. The output results are compared, and a critical appraisal of both theoretical codes is performed.

H. Arp

Recent analyses of Cepheid distances to spiral galaxies have led to an announcement of a Hubble constant of $H_0 = 72 \pm 8$ km/sec/Mpc. The new Cepheid distances, however, show that there are numerous redshift distances with large excesses which cannot be due to peculiar velocities. Ignoring these discordant redshifts, if the Hubble constant is calibrated w

Volker Ossenkopf, Christoph Trojan, Juergen Stutzki

We present observations of 15 massive cores in three different CS transitions from the FCRAO 14m and the KOSMA 3m telescope. We derive physical parameters of these cores using different approaches to the line radiative transfer problem. The local radiative transfer approximations fail to provide reliable values except for the column densities. A self-consist

Nazar Ikhsanov

Observational appearance of a neutron star in the subsonic propeller state which is a companion of a wind-fed mass-exchange close binary system is discussed. During the subsonic propeller state the neutron star magnetosphere is surrounded by a spherical quasi-static plasma envelope, which is extended from the magnetospheric boundary up to the star accretion

M. R. Burleigh, M. A. Barstow, K. J. Schenker, A. I. Sills

We present FUSE H Lyman series spectroscopy of the hot white dwarf companion to the 4th magnitude A1III star Beta Crateris, which shows that is has an unusually low mass, 0.43Msun, and has almost certainly evolved through binary interaction. This system could be a long-sought remnant of Algol-type evolution, although radial velocity measurements appear to sh

Valery V. Kravtsov

I propose and apply a method for deriving ages of the metal-poor globular clusters (GCs) in a distance-independent way, which is based on age indicator related to the main sequence in the two-color diagrams with U-B index. Age of the metal-poor GC NGC 6397 has been estimated, using Yale isochrones of Demarque et al. (1996), to be close to 16 Gyr provided the

Takao Nakagawa

ASTRO-F is the second Japanese space mission for infrared astronomy and is scheduled to be launched into a sun-synchronous polar orbit by the Japanese M-V rocket in February 2004. ASTRO-F has a cooled 67 cm telescope with two focal plane instruments: one is the Far-Infrared Surveyor (FIS) and the other is the Infrared Camera (IRC). The main purpose of FIS is

Duncan A. Forbes, Jean P. Brodie, Soeren S. Larsen

There is now strong evidence that the metal-rich globular clusters (GC) near the center of our Galaxy are associated with the Galactic bulge rather than the disk as previously thought. Here we extend the concept of bulge GCs to the GC systems of nearby spiral galaxies. In particular, the kinematic and metallicity properties of the GC systems favor a bulge ra

Jean P. Brodie

New and archival HST images of the globular cluster systems of 17 relatively nearby galaxies and 6 more distant galaxies have been used to establish the characteristics of GC subpopulations over a range of host galaxy morphological type from E5 to Sa. GC color/metallicity, size and luminosity distributions have been examined in the nearby galaxies and color

S. Dos Santos, O. Doré

Semi-analytic models of X-ray clusters and groups of galaxies, relying on the idea that there was a non-gravitational energy injection in these systems, are able to reproduce many observed correlations, in particular the L_X-T relation and the ``central entropy floor'' in groups. Limiting models exist which describe the behaviour of clusters and grou

Guillermo Garcia-Segura, Jose Alberto Lopez, Jose Franco

The Hubble Space Telescope has revealed the existence of multiple, regularly spaced, and faint concentric shells around some planetary nebulae. Here we present 2(1/2)D magnetohydrodinamic numerical simulations of the effects of a solar-like magnetic cycle, with periodic polarity inversions, in the slow wind of an AGB star. The stellar wind is modeled with a

Jon Urrestilla, Ana Achucarro, Julian Borrill, Andrew R. Liddle

We use large-scale numerical simulations to study the formation and evolution of non-topological defects in a generalized electroweak phase transition described by the Glashow-Salam-Weinberg model without fermions. Such defects include dumbbells, comprising a pair of monopoles joined by a segment of electroweak string. These exhibit complex dynamics, with so

Antoine Georges, Rahul Siddharthan, Serge Florens

We propose a theory of the spin dynamics of frustrated quantum antiferromagnets, which is based on an effective action for a plaquette embedded in a self-consistent bath. This approach, supplemented by a low-energy projection, is applied to the kagome antiferromagnet. We find that a spin-liquid regime extends to very low energy, in which local correlation fu

Joe Kiskis, Rajamani Narayanan

The spectrum of the overlap Dirac operator in the deconfined phase of quenched gauge theory is known to have three parts: exact zeros arising from topology, small nonzero eigenvalues that result in a non-zero chiral condensate, and the dense bulk of the spectrum, which is separated from the small eigenvalues by a gap. In this paper, we focus on the small non

John N. Bahcall, M. C. Gonzalez-Garcia, Carlos Pena-Garay

For active and sterile neutrinos, we present the globally allowed solutions for two neutrino oscillations. We include the SNO CC measurement and all other relevant solar neutrino and reactor data. Five active neutrino oscillation solutions (LMA, LOW, SMA, VAC, and Just So2) are currently allowed at 3 sigma; three sterile neutrino solutions (Just So2, SMA, an

R. Stompor, A. Balbi, J. D. Borrill, P. G. Ferreira

This work describes Cosmic Microwave Background (CMB) data analysis algorithms and their implementations, developed to produce a pixelized map of the sky and a corresponding pixel-pixel noise correlation matrix from time ordered data for a CMB mapping experiment. We discuss in turn algorithms for estimating noise properties from the time ordered data, techni

M. D. Girardeau, E. M. Wright

A number-conserving hybrid Bose-Fermi variational theory is developed and applied to investigation of the BEC-Tonks gas crossover in toroidal and long cylindrical traps of high aspect ratio, where strong many-body correlations and condensate depletion occur.

Sandip Bhattacharyya, Alok Kumar, Swapna Mahapatra

We consider quantization of open string theories in linear dilaton and constant antisymmetric tensor backgrounds and discuss the noncommutativity of space-time coordinates arising in such theories, including their relationship with light-like noncommutativity as well as backgrounds with null isometries. It is argued that the results can also be understood us

Michael Martin Nieto

In modern fundamental theories there is consideration of higher dimensions, often in the context of what can be written as a Schrödinger equation. Thus, the energetics of bound states in different dimensions is of interest. By considering the quantum square well in continuous $D$ dimensions, it is shown that there is always a bound state for $0<D \le 2$. Thi

Marco Tucci, Angela Contaldo, Silvio Bonometto

Using COBE-DMR 4-year data, we find a general expression yielding the likelihood distribution in the 3-dimensional parameter space spanned by the spectral index $n$, the spectral amplitude $a_{10}$ and the false-vacuum density parameter $Ω_Λ$. Using such simple expression, the range of possible normalizations, within a given likelihood interval from top-like

Ana M. Curiel, Maria J. Herrero, David Temes, Jorge F. de Troconiz

In this work we study the indirect effects of squarks and gluinos via supersymmetric QCD radiative corrections in the decays of Higgs particles within the Minimal Supersymmetric Standard Model. We consider a heavy supersymmetric spectrum and focus on the main nondecoupling effects. We propose a set of observables that are sensitive to these corrections and t

Ian G Moss, Wade Naylor

The effective action of the radion in the Randall-Sundrum model is analysed. Fine tunings are needed to obtain the observed mass hierarchy and an invisible radion. since the kinetic terms are important for determining the radion mass, the finite quantum corrections from massless conformally coupled fermions are analysed and found to vanish at one loop order.

Yves Brihaye, Betti Hartmann, Jutta Kunz

We study gravitating monopoles and non-abelian black holes of SU(2) Einstein-Yang-Mills-Higgs theory coupled to a massless dilaton. The domain of existence of these solutions decreases with increasing dilaton coupling constant. The critical solutions of this system are Einstein-Maxwell-dilaton solutions.