May 2002 arXiv papers — page 9

A. Capella, D. Sousa

The ratio of $J/ψ$ over Drell-Yan cross-sections as a function of the energy of the zero degree calorimeter in $Pb$ $Pb$ collisions has been computed in a comovers interaction model and compared with the results of a deconfining model. The predictions of the two models are different both for peripheral events and for very central ones. These differences are

TOF Collaboration

The reaction pp -> pp eta was measured at excess energies of 15 and 41 MeV at an external target of the Juelich Cooler Synchrotron COSY with the Time of Flight Spectrometer. About 25000 events were measured for the excess energy of 15 MeV and about 8000 for 41 MeV. Both protons of the process pp eta were detected with an acceptance of nearly 100% and the eta

L. Ts. Adzhemyan, N. V. Antonov, A. N. Vasil'ev

The field theoretic renormalization group is applied to Kraichnan's model of a passive scalar quantity advected by the Gaussian velocity field with the pair correlation function $\proptoδ(t-t')/k^{d+ε}$. Inertial-range anomalous scaling for the structure functions and various pair correlators is established as a consequence of the existence in the co

B. Banos

We complete the list of normal forms for effective 3-forms with constant coefficients with respect to the natural action of symplectomorphisms in \mathbb{R}^6. We show that the 3-form which corresponds to the Special Lagrangian equation is among the new members of the classification. The symplectic symmetry algebras and their Cartan prolongations for these f

Thomas H. Geisser

We study Weil-etale cohomology, introduced by Lichtenbaum for varieties over finite fields. In the first half of the paper we give an explicit description of the base change from Weil-etale cohomology to etale cohomology. As a consequence, we get a long exact sequence relating Weil-etale cohomology to etale cohomology, show that for finite coefficients the c

Franz Lemmermeyer

It is well known that the Galois group of an extension puts constraints on the structure of the relative ideal class groups. Using only basic parts of the theory of group representations, we give a unified approach to such results.

Massoud Amini, Alireza Medghalchi

We prove the existance and uniqueness of quasi-invariant measure on double cost space $K\backslash G/H$ and study the Fourier and Fourier-Stieltjes algebras of these spaces.

Massoud Amini

We give a characterization of the ''uniform closure'' of the dual of a $C^{*}$-algebra. Some applications in harmonic analysis are given.

Massoud Amini

Starting with a $W^{*}$-algebra $M$ we use the inverse system obtained by cutting down $M$ by its (central) projections to define an inverse limit of $W^{*}$-algebras, and show that how this pro-$W^{*}$-algebra encodes the local structure of $M$. For the $C^{*}$-algebras we do the same thing using their atomic enveloping $W^{*}$-algebra . We investigate the

Massoud Amini

We extend the concept of amenability of a Banach algebra $A$ to the case that there is an extra $\mathfrak A$-module structure on $A$, and show that when $S$ is an inverse semigroup with subsemigroup $E$ of idempotents, then $A=\ell^1(S)$ as a Banach module over $\mathfrak A=\ell^1(E)$ is module amenable iff $S$ is amenable. When $S$ is a discrete group, $\e

Massoud Amini, Alireza Medghalchi

For a locally compact Hausdorff semigroup S, the $L^\infty$ representation algebra R(S) was extensively studied by Dunkl and Ramirez. The Fourier-Stieltjes algebra F(S) of a topological semigroup was studied by Lau. The aim of this paper is to investigate these two algebras and study the amenability of them with respect to the structure of S.

Massoud Amini, Alireza Medghalchi

We introduce the notion of the Fourier and Fouier-Stieltjes algebra of a topological *-semigroup and show that these are commutative Banach algebras. For a class of foundation semigroups, we show that these are preduals of von Neumann algebras.

Massoud Amini

It is known that the generator of a strictly continuous one parameter unitary group in the multiplier algebra of a $C^{*}$-algebra is affiliated to that $C^{*}$-algebra . We show that under natural non degeneracy conditions, this self adjoint unbounded operator lies indeed in the (unbounded) multiplier algebra of the Pedersen's ideal of the $C^{*}$-algeb

Samuel Lelièvre

A nice trick for studying the billiard flow in a rational polygon is to unfold the polygon along the trajectories. This gives rise to a translation or half-translation surface tiled by the original polygon, or equivalently an Abelian or quadratic differential. Veech surfaces are a special class of translation surfaces with a large group of affine automorphis

E. V. Ferapontov

It is demonstrated that hypersurfaces with a flat centroaffine metric are governed by a system of nonlinear PDEs known as the equations of associativity of 2-dimensional topological field theory.

F. Ancona, A. Bressan, G. M. Coclite

This note is concerned with the study of the initial boundary value problem for systems of conservation laws from the point of view of control theory, where the initial data is fixed and the boundary data are regarded as control functions. We first consider the problem of controllability at a fixed time for genuinely nonlinear Temple class systems, and prese

G. Giachetta, L. Mangiarotti, G. Sardanashvily

Completely integrable Hamiltonian systems look promising for controllability since their first integrals are stable under an internal evolution, and one may hope to find a perturbation of a Hamiltonian which drives the first integrals at will. Action-angle coordinates are most convenient for this purpose. Written with respect to these coordinates, a Hamilton

Jan Snellman

Let A denote the ring of arithmetical functions with unitary convolution, and let V be a finite subset of the positive integers having the property that for every v in V, all unitary divisors of v lie in V. We study the truncation A_V, an artinian monomial quotient of a polynomial ring in finitely many indeterminates, isomorphic to the ``Artinified''

Nicolas Marco, Xavier Massaneda, Joaquim Ortega-Cerdà

We characterise interpolating and sampling sequences for the spaces of entire functions f such that f e^{-phi} belongs to L^p(C), p>=1 (and some related weighted classes), where phi is a subharmonic weight whose Laplacian is a doubling measure. The results are expressed in terms of some densities adapted to the metric induced by the Laplacian of phi. They ge

Bertrand Banos

We define a non-degenerated Monge-Ampere structure on a 6-manifold associated with a Monge-Ampere equation as a couple (Ω,ω), such that Ωis a symplectic form and ωis a 3-differential form which satisfies ω\wedgeΩ=0 and which is non-degenerated in the sense of Hitchin. We associate with such a couple an almost (pseudo) Calabi-Yau structure and we study its in

R. M. Skjelnes, C. Walter

We study infinite intersections of open subschemes and the corresponding intersection of Hilbert schemes. If $\{U_i\}$ is the collection of open subschemes of a variety $X$ containing a fixed point $P$, then we show that the Hilbert functor of flat and finite families on the spectrum of the local ring of $P$ is given by the intersection of ${\Cal H}_i$, wher

Tamas Hausel, Michael Thaddeus

We study the moduli spaces of flat SL(r)- and PGL(r)-connections, or equivalently, Higgs bundles, on an algebraic curve. These spaces are noncompact Calabi-Yau orbifolds; we show that they can be regarded as mirror partners in two different senses. First, they satisfy the requirements laid down by Strominger-Yau-Zaslow (SYZ), in a suitably general sense invo

E. Fiorani, G. Giachetta, G. Sardanashvily

A trivial bundle of regular connected invariant manifolds of a completely integrable Hamiltonian system can be provided with action-angle coordinates.

Yuri Rylov

Nondegenerate geometry (T-geometry) with nonsymmetric world function is considered. In application to the space-time geometry the asymmetry of world function means that the past and the future are not equivalent geometrically. T-geometry is described in terms of finite point subspaces and world function between pairs of points of these subsets, i.e. in the l

Andrea Posilicano

Let $A:D(A)\subseteq\H\to\H$ be an injective self-adjoint operator and let $τ:D(A)\to\X$, X a Banach space, be a surjective linear map such that $\|τϕ\|_\X\le c \|Aϕ\|_\H$. Supposing that \text{\rm Range}$ (τ')\cap\H' =\{0\}$, we define a family $A^τ_Θ$ of self-adjoint operators which are extensions of the symmetric operator $A_{|\{τ=0\}.}$. Any $ϕ$

H. L. Carrion, M. Rojas, F. Toppan

The symmetry algebra of a QFT in the presence of an external EM background (named "residual symmetry") is investigated within a Lie-algebraic, model independent scheme. Some results previously encountered in the literature are here extended. In particular we compute the symmetry algebra for a constant EM background in D=3 and D=4 dimensions. In D= 3

M. Cvetic, N. D. Lambert

We discuss the low energy effective action for the Bosonic and Fermionic zero-modes of a smooth BPS Randall-Sundrum domain wall, including the induced supergravity on the wall. The result is a pure supergravity in one lower dimension. In particular, and in contrast to non-gravitational domain walls or domain walls in a compact space, the zero-modes represent

Danny Birmingham, Massimiliano Rinaldi

We explore the bubble spacetimes which can be obtained from double analytic continuations of static and rotating black holes in anti-de Sitter space. In particular, we find that rotating black holes with elliptic horizon lead to bubble spacetimes only in dimension greater than five. For dimension greater than seven, the topology of the bubble can be non-sphe

Heinz J. Rothe

Using well known Lagrangean techniques for uncovering the gauge symmetries of a Lagrangean, we derive the transformation laws for the phase space variables corresponding to local symmetries of the Hamilton equations of motion. These transformation laws are shown to coincide with those derived by Hamiltonian methods based on the Dirac conjecture. The connecti

A. Smailagic, E. Spallucci

We find transformation matrices allowing to express non-commutative three dimensional harmonic oscillator in terms of an isotropic commutative oscillator, following ``philosophy of simplicity'' approach. Non-commutative parameters have physical interpretation in terms of an external magnetic field. Furthermore, we show that for a particular choice of

Inyong Cho

We investigate O(4) textures in a background with a positive cosmological constant. We find static solutions which co-move with the expanding background. There exists a solution in which the scalar field is regular at the horizon. This solution has a noninteger winding number smaller than one. There also exist solutions in which scalar-field derivatives are

Kazuo Fujikawa

A general path integral analysis of the separable Hamiltonian of Liouville-type is reviewed. The basic dynamical principle used is the Jacobi's principle of least action for given energy which is reparametrization invariant, and thus the gauge freedom naturally appears. The choice of gauge in path integral corresponds to the separation of variables in op

R. M. Ellem, V. V. Bazhanov

We examine some excited state energies in the non-unitary integrable quantum field theory obtained from the perturbation of the minimal conformal field theory model $M_{3,5}$ by its operator $ϕ_{2,1}$. Using the correspondence of this IQFT to the scaling limit of the dilute $A_2$ lattice model (in a particular regime) we derive the functional equations for t

M. Eliashvili, G. Tsitsishvili

Chern-Simons type gauge field is generated by the means of the singular area preserving transformations in the lowest Landau level of electrons forming fractional quantum Hall state. Dynamics is governed by the system of constraints which correspond to the Gauss law in the non-commutative Chern-Simons gauge theory and to the lowest Landau level condition in

K. Koepsell, F. Roose

We present a novel global E_7(7) symmetry in five-dimensional maximal supergravity as well as an E_8(8) symmetry in d=4. These symmetry groups which are known to be present after reduction to d=4 and d=3, respectively, appear as conformal extensions of the respective well-known hidden-symmetry groups. A global scaling symmetry of the Lagrangian is the key to

Steven B. Giddings

This is my contribution to the proceedings of Stephen Hawking's 60th birthday celebration. If the ideas of TeV scale gravity are correct, then black holes should be produced at accelerators that probe the TeV scale, and their decays should evidence one of Stephen's greatest discoveries, the phenomenon of black hole radiance.

E. Calzetta, B. L. Hu

In this paper we use an O(N)-invariant scalar field of unbroken symmetry to investigate whether an interacting quantum field at the next-to-leading order Large $N$ approximation may show signs of thermalization. We develop the closed time-path (CTP) two-particle irreducible (2PI) effective action in powers of 1/N, retaining up to next to leading order (O(1))

Keith A. Olive, Maxim Pospelov, Yong-Zhong Qian, Alain Coc

We reconsider several current bounds on the variation of the fine-structure constant in models where all gauge and Yukawa couplings vary in an interdependent manner, as would be expected in unified theories. In particular, we re-examine the bounds established by the Oklo reactor from the resonant neutron capture cross-section of 149Sm. By imposing variations

Biswajoy Brahmachari, Amitava Raychaudhuri

We consider a 5-dimensional SU(5) model wherein the symmetry is broken to the 4-dimensional Standard Model by compactification of the 5th dimension on an S^1/(Z_2 \times Z^\prime_2) orbifold. We identify the members of all SU(5) representations upto 75 which have zero modes. We examine how these light scalars affect gauge coupling unification assuming a sing

Riccardo Rattazzi

Scattering at transplanckian energies offers model independent tests of TeV scale gravity. Black-hole production is one spectacular signal, though a full calculation of the cross section is not yet available. Another signal is given by gravitational elastic scattering, which is maybe less spectacular but which can be nicely computed in the forward region usi

Emilian Dudas, Carlos A. Savoy

A new mechanism for generating neutrino masses without a high-energy mass scale is proposed. The mechanism needs a fundamental mass scale M in the 100-1000 TeV region and a minimal field content beyond the Standard Model one containing a pair of fermion singlets and a pair of weak doublet fermions for each neutrino mass, all of them with a mass of order M. T

Alessandro Strumia, Carla Cattadori, Nicola Ferrari, Francesco Vissani

Assuming neutrino oscillations, global analyses of solar data find that the LOW solution is significantly disfavoured, leaving LMA as the best solution. But the preference for LMA rests on three weak hints: the spectrum of earth matter effects (Super-Kamiokande sees an overall day/night asymmetry only at 1 sigma), the Cl rate (but LMA and LOW predictions are

Thomas Dent

CP has a natural embedding in superstring models as a gauge symmetry involving inversion of the compactified space. Hence the source of CP violation could be geometrical. Such models face the problem of how to suppress contributions to fermion electric dipole moments from softly-broken supersymmetry, as well as other problems of string phenomenology. Stringy

Kazuo Fujikawa

Recent studies of the topological properties of a general class of lattice Dirac operators are reported. This is based on a specific algebraic realization of the Ginsparg-Wilson relation in the form $γ_{5}(γ_{5}D)+(γ_{5}D)γ_{5} = 2a^{2k+1}(γ_{5}D)^{2k+2}$ where $k$ stands for a non-negative integer. The choice $k=0$ corresponds to the commonly discussed Gins

B. Aubert, BABAR Collaboration

We present updated measurements of branching fractions and CP-violating asymmetries for neutral B meson decays to two-body final states of charged pions and kaons. The results are obtained from a data sample of about 60 million Y(4S) --> B-anti-B decays collected between 1999 and 2001 by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. T

ZEUS Collaboration

Diffractive photoproduction of vector mesons, gamma p --> V Y, where Y is a proton-dissociative system, has been measured in ep interactions with the ZEUS detector at HERA using an integrated luminosity of 25 pb^-1. The differential cross section, ds/dt, is presented for -t<12 GeV^2, where t is the square of the four-momentum transferred to the vector meson.

Dorota Gondek-Rosinska, Eric Gourgoulhon

We perform some numerical study of the secular triaxial instability of rigidly rotating homogeneous fluid bodies in general relativity. In the Newtonian limit, this instability arises at the bifurcation point between the Maclaurin and Jacobi sequences. It can be driven in astrophysical systems by viscous dissipation. We locate the onset of instability along

V. D. Ivashchuk, V. N. Melnikov, A. B. Selivanov

A family of black-hole solutions in the model with 1-component perfect fluid is obtained. The metric of any solution contains (n -1) Ricci-flat &#34;internal space&#34; metrics and for certain equations of state coincides with the metric of black brane (or black hole) solution in the model with antisymmetric form. Certain examples (e.g. imitating M2 and M5 b

G. Date

This is a written version of the review talk given at the meeting on &#34;Interface of Gravitational and Quantum Realms&#34; at IUCAA, Pune during December 2001. The talk reviewed the recent work of Martin Bojowald on Loop Quantum Cosmology.

Marek W. Gutowski

Over a quarter of century after the invention of genetic algorithms and miriads of their modifications, as well as successful implementations, we are still lacking many essential details of thorough analysis of it&#39;s inner working. One of such fundamental questions is: how many generations do we need to solve the optimization problem? This paper tries to

Christoph Koch

Graph simulation (using graph schemata or data guides) has been successfully proposed as a technique for adding structure to semistructured data. Design patterns for description (such as meta-classes and homomorphisms between schema layers), which are prominent in the object-oriented programming community, constitute a generalization of this graph simulation

Zhi-Feng Huang, Rashmi C. Desai

The mechanisms of stability or instability in the strained alloy film growth are of intense current interest to both theorists and experimentalists. We consider dislocation-free, coherent, growing alloy films which could exhibit a morphological instability without nucleation. We investigate such strained films by developing a nonequilibrium, continuum model

Zhi-Feng Huang, Rashmi C. Desai

A continuum dynamical model is developed to determine the morphological and compositional instabilities on the free surface of heteroepitaxial alloy films in the absence of growth. We use linear stability analysis to study the early nonequilibrium processes of surface evolution, and calculate the stability conditions and diagrams for different cases of mater

A. Saguia, B. Boechat, M. A. Continentino

We present a new perturbative real space renormalization group (RG) to study random quantum spin chains and other one-dimensional disordered quantum systems. The method overcomes problems of the original approach which fails for quantum random chains with spins larger than S=1/2. Since it works even for weak disorder we are able to obtain the zero temperatur

E. P. Pokatilov, S. N. Klimin, V. M. Fomin, J. T. Devreese

In our recent paper [Phys. Rev. B 65, 075316 (2002)], the selection rules for the Raman scattering in spherical nanocrystals are analyzed. Here we show, that a physically expedient choice of the coordinate system, related to the polarization vector of the incoming or scattered light, simplifies and clarifies the analysis.

Ibrahim Al-Lehyani, Mike Widom

A tile Hamiltonian (TH) replaces the actual atomic interactions in a quasicrystal with effective interactions between and within tiles. We studied Al-Co-Cu decagonal quasicrystals described as decorated Hexagon-Boat-Star (HBS) tiles using {\em ab-initio} methods. The dominant term in the TH counts the number of H, B and S tiles. Phason flips that replace an

A. G. Zilman, S. A. Safran

We study a generic model of self-assembling chains which can branch and form networks with branching points (junctions) of arbitrary functionality. The physical realizations include physical gels, wormlike micells, dipolar fluids and microemulsions. The model maps the partition function of a solution of branched, self-assembling, mutually avoiding clusters o

Y. Y. Xue, B. Lorenz, A. Baikalov, D. H. Cao

The hole concentration (p)(delta), the transition temperature Tc, the intragrain penetration depth lambda, and the Meissner effect were measured for annealed RuSr2(Gd,Ce)2Cu2O10+delta samples. The intragrain superconducting transition temperature Tc} varied from 17 to 40 K while the p changed by only 0.03 holes/CuO2. The intragrain superfluid-density 1/lambd

J. D. Jorgensen, D. G. Hinks, P. G. Radaelli, W. I. F. David

An anisotropic lattice anomaly near the superconducting transition temperature, Tc, was observed in MgB2 by high-resolution neutron powder diffraction. The a-axis thermal expansion becomes negative near Tc, while the c-axis thermal expansion is unaffected. This is qualitatively consistent with a depletion of the boron-boron s-band as the superconducting gap

G. Modugno, M. Modugno, F. Riboli, G. Roati

We produce a quantum degenerate mixture composed by two Bose-Einstein condensates of different atomic species, 41 K and 87 Rb. We study the dynamics of the superfluid system in an elongated magnetic trap, where off-axis collisions between the two interacting condensates induce scissors-like oscillation.

Patrik Recher, Daniel Loss

We discuss several scenarios for the creation of nonlocal spin-entangled electrons which provide a source of electronic Einstein-Podolsky-Rosen (EPR) pairs. The central idea is to exploit the spin correlations naturally present in superconductors in form of Cooper pairs. We show that nonlocal spin-entanglement in form of an effective Heisenberg spin interact

L. Angelani, L. Casetti, M. Pettini, G. Ruocco

We show that the presence and the location of first order phase transitions in a thermodynamic system can be deduced by the study of the topology of the potential energy function, V(q), without introducing any thermodynamic measure. In particular, we present the thermodynamics of an analytically solvable mean-field model with a k-body interaction which -depe

A. Z. Gorski, S. Drozdz, J. Speth

Detailed study of multifractal characteristics of the financial time series of asset values and of its returns is performed using a collection of the high frequency Deutsche Aktienindex data. The tail index ($α$), the Renyi exponents based on the box counting algorithm for the graph ($d_q$) and the generalized Hurst exponents ($H_q$) are computed in parallel

Pavol Farkasovsky

The extrapolation of small-cluster exact-diagonalization calculations is used to examine ferromagnetism in the one-dimensional Hubbard model with a generalized type of hopping. It is found that the long-range hopping with power decaying hopping amplitudes ($t_{ij}\sim q^{|i-j|}$) stabilizes the ferromagnetic state for a wide range of electron interactions $U

Z. Akdeniz, P. Vignolo, A. Minguzzi, M. P. Tosi

We extend to finite temperature a Green&#39;s function method that was previously proposed to evaluate ground-state properties of mesoscopic clouds of non-interacting fermions moving under harmonic confinement in one dimension. By calculations of the particle and kinetic energy density profiles we illustrate the role of thermal excitations in smoothing out t

A. J. Archer, R. Evans, R. Roth

We show that a general density functional approach for calculating the force between two big particles immersed in a solvent of smaller ones can describe systems that exhibit fluid-fluid phase separation: the theory captures effects of strong adsorption (wetting) and of critical fluctuations in the solvent. We illustrate the approach for the Gaussian core mo

Mai Suan Li, Hoang Zung, Daniel Dominguez

We model s-wave and d-wave disordered granular superconductors with a three-dimensional lattice of randomly distributed Josephson junctions with finite self-inductance. The nonlinear ac resistivity of these systems was calculated using Langevin dynamical equations. The current amplitude dependence of the nonlinear resistivity at the peak position is found to

M. Lange, M. J. Van Bael, V. V. Moshchalkov, Y. Bruynseraede

Vortex pinning in a type-II superconducting Pb film covering a Co/Pt multilayer with perpendicular magnetic anisotropy is investigated. Different stable magnetic domain patterns like band and bubble domains can be created in the Co/Pt multilayer, clearly influencing the vortex pinning in the superconducting Pb layer. Most effective pinning is observed for th

A. D. Drozdov, J. deC. Christiansen, R. K. Gupta, A. P. Shah

Experimental data are reported on the elastoplastic response of and moisture diffusion through a vinyl ester resin-montmorillonite clay nanocomposite with various amounts of filler. Two simple models are developed for the elastoplastic behavior of a nanocomposite and for the anomalous diffusion of penetrant molecules. Adjustable parameters in the constitutiv

M. Grether, M. Fortes, M. de Llano, J. L. del Río

We solve the problem of a Bose or Fermi gas in $d$-dimensions trapped by $% δ\leq d$ mutually perpendicular harmonic oscillator potentials. From the grand potential we derive their thermodynamic functions (internal energy, specific heat, etc.) as well as a generalized density of states. The Bose gas exhibits Bose-Einstein condensation at a nonzero critical t

Patrick N. McGraw, Michael Menzinger

We examine numerically the storage capacity and the behaviour near saturation of an attractor neural network consisting of bistable elements with an adjustable coupling strength, the Bistable Gradient Network (BGN). For strong coupling, we find evidence of a first-order &#34;memory blackout&#34; phase transition as in the Hopfield network. For weak coupling,

M. Franz, D. E. Sheehy, Z. Tesanovic

A d-wave superconductor, subject to strong phase fluctuations, is known to suffer an antiferromagnetic instability closely related to the chiral symmetry breaking in (2+1)-dimensional quantum electrodynamics (QED3). On the basis of this idea we formulate a &#34;QED3 in a box&#34; theory of local instabilities of a d-wave superconductor in the vicinity of a s

Brian L. Rachford, Theodore P. Snow, Jason Tumlinson, J. Michael Shull

We report the first ensemble results from the FUSE survey of molecular hydrogen in lines of sight with A_V $\gtrsim$ 1 mag. We have developed techniques for fitting computed profiles to the low-J lines of H2, and thus determining column densities for J = 0 and J = 1, which contain $\gtrsim$99% of the total H2. From these column densities and ancillary data w

Wayne Hu, Charles R. Keeton

We study the prospects for three-dimensional mapping of the dark matter to high redshift through the shearing of faint galaxies images at multiple distances by gravitational lensing. Such maps could provide invaluable information on the nature of the dark energy and dark matter. While in principle well-posed, mapping by direct inversion introduces exceedingl

Tammy A. Smecker-Hane, Andrew McWilliam

We report on the chemical abundances derived from high-dispersion spectra of 14 red giant stars in the Sagittarius dwarf spheroidal (Sgr dSph) galaxy. The stars span a wide range of metallicities, -1.6 < [Fe/H] < -0.1 dex, and exhibit very unusual abundance variations. For metal-poor stars with [Fe/H] < -1, [alpha/Fe] \approx +0.3 similar to Galactic halo st

Zoltan Haiman

For a source of Ly alpha radiation embedded in a neutral intergalactic medium (IGM) prior to the reionization epoch, the emission line is strongly suppressed by the intervening IGM. The damping wing of the so-called Gunn-Peterson trough can extend to the red side of the emission line, and erase a significant fraction of the total line flux. However, the tran

Georgina V. Coldwell, Hector J. Martinez, Diego G. Lambas

We study the galaxy environment of active galaxies, radio-loud and radio-quiet quasars in the redshift range $0.1\leq z\leq0.25$. We use APM galaxies in order to explore the local galaxy overdensity and the $b_J-R$ colour distribution of neighbouring galaxies of these target samples. For comparison, we perform similar analysis on samples of Abell clusters wi

C. Abajas, E. Mediavilla, J. A. Munoz, L. C. Popovic

We discuss the effects of microlensing on the broad emission lines (BELs) of QSOs in the light of recent determinations of the size of the broad line region (BLR) and its scaling with QSO luminosity. Microlensing by star-sized objects can produce significant amplifications in the BEL of some multiple-imaged QSOs, and could be very relevant for high-ionizatio

Celine Boehm, Pierre Fayet, Richard Schaeffer

We discuss the damping of primordial dark matter fluctuations, taking into account explicitly the interactions of dark matter - whatever their intensity - both with itself and with other particle species. Relying on a general classification of dark matter particle candidates, our analysis provides, from structure formation, a new set of constraints on the da

Stefano Ciprini

In April-May 1998 the blazar ON 231 (W Com, B2 1219+28) showed an extraordinary optical outburst alerted by the Perugia Astronomical Observatory. The source reached the most luminous state, observed at least since the beginning of the previous century. BeppoSAX observed ON 231 in the band from 0.1 up to 100 keV, detecting an X-ray spectrum with a peculiar co

G. L. Hoffman, E. E. Salpeter, M. G. Pocceschi

Arecibo mapping is reported of the neutral hydrogen distribution along selected directions out from the centers of two small High Velocity Clouds (HVC), W486 and W491. Both HVCs have a small inner region where the neutral hydrogen column density N_HI decreases slowly and a larger outer region where N_HI declines more rapidly, smoothly and exponentially from

P. Sonnentrucker, S. D. Friedman, D. E. Welty, D. G. York

We present a study of the abundances and physical conditions in the interstellar gas toward the heavily reddened star HD 192639 [E_(B-V) = 0.64], based on analysis of FUSE and HST/STIS spectra covering the range from 912 to 1361 A. This work constitutes a survey of the analyses that can be performed to study the interstellar gas when combining data from diff

S. Corbel, R. P. Fender

We have compiled contemporaneous broadband observations of the black hole candidate X-ray binary GX 339-4 when in the low/hard X-ray state in 1981 and 1997. The data clearly reveal the presence of two spectral components, with thermal and non-thermal spectra, overlapping in the optical -- near-infrared bands. The non-thermal component lies on an extrapolatio

E. Le Floc&#39;h, V. Charmandaris, O. Laurent, I. F. Mirabel

We present our 5-16 micron spectro-imaging observations of VV114, an infrared luminous early-stage merger, taken with the ISOCAM camera on-board ISO. We find that only 40% of the mid-infrared (MIR) flux is associated with a compact nuclear region, while the rest of the emission originates from a rather diffuse component extended over several kpc. This is in

E. Peeters, S. Hony, C. Van Kerckhoven, A. G. G. M. Tielens

Here, we present 6-9 um spectra of a sample of RNe, HII regions, YSOs, evolved stars and galaxies that show strong unidentified infrared bands, obtained with the ISO-SWS. The IR emission features show pronounced variations. 1) The 6.2 um feature shifts and clearly shows profile variations. 2) The 7.7 um complex is comprised of at least two subpeaks peaking a

A. Oscoz, D. Alcalde, M. Serra-Ricart, E. Mediavilla

We report an increase of more than 0.2 mag in the optical brightness of the leading image (A) of the gravitational lens Q0957+561, detected during the 09/2000 -- 06/2001 monitoring campaign (2001 observing season). The brightening is similar to or even greater than the largest change ever detected during the 20 years of monitoring of this system. We discuss

John Menzies, Michael Feast, Toshihiko Tanabe, Patricia Whitelock

The first results of a study of the the dwarf spheroidal galaxy, Leo I, using the new Japanese-South African Infrared Survey Facility (IRSF) are presented. J,H,K_{s} observations show that most, if not all, of at least the top one magnitude of the AGB is populated by carbon stars. These objects form a tight sequence in the K_{s} - (J-K_{s}) plane. In additio

Jae-Woo Lee, Bruce W. Carney

We present a chemical abundance study of three inner old halo clusters NGC 6287, NGC 6293, and NGC 6541, finding [Fe/H] = -2.01 +/- 0.05, -1.99 +/- 0.02, and -1.76 +/- 0.02, respectively, and our metallicity measurements are in good agreement with previous estimates. The mean alpha-element abundances of our program clusters are in good agreement with other g

Scott S. Sheppard, David C. Jewitt

We present a systematic investigation of the rotational lightcurves of trans-Neptunian objects based on extensive optical data from Mauna Kea. Four of 13 objects (corresponding to 31%) in our sample ((33128) 1998 BU48, 2000 GN171, (20000) Varuna and 1999 KR16) were found to exhibit lightcurves with peak-to-peak range > 0.15 magnitude. In a larger sample obta

S. T. Myers, C. R. Contaldi, J. R. Bond, U. -L. Pen

We describe an algorithm for the extraction of the angular power spectrum of an intensity field, such as the cosmic microwave background (CMB), from interferometer data. This new method, based on the gridding of interferometer visibilities in the aperture plane followed by a maximum likelihood solution for bandpowers, is much faster than direct likelihood an

Jan de Gier, Bernard Nienhuis, Paul A. Pearce, Vladimir Rittenberg

We discuss a one-dimensional model of a fluctuating interface with a dynamic exponent $z=1$. The events that occur are adsorption, which is local, and desorption which is non-local and may take place over regions of the order of the system size. In the thermodynamic limit, the time dependence of the system is given by characters of the $c=0$ conformal field

Stephen Godfrey, Jonathan L. Rosner

No spin-singlet $b \bar b$ quarkonium state has yet been observed. In this paper we discuss the production of the singlet P-wave $b\bar{b}$ and $c\bar{c}$ $^1P_1$ states $h_b$ and $h_c$. We consider two possibilities. In the first the $^1P_1$ states are produced via the electromagnetic cascades $\ups(3S) \to η_b(2S) + γ\to h_b + γγ\to η_b +γγγ$ and $ψ&#39;\t

R. Heumann

After setting up a general model for supersymmetric classical mechanics in more than one dimension we describe systems with centrally symmetric potentials and their Poisson algebra. We then apply this information to the investigation and solution of the supersymmetric Coulomb problem, specified by an 1/|x| repulsive bosonic potential.

B. S. Mason, T. J. Pearson, A. C. S. Readhead, M. C. Shepherd

We report measurements of anisotropy in the cosmic microwave background radiation over the multipole range l ~ 200 - 3500 with the Cosmic Background Imager based on deep observations of three fields. These results confirm the drop in power with increasing l first reported in earlier measurements with this instrument, and extend the observations of this decli

STAR Collaboration

We report the first observation of $K^{\star}(892)^{0}\toπK$ in relativistic heavy ion collisions. The transverse momentum spectrum of $(K^{\star0}+\bar{K}^{\star0})/2$ from central Au+Au collisions at $\sqrt{s_{_{NN}}}=130$ GeV is presented. The ratios of the $K^{\star0}$ yield derived from these data to the yields of negative hadrons, charged kaons, and $ϕ

Paul F. Scott, Pedro Carreira, Kieran Cleary, Rod D. Davies

We present the power spectrum of the fluctuations in the cosmic microwave background detected by the Very Small Array (VSA) in its first season of observations in its compact configuration. We find clear detections of first and second acoustic peaks at l~200 and l~550, plus detection of power on scales up to l=800. The VSA power spectrum is in very good agre

Angela C. Taylor, Pedro Carreira, Kieran Cleary, Rod D. Davies

We have observed the cosmic microwave background temperature fluctuations in eight fields covering three separated areas of sky with the Very Small Array at 34 GHz. A total area of 101 square degrees has been imaged, with sensitivity on angular scales 3.6 - 0.4 degrees (equivalent to angular multipoles l=150-900). We describe the field selection and observin

Jose Alberto Rubino-Martin, Rafael Rebolo, Pedro Carreira, Kieran Cleary

We investigate the constraints on basic cosmological parameters set by the first compact-configuration observations of the Very Small Array (VSA), and other cosmological data sets, in the standard inflationary LambdaCDM model. Using a weak prior 40 < H_0 < 90 km/s/Mpc and 0 < tau < 0.5 we find that the VSA and COBE_DMR data alone produce the constraints Omeg

M. de Oliveira Neto, L. A. Maia, S. Carneiro

In the present work we show that planetary mean distances can be calculated with the help of a Schrodinger-type diffusion equation. The obtained results are shown to agree with the observed orbits of all the planets and of the asteroid belt in the solar system, with only three empty states. Furthermore, the equation solutions predict a fundamental orbit at 0

Robert A. Watson, Pedro Carreira, Kieran Cleary, Rod D. Davies

The Very Small Array (VSA) is a synthesis telescope designed to image faint structures in the cosmic microwave background on degree and sub-degree angular scales. The VSA has key differences from other CMB interferometers with the result that different systematic errors are expected. We have tested the operation of the VSA with a variety of blank-field and c