September 2004 arXiv papers — page 5

Ashley P. Willis, David Gubbins

Choosing a simple class of flows, with characteristics that may be present in the Earth's core, we study the ability to generate a magnetic field when the flow is permitted to oscillate periodically in time. The flow characteristics are parameterised by D, representing a differential rotation, M, a meridional circulation, and C, a component characterisin

P Ahmadi, V Ramareddy, G S Summy

We report on the loading of atoms contained in a magneto-optic trap into multiple optical traps formed within the focused beam of a CO_{2} laser. We show that under certain circumstances it is possible to create a linear array of dipole traps with well separated maxima. This is achieved by focusing the laser beam through lenses uncorrected for spherical aber

T. Frick, H. Müther, A. Rios, A. Polls

The single-particle spectral functions in asymmetric nuclear matter are computed using the ladder approximation within the theory of finite temperature Green's functions. The internal energy and the momentum distributions of protons and neutrons are studied as a function of the density and the asymmetry of the system. The proton states are more strongly

U. van Kolck

Effective field theories have been developed for the description of light, shallow nuclei. I review results for two- and three-nucleon systems, and discuss their extension to halo nuclei.

Wei Liang Qian, Ru-Keng Su, Hong Qiu Song

An effective model is used to study the equation of state of warm strange hadronic matter with nucleons, Lambda-hyperons, Xi-hyperons, sigmastar and phi. In the calculation, a newest weak Y-Y interaction deduced from the recent observation of a He double hypernucleus is adopted. Employing this effective model, the results with strong Y-Y interaction and weak

the PHENIX Collaboration, S. S. Adler

The PHENIX experiment has measured mid-rapidity transverse momentum spectra (0.4 < p_T < 4.0 GeV/c) of single electrons as a function of centrality in Au+Au collisions at sqrt(s_NN) = 200 GeV. Contributions to the raw spectra from photon conversions and Dalitz decays of light neutral mesons are measured by introducing a thin (1.7% X_0) converter into the PHE

JLab Hall A, E94-010 Collaborations, :, J. P. Chen

Recent progress from Jefferson Lab has significantly improved our understanding of the nucleon spin structure in the high-$x$ region. Results from two experiments in Hall A are presented. The first experiment is a precision measurement of the neutron spin asymmetry, $A_1^n$, in the high-$x$ (valence quark) region. The results show for the first time that $A_

V. M. Datar, Suresh Kumar, D. R. Chakrabarty, V. Nanal

The low lying states in $^8$Be are believed to have a two-alpha cluster structure and hence a large intrinsic quadrupole deformation. An earlier calculation showed a large collective enhancement in gamma transition probability between the low lying states leading to a 4$^+$ to 2$^+$ gamma branch of $\sim10^{-7}$ and a resonant radiative cross section of 134

M. N. Kuperman, M. Ballard, M. F. Laguna

We present a model for the description of the evolution of contacts among individuals in a network. At each time step each individual is associated with a domain or neighborhood of fully connected agents.The dynamics of this changing neighborhood will later be translated into a situation where the links between individuals are also dynamic. A characterizatio

Peter Henselder, Allen C. Hirshfeld, Thomas Spernat

The formalism of geometric algebra can be described as deformed super analysis. The deformation is done with a fermionic star product, that arises from deformation quantization of pseudoclassical mechanics. If one then extends the deformation to the bosonic coefficient part of superanalysis one obtains quantum mechanics for systems with spin. This approach c

Roman Kozhan

The property of a normal functor to be open-multicommutative proposed by Kozhan and Zarichnyi (2004) is investigated. A number of normal functors related to the functor of probability measures and equipped with convex structure are considered here and it is proved that the functors $cc$, $ccP$, $G_{cc}P$ and $λ_{cc}P$ are open-multicommutative.}

William D. Kirwin, Siye Wu

In quantum mechanics, the momentum space and position space wave functions are related by the Fourier transform. We investigate how the Fourier transform arises in the context of geometric quantization. We consider a Hilbert space bundle H over the space J of compatible complex structures on a symplectic vector space. This bundle is equipped with a projectiv

Mark Adler, Alexei Borodin, Pierre van Moerbeke

Given uniform probability on words of length M=Np+k, from an alphabet of size p, consider the probability that a word (i) contains a subsequence of letters (p, p-1,...,1) in that order and (ii) that the maximal length of the disjoint union of p-1 increasing subsequences of the word is \leq M-N . A generating function for this probability has the form of an i

Jean Bertoin, Alain Rouault

For a subcritical Galton-Watson process $(ζ_n)$, it is well known that under an $X \log X$ condition, the quotient $P(ζ_n > 0)/ Eζ_n$ has a finite positive limit. There is an analogous result for a (one-dimensional) supercritical branching random walk: when $a$ is in the so-called subcritical speed area, the probability of presence around $na$ in the $n$-th

Francois Couchot

It is shown that a local ring R of bounded module type is an almost maximal valuation ring if there exists a non-maximal prime ideal J such that R/J is a maximal valuation domain.

Jean Bertoin, Alain Rouault

Homogeneous fragmentations describe the evolution of a unit mass that breaks down randomly into pieces as time passes. They can be thought of as continuous time analogs of a certain type of branching random walks, which suggests the use of time-discretization to shift known results from the theory of branching random walks to the fragmentation setting. In pa

Vitor Araujo

We consider dynamical systems on compact manifolds, which are local diffeomorphisms outside an exceptional set (a compact submanifold). We are interested in analyzing the relation between the integrability (with respect to Lebesgue measure) of the first hyperbolic time map and the existence of positive frequency of hyperbolic times. We show that some (strong

Do Ngoc Diep

In the paper we describe the C*-algebras of noncommutative spherical tight frames over some C*-algebras and then apply to study the noncommutative version of the universal classifying space.

J. Haglund, M. Haiman, N. Loehr

We prove a combinatorial formula for the Macdonald polynomial H_mu(x;q,t) which had been conjectured by the first author. Corollaries to our main theorem include the expansion of H_mu(x;q,t) in terms of LLT polynomials, a new proof of the charge formula of Lascoux and Schutzenberger for Hall-Littlewood polynomials, a new proof of Knop and Sahi&#39;s combinat

Nathan Brown, Rachel Finck, Matthew Spencer, Kristopher Tapp

We classify left invariant metrics with nonnegative curvature on SO(3) and U(2).

Lorenz Friess

Error in proof of theorem 10.

Rob Schneiderman, Peter Teichner

We continue to develop an obstruction theory for embedding 2-spheres into 4-manifolds in terms of Whitney towers. The proposed intersection invariants take values in certain graded abelian groups generated by labelled trivalent trees, and with relations well known from the 3-dimensional theory of finite type invariants. Surprisingly, the same exact relations

Jan H. Bruinier, Jose I. Burgos Gil, Ulf Kuehn

We prove an arithmetic version of a theorem of Hirzebruch and Zagier saying that Hirzebruch-Zagier divisors on a Hilbert modular surface are the coefficients of an elliptic modular form of weight two. Moreover, we determine the arithmetic self-intersection number of the line bundle of modular forms equipped with its Petersson metric on a regular model of a H

Stefan Wewers

We study equivariant deformations of singular curves with an action of a finite flat group scheme, using a simplified version of Illusie&#39;s equivariant cotangent complex. We apply these methods in a special case which is relevant for the study of the stable reduction of three point covers.

Antonio S. de Castro

The problem of a fermion subject to a general mixing of vector and scalar potentials in a two-dimensional world is mapped into a Sturm-Liouville problem. Isolated bounded solutions are also searched. For the specific case of an inversely linear potential, which gives rise to an effective Kratzer potential in the Sturm-Liouville problem, exact bounded solutio

J. Gegenberg, G. Kunstatter

We implement a suggestion by Bakas and consider the Ricci flow of 3-d manifolds with one Killing vector by dimensional reduction to the corresponding flow of a 2-d manifold plus scalar (dilaton) field. By suitably modifying the flow equations in order to make them manifestly parabolic, we are able to show that the equations for the 2-d geometry can be put in

Falk Rohsiepe

When studying mirror symmetry in the context of K3 surfaces, the hyperkaehler structure of K3 makes the notion of exchanging Kaehler and complex moduli ambiguous. On the other hand, the metric is not renormalized due to the higher amount of supersymmetry of the underlying superconformal field theory. Thus one can define a natural mapping from the classical K

L. Griguolo, D. Seminara, R. J. Szabo

We describe a novel double scaling limit of large N Yang-Mills theory on a two-dimensional torus and its relation to the geometry of the principal moduli spaces of holomorphic differentials.

I. B. Samsonov

The problem of construction of low-energy effective action in N=3 SYM theory is considered within the harmonic superspace (HSS) approach. The low-energy effective action is supposed to be a gauge- and scale-invariant functional in N=3 HSS reproducing the term F^4/ϕ^4 in components. This functional is found as a scale-invariant generalization of the F^4-term

Urs Schreiber

It is shown how the deformation of the superconformal generators on the string&#39;s worldsheet by a nonabelian super-Wilson line gives rise to a covariant exterior derivative on loop space coming from a nonabelian 2-form on target space. The expression obtained this way is new in the context of strings, and its consistency is verified by checking that its g

F. M. Steffens

We study the running of the QCD coupling with the momentum squared ($Q^2$) and the temperature scales in the high temperature limit ($T > T_{c}$), using a mass dependent renormalization scheme to build the Renormalization Group Equations. The approach used guaranty gauge invariance, through the use of the Hard Thermal Loop approximation, and independence of

T. Lappi

The rapidity distribution of gluons produced in heavy ion collisions is studied by a numerical computation in 2+1-dimensional classical Yang-Mills theory. By assuming that the classical source strength g^2 mu depends on rapidity as g^4 mu^2 ~ exp(+- lambda y) and studying collisions of two nuclei with different g^2 mu we find that the rapidity distribution o

J. R. Hiller

Recent progress in the nonperturbative solution of (3+1)-dimensional Yukawa theory and quantum electrodynamics and (1+1)-dimensional super Yang--Mills theory is summarized.

Stephen Godfrey, Shouhua Zhu

We review some recent developments in Higgs physics at a $γγ$ collider. We begin with single Higgs boson production in $γγ$ collisions proceeding via the hadronic content of the photon. For SM Higgs masses of current theoretical interest, the resolved photon contributions are non-negligible in precision cross section measurements. We found that production of

S. Dev, Sanjeev Kumar

The rise-up in boron neutrino spectrum at low energies has been studied within the framework of `pure LMA&#39; scenario. Indirect bounds on the spectral `upturn&#39; have been obtained from the available solar neutrino data. These bounds have been used to demonstrate the efficacy of the precision measurements of the `upturn&#39; for further constraining the

J. Raufeisen

The color dipole formulation provides an intuitive picture of hard processes in high energy scattering. Most importantly, this approach allows one to calculate nuclear effects in a parameter-free way. I review the relation between the dipole approach and transverse momentum factorization and present numerical results for open heavy flavor production in proto

S. F. King

In this talk we show how Lorentz invariance violation (LIV) can occur for Majorana neutrinos, without inducing LIV in the charged leptons via radiative corrections. Such ``electrophobic&#39;&#39; LIV is due to the Majorana nature of the LIV operator together with electric charge conservation. Being free from the strong constraints coming from the charged lep

Gustavo Burdman

We review some aspects of theories with compact extra dimensions. We consider the motivation and the theoretical basis of Large, Universal and Warped Extra Dimensions. We focus on those aspects that are potentially relevant in the phenomenology at colliders.

J. D. Vergados

Neutrinoless double beta decay pops up almost in any extension of the standard model. It is perhaps the only process, which can unambiguously determine whether the massive neutrinos are Majorana or Dirac type particles. In addition from the lifetime of this decay, combined with sufficient knowledge of the relevant nuclear matrix elements, one can set a const

A. G. Akeroyd, S. Kanemura, Y. Okada, E. Senaha

In the MSSM with complex SUSY parameters we consider a specific case where the second heaviest Higgs boson H_2 is SM like, while H_1 and H_3 are both strongly mixed states of CP odd and CP even scalar fields. Such a scenario could be probed at a Linear Collider via the mechanism e^+e^-\to H_1H_3.

Takeo Moroi, Tomo Takahashi

We consider cosmic microwave background (CMB) anisotropy in models with quintessence taking into account of isocurvature fluctuation in the quintessence. It is shown that, if the primordial fluctuation of the quintessence has a correlation with the adiabatic density fluctuations, CMB angular power spectrum $C_l$ at low multipoles can be suppressed. Possible

M. Göckeler, R. Horsley, A. C. Irving, D. Pleiter

We compute the light and strange quark masses m_l = (m_u+m_d)/2 and m_s, respectively, in full lattice QCD with N_f=2 flavors of light dynamical quarks. The renormalization constants, which convert bare quark masses into renormalized quark masses, are computed nonperturbatively, including the effect of quark-line disconnected diagrams. We obtain m_l=4.7(2)(3

Stephen Godfrey, Shouhua Zhu

In this letter, we introduce the ``flipped see-saw mechanism&#39;&#39;, a new type of see-saw mechanism with 4th-generation neutrinos. This mechanism naturally explains the light sterile neutrino which is needed to account for all neutrino oscillation data. At the same time it predicts that another Majorona neutrino should exist with mass of the electro-weak

V. Azcoiti, G. Di Carlo, A. Galante, V. Laliena

A new approach for non zero chemical potential simulations is tested in the Gross-Neveu model for infinite flavor number, where the critical line is reconstructed in a large $μ/T$ interval. A comparison with results from standard imaginary chemical potential approach as well as first results for $N_f=4$ QCD are presented.

Vicente Azcoiti, Giuseppe Di Carlo, Angelo Galante, Victor Laliena

The phenomenon of diquark condensation at non-zero baryon density and zero temperature is analyzed in the strong coupling limit of lattice QCD. The results indicate that there is attraction in the quark-quark channel also at strong coupling, and that the attraction is more effective at high baryon density, but for infinite coupling it is not enough to produc

Vicente Azcoiti, Giuseppe Di Carlo, Angelo Galante, Victor Laliena

We introduce a new approach to analyze the phase diagram of QCD at finite chemical potential and temperature, based on the definition of a generalized QCD action. Several details of the method will be discussed, with particular emphasis on the advantages respect to the imaginary chemical potential approach.

F. Alet, B. Lucini, M. Vettorazzo

A new algorithm for simulating compact U(1) lattice gauge theory in three dimensions is presented which is based on global changes in the configuration space. We show that this algorithm provides an effective way to extract partition functions at given external flux. As an application, we study numerically the finite temperature deconfinement phase transitio

Giulia M. de Divitiis, Nazario Tantalo

We discuss the quantization of the energy levels of two-particle scattering states in a finite volume in the case of Bloch-type boundary conditions. A generalization of the Luescher quantization condition is obtained that can be used in order to calculate the scattering phases, resulting for example by the strong elastic interaction of two pions, at fixed ph

The DELPHI Collaboration, J. Abdallah

A test of the benchmark QED process e+e- -> gamma gamma (gamma) is reported, using the data collected with the DELPHI detector at LEP 2. The data analysed were recorded at centre-of-mass energies ranging from 161 GeV to 208 GeV and correspond to a total integrated luminosity of 656.4 pb^{-1}. The Born cross-section for the process e+e- -> gamma gamma (gamma)

P. Rossi

The existence of an anti-decuplet of pentaquark particles has been predicted some year ago within the chiral soliton model. In the last year, several experimental groups have reported evidence for a S=+1 baryon resonance, with mass ranging from 1.52 and 1.55 GeV and width less than 25 MeV, by looking at the invariant mass of the $K N$ system. This resonance,

A. Satpathy

Measurements of the CKM parameter $\sin(2 β)$ have established $CP$ violation in the $B^0$ meson system arising from the interference between mixing and decay. However, direct CP violation, arising from the interference among different terms in the decay amplitude, had not been observed so far. We report a first observation of direct CP violation in $B^{0} \

Maximiliano Ujevic, Patricio S. Letelier

The stability of general relativistic thin disks is investigated under a general first order perturbation of the energy momentum tensor. In particular, we consider temporal, radial and azimuthal &#34;test matter&#34; perturbations of the quantities involved on the plane $z=0$. We study the thin disks generated by applying the &#34;displace, cut and reflect&#

D. Vogt, P. S. Letelier

An exact but simple general relativistic model for the gravitational field of active galactic nuclei is constructed, based on the superposition in Weyl coordinates of a black hole, a Chazy-Curzon disk and two rods, which represent matter jets. The influence of the rods on the matter properties of the disk and on its stability is examined. We find that in gen

D. Vogt, P. S. Letelier

Using the well-known ``displace, cut and reflect&#39;&#39; method used to generate disks from given solutions of Einstein field equations, we construct static charged disks made of perfect fluid based on the Reissner-Nordström solution in isotropic coordinates. We also derive a simple stability condition for charged and non charged perfect fluid disks. As ex

Sigbjorn Hervik, Robert van den Hoogen, Alan Coley

Using dynamical systems theory and a detailed numerical analysis, the late-time behaviour of tilting perfect fluid Bianchi models of types IV and VII$_h$ are investigated. In particular, vacuum plane-wave spacetimes are studied and the important result that the only future attracting equilibrium points for non-inflationary fluids are the plane-wave solutions

James W. York

The complete form of the constraints following from their conformal structure is extended so as to include constant mean curvature and other mean curvature foliations. This step is demonstrated using the momentum phase space approach. This approach yields equations of exactly the same form as the extended conformal thin sandwich approach. In solving the equa

Sashideep Gutti, T. P. Singh, Pranesh Sundararajan, Cenalo Vaz

We examine the gravitational collapse of an infinite cylindrical distribution of time like dust. In order to simplify the calculation we make an assumption that the axial and azimuthal metric functions are equal. It is shown that the resulting solution describes homogeneous collapse. We show that the interior metric can be matched to a time dependent exterio

Alpay Beler, Ann Borda, Jonathan P. Bowen, Silvia Filippini-Fantoni

This paper considers the move toward and potential of building online communities, with a particular focus on the museum sector. For instance, the increase in the use of `personalized&#39; toolkits that are becoming an integral part of the online presence for learning organizations, like museums, can provide a basis for creating and sustaining communities. A

Krzysztof R. Apt

We provide elementary and uniform proofs of order independence for various strategy elimination procedures for finite strategic games, both for dominance by pure and by mixed strategies. The proofs follow the same pattern and focus on the structural properties of the dominance relations. They rely on Newman&#39;s Lemma established in 1942 and related results

A. V. Korobko, W. Jesse, S. U. Egelhaaf, A. Lapp

The structure of spherical micelles of the diblock copolymer poly(styrene-block-acrylic acid) in water was investigated with small angle neutron scattering (SANS) and contrast matching. We have monitored inter-micelle correlation and the extension of the polyelectrolyte chains in the coronal layer through the overlap concentration. Irrespective of ionic stre

Gil Refael, Hsiu-Hau Lin

Using the topological flux insertion procedure, the ground-state degeneracy of an insulator on a periodic lattice with filling factor $ν=p/q$ was found to be at least $q$-fold. Applying the same argument in a lattice with edges, we show that the degeneracy is modified by the additional edge density $ν_{\mysw{E}}$ associated with the open boundaries. In parti

Manfred Salmhofer, Carsten Honerkamp, Walter Metzner, Oliver Lauscher

We describe a way to continue the fermionic renormalization group flow into phases with broken global symmetry. The method does not require a Hubbard-Stratonovich decoupling of the interaction. Instead an infinitesimally small symmetry-breaking component is inserted in the initial action, as an initial condition for the flow of the selfenergy. Its flow is dr

Christopher Gies, M. D. Lee, D. A. W. Hutchinson

In a two-dimensional Bose-Einstein condensate the reduction in dimensionality fundamentally influences collisions between the atoms. In the crossover regime from three to two dimensions several scattering parameters have been considered. However, finite temperature results are more difficult to obtain. In this work we present the many-body T-matrix at finite

C. Hoffmann, F. Lefloch, M. Sanquer, B. Pannetier

We experimentally investigated the current noise in diffusive Superconductor/Normal metal/Superconductor junctions with lengths between the superconducting coherence length xi_Delta and the phase coherence length L_Phi of the normal metal (xi_Delta < L < L_Phi). We measured the shot noise over a large range of energy covering both the regimes of coherent and

Sebastian Risau-Gusman

We study the properties of random graphs where for each vertex a {\it neighbourhood} has been previously defined. The probability of an edge joining two vertices depends on whether the vertices are neighbours or not, as happens in Small World Graphs (SWGs). But we consider the case where the average degree of each node is of order of the size of the graph (u

Tomoya Ono, Kikuji Hirose

Multishell helical gold nanowires (HGNs) suspended between semi-infinite electrodes are found to exhibit peculiar electron-conduction properties by first-principles calculations based on the density functional theory. Our results that the numbers of conduction channels in the HGNs and their conductances are smaller than those expected from a single-atom-row

M. Malfait, J. Vanacken, W. Van Roy, G. Borghs

We report on in-situ resistivity measurements on GaMnAs during post-growth annealing in different atmospheres. A drop in the resistivity is observed when the GaMnAs is exposed to oxygen, which indicates that the passivation of Mn interstitials (Mn_I) at the free surface occurs through oxidation. The presence of oxygen can therefore be an important annealing

Hirofumi Wada, Yoshihiro Murayama, Masaki Sano

Nonlinear elastic responses of short and stiff polyelectrolytes are investigated by dynamic simulations on a single molecule level. When a polyelectrolyte condensate undergoes a mechanical unfolding, two types of force-extension curves, i.e., a force plateau and a stick-release pattern, are observed depending on the strength of the electrostatic interaction.

I. P. Omelyan, W. Fenz, I. M. Mryglod, R. Folk

A method of integral equations is developed to study inhomogeneous fluids with planar spins in an external field. As a result, the calculations for these systems appear to be no more difficult than those for ordinary homogeneous liquids. The approach proposed is applied to the ferromagnetic XY spin fluid in a magnetic field using a soft mean spherical closur

Pablo Jarillo-Herrero, Sami Sapmaz, Cees Dekker, Leo P. Kouwenhoven

Optical and electronic phenomena in solids arise from the behaviour of electrons and holes (unoccupied states in a filled electron sea). Electron-hole symmetry can often be invoked as a simplifying description, which states that electrons with energy above the Fermi sea behave the same as holes below the Fermi energy. In semiconductors, however, electron-hol

R. Benítez, L. Ramírez-Piscina

We study initial transient stages in directional solidification by means of a non-variational phase field model with fluctuations. This model applies for the symmetric solidification of dilute binary solutions and does not invoke fluctuation-dissipation theorem to account for the fluctuation statistics. We devote our attention to the transient regime during

A. Arranz, C. Palacio

Tantalum nitride thin films have been grown by in situ nitrogen implantation of metallic tantalum at room temperature over the energy range of 0.5-5keV. X-ray photoelectron spectroscopy (XPS) and Factor Analysis (FA) have been used to characterise the chemical composition of the films. The number of the different Ta-N phases formed during nitrogen implantati

A. Jagannathan

We consider the spin 1/2 Heisenberg antiferromagnet on a two dimensional quasiperiodic tiling. The T=0 state is long range ordered, with an inhomogeneous distribution of the staggered moment. An approximate real space renormalization scheme first developed for the square lattice is generalized and used to obtain information on the ground state energy as well

Marko T. Cvitas, Pavel Soldan, Jeremy M. Hutson, Pascal Honvault

We have carried out quantum dynamical calculations of vibrational quenching in Li + Li_2 collisions for both bosonic 7Li and fermionic 6Li. These are the first ever such calculations involving fermionic atoms. We find that for the low initial vibrational states considered here (v less than or equal to 3), the quenching rates are not suppressed for fermionic

A. V. Savin, E. A. Zubova, L. I. Manevitch

We investigate a quasi-1D crystal: 2D system of coupled linear chains of particles with strong intra-chain and weak inter-chain interactions. Nonlinear dynamics of one of these chains when the rest of them are fixed is reduced to the well known Frenkel-Kontorova (FK) model. Its continuum limit, sine-Gordon (sG) equation, predicts two types of soliton solutio

Luciano da Fontoura Costa

Given a complex network, its \emph{L-}paths correspond to sequences of $L+1$ distinct nodes connected through $L$ distinct edges. The \emph{L-}conditional expansion of a complex network can be obtained by connecting all its pairs of nodes which are linked through at least one \emph{L-}path, and the respective conditional \emph{L-}expansion of the original ne

Matthew Browning, Allan Sacha Brun, Juri Toomre

We present the results of 3--D nonlinear simulations of magnetic dynamo action by core convection within A-type stars of 2 solar masses, at a range of rotation rates. We consider the inner 30% by radius of such stars, with the spherical domain thereby encompassing the convective core and a portion of the surrounding radiative envelope. The compressible Navie

C. Vignali, D. M. Alexander, A. Comastri

Recent X-ray surveys with Chandra and XMM-Newton have found several genuine Type II quasars, the long sought-after population of high-luminosity (high-redshift) Seyfert 2 galaxies, and a sizable number of Type II quasar candidates. However, at present it is hard to know whether the on-going X-ray surveys are providing a reliable and nearly complete census of

Kim-Vy H. Tran, Pieter van Dokkum, Garth D. Illingworth, Daniel Kelson

Using wide-field HST/WFPC2 imaging and extensive Keck/LRIS spectroscopy, we present a detailed study of the galaxy populations in MS2053--04, a massive, X-ray luminous cluster at z=0.5866. Analysis of 149 confirmed cluster members shows that MS2053 is composed of two structures that are gravitationally bound to each other; their respective velocity dispersio

Sandhya M. Rao, Jason X. Prochaska, J. Christopher Howk, Arthur M. Wolfe

We present Keck/HIRES abundance measurements and metal-line kinematic profiles of the damped Lyman alpha systems (DLAs) towards the quasars Q0933+733 (z_abs=1.479) and Q0948+433 (z_abs=1.233). These two DLAs have among the five highest HI column densities at any redshift: N(HI)=4.2E21 cm^{-2}. The metal-line data, presented here for the first time, reveal th

C. I. Short, P. H. Hauschildt

We present LTE and NLTE atmospheric models of a star with solar parameters, and study the effect of treating many thousands of Iron group lines out of LTE on the computed atmospheric structure, overall absolute flux distribution, and the moderately high resolution spectrum in the visible and near UV bands. Our NLTE modeling includes the first two or three io

R. L. Shelton, K. D. Kuntz, R. Petre

This paper presents archival ROSAT PSPC observations of the G65.2+5.7 supernova remnant (also known as G65.3+5.7). Little material obscures this remnant and so it was well observed, even at the softest end of ROSAT&#39;s bandpass (~0.11 to 0.28 keV). These soft X-ray images reveal the remnant&#39;s centrally-filled morphology which, in combination with exist

E. P. Kontar, A. G. Emslie, M. Piana, A. M. Massone

Kontar et al. (2004) have shown how to recover mean source electron spectra in solar flares through a physical constraint regularization analysis of the bremsstrahlung photon spectra that they produce. They emphasize the use of non-square inversion techniques, and preconditioning combined with physical properties of the spectra to achieve the most meaningful

Barbara. A. Whitney, Remy Indebetouw, J. E. Bjorkman, Kenneth Wood

We model how the mid-infrared colors of Young Stellar Objects (YSOs) vary with stellar temperature. The spectral energy distribution (SED) of each object has contributions from thermal emission of circumstellar dust, from direct stellar photospheric emission, and from scattered stellar emission. We first isolate the effects of stellar contributions (direct+s

M. Guainazzi, A. C. Fabian, K. Iwasawa, G. Matt

We present Chandra and XMM-Newton observations of a small sample (11 objects) of optically-selected Seyfert~2 galaxies, for which ASCA and BeppoSAX had suggested Compton-thick obscuration of the Active Nucleus (AGN). The main goal of this study is to estimate the rate of transitions between &#34;transmission-&#34; and &#34;reprocessing-dominated&#34; states.

E. P. Kontar, M. Piana, A. M. Massone, A. G. Emslie

Hard X-ray spectra in solar flares provide knowledge of the electron spectrum that results from acceleration and propagation in the solar atmosphere. However, the inference of the electron spectra from solar X-ray spectra is an ill-posed inverse problem. Here we develop and apply an enhanced regularization algorithm for this process making use of physical co

S. Rawlings, M. J. Jarvis

The relationships between supermassive black holes and the properties of their associated dark-matter halos imply that outflows from accreting black holes provide a feedback mechanism regulating galaxy formation. Accreting black holes with weak or undetectable radio jets (radio-quiet quasars) outnumber those with powerful jets (radio-loud quasars) by a facto

D. W. Hoard, C. S. Brinkworth, S. Wachter

We present results from our analysis of the near-infrared (J, H, and Ks) photometry for all cataclysmic variables from the catalog of Downes et al. (2001) that are detected in the (final) All Sky Data Release from the Two Micron All Sky Survey (2MASS).

M. Gliozzi, I. E. Papadakis, R. M. Sambruna, M. Eracleous

We use data from a two-year intensive RXTE monitoring campaign of the broad-line radio galaxy 3C 390.3 to investigate its stationarity. In order to exploit the potential information contained in a time series more efficiently, we use a multi-technique approach. Specifically, the temporal properties are first studied with a technique borrowed from non-linear

D. Cardini

The Mg II k emission line is a good indicator of the level of chromospheric activity in late-type stars. We investigate the dependence of this activity indicator on fundamental stellar parameters. To this purpose we use IUE observations of the Mg II k line in 225 late-type stars of luminosity classes I-V, with different levels of chromospheric activity. We f

M. G. Kitzbichler, S. D. M. White

We compare pure luminosity evolution (PLE) models with recent data at low and high redshift. These models assume that massive galaxies were assembled and formed most of their stars at high redshift (z > 3) and have evolved without merging or substantial dust obscuration since then. Our models span the full range of plausible metallicities, initial mass funct

Melvyn B. Davies, Andrew J. Levan, Andrew R. King

We present a simple, semi--analytical description for the final stages of mergers of black hole (BH) -- neutron star (NS) systems. Such systems are of much interest as gravitational wave sources and gamma--ray burst progenitors. Numerical studies show that in general the neutron star is not disrupted at the first phase of mass transfer. Instead, what remains

Andreas Burkert, Lee Hartmann

We present two-dimensional simulations of finite, self-gravitating gaseous sheets. Unlike the case of infinite sheets, such configurations do not constitute equilibrium states but instead are subject to global collapse unless countered by pressure forces or rotation. The initial effect of finite geometry is to promote concentrations of material at the edges

Victor L. Afanasiev, Olga K. Sil&#39;chenko

The kinematics, structure, and stellar population properties in the centers of two early-type spiral galaxies of the Leo Triplet, NGC 3623 and NGC 3627, are studied by means of integral-field spectroscopy. Unlike our previous targets, NGC 3384/NGC 3368 in the Leo I group and NGC 5574/NGC 5576 in LGG379, NGC 3623 and NGC 3627 do not appear to experience a syn

P. Ventura, M. Castellani

We examine the convective core helium burning phase of intermediate mass stars, and investigate the role of coupling of nuclear burning and mixing on the extension and duration of the blue loop phase. We compare the theoretical scenario with the distribution of stars in the colour-magnitude (CM) diagram of the Large Magellanic Cloud (LMC) cluster NGC1866, wh

Lev R. Yungelson

We discuss application of population synthesis for binary stars to progenitors of SN Ia. We show that the only candidate systems able to support the rate of SNe Ia $\sim 10^{-3} yr^{-1}$ both in old and young populations are merging white dwarfs. In young populations ($\sim 1$ Gyr) edge-lit detonations in semidetached systems with nondegenerate helium star d

Dharam Vir Lal, A. Pramesh Rao

Analysis of Giant Metrewave Radio Telescope low frequency data for an X-shaped source, 3C 223.1 has revealed an unusual result. The radio morphologies of it at 240 and 610 MHz show well defined X-shape with a pair of active jets along the north-south axis and a pair of wings along the east-west axis, that pass symmetrically through the undetected radio core.

Roland Diehl

Gamma-ray lines from radioactive isotopes, ejected into interstellar space by cosmic nucleosynthesis events, are observed with new space telescopes. The Compton Observatory had provided a sky survey for the isotopes 56Co, 22Na, 44Ti, and 26Al, detecting supernova radioactivity and the diffuse glow of long-lived radioactivity from massive stars in the Galaxy.

A. C. Robin, C. Reylé, S. Picaud, M. Schultheis

The bulge is a region of the Galaxy which is of tremendous interest for understanding Galaxy formation. However, measuring photometry and kinematics in it raises several inherent issues, like high extinction in the visible and severe crowding. Here we attempt to estimate the problem of the visibility of the bulge at optical wavelengths, where large CCD mosai

Olivier Richard, Georges Michaud, Jacques Richer

The WMAP determination of the baryon-to-photon ratio implies, through Big Bang nucleosynthesis, a cosmological Li abundance larger, by a factor of 2 to 3, than the Li abundance plateau observed in the oldest Pop II stars. It is however inescapable that there be a reduction by a factor of at least 1.6 to 2.0 of the surface Li abundance during the evolution of