July 2006 arXiv papers — page 28

Armen Edigarian, Ragnar Sigurdsson

We study a disc formula for the relative extremal function for Borel sets in complex manifolds.

A. Favaron, A. Lorenzi

We are concerned with the problem of recovering the radial kernel $k$, depending also on time, in the parabolic integro-differential equation $$D_{t}u(t,x)={\cal A}u(t,x)+\int_0^t k(t-s,|x|){\cal B}u(s,x)ds +\int_0^t D_{|x|}k(t-s,|x|){\cal C}u(s,x)ds+f(t,x),$$ ${\cal A}$ being a uniformly elliptic second-order linear operator in divergence form. We single ou

A. Favaron, A. Lorenzi

We are concerned with the problem of recovering the radial kernel $k$, depending also on time, in a parabolic integro-differential equation $$D_{t}u(t,x)={\cal A}u(t,x)+\int_0^t k(t-s,|x|){\cal B}u(s,x)ds +\int_0^t D_{|x|}k(t-s,|x|){\cal C}u(s,x)ds+f(t,x),$$ ${\cal A}$ being a uniformly elliptic second-order linear operator in divergence form. We single out

Marta Sanz-Solé, Iván Torrecilla-Tarantino

We prove the existence and smoothness of density for the solution of a hyperbolic SPDE with free term coefficients depending on time, under hypoelliptic non degeneracy conditions. The result extends those proved in Cattiaux and Mesnager, PTRF 2002, to an infinite dimensional setting.

Jia Yuan, Junyong Zhang

In this paper we prove sharp Hardy inequalities by using Maximal function theory. Our results improve and extend the well-known results of G.Hardy \cite{Ha04}, T.Cazenave \cite {Ca03}, J.-Y.Chemin\cite {Ch06} and T.Tao\cite {TT06}.

Viktor Schroeder

We give a short review of a construction of Frink to obtain a metric space from a quasi-metric space. By an example we illustrate the limits of the construction.

Wu Zhixiang

We define a new kind quantized enveloping algebra of a generalized Kac-Moody algebra ${\mathcal G}$ by adding a new generator $J$ satisfying $J^m=J$ for some integer $m$. We denote this algebra by $wU_q^τ({\mathcal G})$. This algebra is a weak Hopf algebra if and only if $m=2,3$. In general, it is a bialgebra, and contains a Hopf subalgebra. This Hopf subalg

Susumu Ariki, Andrew Mathas, Hebing Rui

Nazarov \cite{Nazarov:brauer} introduced an infinite dimensional algebra, which he called the \textit{affine Wenzl algebra}, in his study of the Brauer algebras. In this paper we study certain ``cyclotomic quotients'' of these algebras. We construct the irreducible representations of these algebras in the generic case and use this to show that these

Tamas Forgacs, Dror Varolin

We present sufficient conditions on a smooth uniformly flat hypersurface W in the unit ball to be an interpolation hypersurface or a sampling hypersurface for generalized Bergman spaces associated to the unit ball with its Bergman metric. The conditions are phrased in terms of a geometric Beurling-type densities, similar to the densities defined for hypersur

Eli Hawkins

Noncommutatively deformed geometries, such as the noncommutative torus, do not exist generically. I showed in a previous paper that the existence of such a deformation implies compatibility conditions between the classical metric and the Poisson bivector (which characterizes the noncommutativity). Here I present another necessary condition: the vanishing of

Dror Varolin

Hermitian algebraic functions were introduced by Catlin and D'Angelo under the name of "globalizable metrics". Catlin and D'Angelo proved that any Hermitian algebraic function without non-trivial zeros is a quotient of squared norms, thus giving an answer to a Hermitian analogue of Hilbert's 17th problem in the non-degenerate case. The re

Lisa Jeffrey, Joon-Hyeok Song

In this paper we prove a residue formula for intersection pairings of reduced spaces of certain quasi-Hamiltonian G-spaces, by constructing the corresponding Hamiltonian G-space. Our argument closely follows the methods of a 1998 paper of the first author and F. Kirwan on intersection numbers in moduli spaces (for G=SU(n)). For the more general class of comp

Tom Braden

We show that certain categories of perverse sheaves on a pair of affine toric varieties defined by dual cones are Koszul dual in the sense of Beilinson, Ginzburg and Soergel. The functor expressing this duality is constructed explicitly using a combinatorial model for mixed sheaves on toric varieties.

Florin P. Boca, Alexandru Zaharescu

We study the free path length and the geometric free path length in the model of the periodic two-dimensional Lorentz gas (Sinai billiard). We give a complete and rigorous proof for the existence of their distributions in the small-scatterer limit and explicitly compute them. As a corollary one gets a complete proof for the existence of the constant term $c=

Leonid Polterovich, Mikhail Sodin

Given an orientation-preserving diffeomorphism of the interval [0;1], consider the uniform norm of the differential of its n-th iteration. We get a function of n called the growth sequence. Its asymptotic behaviour is an interesting invariant which naturally appears both in geometry of the diffeomorphisms groups and in smooth dynamics. Our main result is the

Philip D. Mannheim, Ionel Simbotin

We establish the completeness of some characteristic sets of non-normalizable modes by constructing fully localized square steps out of them, with each such construction expressly displaying the Gibbs phenomenon associated with trying to use a complete basis of modes to fit functions with discontinuous edges. As well as being of interest in and of itself, ou

Oscar Varela

In this PhD Thesis, supersymmetry and its formulation in the context of D=11 supergravity is discussed from several perspectives. The role of generalized holonomy as a classification tool of supersymmetric supergravity solutions is reviewed, with particular emphasis on how successive supercovariant derivatives of the generalized curvature may be needed to pr

Peter Svrcek

String theory axions appear to be promising candidates for explaining cosmological constant via quintessence. In this paper, we study conditions on the string compactifications under which axion quintessence can happen. For sufficiently large number of axions, cosmological constant can be accounted for as the potential energy of axions that have not yet rela

Matthew J. Strassler

A hidden valley sector may havea profound impact on the classic phenomenology of supersymmetry. This occurs if the LSP lies in the valley sector. In addition to reducing the standard missing energy signals and possibly providing displaced vertices (phenomena familiar from gauge-mediated and R-parity-violating models) it may lead to a variable multiplicity of

Jeppe R. Andersen

We discuss how the multi-Regge factorisation of QCD amplitudes can be used in the study of multi-jet processes at colliders. We describe how the next-to-leading logarithmic (NLL) BFKL evolution can be combined with energy and momentum conservation. By recalculating the quark contribution to the next-to-leading logarithmic corrections to the BFKL kernel we ca

S. T. Petcov, T. Schwetz

We consider the determination of the solar neutrino oscillation parameters $Δm^2_{21}$ and $θ_{12}$ by studying oscillations of reactor anti-neutrinos emitted by nuclear power plants (located mainly in France) with a detector installed in the Frejus underground laboratory. The performances of a water Cerenkov detector of 147 kt fiducial mass doped with 0.1%

C. P. Korthals Altes

In this talk we review how a dilute gas of magnetic monopoles in the adjoint describes the spatial k-Wilson loops. We formulate an effective theory from $S_{MQCD}$ by integrating out dof's down to scales in between the magnetic screening mass and the string tension and relate the 3d pressure and the string tension. Lattice data are consistent with the ga

Gavin P. Salam

A brief overview of some recently active topics in perturbative QCD, including: string-inspired recursion techniques at tree level; recursion approaches and automation of standard techniques for 1-loop calculations; the status of NNLO jet calculations; and non-trivial structures that appear in higher-order calculations.

Maarten Golterman, Santi Peris

Although there are phenomenological indications that the low-energy constants in the chiral lagrangian may be understood in terms of a finite number of hadronic resonances, it remains unclear how this follows from QCD. One of the arguments usually given is that low-energy constants are associated with chiral symmetry breaking, while QCD perturbation theory s

Joseph D. Lykken

A concise look at the big picture of particle physics, including the status of the Standard Model, neutrinos, supersymmetry, extra dimensions and cosmology. Based upon the theoretical summary presented at the XLIst Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, 11-18 March 2006.

Giacomo Cacciapaglia, Csaba Csáki, Guido Marandella, John Terning

We present an example of a realistic Higgsless model that makes use of alternative $SU(2)_R$ assignments for the top and bottom quarks recently proposed by Agashe et al. which results in an enhanced custodial symmetry. Using these new representat ions reduces the deviations in the $Zb_\ell\bar{b}_\ell$ coupling to $\sim 4%$ for a wide range of parameters, wh

Harvey B. Meyer

Using a three-level algorithm we perform a high-precision lattice computation of the static force up to 1fm in the 2+1 dimensional SU(5) gauge theory. Discretization errors and the continuum limit are discussed in detail. By comparison with existing SU(2) and SU(3) data it is found that σr_0^2=1.65-π/24 holds at an accuracy of 1% for all N>=2, where r_0 is t

D0 Collaboration, V. Abazov

We report a search for the standard model (SM) Higgs boson based on data collected by the D0 experiment at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 260 pb^-1. We study events with missing transverse energy and two acoplanar b-jets, which provide sensitivity to the ZH production cross section in the neutrino-neutrino-b-b ch

D. South

The search for events containing isolated leptons (electrons or muons) and missing transverse momentum produced in $e^{\pm}p$ collisions is performed with the H1 detector at HERA in the period 1994--2005. The analysed data sample corresponds to an integrated luminosity of 279 pb$^{-1}$, which includes 53 pb$^{-1}$ of $e^{+}p$ data and 107 pb$^{-1}$ of $e^{-}

H. Stenzel

A review of multijet rates and event-shape variables sensitive to multijet configuration with applications to measurements of alpha_s, QCD color factors and tests of power corrections is presented

Barry R. Holstein

a previous evaluation of the one-graviton loop corrections to the energy-momentum tensor has been extended to particles with unit spin and speculations are presented concerning general properties of such forms.

J. Fernando Barbero G., Iñaki Garay, Eduardo J. S. Villaseñor

The purpose of this paper is to discuss in detail the use of scalar matter coupled to linearly polarized Einstein-Rosen waves as a probe to study quantum gravity in the restricted setting provided by this symmetry reduction of general relativity. We will obtain the relevant Hamiltonian and quantize it with the techniques already used for the purely gravitati

Felice Manganiello

In this article, we illustrate an algorithm for the computation of the weight distribution of CRC codes. The recursive structure of CRC codes will give us an iterative way to compute the weight distribution of their dual codes starting from just some ``representative'' words. Thanks to MacWilliams Theorem, the computation of the weight distribution o

Vladimir Vovk

In this paper we introduce the class of stationary prediction strategies and construct a prediction algorithm that asymptotically performs as well as the best continuous stationary strategy. We make mild compactness assumptions but no stochastic assumptions about the environment. In particular, no assumption of stationarity is made about the environment, and

Antonis Sidiropoulos, Dimitrios Katsaros, Yannis Manolopoulos

What is the value of a scientist and its impact upon the scientific thinking? How can we measure the prestige of a journal or of a conference? The evaluation of the scientific work of a scientist and the estimation of the quality of a journal or conference has long attracted significant interest, due to the benefits from obtaining an unbiased and fair criter

Khalil Djelloul

We present in this paper a general algorithm for solving first-order formulas in particular theories called "decomposable theories". First of all, using special quantifiers, we give a formal characterization of decomposable theories and show some of their properties. Then, we present a general algorithm for solving first-order formulas in any decompo

Abdelaziz Amraoui, Andrea Montanari, Ruediger Urbanke

We explain how to optimize finite-length LDPC codes for transmission over the binary erasure channel. Our approach relies on an analytic approximation of the erasure probability. This is in turn based on a finite-length scaling result to model large scale erasures and a union bound involving minimal stopping sets to take into account small error events. We s

Shi Zhou

The internet structure is extremely complex. The Positive-Feedback Preference (PFP) model is a recently introduced internet topology generator. The model uses two generic algorithms to replicate the evolution dynamics observed on the internet historic data. The phenomenological model was originally designed to match only two topology properties of the intern

Vassiliy Lubchenko, P. G. Wolynes

We review the Random First Order Transition Theory of the glass transition, emphasizing the experimental tests of the theory. Many distinct phenomena are quantitatively predicted or explained by the theory, both above and below the glass transition temperature $T_g$. These include: the viscosity catastrophe and heat capacity jump at $T_g$, and their connecti

L. N. Bulaevskii, A. E. Koshelev

We derive the radiation power from a single Josephson junction (JJ) and from layered superconductors in the flux-flow regime. For the JJ case we formulate the boundary conditions for the electric and magnetic fields at the edges of the superconducting leads using the Maxwell equations in the dielectric media and find dynamic boundary conditions for the phase

Jacek Mulak, Maciej Mulak, Ryszard Gonczarek

The variation ranges of the axial B_{k0} crystal-field parameters, for k=2,4,6, of tetragonal including cubic crystal-field Hamiltonians H_{CF} for all possible orientations of the relevant reference frame are studied. The distinguished z-axis directions fixed by the maximal absolute values of B_{k0} are analyzed. The diagrams for any tetragonal H_{CF} param

I. Neder, M. Heiblum, D. Mahalu, V. Umansky

Determination of the path taken by a quantum particle leads to a suppression of interference and to a classical behavior. We employ here a quantum 'which path' detector to perform accurate path determination in a two-path-electron-interferometer; leading to full suppression of the interference. Following the dephasing process we recover the interfere

M. Trigo, T. A. Eckhause, M. Reason, R. S. Goldman

Coherent time-domain optical experiments on GaAs-AlAs superlattices reveal the exis-tence of an unusually long-lived acoustic mode at ~ 0.6 THz, which couples weakly to the environment by evading the sample boundaries. Classical as well as quantum states that steer clear of surfaces are generally shown to occur in the spectrum of periodic struc-tures, for mo

Seth T. Rittenhouse, M. J. Cavagnero, Javier von Stecher, Chris H. Greene

We present a unique theoretical description of the physics of the spherically trapped $N$-atom degenerate Fermi gas (DFG) at zero temperature based on an ordinary Schrödinger equation with a microscopic, two body interaction potential. With a careful choice of coordinates and a variational wavefunction, the many body Schrödinger equation can be accurately de

L. Mahadevan, A. Vaziri, Moumita Das

The response of low-dimensional solid objects combines geometry and physics in unusual ways, exemplified in structures of great utility such as a thin-walled tube that is ubiquitous in nature and technology. Here we provide a particularly surprising consequence of this confluence of geometry and physics in tubular structures: the anomalously large persistenc

Benjamin Balke, Hem C. Kandpal, Gerhard H. Fecher, Claudia Felser

Electronic structure calculation were used to predict a new material for spintronic applications. Co2Mn0.5Fe0.5Si is one example which is stable against on-site correlation and disorder effects due to the position of the Fermi energy in the middle of the minority band gap. Experimentally the sample were made exhibiting L21 structure and a high magnetic order

Jesús Casado-Pascual

A rather simple random walk model on a one-dimensional lattice is put forward. The lattice as a whole switches randomly between two possible states which are spatially symmetric. Both lattice states are identical, but translated by one site with respect to each other, and consist of infinite arrays of absorbing sites separated by two non-absorbing sites. Exa

Hiroshi Miyazaki, Tomohiko Hiwasa, Masataka Oko, Isao Harada

A possible spin-reorientation transition in field-induced magnetic ordering phases of the S=1 Haldane system with large easy-plane anisotropy is proposed, using an effective Lagrangian formalism as well as the density matrix renormalization group method. Such a spin-reorientation transition is predicted in the case where the applied magnetic field is incline

J. M. D. Lane, M. P. Marder

We develop a Continuous Hugoniot Method for the efficient simulation of shock wave fronts with molecular dynamics. This approach achieves a significantly improved efficiency in the generation of a dense sampling of steady-state shock front states, and allows for the study of shocks as a function of a continuous shock strength parameter, $v_p$. This is, to ou

Gianluca Stefanucci, Stefan Kurth, E. K. U. Gross, Angel Rubio

The aim of this review is to give a pedagogical introduction to our recently proposed ab initio theory of quantum transport.

Beata J. Dabrowska-Wuester, Sebastian Wuester, Ashton S. Bradley, Matthew J. Davis

We study quantum effects in the dynamics of a Bose-Einstein condensate loaded onto the edge of a Brillouin zone of a one-dimensional periodic potential created by an optical lattice. We show that quantum fluctuations trigger the dynamical instability of the Bloch states of the condensate and can lead to the generation of arrays of matter-wave gap solitons. O

R. K. Bhaduri, W. van Dijk, M. K. Srivastava

Quantum effects in statistical mechanics are important when the thermal wavelength is of the order of, or greater than, the mean interatomic spacing. This is examined at depth taking the example of a hard-sphere Boltzmann gas. Using the virial expansion for the equation of state, it is shown that the interaction energy of a classical hard-sphere gas is exact

Peng Li, Guang-Ming Zhang, Shun-Qing Shen

A bond-operator mean-field theory in the SU(3) bosons representation is developed to describe the antiferro-nematic phase of the spin-1 bilinear-biquadratic model. The calculated static structure factors reveal delicately that the antiferro-nematic state may exhibit both the ferro- and antiferro-quadruple long-range orders, which is reminiscent of the ferrim

Markus Bier, Ludger Harnau, S. Dietrich

Surface properties of mixtures of charged platelike colloids and salt in contact with a charged planar wall are studied within density functional theory. The particles are modeled by hard cuboids with their edges constrained to be parallel to the Cartesian axes corresponding to the Zwanzig model and the charges of the particles are concentrated in their cent

Satoru Konabe, Tetsuro Nikuni

Starting from an effective action for the order parameter field, we derive a coupled set of generalized hydrodynamic equations for a Bose condensate in an optical lattice at finite temperatures. Using the linearized hydrodynamic equations, we study the microscopic mechanism of the Landau instability due to the collisional damping process between condensate a

Y. F. Wu, Y. F. Lu, G. Yan, J. S. Li

The MgB2 bulks were prepared by high energy milling of Mg and B powder. The correlations among milling times, microstructure and superconducting properties were investigated in MgB2 bulks. Samples were characterized by x-ray diffraction (XRD), energy dispersive spectrometry (EDX) and scanning electron microscope (SEM), and the magnetization properties were e

Pablo San-Jose, Elsa Prada

We study the effect of inelastic scattering on the spin entanglement detection and discrimination scheme proposed by Egues, Burkard, and Loss [Phys. Rev. Lett. \textbf{89}, 176401 (2002)]. The finite-backscattering beam splitter geometry is supplemented by a phenomenological model for inelastic scattering, the charge-conserving voltage probe model, convenien

Y. Y. Wang, M. W. Wu

We propose a scheme to manipulate the spin relaxation in vertically coupled semiconductor double quantum dots. Up to {\em twelve} orders of magnitude variation of the spin relaxation time can be achieved by a small gate voltage applied vertically on the double dot. Different effects such as the dot size, barrier height, inter-dot distance, and magnetic field

Yulia Gilman, Philip B. Allen, Mark S. Hybertsen

Density functional theory within the generalized-gradient approximation is used to study the adsorption of the isocyanides CNH and CNCH3 on the gold (111) surface at several coverages. It is found that these molecules are highly selective in their adsorption site preference. Adsorption is possible only at the top site, although binding is rather weak and dip

Edward R. D. Scott

Peak temperatures inside meteorite parent bodies are closely linked to accretion times. Most iron meteorites come from bodies that accreted <0.5 Myr after CAIs formed and were melted by 26Al and 60Fe, probably inside 2 AU. Chondrite groups accreted intermittently over 4 Myr starting 1 Myr after CAIs formed when planetary embryos may already have formed at ~1

Wayne Hu, Dragan Huterer, Kendrick M. Smith

Supernova distance and primary CMB anisotropy measurements provide powerful probes of the dark energy evolution in a flat universe but degrade substantially once curvature is marginalized. We show that lensed CMB polarization power spectrum measurements, accessible to next generation ground based surveys such as SPTpol or QUIET, can remove the curvature dege

Kendrick M. Smith, Wayne Hu, Manoj Kaplinghat

Gravitational lensing distorts the cosmic microwave background (CMB) temperature and polarization fields and encodes valuable information on distances and growth rates at intermediate redshifts into the lensed power spectra. The non-Gaussian bandpower covariance induced by the lenses is negligible to l=2000 for all but the B polarization field where it incre

R. I. Hynes, E. L. Robinson, K. J. Pearson, D. M. Gelino

We present simultaneous multicolor infrared and optical photometry of the black hole X-ray transient XTE J1118+480 during its short 2005 January outburst, supported by simultaneous X-ray observations. The variability is dominated by short timescales, ~10s, although a weak superhump also appears to be present in the optical. The optical rapid variations, at l

Mark S. Giampapa, Jeffrey C. Hall, Richard R. Radick, Sallie L. Baliunas

We present the results of a spectroscopic survey of the Ca II H & K core strengths in a sample of 60 solar-type stars that are members of the solar-age and solar-metallicity open cluster M67. We adopt the HK index, defined as the summed H+K core strengths in 0.1 nm bandpasses centered on the H and K lines, respectively, as a measure of the chromospheric acti

Emory F. Bunn

Cosmic microwave background (CMB) polarization observations will require superb control of systematic errors in order to achieve their full scientific potential, particularly in the case of attempts to detect the B modes that may provide a window on inflation. Interferometry may be a promising way to achieve these goals. This paper presents a formalism for c

Brent Groves, Timothy Heckman, Guinevere Kauffmann

Current emission-line based estimates of the metallicity of active galactic nuclei (AGN) at both high and low redshifts indicate that AGN have predominantly solar to supersolar metallicities. This leads to the question: do low metallicity AGN exist? In this paper we use photoionization models to examine the effects of metallicity variations on the narrow emi

J. M. Pittard

A key process within astronomy is the exchange of mass, momentum, and energy between diffuse plasmas in many types of astronomical sources (including planetary nebulae, wind-blown bubbles, supernova remnants, starburst superwinds, and the intracluster medium) and dense, embedded clouds or clumps. This transfer affects the large scale flows of the diffuse pla

K. J. H. Phillips, C. Chifor, B. R. Dennis

Analysis of RHESSI 3--10 keV spectra for 27 solar flares is reported. This energy range includes thermal free--free and free--bound continuum and two line features, at 6.7keV and 8keV, principally due to highly ionized iron (Fe). We used the continuum and the flux in the so-called Fe-line feature at 6.7keV to derive the electron temperature T_e, the emission

Jacco Vink, Johan Bleeker, Kurt van der Heyden, Andrei Bykov

We report here X-ray imaging spectroscopy observations of the northeastern shell of the supernova remnant RCW 86 with Chandra and XMM-Newton. Along this part of the shell the dominant X-ray radiation mechanism changes from thermal to synchrotron emission. We argue that both the presence of X-ray synchrotron radiation and the width of the synchrotron emitting

N. R. Deacon, N. C. Hambly

We present predictions for the numbers of ultra--cool dwarfs in the Galactic disk population that could be detected by the WFCAM/UKIDSS Large Area Survey and Ultra Deep Survey. Simulated samples of objects are created with masses and ages drawn from different mass functions and birthrates. Each object is then given absolute magnitudes in different passbands

T. Ueta, A. K. Speck, R. E. Stencel, F. Herwig

We present the first results of the MIRIAD (MIPS [Multiband Imaging Photometer for Spitzer] Infra-Red Imaging of AGB [asymptotic giant branch] Dustshells) project using the Spitzer Space Telescope. The primary aim of the project is to probe the material distribution in the extended circumstellar envelopes (CSE) of evolved stars and recover the fossil record

L. La Porta, C. Burigana, W. Reich, P. Reich

The aim of the present analysis is to improve the knowledge of the statistical properties of the Galactic diffuse synchrotron emission, which constrains sensitive CMB anisotropy measurements. We have analysed the new DRAO 1.4 GHz polarization survey together with the Stockert 1.4 GHz total intensity survey and derived the angular power spectra (APSs) of the

C. Koen, P. F. L. Maxted

The results of 27 hours of time series photometry of SDSS 121209.31+013627.7 are presented. The binary period established from spectroscopy is confirmed and refined to 0.061412 d (88.43 minutes). The photometric variations are dominated by a brightening of about 16 mmag, lasting a little less than half a binary cycle. The amplitude is approximately the same

C. Argiroffi, F. Favata, E. Flaccomio, A. Maggio

We study X-ray emission from young stars by analyzing deep XMM-Newton observations of two regions of the Upper Scorpius association, having an age of 5 Myr. Based on near infrared and optical photometry we identify 22 Upper Scorpius photometric members among the 224 detected X-ray sources. We derive coronal properties of Upper Scorpius stars by performing X-

Vassilis Charmandaris, the Spitzer/IRS Instrument Team

In this paper I summarize the science motivations, as well as a few mid-infrared spectroscopic methods used to identify the principal mechanisms of energy production in dust enshrouded galactic nuclei. The development of the various techniques is briefly discussed. Emphasis is given to the use of the data which are becoming available with the infrared spectr

N. Guessoum, P. Jean, N. Prantzos

We consider the production of positrons in microquasars, i.e. X-ray binary systems that exhibit jets frequently, but not continuously. We estimate the production rate of positrons in microquasars, both by simple energy considerations and in the framework of various proposed models. We then evaluate the collective emissivity of the annihilation radiation prod

Y. Q. Chen, G. Zhao

We have investigated the abundance anomalies of lithium for stars with planets in the temperature range of 5600--5900 K reported by Israelian and coworkers, as compared to 20 normal stars at the same temperature and metallicity ranges. Our result indicates a higher probability of lithium depletion for stars with planets in the main--sequence stage. It seems

Yu. N. Gnedin, M. Yu. Piotrovich, T. M. Natsvlishvili

The birefringent effects of photon-pseudoscalar boson (Goldstone) particle mixing in intergalactic magnetic field are calculated for cosmological objects. We use the recent results of PVLAS collaboration that reported recently the observation of a rotation of the polarization plane of light propagating through a transverse static magnetic field. Such results

Shay Zucker, Tsevi Mazeh

We propose a new approach to measure differential radial velocities, mainly for single-lined spectroscopic binaries. The proposed procedure - TIRAVEL (Template Independent RAdial VELocities) - does not rely on a prior theoretical or observed template, but instead looks for a set of relative Doppler shifts that simultaneously optimizes the alignment of all th

G. Alecian, M. J. Stift

The present paper addresses some of the problems in the buildup of element stratification in stellar magnetic atmospheres due to microscopic diffusion, in particular the redistribution of momentum among the various ionisation stages of a given element and the calculation of diffusion velocities in the presence of inclined magnetic fields. We have considerabl

Fabien Malbet, Pierre Kern, Jean-Philippe Berger, Laurent Jocou

VLTi Spectro-Imager (VSI) is a proposition for a second generation VLTI instrument which is aimed at providing the ESO community with the capability of performing image synthesis at milli-arcsecond angular resolution. VSI provides the VLTI with an instrument able to combine 4 telescopes in a baseline version and optionally up to 6 telescopes in the near-infr

J. Puls, N. Markova, S. Scuderi

We discuss recent evidence that currently accepted mass-loss rates may need to be revised downwards, as a consequence of previously neglected ``clumping&#39;&#39; of the wind. New results on the radial stratification of the corresponding clumping factors are summarized. We investigate the influence of clumping on the ionization equilibrium of phosphorus, whi

L. Binette, R. J. Wilman, M. Villar-Martin, R. A. E. Fosbury

We present photoionization calculations for the spatially-extended absorbers observed towards the extended emission line spectrum of two high-redshift radio galaxies: 0943-242 (z=2.922) and 0200+015 (z=2.230), with the aim of reproducing the absorber column ratio, N(CIV)/N(HI). We explore the effects of using different UV continua in the photoionization calc

Y. Q. Chen, G. Zhao

Abundances of 18 elements are determined for the common proper-motion pair, HD134439 and HD134440, which shows high [Mn/Fe] and low [α/Fe] ratios as compared to normal halo stars. Moreover, puzzling abundances are indicated from elements whose origins are normally considered to be from the same nucleosynthesis history. Particularly, we have found that [Mg/Fe

Z. Fan, J. Ma, R. de Grijs, Y. Yang

The large majority of extragalactic star cluster studies performed to date essentially use multi-colour photometry, combined with theoretical stellar synthesis models, to derive ages, masses, extinction estimates, and metallicities. M31 offers a unique laboratory for studies of globular cluster (GC) systems. In this paper, we obtain new age estimates for 91

Peter Todd Williams

We discuss non-self-gravitating hydrodynamic disks in the thin disk limit. These systems are stable according to the Rayleigh criterion, and yet there is some evidence that the dissipative and transport processes in these disks are hydrodynamic in nature at least some of the time. We draw on recent work on the hydrodynamics of laboratory shear flows. Such fl

Andrew R Liddle, David Parkinson, Samuel M Leach, Pia Mukherjee

We use the three-year WMAP observations to determine the normalization of the matter power spectrum in inflationary cosmologies. In this context, the quantity of interest is not the normalization marginalized over all parameters, but rather the normalization as a function of the inflationary parameters n and r with marginalization over the remaining cosmolog

William E. Harris, Gretchen L. H. Harris, Pauline Barmby, Dean E. McLaughlin

We report the first results from an imaging program with the ACS camera on HST designed to measure the structural characteristics of a wide range of globular clusters in NGC 5128, the nearest giant elliptical galaxy. From 12 ACS/WFC fields, we have measured a total of 62 previously known globular clusters and have discovered 69 new high-probability cluster c

P. M. Chesler, A. Vuorinen

We use perturbation theory to compute the diffusion coefficient of a heavy quark or scalar moving in N=4 SU(N_c) Super Yang-Mills plasma to leading order in the coupling and the ratio T/M<<1. The result is compared both to recent strong coupling calculations in the same theory and to the corresponding weak coupling result in QCD. Finally, we present a compac

Stefanos Papanikolaou, Erik Luijten, Eduardo Fradkin

We study phase diagrams of a class of doped quantum dimer models on the square lattice with ground-state wave functions whose amplitudes have the form of the Gibbs weights of a classical doped dimer model. In this dimer model, parallel neighboring dimers have attractive interactions, whereas neighboring holes either do not interact or have a repulsive intera

Ian D. McGreer, Robert H. Becker, David J. Helfand, Richard L. White

From examination of only 4 deg^2 of sky in the NOAO Deep Wide-Field Survey (NDWFS) region, we have identified the first radio-loud quasar at a redshift z>6. The object, FIRST J1427385+331241, was discovered by matching the FLAMEX IR survey to FIRST survey radio sources with NDWFS counterparts. One candidate z>6 quasar was found, and spectroscopy with the Kec

Zach Medin, Dong Lai

We present new, ab initio calculations of the electronic structure of one-dimensional infinite chains and three-dimensional condensed matter in strong magnetic fields ranging from B=10^12 G to 2x10^15 G, appropriate for observed magnetic neutron stars. At these field strengths, the magnetic forces on the electrons dominate over the Coulomb forces, and to a g

Lorenzo Cornalba, Miguel S. Costa, Joao Penedones, Pedro Vieira

We give evidence in favour of a string/black hole transition in the case of BPS fundamental string states of the Heterotic string. Our analysis goes beyond the counting of degrees of freedom and considers the evolution of dynamical quantities in the process. As the coupling increases, the string states decrease their size up to the string scale when a small

P. Fazekas, N. Barisic, I. Kezsmarki, L. Demko

The metal-insulator transition (MIT) of BaVS3 is suppressed under pressure and above the critical pressure of p~2GPa the metallic phase is stabilized. We present the results of detailed magnetoresistivity measurements carried out at pressures near the critical value, in magnetic fields up to B=12T. We found that slightly below the critical pressure the struc

Bhaskar Dutta, Yukihiro Mimura

We study B_s-\bar{B}_s mixing in grand unified SO(10), SU(5) models where the mixings among the second and third generation squarks arise due to the existence of flavor violating sources in the Dirac and Majorana couplings which are responsible for neutrino mixings. We find that when the branching ratio of tau->mu gamma decay is enhanced to be around the cur

Fred H. Thaheld

For over 7 decades it has been debated as to whether nonlocality is strictly of an uncontrollable nature. Based upon polarization measurements with entangled photons, it has been revealed that nonlocality cannot be used to achieve controllable superluminal communication. A simple series of experiments is proposed which may reveal that a rudimentary form of c

J. E. Moore, L. Balents

The topological invariants of a time-reversal-invariant band structure in two dimensions are multiple copies of the $\mathbb{Z}_2$ invariant found by Kane and Mele. Such invariants protect the topological insulator and give rise to a spin Hall effect carried by edge states. Each pair of bands related by time reversal is described by a single $\mathbb{Z}_2$ i

Stephen D. H. Hsu

We derive a fundamental upper bound on the rate at which a device can process information (i.e., the number of logical operations per unit time), arising from quantum mechanics and general relativity. In Planck units a device of volume V can execute no more than the cube root of V operations per unit time. We compare this to the rate of information processin

R. J. Ivison, S. C. Chapman, S. M. Faber, Ian Smail

We describe AEGIS20 - a radio survey of the Extended Groth Strip (EGS) conducted with the Very Large Array (VLA) at 1.4GHz. The resulting catalog contains 1,123 emitters and is sensitive to ultraluminous starbursts to z<=1.3, well matched to the redshift range of the DEEP2 spectroscopic survey in this region. We use stacking techniques to explore the uJy-lev

Matt Thomas, Bo Pang, Lillian Lee

We investigate whether one can determine from the transcripts of U.S. Congressional floor debates whether the speeches represent support of or opposition to proposed legislation. To address this problem, we exploit the fact that these speeches occur as part of a discussion; this allows us to use sources of information regarding relationships between discours