September 2003 arXiv papers — page 10

Veit Elser

Bit retrieval, the problem of determining a binary sequence from its cyclic autocorrelation, is a special case of the phase retrieval problem. Algorithms for phase retrieval are extensively used in several scientific disciplines, and yet, very little is known about the complexity of these algorithms or phase retrieval in general. Here we show that bit retrie

Leonardo Zapponi

Let k be an algebraically closed field of positive characteristic. The goal of this paper is to characterize the proper smooth curves X/k of positive genus g equipped with a k-rational point P such that X¶can be realized as an etale cover of the affine line. A first elementary analysis shows that such a cover exists if and only if there exists an exact regul

Rami Kanhouche

We present a new modified Burg-Like algorithm for spectral estimation and adaptive signal processing, that yield the same prediction coefficients given by the Levinson algorithm for the solution of the normal equations. An equivalency proof is given for both the 1D signal and 2D signal cases. Numerical simulations illustrate the improved accuracy and stabili

David W. Kribs

Non-commutative versions of Arveson's curvature invariant and Euler characteristic for a commuting $n$-tuple of operators are introduced. The non-commutative curvature invariant is sensitive enough to determine if an $n$-tuple is free. In general both invariants can be thought of as measuring the freeness or curvature of an $n$-tuple. The connection with

David W. Kribs

The non-commutative analytic Toeplitz algebra is the weak operator topology closed algebra generated by the left regular representation of the free semigroup on $n$ generators. The structure theory of contractions in these algebras is examined. Each is shown to have an $H^\infty$ functional calculus. The isometries defined by words are shown to factor only a

Roberto Frigerio

For any g>1 we construct a graph G_g in S^3 whose exterior M_g supports a complete finite-volume hyperbolic structure with one toric cusp and a connected geodesic boundary of genus g. We compute the canonical decomposition and the isometry group of M_g, showing in particular that any self-homeomorphism of M_g extends to a self-homeomorphism of the pair (S^3,

V. C. Barbosa

For $k\ge 1$, we consider interleaved $k$-tuple colorings of the nodes of a graph, that is, assignments of $k$ distinct natural numbers to each node in such a way that nodes that are connected by an edge receive numbers that are strictly alternating between them with respect to the relation $<$. If it takes at least $χ_{int}^k(G)$ distinct numbers to provide

Denis Kochan

The aim of this paper is to present a short introduction to supergeometry on pure odd supermanifolds. (Pseudo)differential forms, Cartan calculus (DeRham differential, Lie derivative, "inner" product), metric, inner product, Killing's vector fields, Hodge star operator, integral forms, co-differential and connection on odd Riemannian supermanifolds are intro

Marek Jarnicki, Peter Pflug

We discuss continuity and upper semicontinuity of the Wu pseudometric.

Urs Frauenfelder

We prove the Arnold-Givental conjecture for a class of Lagrangian submanifolds in Marsden-Weinstein quotients which are fixpoint sets of some antisymplectic involution. For these Lagrangians the Floer homology cannot in general be defined by standard means due to the bubbling phenomenon. To overcome this difficulty we consider moment Floer homology whose bou

David W. Kribs

Noncommutative multivariable versions of weighted shifts arise naturally as `weighted&#39; left creation operators acting on Fock space. We investigate the unital weak operator topology closed algebras they generate. The unweighted case yields noncommutative analytic Toeplitz algebras. The commutant can be described in terms of weighted right creation operat

Jesús A. De Loera, Tyrrell B. McAllister

This paper is a study of the polyhedral geometry of Gelfand-Tsetlin patterns arising in the representation theory $\mathfrak{gl}_n \C$ and algebraic combinatorics. We present a combinatorial characterization of the vertices and a method to calculate the dimension of the lowest-dimensional face containing a given Gelfand-Tsetlin pattern. As an application, we

Roger Bielawski

We study manifolds arising as spaces of sections of complex manifolds fibering over the projective line with normal bundle of each section isomorphic to several copies of O(k). Such manifolds provide a natural setting for certain integrable systems, &#34;monopoles&#34;, which comprise the Bogomolny hierarchy and the self-dual hierarchy.

Dr. W. B. Vasantha Kandasamy

The author studies the Smarandache Fuzzy Algebra, which, like its predecessor Fuzzy Algebra, arose from the need to define structures that were more compatible with the real world where the grey areas mattered, not only black or white. This book has seven chapters, which are divided into two parts. Part I contains the first chapter, and Part II encloses the

Boaz Tsaban

*** Note the comment above *** This is a special issue dedicated to the announcement of Shelah&#39;s recent solution of the Minimal Tower problem, one of the oldest and most important problems in infinite combinatorics which also motivated some new studies in SPM (see fourth issue of this bulletin). We give some background and personal perspectives on the pr

Sangmin Lee

We study the 3-form flux $H_{\m\nł}$ associated with the semi-classical geometry of $G/H$ gauged WZW models. We derive a simple, general expression for the flux in an orthonormal frame and use it to explicitly verify conformal invariance to the leading order in $\a&#39;$. For supersymmetric models, we briefly revisit the conditions for enhanced supersymmetry

W. Bietenholz, F. Hofheinz, J. Nishimura

In the recent years, field theory on non-commutative (NC) spaces has attracted a lot of attention. Most literature on this subject deals with perturbation theory, although the latter runs into grave problems beyond one loop. Here we present results from a fully non-perturbative approach. In particular, we performed numerical simulations of the λϕ^{4} model w

Pavel Kovtun, Dam T. Son, Andrei O. Starinets

We show that long-time, long-distance fluctuations of plane-symmetric horizons exhibit universal hydrodynamic behavior. By considering classical fluctuations around black-brane backgrounds, we find both diffusive and shear modes. The diffusion constant and the shear viscosity are given by simple formulas, in terms of metric components. For a given metric, th

V. Branchina, K. A. Meissner, G. Veneziano

This paper has been withdrawn by the authors.

Matthias Burkardt

The physical interpretation of generalized parton distributions (in the limit $ξ=0$) as Fourier transforms of impact parameter dependent parton distributions is discussed. Particular emphasis is put on the role of the target polarization. For transversely polarized targets we expect a significant deviation from axial symmetry for the distribution in the tran

Ignacio Bediaga, Fernando S. Navarra, Marina Nielsen

We use the QCD sum rules to evaluate the form factors associated with the semileptonic decays of $D_s$ and $D$ mesons into $f_0(980)$. We consider the $f_0(980)$ meson as a quark-antiquark state with a mixture of strange and light components. The decay rates are evaluated in terms of the mixing angle. Using the same form factors to evaluate nonleptonic decay

John F. Beacom, Nicole F. Bell, Dan Hooper, Sandip Pakvasa

We have previously shown that the decay of high-energy neutrinos from distant astrophysical sources would be revealed by flavor ratios that deviate strongly from the $ϕ_{ν_e}:ϕ_{ν_μ}:ϕ_{ν_τ} = 1:1:1$ expected from oscillations alone. Here we show that the deviations are significantly larger when the mixing angle $θ_{13}$ and the CP phase $δ$ are allowed to b

Anna Kulesza, George Sterman, Werner Vogelsang

We study the application of the joint resummation formalism to Higgs production via gluon-gluon fusion at the LHC, defining inverse transforms by analytic continuation. We work at next-to-leading logarithmic accuracy. We find that at low Q_T the resummed Higgs Q_T distributions are comparable in the joint and pure-Q_T formalisms, with relatively small influe

Zuxiang Dai

At first we introduce the Neutrino in the standard Model, then the Dirac and Majorana Masses. After introducing the See-Saw Mechanism, we discuss the neutrino oscillations and the neutrino in astrophysics and cosmology. We finish this paper with a brief summary of the neutrino experiments.

Ali N. Khorramian, A. Mirjalili, S. Atashbar Tehrani

In this paper polarized valon distribution is derived from unpolarized valon distribution. In driving polarized valon distribution some unknown parameters exist which must be determined by fitting to experimental data. Here we have used Bernstein polynomial method to fit QCD predictions for the moments of $g_1^p$ structure function, to suitably the construct

Claude Semay, Bernard Silvestre-Brac, Ilya M. Narodetskii

The relations existing between the auxiliary field (einbein field) formalism and the spinless Salpeter equation are studied in the case of two particles with the same mass, interacting via a confining potential. The problem of non-orthogonality for radial excited states in the auxiliary field formalism is discussed and found to be non-crucial. It is shown th

She-Sheng Xue

Motivated by the theoretical paradox between the parity-violating gauge symmetries of the standard model and the fundamental regulator, we propose that the extension of the standard model to the high-energy region should be made by adding effective high-dimension operators whose dynamics gives an infrared scaling region, where not only the standard model app

W. Kamleh, D. B. Leinweber, A. G. WIlliams

The use of APE smearing or other blocking techniques in fermion actions can provide many advantages. There are many variants of these fat link actions in lattice QCD currently, such as FLIC fermions. The FLIC fermion formalism makes use of the APE blocking technique in combination with a projection of the blocked links back into the special unitary group. Th

Philippe de Forcrand, Oliver Jahn

A missing piece is added to the Svetitsky-Yaffe conjecture. The spin model in the same universality class as the (2+1)d SU(4) theory, the 2d Ashkin-Teller model, has a line of continuously varying critical exponents. The exponents measured in the gauge theory correspond best to the Potts point on the Ashkin-Teller line.

Yasumichi Aoki, RBC collaboration

We report on our on-going project to calculate the nucleon decay matrix elements with domain-wall fermions. Operator mixing is discussed employing a non-perturbative renormalization. Bare matrix elements of all the possible decay modes induced by the dimension-six operators are calculated with the direct method, which are compared with the indirect calculati

Yasumichi Aoki, RBC collaboration

We report on our on-going project to calculate proton decay matrix elements using domain-wall fermions on the lattice. By summarizing the history of the proton decay calculation on the lattice, we reveal the systematic errors of those calculations. Then we discuss our approach to tackle those uncertainties and show our preliminary results on the matrix eleme

A. Schoning

In this talk a search for the single production of top quarks performed at the H1 experiment is presented. No evidence for anomalous top production via FCNC processes is found and limits on the anomalous magnetic coupling constant κ_{tuγ} are given.

Winfried A. Mitaroff

The e-e+ collider LEP, running at sqrt{s} = m(Z0), has been a copious source of b-hadrons produced in decays Z0 -> b \b. We present recent studies using up to 4*10^6 hadronic Z0 decays acquired by the DELPHI detector between 1992 and 2000. They rely on efficient particle identification, precise track and vertex reconstruction and sophisticated data analysis

Yuri N. Obukhov

The curved geometry of a spacetime manifold arises as a solution of Einstein&#39;s gravitational field equation. We show that the metric of a spherically symmetric gravitational field configuration can be viewed as an optical metric created by the moving material fluid with nontrivial dielectric and magnetic properties. Such a &#34;hydrodynamical&#34; approa

Zuxiang Dai

This paper concerns the generation and evolution of the cosmological (large-scale $\sim Mpc$) magnetic fields in an inflationary universe. The universe during inflation is represented by de Sitter space-time. We started with the Maxwell equations in spatially flat Friedmann-Robertson-Walker (FRW) Cosmologies. Then we calculated the wave equations of the magn

G. M. Kremer

The Universe is modeled as a binary mixture whose constituents are described by a van der Waals fluid and by a dark energy density. The dark energy density is considered either as the quintessence or as the Chaplygin gas. The irreversible processes concerning the energy transfer between the van der Waals fluid and the gravitational field are taken into accou

V. C. Barbosa

We discuss general models of resource-sharing computations, with emphasis on the combinatorial structures and concepts that underlie the various deadlock models that have been proposed, the design of algorithms and deadlock-handling policies, and concurrency issues. These structures are mostly graph-theoretic in nature, or partially ordered sets for the esta

A. H. L. Porto, V. C. Barbosa

We introduce a novel definition of approximate palindromes in strings, and provide an algorithm to find all maximal approximate palindromes in a string with up to $k$ errors. Our definition is based on the usual edit operations of approximate pattern matching, and the algorithm we give, for a string of size $n$ on a fixed alphabet, runs in $O(k^2 n)$ time. W

L. M. A. Drummond, V. C. Barbosa

Matrix clocks are a generalization of the notion of vector clocks that allows the local representation of causal precedence to reach into an asynchronous distributed computation&#39;s past with depth $x$, where $x\ge 1$ is an integer. Maintaining matrix clocks correctly in a system of $n$ nodes requires that everymessage be accompanied by $O(n^x)$ numbers, w

L. D. Penso, V. C. Barbosa

We consider a connected undirected graph $G(n,m)$ with $n$ nodes and $m$ edges. A $k$-dominating set $D$ in $G$ is a set of nodes having the property that every node in $G$ is at most $k$ edges away from at least one node in $D$. Finding a $k$-dominating set of minimum size is NP-hard. We give a new synchronous distributed algorithm to find a $k$-dominating

V. C. Barbosa, C. A. G. Assis, J. O. do Nascimento

We introduce two novel evolutionary formulations of the problem of coloring the nodes of a graph. The first formulation is based on the relationship that exists between a graph&#39;s chromatic number and its acyclic orientations. It views such orientations as individuals and evolves them with the aid of evolutionary operators that are very heavily based on t

P. D. Drummond, P. Deuar, J. F. Corney, K. V. Kheruntsyan

We review progress towards direct simulation of quantum dynamics in many-body systems, using recently developed stochastic gauge techniques. We consider master equations, canonical ensemble calculations and reversible quantum dynamics are compared, as well the general question of strategies for choosing the gauge.

D. Rychtarik, B. Engeser, H. -C. Nägerl, R. Grimm

We report on the creation of a two-dimensional Bose-Einstein condensate of cesium atoms in a gravito-optical surface trap. The condensate is produced a few micrometer above a dielectric surface on an evanescent-wave atom mirror. After evaporative cooling by all-optical means, expansion measurements for the tightly confined vertical motion show energies well

J. R. L. de Almeida, J. R. Steiner, S. M. Rezende

In the investigations of antiferromagnetic (AF)/ ferromagnetic (FM) bilayer samples, often distinct experimental techniques yield different values for the measured exchange anisotropy field (HE). We propose that the observed discrepancy may be accounted in part by the dependence of the unidirectional anisotropy with the value of the external applied field (h

Ahsan M. Nazmul, S. Kobayashi, S. Sugahara, M. Tanaka

We demonstrate the electrical and optical control of ferromagnetism in semiconductor heterostructures at high temperatures of 100-117 K. The heterostructures consist of Mn delta-doped GaAs and p-type AlGaAs, where the overlap of the hole wavefunction with the Mn delta-doping profile leads to high ferromagnetic transition temperature TC of over 100 K (max. 17

H. J. Kang, Pengcheng Dai, J. W. Lynn, M. Matsuura

Mang et al. report the observation of a cubic (Nd,Ce)2O3 impurity phase grown epitaxially in annealed samples of electron-doped Nd2-xCexCuO4 (NCCO) and argue that our observed magnetic scattering in NCCO [Nature 423,522(2003)]is due entirely to (Nd,Ce)2O3. Here we show why this is incorrect.

Yu. Talanov, H. Adrian, M. Basset, G. Jakob

We report the results of studying the influence of the uranium-ion irradiation of the Bi_2Sr_2CaCu_2O_8 thin films on the high-temperature part (close to critical temperature) of their irreversibility line. We studied irreversible properties of the films by measuring the hysteresis of nonresonant microwave absorption. The results have revealed the shift of i

Yu. E. Lozovik, V. A. Sharapov, A. S. Arkhipov

The new method for the simulation of nonstationary quantum processes is proposed. The method is based on the tomography representation of quantum mechanics, {\it i.e.}, the state of the system is described by the {\it nonnegative} function (quantum tomogram). In the framework of the method one uses the ensemble of trajectories in the tomographic space to rep

Yu. E. Lozovik, A. V. Filinov, A. S. Arkhipov

We demonstrate a new method of simulation of nonstationary quantum processes, considering the tunneling of two {\it interacting identical particles}, represented by wave packets. The used method of quantum molecular dynamics (WMD) is based on the Wigner representation of quantum mechanics. In the context of this method ensembles of classical trajectories are

Bernhard Wunsch, Alexander Chudnovskiy

We study the energy spectrum and the persistent current in an ideal one-dimensional mesoscopic ring coupled to a fermionic reservoir. We find that the tunnel coupling in general leads to the suppression of the persistent current. However, with increasing coupling, the effective level structure of the ring coupled to the reservoir changes and quasistates with

M. Marlo, A. Harju, R. M. Nieminen

We study the effects of electron-electron correlations and confinement potential on the far-infrared spectrum of a lateral two-electron quantum dot molecule by exact diagonalization. The calculated spectra directly reflect the lowered symmetry of the external confinement potential. Surprisingly, we find interactions to drive the spectrum towards that of a hi

A. L. Chudnovskiy, S. E. Ulloa

We investigate theoretically the linear conductance of a two-level quantum dot as a function of the gate voltage and different strength of coupling to the external electronic system (the reservoir). Apart from the weak coupling regime, characterized by the Kondo-enhancement of the conductance in the spinful ground state, a strong coupling regime, which can b

Yu. N. Chiang, O. G. Shevchenko

The dissipative component of electron transport through the doubly connected SNS Andreev interferometer indium (S)-aluminium (N)-indium (S) has been studied. Within helium temperature range, the conductance of the individual sections of the interferometer exhibits phase-sensitive oscillations of quantum-interference nature. In the non-domain (normal) state o

Eran Bouchbinder, Joachim Mathiesen, Itamar Procaccia

The calculation of the stress field around an arbitrarily shaped crack in an infinite two-dimensional elastic medium is a mathematically daunting problem. With the exception of few exactly soluble crack shapes the available results are based on either perturbative approaches or on combinations of analytic and numerical techniques. We present here a general s

Y. Alhassid, Y. V. Fyodorov, T. Gorin, W. Ihra

We derive an expression for the total photodissociation cross section of a molecule incorporating both indirect processes that proceed through excited resonances, and direct processes. We show that this cross section exhibits generalized Beutler-Fano line shapes in the limit of isolated resonances. Assuming that the closed system can be modeled by random mat

Jing Ma, X. L. Lei

We investigate the linear and nonlinear dc transport through an interacting quantum dot connected to two ferromagnetic electrodes around Kondo regime with spin-flip scattering in the dot. Using a slave-boson mean field approach for the Anderson Hamiltonian having finite on-site Coulomb repulsion, we find that a spin-flip scattering always depresses the Kondo

Dan Tillberg, Jon Machta

Diffusion limited aggregation is studied from the perspective of computational complexity. A parallel algorithm is exhibited that requires a number of steps that scales as the depth of the tree defined by the cluster. The existence of this algorithm suggests a connection between a fundamental computational and structural property of DLA.

V. C. Barbosa, R. G. Ferreira

We study combinatorial indicators related to the characteristic phase transitions associated with coloring a graph optimally and finding a maximum independent set. In particular, we investigate the role of the acyclic orientations of the graph in the hardness of finding the graph&#39;s chromatic number and independence number. We provide empirical evidence t

Aiguo Xu, G. Gonnella, A. Lamura

We introduce new versions of lattice Boltzmann methods (LBM) for incompressible binary mixtures where fluctuations of total density are inhibited. As a test for the improved algorithms we consider the problem of phase separation of two-dimensional binary mixtures quenched from a disordered state into the coexistence region. We find that the stability propert

P. D. Drummond, P. Deuar

The general idea of a stochastic gauge representation is introduced and compared with more traditional phase-space expansions, like the Wigner expansion. Stochastic gauges can be used to obtain an infinite class of positive-definite stochastic time-evolution equations, equivalent to master equations, for many systems including quantum time-evolution. The met

D. van der Marel

A many-body wavefuction is postulated, which is sufficiently general to describe superconducting pair-correlations, and/or spin-correlations, which can occur either as long-range order or as finite-range correlations. The proposed wave-function appears to summarize some of the more relevant aspects of the rich phase-diagram of the high-Tc cuprates. Some of t

H. Kadowaki, B. Fåk, T. Fukuhara, K. Maezawa

Neutron scattering shows that non-Fermi-liquid behavior of the heavy-fermion compound CeNi_2Ge_2 is brought about by the development of low-energy spin fluctuations with an energy scale of 0.6 meV. They appear around the antiferromagnetic wave vectors $({1/2} {1/2} 0)$ and $(0 0 {3/4})$ at low temperatures, and coexist with high-energy spin fluctuations with

JaeSub Hong, Charles J. Hailey

We present a new result on long-term periodicity searches of the X-ray emission from 4U1700-377 using RXTE ASM and CGRO BATSE data. The hard X-ray data (20 - 200 keV) from early BATSE observations (1780 days from JD 2448370, before RXTE observations started) show evidence of a 13.8 day periodicity. The long term periodicity became substantially less prominen

H. G. Roe, T. K. Greathouse, M. J. Richter, J. H. Lacy

We present the first observations of propane (C$_3$H$_8$) on Titan that unambiguously resolve propane features from other numerous stratospheric emissions. This is accomplished using a $R=λ/δλ\approx10^5$ spectrometer (TEXES) to observe propane&#39;s $ν_{26}$ rotation-vibration band near 748 cm$^{-1}$. We find a best-fit fractional abundance of propane in Ti

Paul Martini, Donald P. Schneider

We present a new method to measure the episodic lifetime of quasars with current and future large-scale sky surveys. Future photometric observations of large samples of confirmed quasars can provide a direct measurement (or interesting lower limit) to the lifetime of an individual episode of quasar activity (t_Q) and potentially enable the study of post-quas

Naveen A. Reddy, Min S. Yun

We have studied the radio and far-infrared (FIR) emission from 114 galaxies in the 7 nearest clusters (<100 Mpc) with prominent X-ray emission to investigate the impact of the cluster environment on the star formation and AGN activity in the member galaxies. The X-ray selection criterion is adopted to focus on the most massive and dynamically relaxed cluster

T. Shahbaz, V. S. Dhillon, T. R. Marsh, C. Zurita

We present high time-resolution multicolour observations of the quiescent soft X-ray transient V404 Cyg obtained with ULTRACAM. Superimposed on the secondary star&#39;s ellipsoidal modulation are large flares on timescales of a few hours, as well as several distinct rapid flares on timescales of tens of mins. The rapid flares, most of which show further vari

W. M. Lane, T. E. Clarke, G. B. Taylor, R. A. Perley

We present new, low-frequency images of the powerful FR I radio galaxy Hydra A (3C 218). Images were made with the Very Large Array (VLA) at frequencies of 1415, 330, and 74 MHz, with resolutions on the order of 20&#34;. The morphology of the source is seen to be more complex and even larger than previously known, and extends nearly 8&#39; (530 kpc) in a Nor

Christophe Pichon, Evan Scannapieco, Bastien Aracil, Patrick Petitjean

We measure the spatial clustering of metals in the intergalactic medium from z = 1.7 to 3.0, as traced by 643 CIV and 104 SiIV N >= 10^12 cm^-2 absorption systems in 19 high signal-to-noise (40-80) and high resolution (R = 45000) quasar spectra. The number densities and two-point correlation functions of both these species are largely constant with redshift,

Pavel Kroupa, Jerome Bouvier

(abridged) Sub-stellar mass objects have fundamentally different binary properties than stars implying that they cannot have the same formation history. They are rather unfinished stars having either been ejected by their siblings from compact groups of accreting hydrostatic cores, or having lost their accretion envelopes through photo-evaporation by nearby

Stanislav Boldyrev, Carl R. Gwinn

Observations of radio signals from distant pulsars provide a valuable tool for investigation of interstellar turbulence. The time-shapes of the signals are the result of pulse broadening by the fluctuating electron density in the interstellar medium. While the scaling of the shapes with the signal frequency is well understood, the observed anomalous scaling

J. Dupuis, P. Chayer, S. Vennes, G. Hebrard

We present an analysis of the Far Ultraviolet Spectroscopic Explorer (FUSE) spectrum of the ultramassive (M = 1.31 solar mass), magnetic (B_s = 2.3 MG) white dwarf PG 1658+441. The far ultraviolet (FUV) spectrum exhibits very broad Lyman lines and quasi-molecular Lyman beta satellites, but weak Lyman gamma satellites may also be present. PG 1658+441 is the h

Jose Gaite

The process of gravitational accretion of initially homogeneous gas onto a solid ball is studied with methods of fluid dynamics. The fluid partial differential equations for polytropic flow can be solved exactly in an early stage, but this solution soon becomes discontinuous and gives rise to a shock wave. Afterwards, there is a crossover between two interme

Roger A. Chevalier

The association of a supernova with a gamma-ray burst (GRB 030329) implies a massive star progenitor, which is expected to have an environment formed by pre-burst stellar winds. Although some sources are consistent with the expected wind environment, many are not, being better fit by a uniform density environment. One possibility is that this is a shocked wi

Andy Gibb, Melvin Hoare, Lee Mundy, Friedrich Wyrowski

We present subarcsecond observations at 2.7 and 1.4 mm of a sample of massive young stellar objects made with the BIMA millimetre array. For most sources the continuum emission on the smallest scales at 2.7 mm is dominated by free-free emission from the stellar wind or jet. Strong emission at 1.4 mm shows the presence of significant dust associated with Cep

M. H. Pinsonneault, D. M. Terndrup, R. B. Hanson, J. R. Stauffer

We continue our series of papers on open cluster distances by comparing multicolor photometry of single stars in the Hyades to theoretical isochrones constructed with various color-temperature relations. After verifying that the isochrone effective temperatures agree well with spectroscopically determined values, we argue that mismatches between the photomet

Mark R. McGovern, J. Davy Kirkpatrick, Ian S. McLean, Adam J. Burgasser

We report the initial results of the Brown Dwarf Spectroscopic Survey Gravity Project, to study gravity sensitive features as indicators of youth in brown dwarfs. Low-resolution (R~2000) J-band and optical (R~1000) observations using NIRSPEC and LRIS at the W.M. Keck Observatory reveal transitions of TiO, VO, K I, Na I, Cs I, Rb I, CaH, and FeH. By comparing

M. Gliozzi, R. M. Sambruna, W. N. Brandt, R. Mushotzky

We report on the nuclear X-ray properties of the radio galaxy NGC 6251 observed with XMM-Newton. NGC 6251 is a well-known radio galaxy with intermediate FRI/II radio properties. It is optically classified as a Seyfert 2 and hosts a supermassive black hole with mass~6e8 solar masses. The 0.4-10 keV EPIC pn continuum is best fitted by two thermal components (k

Luka C. Popovic

The Boltzmann-plot (BPT) method for laboratory plasma diagnostic was used for a quick estimate of physical conditions in the Broad Line Region (BLR) of 14 Active Galactic Nuclei (AGNs). For the BLR of nine AGNs, where PLTE exist, the estimated electron temperature are in the range T $\sim$ 130000K - 37000K are in good agreement with previous estimates. The e

S. Molkov, A. Lutovinov, S. Grebenev

We present results of observations of the Aql X-1 field performed in March-April 2003 with the INTEGRAL observatory. This TOO (Target Of Opportunity) INTEGRAL observations was initiated upon receiving an indication from the ASM/RXTE that the source started an outburst. Thirteen X-ray sources were detected by the INTEGRAL imagers, JEM-X and IBIS, during these

Stephen Serjeant, Diana Harrison

We present new determinations of the local sub-mm luminosity functions. We find the local sub-mm luminosity density converging to 7.3+/-0.2 x 10^19 W/Hz/Mpc^3 /h_65 at 850um solving the ``sub-mm Olbers&#39; Paradox.&#39;&#39; Using the sub-mm colour temperature relations from the SCUBA Local Universe Galaxy Survey, and the discovery of excess 450um excess em

S. Kitsionas, E. Hatziminaoglou, I. Georgantopoulos, A. Georgakakis

The technique of estimating redshifts using photometric rather than spectroscopic observations has recently received great attention due to its simplicity and the accuracy of the results obtained. In this work, we estimate photometric redshifts for an X-ray selected QSO sample. This is the first time this technique is applied on such a sample. We first calcu

Pierre Sikivie

The recently discovered ring of stars near Galactocentric distance $r = 20$ kpc is interpreted as baryonic matter accreted onto the second caustic ring of dark matter in our galaxy. Caustic rings of dark matter were predicted in the Galactic plane at radii $a_n \simeq 40 kpc/n$ where $n=1,2,3 ..$. They can reveal themselves by their gravitational influence o

J. Michael Shull, Jason Tumlinson, Mark L. Giroux, Gerard A. Kriss

We provide an in-depth analysis of the He II and H I absorption in the intergalactic medium (IGM) at redshifts z = 2.3-2.9 toward HE 2347-4342, using spectra from the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Ultraviolet-Visual Echelle Spectrograph (UVES) on the VLT telescope. Following up on our earlier study (Kriss et al. 2001, Science, 293, 11

Karen T. Lewis, Michael Eracleous, Jules P. Halpern, Thaisa Storchi-Bergmann

An increasing number of AGNs exhibit broad, double-peaked Balmer emission lines, which are thought to arise from the outer regions of the accretion disk which fuels the AGN. The line profiles are observed to vary on a characteristic timescales of 5-10 years. The variability is not a reverberation effect; it is a manifestation of physical changes in the disk.

Stefano Zibetti, Simon D. M. White, Jon Brinkmann

We present a statistical analysis of halo emission for a sample of 1047 edge-on disk galaxies imaged in five bands by the Sloan Digital Sky Survey (SDSS). Stacking the homogeneously rescaled images of the galaxies, we can measure surface brightnesses as deep as mu_r~31 mag/arcsec^2. The results strongly support the almost ubiquitous presence of stellar halos

Tim Huege, Heino Falcke

Cosmic ray air showers have been known for over 30 years to emit pulsed radio emission in the frequency range from a few to a few hundred MHz, an effect that offers great opportunities for the study of extensive air showers with upcoming fully digital &#34;software radio telescopes&#34; such as LOFAR and the enhancement of particle detector arrays such as KA

A. C. Goncalves, M. Serote Roos

We report on the spectroscopic study of 19 low luminosity Flat Radio Spectrum (LL FRS) sources selected from Marcha&#39;s et al. (1996) 200 mJy sample. In the optical, these objects are mainly dominated by the host galaxy starlight. After correcting the data for this effect, we obtain a new set of spectra clearly displaying weak emission lines; such features

S. Demers, P. Battinelli

We present a CFH12K wide field survey of the carbon star population in and around NGC 3109. Carbon stars, the brightest members of the intermediate-age population, were found nearly exclusively in and near the disk of NGC 3109, ruling out the existence of an extensive intermediate-age halo like the one found in NGC 6822. Over 400 carbon stars identified have

Zhanwen Han, Philipp Podsiadlowski

We have carried out a detailed study of one of the most popular evolutionary channels for the production of Type Ia supernova (SN Ia) progenitors, the semi-degenerate channel (CO+MS), where a carbon/oxygen (CO) white dwarf (WD) accretes matter from an unevolved or slightly evolved non-degenerate star until it reaches the Chandrasekhar mass limit. Employing E

A. Reiners, J. H. M. M. Schmitt Hamburger Sternwarte

We obtained high quality spectra of 135 stars of spectral types F and later and derived ``overall&#39;&#39; broadening functions in selected wavelength regions utilizing a Least Squares Deconvolution (LSD) procedure. Precision values of the projected rotational velocity $v \sin{i}$ were derived from the first zero of the Fourier transformed profiles and the

G. Cusumano

During its life, BeppoSAX observed several isolated pulsars, giving important contributions to the knowledge of the phenomenology and properties of the X-ray emission from this class of sources. In this paper I review the spectral and timing results obtained from BeppoSAX observations. In particular, results on three Crab-like (Crab, PSR B1509-58 and PSR B05

A. A. Cole, T. A. Smecker-Hane, E. Tolstoy, T. L. Bosler

We have obtained spectra with resolution 2.5 Angstroms in the region 7500-9500 Angstroms for 116 red giants in 5 Galactic globular clusters and 6 old open clusters (5 with published metallicities, and one previously unmeasured). The signal-to-noise ranges from 20 to 85. We measure the equivalent widths of the infrared Ca II triplet absorption lines in each s

M. R. Truss, G. A. Wynn, P. J. Wheatley

We propose a simple explanation for the constant mean brightness observed between outbursts in dwarf novae. Secular changes in the total energy dissipation rate of the accretion disc brought about by variations in surface density, temperature and disc radius can be regulated by the gradual cooling of a small, critically-stable hot inner region. The hypothesi

M. Bruggen, T. A. Ensslin, F. Miniati

In this paper we compute the luminosity function of radio relics. In our calculation we include only those relics that are produced by the compression of former radio cocoons. This compression is provided by shocks that are generated in the process of structure formation. Starting from an analytical model for the luminosity evolution of ageing radio cocoons,

M. Dominik, M. D. Albrow, J. -P. Beaulieu, J. A. R. Caldwell

With round-the-clock monitoring of galactic bulge microlensing events, the PLANET experiment constrains the abundance and can yield the discovery of planets down to the mass of earth around galactic disk and bulge stars. Data taken until 1999 imply that less than 1/3 of bulge M-dwarfs are surrounded by jupiter-mass companions at orbital radii between 1 and 4

Erandy Ramirez, Andrew R. Liddle

We formalize the Hubble slow-roll formalism for inflationary dynamics in Randall-Sundrum Type II braneworld cosmologies, defining Hubble slow-roll parameters which can be used along with the Hamilton-Jacobi formalism. Focussing on the high-energy limit, we use these to calculate the exact power spectrum for power-law inflation, and then perturb around this s

E. Piconcelli, M. Cappi, L. Bassani, G. Di Cocco

We report on the spectral properties of a sample of 90 hard X-ray selected serendipitous sources detected in 12 XMM observations with 1<F(2-10)<80 10^(-14) erg/cm2/s. Approximately 40% of the sources are optically identified with 0.1<z<2 and most of them are classified as broad line AGNs. A simple model consisting of power law modified by Galactic absorption

Y. Uchida, H. Kigure, S. Hirose, M. Nakamura

Using the numerical data of MHD simulation for AGN jets based on our ``sweeping magnetic twist model&#39;&#39;, we calculated the Faraday rotation measure (FRM) and the Stokes parameters to compare with observations. We propose that the FRM distribution can be used to discuss the 3-dimensional structure of magnetic field around jets, together with the projec

J. H. You, D. B. Liu, W. P. Chen, L. Chen

When thermal relativistic electrons with isotropic distribution of velocities move in a gas region, or impinge upon the surface of a cloud that consists of a dense gas or doped dusts, the Cerenkov effect produces peculiar atomic or ionic emission lines -- the Cerenkov line-like radiation. This newly recognized emission mechanism may find wide applications in