October 2004 arXiv papers — page 4

Ralf Meyer

Let A be an algebra with a countable basis and let B be, say, a Frechet algebra that contains A as a dense subalgebra. This embedding induces a functor from the derived category of B-modules to the derived category of A-modules. In many important examples, this functor is fully faithful. We study this property in some detail, giving several equivalent condit

Pascal Hubert, Samuel Lelièvre

We study the congruence problem for subgroups of the modular group that appear as Veech groups of square-tiled surfaces in the minimal stratum of abelian differentials of genus two.

Kenley Jung

Suppose $N \subset M$ is an inclusion of $II_1$-factors of finite index. If $N$ can be generated by a finite set of elements, then there exist finite generating sets $X$ for $N$ and $Y$ for $M$ such that $δ_0(X) \geq δ_0(Y)$, where $δ_0$ denotes Voiculescu's microstates (modified) free entropy dimension. Moreover given $ε>0$ one has $δ_0(F) \geq δ_0(G) \

Henrik Bäärnhielm

This is the report of a project with the aim to make a new implementation of the Schreier-Sims algorithm in GAP, specialized for matrix groups. The standard Schreier-Sims algorithm is described in some detail, followed by descriptions of the probabilistic Schreier-Sims algorithm and the Schreier-Todd-Coxeter-Sims algorithm. Then we discuss our implementation

M. M. Dodson, S. Kristensen, J. Levesley

An asymptotic formula which holds almost everywhere is obtained for the number of solutions to the Diophantine inequalities |qA-p|<ψ(|q|), where A is an n by m matrix (m>1) over the field of formal Laurent series with coefficients from a finite field, and p and q are vectors of polynomials over the same finite field.

Eun Soo Lee

We construct an endomorphism of the Khovanov invariant to prove H-thinness and pairing phenomena of the invariants for alternating links. As a consequence, it follows that the Khovanov invariant of an oriented nonsplit alternating link is determined by its Jones polynomial, signature, and the linking numbers of its components.

R. Jackiw

A fluid, like a quark-gluon plasma, may possess degrees of freedom indexed by a group variable, which retains its identity even in the fluid/continuum description. Conventional Eulerian fluid mechanics is extended to encompass this possibility.

Katrin Becker, Li-Sheng Tseng

We study the structure of warped compactifications of type IIB string theory to six space-time dimensions. We find that the most general four-manifold describing the internal dimensions is conformal to a Kahler manifold, in contrast with the heterotic case where the four-manifold must be conformally Calabi-Yau.

James Bedford, Andreas Brandhuber, Bill Spence, Gabriele Travaglini

We extend the twistor string theory inspired formalism introduced in hep-th/0407214 for calculating loop amplitudes in N=4 super Yang-Mills theory to the case of N=1 (and N=2) super Yang-Mills. Our approach yields a novel representation of the gauge theory amplitudes as dispersion integrals, which are surprisingly simple to evaluate. As an application we cal

Callum Quigley, Moshe Rozali

Using CSW rules for constructing scalar Feynman diagrams from MHV vertices, we compute the contribution of $\mathcal {N}=1$ chiral multiplet to one-loop MHV gluon amplitude. The result agrees with the one obtained previously using unitarity-based methods, thereby demonstrating the validity of the MHV-diagram technique, in the case of one-loop MHV amplitudes,

Sophie de Buyl, Axel Kleinschmidt

The emergence of higher spin fields in the Kac-Moody theoretic approach to M-theory is studied. This is based on work done by Schnakenburg, West and the second author. We then study the relation of higher spin fields in this approach to other results in different constructions of higher spin field dynamics. Of particular interest is the construction of space

Thomas Mohaupt, Frank Saueressig

We study five-dimensional Kasner cosmologies in the vicinity of a conifold locus occurring in a time-dependent Calabi-Yau compactification of M-theory. The dynamics of M2-brane winding modes, which become light in this region, is taken into account using a suitable gauged supergravity action. We find cosmological solutions which interpolate between the two b

Thomas Mohaupt, Frank Saueressig

We construct gauged supergravity actions which describe the dynamics of M-theory on a Calabi-Yau threefold in the vicinity of a conifold transition. The actions explicitly include N charged hypermultiplets descending from wrapped M2-branes which become massless at the conifold point. While the vector multiplet sector can be treated exactly, we approximate th

J. Polonyi, K. Sailer

Renormalization group in the internal space consists of the gradual change of the coupling constants. Functional evolution equations corresponding to the change of the mass or the coupling constant are presented in the framework of a scalar model. The evolution in the mass which yields the functional generalization of the Callan-Symanzik equation for the one

J. L. Diaz-Cruz, R. Noriega-Papaqui, A. Rosado

We study the fermionic couplings of the neutral Higgs bosons in the THDM, assuming a four-texture structure for the Yukawa matrices. We then derive the low-energy constraints on the model, focusing in b-quark and lepton physics, and apply them to study Higgs boson detection at future colliders.

A. A. Arkhipov

It is shown that newly performed experimental studies by the Belle Collaboration are excellently incorporated in the unified picture for hadron spectra developed early. From our analysis it follows that the measured values for the masses of the BELLE states exactly coincide with the calculated masses of the states living in the corresponding KK towers.

A. V. Efremov

A short review of single spin asymmetries in deep inelastic semi-inclusive processes, connected with prediction of chiral quark-soliton model for the nucleon transversity distributions, its possible theoretical understanding in the framework of QCD-induced approach and arising difficulties is given.

D. Harnett, T. G. Steele

One-loop quark contributions to the dimension-four gluon condensate term in the operator product expansion (OPE) of the scalar glueball correlation function are calculated in the MS-bar scheme in the chiral limit of $n_f$ quark flavours. The presence of quark effects is shown not to alter the cancellation of infrared (IR) singularities in the gluon condensat

Alexander Belyaev

Supersymmetry remains compelling theory over 30 years in spite of lack of its discovery. It could be already near the corner our days, therefore present and upcoming experiments are crucial for constraining or even discovery of the supersymmetry.

Ailin Zhang, T. G. Steele

Investigations of the mass and decays of the exotic hybrid are reviewed, including calculation of the pion1 to eta pion, eta-prime pion decay widths within the QCD sum rules technique. In this calculation, the recently-proposed eta, eta-prime quark mixing scheme is employed. The results indicate that the decay width Gamma(pion1 to eta pion) around 250 MeV is

Tomoaki Nagasawa, Makoto Sakamoto

We propose a higher dimensional scenario to solve the gauge hierarchy problem. In our formulation, a crucial observation is that a supersymmetric structure is hidden in the 4d spectrum of any gauge invariant theories with compact extra dimensions and that the gauge symmetry breaking is directly related to the supersymmetry breaking.

I. Masina, C. A. Savoy

We shortly review and emphasize how l_j -> l_i gamma experiments and the searches for lepton e.d.m. are constraining New Physics model building. They are pure signals of new phenomena around the TeV scale since the SM contributions are definitely negligible. It is quite remarkable that they also give effective tests of the LFV & CPV in seesaw couplings and i

A. Gokalp, Y. Sarac, O. Yilmaz

We investigate f_0-sigma mixing in the framework of light cone QCD sum rules and by employing the experimental results about the decay widths and the masses of these scalar mesons we estimate the scalar mixing angle by using sigma meson data and f_0 meson data. The two values we thus obtain of the scalar mixing angle are not entirely consistent with each oth

John F. Gunion

In the Randall-Sundrum model there can be a rich new phenomenology associated with Higgs-radion mixing. A photon-photon collider would provide a crucial complement to the LHC and a future ILC collider for fully determining the parameters of the model and definitively testing it.

Benjamin Grinstein

In the ratio of ratios of rates for radiative and semileptonic decays of B and D to K* and rho mesons the non-computable form factors mostly cancel out. The resulting method for the determination of Vub is largely free of hadronic uncertainties, raising the prospect of a precise determination of Vub.

Hai-Jhun Wanng, Hui Yang, Jun-Chen Su

The KN and KbarN low-energy elastic scattering is consistently studied in the framework of the QCD-inspired quark potential model. The model is composed of the t-channel one-gluon exchange potential, the s-channel one-gluon exchange potential and the harmonic oscillator confinement potential. By means of the resonating group method, nonlocal effective intera

O. V. Utyuzh, G. Wilk, Z. Wlodarczyk

We look at multiparticle production processes from the nonextensive point of view. Nonextensivity means here the systematic deviations in exponential formulas provided by the usual statistical approach for description of some observables like transverse momenta or rapidity distributions. We show that they can be accounted for by means of single parameter q w

V. Lubicz

Understanding flavor physics is one of the most important tasks of particle physics today, which is motivating an extraordinary experimental and theoretical investigational effort. Important progress in this field has already been achieved in the last few years, with Lattice QCD calculations playing an essential role in this effort. I will describe some latt

K-I. Ishikawa

Recent progress in unquenched lattice QCD simulations is reviewed with emphasis on understanding of chiral behavior for light quark masses.

Amiran Tomaradze

Using the ~ 6 pb-1 of e+e- annihilation data taken at psi-prime(3686) with CLEO III and CLEO-c detectors with estimated ~ 3.0 million psi-prime events, we have searched for the h_c(1^1P_1) state of charmonium in the reaction psi-prime(3686) -> pi^{0} hc -> (gamma gamma) (gamma eta_c). The preliminary results are reported.

N. Menaa

In 60 pb$^{-1}$ of data taken on the $ψ(3770)$ resonance with the CLEO-c detector, we find 8 $D^+\toμ^+ν$ event candidates that are mostly signal, containing only 1 estimated background. Using this statistically compelling sample, we measure the value of ${\cal{B}}(D^+\toμ^+ν)=(3.5\pm 1.4 \pm 0.6)\times 10^{-4}$, and determine $f_{D^+}=(198\pm 41\pm 17)$ MeV

S. B. Athar

Using data recorded by the CLEO III detector at CESR, we have made measurements of some properties of the Sigma_c^{*++} and Sigma_c^{*0} charmed baryons. In particular: Gamma(Sigma_c^{*++})=14.4^{+1.6}_{-1.5}+-1.4 MeV, M(Sigma_c^{*++})-M(Lambda_c^+) = 231.5+-0.4+-0.3 MeV, Gamma(Sigma_c^{*0})=16.6^{+1.9}_{-1.7}+-1.4 MeV, M(Sigma_c^{*0})-M(Lambda_c^+) = 231.4+

R. Sia

Based on data collected by the CLEO III detector at CESR, we started a series of investigations to open the mysteries of the $Υ$(5S) resonance decay properties. $B_s$ mesons are expected to decay predominantly into $D_s$ meson, while the lighter $B$ mesons decay into $D_s$ only about 10% of the time. We exploit this difference to present the first evidence o

D0 Collaboration, V. M. Abazov

We describe a measurement of the mass of the top quark from the purely hadronic decay modes of t-tbar pairs using all-jet data produced in p-pbar collisions at sqrt{s} = 1.8 TeV at the Fermilab Tevatron Collider. The data, which correspond to an integrated luminosity of 110.2 pb^-1, were collected with the Dzero detector from 1992 to 1996. We find a top quar

Claudia Patrignani

I present preliminary results on the search for $h_c$ in its $η_cγ$ and $J/ψπ^0$ decay modes. We observe an excess of η_cγ$ events near 3526 MeV that has a probability ${\cal P} \sim 0.001$ to arise from background fluctations. The resonance parameters are $M=3525.8 \pm 0.2 \pm 0.2 $MeV, $Γ\leq$ 1 MeV, and $10.6\pm 3.7\pm3.4(br) < Γ_{\bar{p}p}B_{η_cγ} < 12.8

Jerzy Lewandowski, Tomasz Pawlowski

With a help of a generalized Raychaudhuri equation non-expanding null surfaces are studied in arbitrarily dimensional case. The definition and basic properties of non-expanding and isolated horizons known in the literature in the 4 and 3 dimensional cases are generalized. A local description of horizon&#39;s geometry is provided. The Zeroth Law of black hole

Angelo Tartaglia

Space time is described as a continuum four-dimensional medium similar to ordinary elastic continua. Exploiting the analogy internal stress states are considered. The internal &#39;&#39;stress&#39;&#39; is originated by the presence of defects. The defects are described according to the typical Volterra process. The case of a point defect in an otherwise iso

Rituparno Goswami, Pankaj S Joshi

We construct here a class of collapsing scalar field models with a non-zero potential, which result in a naked singularity as collapse end state. The weak energy condition is satisfied by the collapsing configuration. It is shown that physically it is the rate of collapse that governs either the black hole or naked singularity formation as the final state fo

O. Benhar, V. Ferrari, L. Gualtieri

The frequencies and damping times of neutron star (and quark star) oscillations have been computed using the most recent equations of state available in the literature. We find that some of the empirical relations that connect the frequencies and damping times of the modes to the mass and radius of the star, and that were previously derived in the literature

Luis C. B. Crispino, Atsushi Higuchi, George E. A. Matsas

It was shown recently that in four dimensions scalar sources with fixed proper acceleration minimally coupled to a massless Klein-Gordon field lead to the same responses when they are (i) uniformly accelerated in Minkowski spacetime (in the inertial vacuum) and (ii) static in the Schwarzschild spacetime (in the Unruh vacuum). Here we show that this equivalen

Homer G. Ellis

A novel but elementary geometric construction produces on the seven-dimensional manifold of rotated spheres in Euclidean three-space a finslerian geometry whose geodesics are interpreted as the paths of free, spinning, spherical particles moving through de Sitter&#39;s expanding universe. A particle of nonzero inertial rest mass typically follows a helical t

M. Sharif

In recent papers [1-3], we have discussed matter symmetries of non-static spherically symmetric spacetimes, static plane symmetric spacetimes and cylindrically symmetric static spacetimes. These have been classified for both cases when the energy-momentum tensor is non-degenerate and also when it is degenerate. Here we add up some consequences and the missin

Viktor Kuncak, Martin Rinard

Spatial conjunction is a powerful construct for reasoning about dynamically allocated data structures, as well as concurrent, distributed and mobile computation. While researchers have identified many uses of spatial conjunction, its precise expressive power compared to traditional logical constructs was not previously known. In this paper we establish the e

A. A. Houck, J. Labaziewicz, E. K. Chan, J. A. Folk

We present gate-dependent transport measurements of Kondo impurities in bare gold break junctions, generated with high yield using an electromigration process that is actively controlled. Thirty percent of measured devices show zero-bias conductance peaks. Temperature dependence suggests Kondo temperatures \~7K. The peak splitting in magnetic field is consis

X. Y. Dong, C. Adelmann, J. Q. Xie, C. J. Palmstrom

Electrical spin injection from the Heusler alloy Co_2MnGe into a p-i-n Al_0.1Ga_0.9As/GaAs light emitting diode is demonstrated. A maximum steady-state spin polarization of approximately 13% at 2 K is measured in two types of heterostructures. The injected spin polarization at 2 K is calculated to be 27% based on a calibration of the spin detector using Hanl

F. C. Alcaraz, Yu. G. Stroganov

We present a new conjecture for the $SU_q(N)$ Perk-Schultz models. This conjecture extends a conjecture presented in our article (Alcaraz FC and Stroganov YuG (2002) J. Phys. A vol. 35 pg. 6767-6787, and also in cond-mat/0204074).

Xi Yang, Andrew Beckwith

In the persistent photoconductivity (PPC) phenomenon, illumination of a YBCO thin film junction with a 1mW He-Ne laser leads to the decrease of the critical critical voltage (similar to the threshold voltage). The decrease of the critical votage was reversed by illumination with incadenscent light. The critical voltage across the junction was experimentally

Marius Costeniuc, Richard S. Ellis, Hugo Touchette

Using the theory of large deviations, we analyze the phase transition structure of the Curie-Weiss-Potts spin model, which is a mean-field approximation to the Potts model. This analysis is carried out both for the canonical ensemble and the microcanonical ensemble. Besides giving explicit formulas for the microcanonical entropy and for the equilibrium macro

S. Mercone, C. A. Perroni, V. Cataudella, C. Adamo

The resistivity of thin $La_{0.7}A_{0.3}MnO_{3}$ films ($A=Ca, Sr$) is investigated in a wide temperature range. The comparison of the resistivities is made among films grown by different techniques and on several substrates allowing to analyze samples with different amounts of disorder. In the low-temperature nearly half-metallic ferromagnetic state the pro

K. Yamaura, Q. Huang, M. Moldovan, D. P. Young

The sodium rhodate NaRh2O4 was synthesized for the first time and characterized by neutron and x-ray diffraction studies, measurements of magnetic susceptibility, specific heat, electrical resistivity, and the Seebeck coefficient. NaRh2O4 crystallizes in the CaFe2O4-type structure, which is comprised of a characteristic RhO6 octahedra network. The compound i

Hu Cao, Feiming Bai, Jiefang Li, D. Viehland

Structural phase transformations in (001)-oriented (1-x)Pb(Mg1/3Nb2/3O3)-32%PbTiO3 (PMN-x%PT) crystals have been investigated by x-ray diffraction. A C->T->MC sequence was observed in both the field-cooled (FC) and zero-field-cooled (ZFC) conditions. Most interestingly, an anomalous increase in the C->T phase boundary with increasing field has been observed,

F. Brouers, O. Sotolongo

We show that if one uses the invariant form of the Boltzmann-Shannon continuous entropy, it is possible to obtain the generalized Pareto-Tsallis density function, using an appropriate &#34;prior&#34; measure m_{q}(x) and a &#34;Boltzman constraint&#34; which formally is equivalent to the Tsallis q-average constraint on the random variable X. We derive the Ts

J. M. Pruneda, Emilio Artacho

Using first principles calculations we have studied the formation energies, electron and hole affinities, and electronic levels of intrinsic point defects in zircon. The atomic structures of charged interstitials, vacancies, Frenkel pairs and anti-site defects are obtained. The limit of high concentration of point defects, relevant for the use of this materi

B. Fak, D. F. McMorrow, P. G. Niklowitz, S. Raymond

Single crystals of the heavy-fermion compound YbAgGe have been studied by neutron scattering. The magnetic ordering occurring below T1=0.5 K is characterized by a commensurate propagation vector k=(1/3,0,1/3) and the moments in the basal plane of the hexagonal structure. The dynamic magnetic susceptibility is dominated by quasielastic spin fluctuations with

J. Gomez-Gardenes, L. M. Floria, M. Peyrard, A. R. Bishop

In an extensive numerical investigation of nonintegrable translational motion of discrete breathers in nonlinear Schrodinger lattices, we have used a regularized Newton algorithm to continue these solutions from the limit of the integrable Ablowitz-Ladik lattice. These solutions are shown to be a superposition of a localized moving core and an excited extend

K. Doll

The adsorption of CO on the Pt(111) surface in a root3 x root3 pattern has been studied with the gradient corrected functional of Perdew and Wang and the B3LYP hybrid functional. A slab which is periodic in two dimensions is used to model the system. The Perdew-Wang functional incorrectly gives the fcc site as the most favorable adsorption site, in accord wi

N. Magnani, S. Carretta, G. Amoretti, L. Pareti

The fundamental magnetic interactions of Pr$_{2}$Fe$_{17}$ are studied by inelastic neutron scattering and anisotropy field measurements. Data analysis confirms the presence of three magnetically inequivalent sites, and reveals an exceptionally large value of the exchange field. The unexpected importance of $J$-mixing effects in the description of the ground

A. Lupascu, C. J. P. M. Harmans, J. E. Mooij

We present a readout method for superconducting flux qubits. The qubit quantum flux state can be measured by determining the Josephson inductance of an inductively coupled DC superconducting quantum interference device (DC-SQUID). We determine the response function of the DC-SQUID and its back-action on the qubit during measurement. Due to driving, the qubit

Ebru Ergun, Ugur Tirnakli

Sensitivity to initial conditions in the coherent noise model of biological evolution, introduced by Newman, is studied by making use of damage spreading technique. A power-law behavior has been observed, the associated exponent $α$ and the dynamical exponent $z$ are calculated. Using these values a clear data collapse has been obtained.

Michele Fabrizio, Erio Tosatti

A single Anderson impurity model recently predicted, through its unstable fixed point, the phase diagram of a two band model correlated conductor, well confirmed by Dynamical Mean Field Theory in infinite dimensions. We study here the one dimensional version of the same model and extract its phase diagram in this opposite limit of reduced dimensionality. As

J. Gomez-Gardenes, F. Falo, L. M. Floria

Using continuation methods from the integrable Ablowitz-Ladik lattice, we have studied the structure of numerically exact mobile discrete breathers in the standard Discrete Nonlinear Schrodinger equation. We show that, away from that integrable limit, the mobile pulse is dressed by a background of resonant plane waves with wavevectors given by a certain sele

Bhupalendra Behera, Ferenc Kun, Sean McNamara, Hans J. Herrmann

The break-up of a two-dimensional circular disc by normal and oblique impact on a hard frictionless plate is investigated by molecular dynamics simulations. The disc is composed of numerous unbreakable randomly shaped convex polygons connected together by simple elastic beams that break when bent or stretched beyond a certain limit. It is found that for both

G. A. Gogadze

Theory of the reentrant effect in susceptibility of mesoscopic cylindrical NS samples is proposed, which is essentially based on the properties of the Andreev levels. The specific feature of the quantum levels of the structure is that in a varying magnetic field (or temperature) each level periodically comes into coincidence with the chemical potential of th

Masao Iwamatsu, Yutaka Okabe

Basin-Hopping (BH) or Monte-Carlo Minimization (MCM) is so far the most reliable algorithms in chemical physics to search for the lowest-energy structure of atomic clusters and macromolecular systems. BH transforms the complex energy landscape into a collection of basins, and explores them by hopping, which is achieved by random Monte Carlo moves and accepta

M. Angst, S. L. Bud&#39;ko, R. H. T. Wilke, P. C. Canfield

The temperature dependence of the upper critical field, Hc2, for both field directions in partially substituted polycrystalline MgB2 was determined. Whereas the suppression of Tc is similar for aluminum and carbon substituted samples, Hc2 is affected by the substitution in profoundly different ways. In the case of Al substitution changes can tentatively be d

S. H. Baek, F. Borsa, Y. Furukawa, Y. Hatanaka

$^{57}$Fe and $^1$H relaxation measurements have been performed in single crystal and oriented powder of enriched $^{57}$Fe8 molecular cluster in the temperature range 0.05--1.7 K in zero external field and with small perturbing longitudinal field ($< 1$ T). On the basis of the experimental results it is argued that in zero external field the nuclear spin-la

B. J. Kowalski, I. A. Kowalik, R. J. Iwanowski, E. Lusakowska

Spontaneous formation of grains has been observed for the MnAs layer grown by means of MBE on the GaN(0001)-(1x1) surface. Electronic structure of the system was investigated in situ by resonant photoemission spectroscopy. Density of the valence band states of MnAs and its changes due to increase of the layer thickness were revealed.

Martina Hentschel, Denis Ullmo, Harold U. Baranger

We study the x-ray edge problem for a chaotic quantum dot or nanoparticle displaying mesoscopic fluctuations. In the bulk, x-ray physics is known to produce deviations from the naively expected photoabsorption cross section in the form of a peaked or rounded edge. For a coherent system with chaotic dynamics, we find substantial changes and in particular that

A. Lupascu, C. J. M. Verwijs, R. N. Schouten, C. J. P. M. Harmans

We present a new readout method for a superconducting flux qubit, based on the measurement of the Josephson inductance of a superconducting quantum interference device that is inductively coupled to the qubit. The intrinsic flux detection efficiency and back-action are suitable for a fast and nondestructive determination of the quantum state of the qubit, as

F. Laviano, D. Botta, A. Chiodoni, R. Gerbaldo

We created local pinning modulations in YBCO films by means of confined high energy heavy ion irradiation. The high energy of the ions allows us to introduce nanometric size defects with a well defined anisotropy. The dose was chosen in such a way to reduce the local critical current of the irradiated area. We used a quantitative magneto-optical analysis to

K. Davidson, J. C. Martin, R. M. Humphreys, K. Ishibashi

During $η$ Car&#39;s spectroscopic event in mid-2003, the stellar wind&#39;s bright H$α$ and H$β$ emission lines temporarily had a distinctive shape unlike that reported on any previous occasion, and particularly unlike the 1997--98 event. Evidently the structure of the wind changed between 1997 and 2003. Combining this with other evidence, we suspect that t

O. Manuel, Stig Friberg

Measurements are reviewed showing that the interior of the Sun, the inner planets, and ordinary meteorites consist mostly of the same elements: Iron, oxygen, nickel, silicon, magnesium, sulfur and calcium. These results do not support the standard solar model.

Dmitri A. Uzdensky

We consider a stationary axisymmetric force-free degenerate magnetosphere of a rotating Kerr black hole surrounded by a thin Keplerian infinitely-conducting accretion disk. We focus on the closed-field geometry characterize by a direct magnetic coupling between the disk and the hole&#39;s event horizon. We first argue that the hole&#39;s rotation necessarily

Sivakumar G. Manickam

The topologies are obtained for accretion flows around black holes as the parameters, accretion rate and specific angular momentum are varied. Paczy{ń}ski-Wiita pseudo-Newtonian potential is used to mimic the gravitational field of a Schwarzschild black hole. Both stellar mass($14M_{\odot}$) and supermassive($10^8M_{\odot}$) black holes are considered. The e

Selcuk Bayin

In this paper we present an alternative explanation to the acceleration of the universe and the dark energy problems in terms of the Friedmann Thermodynamics. This model has the capability of making definite predictions in-line with the current observations of the universe. According to this model, cosmos was expanding slower at the beginning. During the gal

Gianfranco De Zotti, Roberto Ricci, Dino Mesa, Laura Silva

We present detailed predictions of the contributions of the various source populations to the counts at frequencies of tens of GHz. New evolutionary models are worked out for flat-spectrum radio quasars, BL Lac objects, and steep-spectrum sources. Source populations characterized by spectra peaking at high radio frequencies, such as extreme GPS sources, ADAF

Terry J. Jones, Charles E. Woodward, Martha L. Boyer, Robert D. Gehrz

We present observations of the giant HII region complex N159 in the LMC using IRAC on the {\it Spitzer Space Telescope}. One of the two objects previously identified as protostars in N159 has an SED consistent with classification as a Class I young stellar object (YSO) and the other is probably a Class I YSO as well, making these two stars the youngest stars

C. Marois

The technique of simultaneous spectral differential imaging (SSDI) is used to image directly brown dwarfs and exoplanets around nearby stars. An analytical PSF model is first presented with numerical simulations to estimate the PSF noise attenuation performance. A three-wavelength infrared camera (TRIDENT) implementing the SSDI technique is then described. R

A. Gianninas, P. Dufour, P. Bergeron

We report the discovery of a new metal-rich DAZ white dwarf, GD 362. High signal-to-noise optical spectroscopy reveals the presence of spectral lines from hydrogen as well as CaI, CaII, MgI, and FeI. A detailed model atmosphere analysis of this star yields an effective temperature of Teff = 9740 +/- 50 K, a surface gravity of log g = 9.12 +/- 0.07, and photo

D. Sauer, A. W. A. Pauldrach, T. Hoffmann, W. Hillebrandt

We present the current status of our construction of synthetic spectra for type Ia supernovae. These properly take into account the effects of NLTE and an adequate representation of line blocking and blanketing. The models are based on a sophisticated atomic database. We show that the synthetic spectrum reproduces the observed spectrum of &#39;normal&#39; SN

Yu. N. Efremov

Star complexes are the highest level groupings in the hierarchy of the embedded young stars, clusters and associations, which obey the size - age relation. Starburst clumps, superassociations, supergiant HII regions are different titles for the groupings of the same size as complexes but with active star formation over all the grouping. The coherent star for

K. Werner, J. J. Drake

H1504+65 is a young white dwarf with an effective temperature of 200,000 K and is the hottest post-AGB star ever analysed with detailed model atmospheres. Chandra LETG+HRC-S spectra have revealed the richest X-ray absorption line spectrum recorded from a stellar photosphere to date. The line forming regions in this extremely hot photosphere produce many tran

Thomas Rauch, Marina Orio, R. Gonzales-Riestra, Martin Still

Half a year after its outburst, the nova V4743 Sgr evolved into the brightest super-soft X-ray source in the sky with a flux maximum around 30A, exhibiting resonance lines of C V, C VI, N VI, N VII, and O VII. We present preliminary results of an analysis of the XMM-Newton RGS spectra by means of NLTE model-atmosphere techniques.

Thomas Rauch, Florian Kerber

Planetary Nebulae (PNe) are the result of heavy mass loss of the asymptotic giant branch (AGB) stars. They are understood in terms of Kwok&#39;s (1978) interacting-winds model as the product of the mass-loss history on the AGB and the central star (CS) evolution. Since the CS are close to the end of nuclear burning and at their hottest stage of evolution the

Thomas Rauch, Elke Reiff, Klaus Werner, Falk Herwig

95% of all stars end their lives as white dwarfs. About 20% of the hot post-AGB stars are hydrogen deficient. Most of these are the result of a late helium-shell flash, but the evolutionary status of a fraction of about 10-20% of the hottest hydrogen-deficient stars, namely four O(He) stars, is as yet unexplained. They could be the long-searched hot successo

G. Gräfener, W. -R. Hamann

We present the first non-LTE atmosphere models for WR stars that incorporate a self-consistent solution of the hydrodynamic equations. The models account for iron-group line-blanketing and clumping, and compute the hydrodynamic structure of a radiatively driven wind consistently with the non-LTE radiation transport in the co-moving frame. We construct a self

Thomas Rauch, Klaus Werner

AA Dor (LB 3459) is an eclipsing, close, single-lined, post common-envelope binary (PCEB) consisting of an sdOB primary star and an unseen secondary with an extraordinary small mass - formally a brown dwarf. The brown dwarf may have been a former planet which survived a common envelope phase and has even gained mass. A recent determination of the components&

E. Pancino

I present preliminary results for a sample of ~700 red giants in omega Cen, observed during the Ital-FLAMES Consortium GTO time in May 2003, for the Bologna Project on omega Cen. Preliminary Fe and Ca abundances confirm previous results: while the metal-poor and intermediate populations show a normal halo alpha-enhancement of [alpha/Fe]=$+0.3, the most metal

Satoki Matsushita, Ryohei Kawabe, Kotaro Kohno, Hironori Matsumoto

We present high spatial resolution (2.3&#34;x1.9&#34; or 43 pc x 36 pc at D = 3.9 Mpc) 100 GHz millimeter-wave continuum emission observations with the Nobeyama Millimeter Array toward an expanding molecular superbubble in the central region of M82. The 100 GHz continuum image, which is dominated by free-free emission, revealed that the four strongest peaks

Tim Huege, Heino Falcke

Radio emission from cosmic ray air showers has the potential to become an additional, cost-effective observing technique for cosmic ray research, being largely complementary to the well-established particle detector and air fluorescence techniques. We present Monte Carlo simulatios of radio emission from extensive air showers in the scheme of coherent geosyn

B. Sbarufatti, A. Treves, R. Falomo, J. Heidt

We report redshift measurements for 12 BL Lacertae objects from a program aimed at obtaining high signal to noise (up to ~ 500) optical spectroscopy of a mixed sample of objects. The new observations, gathered with the 8 m ESO Very Large Telescope, allowed us to detect weak spectral features down to a line equivalent width as small as ~ 1 Angstrom. The new r

K. Werner, T. Rauch, R. Napiwotzki, N. Christlieb

We present high-resolution VLT spectra of a new DO white dwarf and a new PG1159 star, which we identified in the ESO SPY survey. The PG1159 star is a low-gravity, extremely hot (Teff=160,000 K, log g=6) star, having a C/He dominated atmosphere with considerable amounts of O and Ne (He=38%, C=54%, O=6%, Ne=2% by mass). It is located within the planetary nebul

K. Werner, N. J. Hammer, T. Nagel, T. Rauch

We discuss the possibility to detect O/Ne white dwarfs by evidence for Ne overabundances. The hottest known WD, H1504+65, could be the only single WD for which we might be able to proof its O/Ne nature directly. Apart from this, strong Ne abundances are known or suspected only from binary systems, namely from a few novae, and from a handful of LMXBs. We try

K. Werner, T. Rauch, J. W. Kruk

FUSE spectroscopy has proved that extremely hot hydrogen-deficient post-AGB stars (PG1159 stars) display matter on their surface that usually remains hidden in the region between the H- and He-burning shells of the former AGB star. Hence, the spectral analysis of PG1159 stars allows to study directly the chemistry of this intershell region which is the outco

A. M. Bykov, A. M. Krassilchtchikov, Yu. A. Uvarov, H. Bloemen

Spatially resolved images of the galactic supernova remnant G78.2+2.1 (gamma-Cygni) in hard X-ray energy bands from 25 keV to 120 keV are obtained with the IBIS-ISGRI imager aboard the International Gamma-Ray Astrophysics Laboratory INTEGRAL. The images are dominated by localized clumps of about ten arcmin in size. The flux of the most prominent North-Wester

S. Matarrese, S. Mollerach, A. Notari, A. Riotto

We derive the minimal seed magnetic field which unavoidably arises in the radiation and matter eras, prior to recombination, by the rotational velocity of ions and electrons, gravitationally induced by the non-linear evolution of primordial density perturbations. The resulting magnetic field power-spectrum is fully determined by the amplitude and spectral in

M. Stritzinger, B. Leibundgut

By coupling observations of type Ia supernovae with results obtained from the best available numerical models we constrain the Hubble constant, independently of any external calibrators. We find an absolute lower limit of Ho > 50 km/s/Mpc. In addition, we construct a Hubble diagram with UVOIR light curves of 12 type Ia supernovae located in the Hubble flow,

A. V. Olinto

We review the current state and future prospect of ultra high energy cosmic ray physics and the relationship between cosmic rays and gamma-ray astrophysics.

Chip Kobulnicky

I review the observational characteristics of intermediate-to-high redshift star forming galaxies, including their star formation rates, dust extinctions, ISM kinematics, and chemical compositions. I present evidence that the mean rate of metal enrichment, Delta{Z}/Delta{z}, from z=0--3, as determined from nebular oxygen abundance measurements in star formin

J. R. Dickel, V. J. McIntyre, R. A. Gruendl, D. K. Milne

Detailed 4.8- and 8.6-GHz radio images of the entire Large Magellanic Cloud with half-power beamwidths of 33&#34; at 4.8 GHz and 20&#34; at 8.6 GHz have been obtained using the Australia Telescope Compact Array. A total of 7085 mosaic positions were used to cover an area of 6 degrees on a side. Full polarimetric observations were made. These images have suff