June 2005 arXiv papers — page 7

M. A. Sozanski, J. J. Zebrowski

A simple model of an irreversible process is introduced. The equation of iterations in the model includes a noise generation term. We study the properties of the system when the noise generation term is a stochastic process (e.g. a random number generator) or a deterministic process (e.g. a chaotic map). We compare the time series obtained from the above imp

Nikos I. Karachalios

We discuss the existence of breather solutions for a Discrete Nonlinear Schrödinger equation in an infinite $N$-dimensional lattice, involving site dependent anharmonic parameter. We give a simple proof on the existence of (nontrivial) breather solutions based on variational approach, assuming that the sequence of anharmonic parmeters is in an appropriate se

Antoine Coste, Giovanni Felder

We present remarkable properties of the groups SL2(Z/NZ) which might be useful in detailed studies of some quotients appearing in Conformal Field Theories.

Mariusz Ciesielski, Jacek Leszczynski

In this paper we present in one-dimensional space a numerical solution of a partial differential equation of fractional order. This equation describes a process of anomalous diffusion. The process arises from the interactions within the complex and non-homogeneous background. We presented a numerical method which bases on the finite differences method. We co

F. Hivert, J. -C. Novelli, J. -Y. Thibon

After reformulating the representation theory of 0-Hecke algebras in an appropriate family of Yang-Baxter bases, we investigate certain specializations of the Ariki-Koike algebras, obtained by setting q=0 in a suitably normalized version of Shoji's presentation. We classify the simple and projective modules, and describe restrictions, induction products,

Andrew Schultz

For positive integers m and r, one can easily show there exist integers N such that for every map D:{1,2,...,N} -> {1,2,...,r} there exist 2m integers x_1 < ... < x_m < y_1 < ... < y_m which satisfy: (a) D(x_1) = ... = D(x_m), (b) D(y_1) = ... = D(y_m), and (c) 2(x_m-x_1) \leq y_m-x_1. In this paper we investigate the minimal such integer, which we call g(m,

P. Di Francesco

We discuss the enumeration of planar graphs using bijections with suitably decorated trees, which allow for keeping track of the geodesic distances between faces of the graph. The corresponding generating functions obey non-linear recursion relations on the geodesic distance. These are solved by use of stationary multi-soliton tau-functions of suitable reduc

P. Di Francesco, E. Guitter

We investigate the integrability of the discrete non-linear equation governing the dependence on geodesic distance of planar graphs with inner vertices of even valences. This equation follows from a bijection between graphs and blossom trees and is expressed in terms of generating functions for random walks. We construct explicitly an infinite set of conserv

Johanna Michor, Gerald Teschl

We investigate trace formulas for Jacobi operators which are trace class perturbations of quasi-periodic finite-gap operators using Krein&#39;s spectral shift theory. In particular we establish the conserved quantities for the solutions of the Toda hierarchy in this class.

Anne Micheli, Dominique Rossin

There exists a bijection between one stack sortable permutations --permutations which avoid the pattern 231-- and planar trees. We define an edit distance between permutations which is coherent with the standard edit distance between trees. This one-to-one correspondence yields a polynomial algorithm for the subpermutation problem for $(231)$ avoiding permut

Juergen Herzog, Dorin Popescu

Stanley showed that monomial complete intersections have the strong Lefschetz property. Extending this result we show that a simple extension of an Artinian Gorenstein algebra with the strong Lefschetz property has again the strong Lefschetz property.

P. -E. Caprace, B. Muehlherr

A subgroup of a Kac-Moody group is called bounded if it is contained in the intersection of two finite type parabolic subgroups of opposite signs. In this paper, we study the isomorphisms between Kac-Moody groups over arbitrary fields of cardinality at least 4, which preserve the set of bounded subgroups. We show that such an isomorphism between two such Kac

Frederic Campana, Mihai Paun

Let $ϕ:\Bbb C^n\to X$ a holomorphic map to an $n$-dimensional connected compact complex manifold $X$. We establish links between the positivity properties of the canonical bundle of $X$ and the rate of growth of $ϕ$ which extend results of Kodaira and Kobayashi-Ochiai. For example: if the average degree of $ϕ$ on balls of radius $r$ grows slowlier than $r^{2

Patrick Dehornoy

We investigate a group $B\_\bullet$ that includes Artin&#39;s braid group $B\_\infty$ and Thompson&#39;s group $F$. The elements of $B\_\bullet$ are represented by braids diagrams in which the distances between the strands are not uniform and, besides the usual crossing generators, new rescaling operators shrink or strech the distances between the strands. W

James A. Mingo, Piotr Sniady, Roland Speicher

We extend the relation between random matrices and free probability theory from the level of expectations to the level of fluctuations. We show how the concept of &#34;second order freeness&#34;, which was introduced in Part I, allows one to understand global fluctuations of Haar distributed unitary random matrices. In particular, independence between the un

Brian Feldstein, Lawrence J. Hall, Taizan Watari

An anthropic understanding of the cosmological constant requires that the vacuum energy at late time scans from one patch of the universe to another. If the vacuum energy during inflation also scans, the various patches of the universe acquire exponentially differing volumes. In a generic landscape with slow-roll inflation, we find that this gives a steeply

G. W. Gibbons, M. J. Perry, C. N. Pope

We show that one may pass from bulk to boundary thermodynamic quantities for rotating AdS black holes in arbitrary dimensions so that if the bulk quantities satisfy the first law of thermodynamics then so do the boundary CFT quantities. This corrects recent claims that boundary CFT quantities satisfying the first law may only be obtained using bulk quantitie

Nick Halmagyi, Annamaria Sinkovics, Piotr Sulkowski

We show that Calabi-Yau crystals generate certain Chern-Simons knot invariants, with Lagrangian brane insertions generating the unknot and Hopf link invariants. Further, we make the connection of the crystal brane amplitudes to the topological vertex formulation explicit and show that the crystal naturally resums the corresponding topological vertex amplitud

José Figueroa-O&#39;Farrill, Sunil Gadhia

We construct examples of isometric M-theory backgrounds which preserve a different amount of supersymmetry depending on the choice of spin structure. These examples are of the form AdS_4 x L, where L is a seven-dimensional lens space whose fundamental group is cyclic of order 4k.

J. R. Hiller, S. S. Pinsky, N. Salwen, U. Trittmann

We solve N=(8,8) super Yang-Mills theory in 1+1 dimensions at strong coupling to directly confirm the predictions of supergravity at weak coupling. We do our calculations in the large-N_c approximation using Supersymmetric Discrete Light-Cone Quantization with up to 3*10^{12} basis states. We calculate the stress-energy correlator <T^{++}(r) T^{++}(0)> as a

Hari K. Kunduri, James Lucietti

We deform the supersymmetric black ring of five dimensional supergravity coupled to N-1 vector multiplets to obtain an asymptotically Goedel supersymmetric black ring. For the U(1)^3 model we lift this solution to obtain a three charge D1-D5-P supertube which asymptotes to a 1/2 supersymmetric plane wave of Type IIB supergravity. Further, we also show how on

Frank Saueressig, Ulrich Theis, Stefan Vandoren

This letter discusses the orientifold projection of the quantum corrections to type IIA strings compactified on rigid Calabi-Yau threefolds. It is shown that N=2 membrane instanton effects give a holomorphic contribution to the superpotential, while the perturbative corrections enter into the Kahler potential. At the level of the scalar potential the correct

Laura Tamassia

In this thesis my papers hep-th/0104190, hep-th/0310214, hep-th/0405072 and hep-th/0406065 are put into context. The thesis is mainly focused on noncommutative field theory and string theory, so results in the papers that are not related to this main theme are not discussed in detail. The thesis is almost selfcontained and in particular the first chapter mig

Bobby Ezhuthachan, Suresh Govindarajan, T. Jayaraman

We study fractional 2p-branes and their intersection numbers in non-compact orbifolds as well the continuation of these objects in Kahler moduli space to coherent sheaves in the corresponding smooth non-compact Calabi-Yau manifolds. We show that the restriction of these objects to compact Calabi-Yau hypersurfaces gives the new fractional branes in LG orbifol

Ivan Vitev

Final state medium-induced gluon radiation in ultradense nuclear matter is shown to favor large angle emission when compared to vacuum bremsstrahlung due to the suppression of collinear gluons. In a simple model of momentum transfers from the medium to the jet+gluon system the phase space distribution of non-Abelian bremsstrahlung is examined to first order

Alex Kovner

I describe recent work on inclusion of Pomeron loops in the high energy evolution. In particular I show that the complete eikonal high energy evolution kernel must be selfdual.

G. A. Kozlov

A leptonic $(\bar l l)$ decay of a heavy quark-antiquark bound state $T(\bar QQ)$ with a Higgs-boson $H$ emission is investigated. The applying of the well-known low-energy theorem to meson-Higgs coupling allows one to estimate the probability of the decay $T(\bar QQ)\to \bar ll H$. The only a simple version of the Standard Model extension containing two-Hig

M. Beccaria, A. Ferrari, F. M. Renard, C. Verzegnassi

In this paper, we review the production cross section for charged and neutral Higgs bosons pairs in $e^{+}e^{-}$ collisions beyond the tree level, in the framework of the Minimal Supersymmetric Standard Model (MSSM). A complete list of formulas for all electroweak contributions at the one loop level is given. A numerical code has been developed in order to c

M. G. Ryskin, A. D. Martin, V. A. Khoze

We consider diffractive processes which can be measured at the LHC. Analysis of diffractive events will give unique information about the high energy asymptotics of hadron scattering. In semihard diffraction one may study the partonic structure of the Pomeron. Central Exclusive Diffractive production provides a possibility to investigate the new particles (H

K. Moenig, A. Rosca

This study investigates the potential of a photon collider for measuring the two photon partial width times the branching ratio of a light Higgs boson. The analysis is based on the reconstruction of the Higgs events produced in the gamma gamma -> h process, followed by Higgs decay into a b bbar pair. A statistical error of the measurement of the two-photon w

Yu. S. Kalashnikova

The effects of charmed meson loops on the spectrum of charmonium are considered, with special attention paid to the levels above open-charm threshold. It is found that the coupling to charmed mesons generates a structure at the D \bar{D}* threshold in the 1++ partial wave. The implications for the nature of the X(3872) state are discussed.

F. Ellinghaus, W. -D. Nowak, A. V. Vinnikov, Z. Ye

We investigate the possibility to acquire information on the generalized parton distribution E and, through a model for E, also on the u-quark total angular momentum J_u by studying deeply virtual Compton scattering and hard exclusive rho0 electroproduction on a transversely polarized hydrogen target at HERMES. It is found that a change in J_u from zero to 0

Gino Isidori, Guido Martinelli, Paolo Turchetti

We show that long distance contributions to the rare decays K -> pi nu nu-bar and K -> pi l+ l- can be computed using lattice QCD. The proposed approach requires well established methods, successfully applied in the calculations of electromagnetic and semileptonic form factors. The extra power divergences, related to the use of weak four-fermion operators, c

The BABAR Collaboration, B. Aubert

An improved measurement of the process B+- --> rho+- pi0 is presented. The data sample of 211/fb comprises 232 million Y(4S) --> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. The yield and CP asymmetry are calculated using an extended maximum likelihood fitting method. The branching fraction and asymmetry a

BaBar Collaboration, B. Aubert

A search for lepton-flavor and lepton-number violation in the decay of the tau lepton into one charged lepton and two charged hadrons is performed using 221.4 $\mathrm{fb}^{-1}$ of data collected at an $e^+e^-$ center-of-mass energy of 10.58 GeV with the BaBar detector at the PEP-II storage ring. In all 14 decay modes considered, the observed data are compat

Gianluca Allemandi, Mauro Francaviglia, Matteo Luca Ruggiero, Angelo Tartaglia

Alternative theories of gravity have been recently studied in connection with their cosmological applications, both in the Palatini and in the metric formalism. The aim of this paper is to propose a theoretical framework (in the Palatini formalism) to test these theories at the solar system level and possibly at the galactic scales. We exactly solve field eq

Stephen Parrott

We study the behavior in the remote past and future of solutions of an equation of motion for charged particles proposed by F. Rohrlich, for the special case in which the motion is in one spatial dimension. We show that if an external force is applied for a finite time, some solutions exhibit the property of ``preacceleration&#39;&#39;, meaning that the part

Samuel Thibault

With the current trend of multiprocessor machines towards more and more hierarchical architectures, exploiting the full computational power requires careful distribution of execution threads and data so as to limit expensive remote memory accesses. Existing multi-threaded libraries provide only limited facilities to let applications express distribution indi

Nicolas Baudru, Rémi Morin

Zielonka&#39;s theorem shows that each regular set of Mazurkiewicz traces can be implemented as a system of synchronized processes with a distributed control structure called asynchronous automaton. This paper gives a polynomial algorithm for the synthesis of a non-deterministic asynchronous automaton from a regular Mazurkiewicz trace language. This new cons

Y. D. Shen, Q. Yang, J. H. You, L. Y. Yuan

Recursive loops in a logic program present a challenging problem to the PLP framework. On the one hand, they loop forever so that the PLP backward-chaining inferences would never stop. On the other hand, they generate cyclic influences, which are disallowed in Bayesian networks. Therefore, in existing PLP approaches logic programs with recursive loops are co

N. M. R. Peres, F. Guinea, A. H. Castro Neto

We present a theoretical description of the electronic properties of graphene in the presence of disorder, electron-electron interactions, and particle-hole symmetry breaking. We show that while particle-hole asymmetry, long-range Coulomb interactions, and extended defects lead to the phenomenon of self-doping, local defects determine the transport and spect

Vassiliy Lubchenko, Peter G. Wolynes

The quantum excitations in glasses have long presented a set of puzzles for condensed matter physicists. A common view is that they are largely disordered analogs of elementary excitations in crystals, supplemented by two level systems which are chemically local entities coming from disorder. A radical revision of this picture argues that the excitations in

A. Donev, S. Torquato, F. H. Stillinger, R. Connelly

O&#39;Hern, Silbert, Liu and Nagel [Phys. Rev. E. 68, 011306 (2003)] (OSLN) claim that a special point $J$ of a &#34;jamming phase diagram&#34; (in density, temperature, stress space) is related to random close packing of hard spheres, and that it represents, for their suggested definitions of jammed and random, the recently introduced maximally random jamme

V. Sih, R. C. Myers, Y. K. Kato, W. H. Lau

Spin-orbit coupling in semiconductors relates the spin of an electron to its momentum and provides a pathway for electrically initializing and manipulating electron spins for applications in spintronics and spin-based quantum information processing. This coupling can be regulated with quantum confinement in semiconductor heterostructures through band structu

C. Mueller, V. Zestrea, V. Tsurkan, S. Horn

Using surface acoustic waves, the elastomagnetic coupling could be studied in thin single crystalline plates of the ferrimagnetic semiconductor FeCr2S4 by measuring the attenuation and the frequency tracking in the temperature range 4.2 K to 200 K. The data clearly display the anomalies found in low-field magnetization measurements.

Elizabeta Ćavar, Marie-Christine Blüm, Marina Pivetta, François Patthey

Using the highly localized current of electrons tunneling through a double barrier Scanning Tunneling Microscope (STM) junction, we excite luminescence from a selected C$_{60}$ molecule in the surface layer of fullerene nanocrystals grown on an ultrathin NaCl film on Au(111). In the observed luminescence fluorescence and phosphorescence spectra, pure electro

Arindam Ghosh, Matthew Wright, Christophe Siegert, Michael Pepper

Nonequilibrium transport measurements in mesoscopic quasi-ballistic 2D electron systems show an enhancement in the differential conductance around the Fermi energy. At very low temperatures, such a zero-bias anomaly splits, leading to a suppression of linear transport at low energies. We also observed a scaling of the nonequilibrium characteristics at low en

Jian-Guo Liu, Zhong-Tuo Wang, Yan-Zhong Dang

The scale-fee networks, having connectivity distribution $P(k)\sim k^{-α}$ (where $k$ is the site connectivity), is very resilient to random failures but fragile to intentional attack. The purpose of this paper is to find the network design guideline which can make the robustness of the network to both random failures and intentional attack maximum while kee

J. -S. Caux, R. Hagemans, J. -M. Maillet

We compute all dynamical spin-spin correlation functions for the spin-1/2 $XXZ$ anisotropic Heisenberg model in the gapless antiferromagnetic regime, using numerical sums of exact determinant representations for form factors of spin operators on the lattice. Contributions from intermediate states containing many particles and string (bound) states are includ

Shogo Shinkai, Hiroaki Ikeda, Kosaku Yamada

We investigate the normal selfenergy and the mass enhancement factor in the Hubbard model on the two-dimensional square lattice. Our purpose in this paper is to evaluate the mass enhancement factor more quantitatively than the conventional third order perturbation theory. We calculate it by expanding perturbatively up to the fourth order with respect to the

M. N. Popescu, S. Dietrich, G. Oshanin

The use of ultra-thin, i.e., monolayer films plays an important role for the emerging field of nano-fluidics. Since the dynamics of such films is governed by the interplay between substrate-fluid and fluid-fluid interactions, the transport of matter in nanoscale devices may be eventually efficiently controlled by substrate engineering. For such films, the dy

Hyun-Jung Lee, Ralf Bulla, Matthias Vojta

The numerical renormalization group method is used to investigate zero temperature phase transitions in quantum impurity systems, in particular in the particle-hole symmetric soft-gap Anderson model. The model displays two stable phases whose fixed points can be built up of non-interacting single-particle states. In contrast, the quantum phase transitions tu

P. Lalanne, J. C. Rodier, J. P. Hugonin

Recent works dealt with the optical transmission on arrays of subwavelength holes perforated in a thick metallic film. We have performed simulations which quantitatively agree with experimental results and which unambiguously evidence that the extraordinary transmission is due to the excitation of a surface-plasmon-polariton (SPP) mode on the metallic film i

J. Planelles, J. I. Climente, J. L. Movilla

When a magnetic field pierces a multiple-connected quantum system, the corresponding wavefunction is altered although no net Lorentz force acts upon its carriers. This is the so called Aharonov-Bohm effect. The most simple multiply-connected quantum system is a quantum ring QR. Nowadays it is possible to obtain QRs in the nanoscopic range providing spectrosc

Kenji Yonemitsu

To clarify the mechanism of recently reported, ambipolar carrier injections into quasi-one-dimensional Mott insulators on which field-effect transistors are fabricated, we employ the one-dimensional Hubbard model attached to a tight-binding model for source and drain electrodes. To take account of the formation of Schottky barriers, we add scalar and vector

Anthony Saugey, Laurent Joly, Christophe Ybert, Jean-Louis Barrat

We study the influence of the boundary conditions at the solid liquid interface on diffusion in a confined fluid. Using an hydrodynamic approach, we compute numerical estimates for the diffusion of a particle confined between two planes. Partial slip is shown to significantly influence the diffusion coefficient near a wall. Analytical expressions are derived

R. Held, J. Xu, A. Schmehl, C. W. Schneider

A new concept for nonvolatile superconducting memories is proposed. The devices combine ferromagnetic dots for the storage of the data and Josephson junctions for their readout. Good scalability is expected for large scale integration. First memory cells have been implemented using 3 $μ$m-Nb-technology and permalloy dots. Nonvolatile data storage at 300 K wa

A. Minguzzi, D. M. Gangardt

Using a scaling transformation we exactly determine the dynamics of an harmonically confined Tonks-Girardeau gas under arbitrary time variations of the trap frequency. We show how during a one-dimensional expansion a ``dynamical fermionization&#39;&#39; occurs as the momentum distribution rapidly approaches an ideal Fermi gas distribution, and that under a s

M. Yokoyama, C. Satoh, A. Saitou, H. Kawanaka

We have performed the powder neutron diffraction measurements on the solid solutions of SrRu_{1-x}Mn_xO_3, and found that the itinerant ferromagnetic order observed in pure SrRuO_3 changes into the C-type antiferromagnetic (AF) order with nearly localized d electrons in the intermediate Mn concentration between x=0.4 and 0.6. With increasing x, the AF moment

O. G. Balev

At filling factor $ν=1/m$, $m$ odd integer, I present variational ground-state and excited-state wave functions, of two-dimensional electron system with homogeneous ion background, that show the condensation into a liquid-crystal state. For $m=1, 3, 5$, the ground-state energy per electron is substantially lower than the Laughlin one, for uniform liquid stat

Alexander V Turbiner

A model of a mixed helium-hydrogenic atmosphere of the isolated neutron star 1E1207.4-5209 is proposed. It is based on the assumption that the main components in the atmosphere are the exotic molecular ions $He_2^{3+}$ and $H_3^{2+}$ with the presence of $He^{+}, (HeH)^{2+}, H_2^{+}$ under a surface magnetic field $\approx 4.4 \times 10^{13}$ G. In addition

Peregrine M. McGehee, Andrew A. West, J. Allyn Smith, Kurt S. J. Anderson

Multi-epoch imaging of the Orion equatorial region by the Sloan Digital Sky Survey has revealed that significant variability in the blue continuum persists into the late-M spectral types, indicating that magnetospheric accretion processes occur below the substellar boundary in the Orion OB1 association. We investigate the strength of the accretion-related co

A. Moro-Martin, R. Malhotra

Main sequence stars are commonly surrounded by debris disks, formed by cold far-IR-emitting dust that is thought to be continuously replenished by a reservoir of undetected dust-producing planetesimals. We have investigated the orbital evolution of dust particles in debris disks harboring massive planets. Small dust grains are blown out by radiation pressure

D. R. Ballantyne

This paper presents a timing study and broadband spectral analysis of the broad-line radio galaxy 4C+74.26 based on a 35 ks XMM-Newton observation. As found in previous datasets, the source exhibits no evidence for rapid variability, and its 0.2-10 keV lightcurve is well fit by a constant. An excellent fit to the pn 0.3-12 keV spectrum was found using a cont

Robyn Levine, Nickolay Y. Gnedin

We combine cosmological simulations with an AGN luminosity function constrained by optical surveys in order to create a realistic AGN distribution in which to model AGN outflows. The outflows are modeled with assumptions of spherical symmetry and energy conservation. We study the importance of the kinetic luminosity of AGN outflows in determining the fractio

A. Moro-Martin, S. Wolf, R. Malhotra

Main sequence stars are commonly surrounded by debris disks, composed of cold dust continuously replenished by a reservoir of undetected dust-producing planetesimals. In a planetary system with a belt of planetesimals (like the Solar System&#39;s Kuiper Belt) and one or more interior giant planets, the trapping of dust particles in the mean motion resonances

Ayesha Begum, Jayaram N. Chengalur

We present a deep Giant Metrewave Radio Telescope (GMRT) search for HI 21 cm emission from three dwarf galaxies, viz. POX 186, SC 24 and KKR 25. Based, in part, on previous single dish HI observations, these galaxies have been classified as a BCD, a dwarf irregular and a transition galaxy respectively. However, in conflict with previous single dish detection

J. J. M. in &#39;t Zand, A. Cumming, M. V. van der Sluys, F. Verbunt

2S 0918-549 is a low-mass X-ray binary (LMXB) with a low optical to X-ray flux ratio. Probably it is an ultracompact binary with an orbital period shorter than 60 min. Such binaries cannot harbor hydrogen rich donor stars. As with other (sometimes confirmed) ultracompact LMXBs, 2S 0918-549 is observed to have a high neon-to-oxygen abundance ratio (Juett et a

P. D. Klaassen, R. Plume, S. J. Gibson, A. R. Taylor

We have observed 12CO J = 2-1 and J = 1-0, and 13CO J = 1-0 emission in two regions of HI Self-Absorption (HISA) in Perseus: a small, isolated HISA feature called the globule and a more extended HISA cloud called the complex. Using both Large Velocity Gradient and Monte Carlo radiative transfer codes we found that, in the globule, N(12CO) < 6.0x10^15 cm-2 wh

Niayesh Afshordi, Matias Zaldarriaga, Kazunori Kohri

An interesting dynamical model for dark energy which does not require extremely light scalar fields such as quintessence, and at the same time explains the (near-) coincidence between the neutrino and dark energy densities is the model of dark energy coupled to mass varying neutrinos (MaVaNs). Despite the attractions of this model, we show that, generically,

Kenneth Rines, Margaret J. Geller, Michael J. Kurtz, Antonaldo Diaferio

We investigate the environmental dependence of star formation in cluster virial regions and infall regions as part of CAIRNS (Cluster And Infall Region Nearby Survey), a large spectroscopic survey of the infall regions surrounding nine nearby rich clusters of galaxies. Our long-slit spectroscopy yields estimates of star formation rates in environments from c

Mario G. Abadi, Julio F. Navarro, Matthias Steinmetz

(Abridged) We use numerical simulations to investigate the origin and structure of the luminous halos that surround isolated galaxies. These stellar structures extend out to several hundred kpc away from a galaxy, and consist of stars shed by merging subunits during the many accretion events that characterize the hierarchical assembly of galaxies. Such origi

Sukanya Chakrabarti, Christopher F. McKee

We present analytic radiative transfer solutions for the spectra of unresolved, spherically symmetric, centrally heated, dusty sources. We find that the dust thermal spectrum possesses scaling relations that provide a natural classification for a broad range of sources, from low-mass protostars to dusty galaxies. In particular, we find that, given our assump

Rowan Temple, Somak Raychaudhury, Ian Stevens

We present XMM-Newton observations of NCG891, a nearby edge-on spiral galaxy. We analyse the extent of the diffuse emission emitted from the disk of the galaxy, and find that it has a single temperature profile with best fitting temperature of 0.26 keV, though the fit of a dual-temperature plasma with temperatures of 0.08 and 0.30 keV is also an acceptable f

Valerio Carruba, Tatiana Michtchenko, Fernando Roig, Sylvio Ferraz-Mello

Among the largest objects in the main belt, asteroid 4 Vesta is unique in showing a basaltic crust. It is also the biggest member of the Vesta family, which is supposed to originate from a large cratering event about 1 Gyr ago (Marzari et al. 1996). Most of the members of the Vesta family for which a spectral classification is available show a V-type spectra

S. di Serego Alighieri, J. Vernet, A. Cimatti, B. Lanzoni

We have performed VLT spectroscopy of an almost complete sample of 18 early-type galaxies with 0.88 < z < 1.3 plus two at z=0.67, selected from the K20 survey, and derived the velocity dispersion for 15+2 of them. By combining these data with HST and VLT images, we study the Fundamental Plane (FP), the Faber-Jackson and the Kormendy relations at z~1, and com

M. Schuessler, M. Rempel

After a dynamically active emergence phase, magnetic flux at the solar surface soon ceases to show strong signs of the subsurface dynamics of its parent magnetic structure. This indicates that some kind of disconnection of the emerged flux from its roots in the deep convection zone should take place. We propose a mechanism for the dynamical disconnection of

Ata Sarajedini, Pascale Jablonka

We have used Hubble Space Telescope Wide Field Planetary Camera 2 observations to construct a color-magnitude diagram (CMD) for the bulge of M31 at a location ~1.6 kpc from the galaxy&#39;s center. Using scaled-solar abundance theoretical red giant branches with a range of metallicities, we have translated the observed colors of the stars in the CMD to abund

S. Guziy, J. Gorosabel, A. J. Castro-Tirado, A. de Ugarte Postigo

We present UBVRI-band observations taken ~300 days after the BeppoSAX gamma-ray burst GRB 000214. This GRB did not show a detectable optical afterglow, however due to the localization of a previously unknown, fading, X-ray source at a tentative redshift in the range 0.37-0.47, we have searched with the ESO 3.6 m telescope for objects with photometric redshif

L. Pasquini, P. Bonifacio, P. Molaro, P. Francois

Li abundances for 9 Turnoff (TO) stars of the intermediate metallicity cluster ([Fe/H]=-1.4) NGC6752 are presented. The cluster is known to show abundance anomalies and anticorrelations observed in both evolved and main sequence stars. We find that Li abundance anticorrelates with Na (and N) and correlates with O in these Turn-Off stars. For the first time w

Joel H. Kastner, Geoffrey Franz, Nicolas Grosso, John Bally

We investigate the X-ray and near-infrared emission properties of a sample of pre-main sequence (PMS) stellar systems in the Orion Nebula Cluster (ONC) that display evidence for circumstellar disks (``proplyds&#39;&#39;) and optical jets in Hubble Space Telescope (HST) imaging. Approximately 70% of ~140 proplyds were detected as X-ray sources in the Chandra

A. Fuente, R. Neri, P. Caselli

We report high angular resolution (~0.6&#39;&#39;x0.5&#39;&#39; at 1.3mm) observations of the Class 0 intermediate-mass (IM) protostar NGC 7129--FIRS 2 using the PdBI. Our observations show the existence of a hot core at the position of the Class 0 object. This is, up to our knowledge, the first IM hot core detected so far. Interferometric maps of the region

P. B. Price

Two classes of natural solid media (glacial ice and salt domes) are under consideration as media in which to deploy instruments for detection of neutrinos with energy >1e18 eV. Though insensitive to 1e11 to 1e16 eV neutrinos for which observatories (e.g., AMANDA and IceCube) that utilize optical Cherenkov radiation detectors are designed, radio and acoustic

A. G. Aksenov, M. Milgrom, V. V. Usov

We consider a time dependent, spherically outflowing wind, in Schwarzschild space-time, consisting of electron-positron pairs and photons . Without assuming thermal equilibrium, we account for the microphysics, including two-body processes and their radiative three-body variants. We present a finite-difference scheme for solving the general relativistic kine

Kuassivi, A. Bonanno, R. Ferlet

We report on the detection of pulsations in the far ultraviolet (hereafter FUV) light curves of PG1219+534, PG1605+072, and PG1613+426 obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) in time-tagged mode (TTAG). Exposures of the order of a few Ksecs were sufficient to observe the main frequencies of PG1219+534 and PG1605+072 and confirm the de

A. Marcolini, D. K. Strickland, A. D&#39;Ercole, T. M. Heckman

In this paper we present high-resolution hydrodynamical models of warm ionized clouds embedded in a superwind, and compare the OVI and soft X-ray properties to the existing observational data. These models include thermal conduction, which we show plays an important role in shaping both the dynamics and radiative properties of the resulting wind/cloud intera

D. J. Wilner, P. D&#39;Alessio, N. Calvet, M. J. Claussen

We present Very Large Array observations at 3.5 cm of the nearby young star TW Hya that show the emission is constant in time over weeks, months and years, and spatially resolved with peak brightness temperature ~10 K at ~0.25 (15 AU) resolution. These features are naturally explained if the emission mechanism at this wavelength is thermal emission from dust

M. Briquet, K. Lefever, K. Uytterhoeven, C. Aerts

We present the results of a detailed analysis of 121 ground-based high-resolution high S/N spectroscopic measurements spread over 3 years for the Beta Cephei star Theta Ophiuchi. We discovered Theta Oph to be a triple system. In addition to the already known Speckle B5 companion of the B2 primary, we showed the presence of a low-mass spectroscopic companion

Rajesh Gopal, Shiv K. Sethi

We compute the secondary CMBR anisotropy signal from the reionization of the universe in the presence of tangled magnetic fields. We consider the tangled magnetic-field-induced scalar, vector, and tensor modes for our analysis. The most interesting signal for l<10 arise from tensor perturbations. In particular, we show that the enhancement observed by WMAP i

A. Vecchio, V. Carbone, F. Lepreti, L. Primavera

The spatio-temporal dynamics of the solar photosphere is studied by performing a Proper Orthogonal Decomposition (POD) of line of sight velocity fields computed from high resolution data coming from the MDI/SOHO instrument. Using this technique, we are able to identify and characterize the different dynamical regimes acting in the system. Low frequency oscil

G. Handler, R. R. Shobbrook, T. Mokgwetsi

We have carried out a three-site photometric campaign for the Beta Cephei star Theta Ophiuchi from April to August 2003. 245 hours of differential photoelectric uvy photometry were obtained during 77 clear nights. The frequency analysis of our measurements resulted in the detection of seven pulsation modes within a narrow frequency interval between 7.116 and

Rami Rekola, Helmut Jerjen, Chris Flynn

We present Surface Brightness Fluctuation distances of nine early-type dwarf galaxies and the S0 galaxy NGC 4150 in the Local Volume based on deep B- and R-band CCD images obtained with the 2.56 metre Nordic Optical Telescope. Typically, six stellar fields at various galactocentric distances have been chosen for each galaxy as appropriately free of foregroun

J. Ritzerveld

In this Letter, we argue that the standard analytical derivations of properties of HII regions, such as the speed, shape and asymptotic position of ionisation fronts require a more precise treatment. These derivations use the on the spot approximation, which in effect ignores the diffuse component of the radiation field. We show that, in fact, HII regions ar

R. De Propris, J. Liske, S. P. Driver, P. Allen

We derive the number of dynamically close companions per galaxy ($N_c$) and their total luminosity ($L_c$) for galaxies in the Millennium Galaxy Catalogue: $N_c$ is similar to the fraction of galaxies in close pairs and is directly related to the galaxy merger rate. We find $N_c=0.0174 \pm 0.0015$ and $L_c=(252 \pm 30) \times 10^6$ $L_{\odot}$ for galaxies w

G. Meylan, F. Courbin, C. Lidman, J. -P. Kneib

We report on new high-resolution near-infrared images of the gravitationally lensed radio source PKS1830-211, a quasar at z=2.507. These adaptive optics observations, taken with the Very Large Telescope (VLT), are further improved through image deconvolution. They confirm the presence of a second object along the line of sight to the quasar, in addition to t

Christopher Thom, Brad K. Gibson, Norbert Christlieb

We present a catalogue of 430 Field Horizontal Branch (FHB) stars, selected from the Hamburg/ESO Survey (HES), which fortuitously align with high column density neutral hydrogen (HI) High-Velocity Cloud (HVC) gas. These stars are ideal candidates for absorption-line studies of HVCs, attempts at which have been made for almost 40 years with little success. A

Takaaki Tanaka, Masahiko Sugiho, Aya Kubota, Kazuo Makishima

Spectral studies of a luminous X-ray source, NGC 253 X21, are presented based on archival Chandra and XMM-Newton data. The Chandra observation on 1999 December 16 detected the source at a bolometric luminosity of 0.3 x 10^39 erg/s (assuming isotropic emission), while an XMM-Newton observation on 2000 June 3 revealed a short-term source variation in the range

Naohisa Inada, Scott Burles, Michael D. Gregg, Robert H. Becker

We report the discovery of a new two-image gravitationally lensed quasar, SDSS J024634.11-082536.2 (SDSS J0246-0825). This object was selected as a lensed quasar candidate from the Sloan Digital Sky Survey (SDSS) by the same algorithm that was used to discover other SDSS lensed quasars (e.g., SDSS J0924+0219). Multicolor imaging with the Magellan Consortium&

U. S. Kamath, G. C. Anupama, N. M. Ashok, Y. D. Mayya

Optical and near-infrared spectroscopic observations of the fast nova V1494 Aquilae 1999 #2 covering various phases -- early decline, transition and nebular -- during the first eighteen months of its post-outburst evolution are presented in this paper. During this period, the nova evolved in the P_fe P_fe^o C_o spectral sequence. The transition from an optic

M. Tsujimoto, N. Kobayashi, Y. Tsuboi

We present the results of X-ray and near-infrared (NIR) observations of L1448, a star-forming region in the Perseus cloud complex using the Chandra X-ray Observatory and the 4 m telescope at the Kitt Peak National Observatory. We detect 72 X-ray sources in a ~17 arcmin x 17 arcmin region with a ~68 ks ACIS exposure, for which we conduct follow-up NIR imaging