July 2002 arXiv papers — page 10

G. Fabricius, A. López García

In this work we perform an ab-initio study of CdTiO3 perovskite in its orthorhombic phase using FLAPW method. Our calculations help to decide between the different cristallographic structures proposed for this perovskite from X-Ray measurements. We compute the electric field gradient tensor (EFG) at Cd site and obtain excellent agreement with available exper

Kae Nemoto, Samuel L. Braunstein

The Partition Ensemble Fallacy was recently applied to claim no quantum coherence exists in coherent states produced by lasers. We show that this claim relies on an untestable belief of a particular prior distribution of absolute phase. One's choice for the prior distribution for an unobservable quantity is a matter of `religion'. We call this princi

Dominik Janzing, Thomas Decker, Thomas Beth

An n-qubit quantum register can in principle be completely controlled by operating on a single qubit that interacts with the register via an appropriate fixed interaction. We consider a hypothetical system consisting of n spin-1/2 nuclei that interact with an electron spin via a magnetic interaction. We describe algorithms that measure non-trivial joint obse

Véronique Zehnlé, Jean Claude Garreau

In this paper, we develop an analytical approach to Doppler cooling of atoms by one- or two-photon transitions when the natural width of the excited level is so small that the process leads to a Doppler temperature comparable to the recoil temperature. A ``quenching'' of the sharp line is introduced in order to allow control of the time scale of the

Anjana Sinha, Rajkumar Roychoudhury

The one-dimensional Coulomb-like potential with a real coupling constant beta, and a centrifugal-like core of strength G = alpha^2 - {1/4}, viz. V(x) = {alpha^2 - (1/4)}/{(x-ic)^2} + beta/|x-ic|, is discussed in the framework of PT-symmetry. The PT-invariant exactly solvable model so formed, is found to admit a double set of real and discrete energies, numbe

Wim van Dam, Gadiel Seroussi

We present an efficient quantum algorithm for estimating Gauss sums over finite fields and finite rings. This is a natural problem as the description of a Gauss sum can be done without reference to a black box function. With a reduction from the discrete logarithm problem to Gauss sum estimation we also give evidence that this problem is hard for classical a

Satoshi Ishizaka

We study the closest disentangled state to a given entangled state in any system (multi-party with any dimension). We obtain the set of equations the closest disentangled state must satisfy, and show that its reduction is strongly related to the extremal condition of the local filtering on each party. Although the equations we obtain are not still tractable,

Richard N. Steinberg, Michael C. Wittmann, Edward F. Redish

Students in introductory calculus-based physics not only have difficulty understanding the fundamental physical concepts, they often have difficulty relating those concepts to the mathematics they have learned in math courses. This produces a barrier to their robust use of concepts in complex problem solving. As a part of the Activity-Based Physics project,

Michael C. Wittmann, Richard N. Steinberg, Edward F. Redish

We report on our study of student understanding of the physics of mechanical waves, specifically the propagation and superposition of simple wavepulses traveling on long, taut strings. We introduce the terms "particle pulses mental model" to describe the reasoning approach that students use to guide their thinking in wave propagation and superpositio

V. P. Dmitriyev

Maxwell's equations comprise both electromagnetic and gravitational fields. The transverse part of the vector potential belongs to magnetism, the longitudinal one is concerned with gravitation. The Coulomb gauge indicates that longitudinal components of the fields propagate instantaneously. The delta-function singularity of the field of the divergence of

Keith W. Oliver, Lei Bao

We are trying to identify resources students are using to reason in quantum mechanics. In this process we realize students must have not only the right resources available but sophisticated for evaluating and controlling their thought processes. We will discuss examples from student interviews to illustrate our point.

V. D. Ryzhikov, S. V. Naydenov, D. N. Kozin, E. K. Lisetskaya

Results of experimental studies of detector arrays S-PD (scintillator-photodiode) and PRD (scintillator-photoreceiving device) used for X-ray digital radiography have shown that there exist further possibilities to increase spatial resolution of this system up to 2-3 line pairs per mm. Theoretical analysis and experimental studies show that the two-energy de

C. J. Horowitz, J. Piekarewicz

Recent observations by the Chandra observatory suggest that some neutron stars may cool rapidly, perhaps by the direct URCA process which requires a high proton fraction. The proton fraction is determined by the nuclear symmetry energy whose density dependence may be constrained by measuring the neutron radius of a heavy nucleus, such as 208Pb. Such a measur

Jan Tõke, Jun Lu, W. Udo Schröder

Statistical fragment emission from excited nuclear systems is studied within the framework of a schematic Fermi-gas model combined with Weisskopf's detailed balance approach. The formalism considers thermal expansion of finite nuclear systems and pays special attention to the role of the diffuse surface region in the decay of hot equilibrated systems. It

I. Hamamoto, H. Sagawa

Isoscalar dipole (compression) mode is studied first using schematic harmonic-oscillator model and, then, the self-consistent Hartree-Fock (HF) and random phase approximation (RPA) solved in coordinate space. Taking ^{208}Pb and the SkM* interaction as a numerical example, the spurious component and the strength in the continuum are carefully examined using

Paul A. Houle, Christopher L. Henley

A cluster of three spins coupled by single-axis anisotropic exchange exhibits classical behaviors ranging from regular motion at low and high energies, to chaotic motion at intermediate energies. A change of variable, taking advantage of the conserved z-angular momentum, combined with a 3-d graphical presentation (described in the Appendix), produce Poincare

Pham Anh Minh, Grant Walker

This paper provides analogues of the results of [G.Walker and R.M.W. Wood, Linking first occurrence polynomials over F_2 by Steenrod operations, J. Algebra 246 (2001), 739--760] for odd primes p. It is proved that for certain irreducible representations L(lambda) of the full matrix semigroup M_n(F_p), the first occurrence of L(lambda) as a composition factor

Robert Mendris, Andras Nemethi

We consider suspension hypersurface singularities of type g=f(x,y)+z^n, where f is an irreducible plane curve singularity. For such germs, we prove that the link of g determines completely the Newton pairs of f and the integer n except for two pathological cases, which can be completely described. Even in the pathological cases, the link and the Milnor numbe

R. H. Hardin, N. J. A. Sloane

Evidence is presented to suggest that, in three dimensions, spherical 6-designs with N points exist for N=24, 26, >= 28; 7-designs for N=24, 30, 32, 34, >= 36; 8-designs for N=36, 40, 42, >= 44; 9-designs for N=48, 50, 52, >= 54; 10-designs for N=60, 62, >= 64; 11-designs for N=70, 72, >= 74; and 12-designs for N=84, >= 86. The existence of some of these des

Burt Totaro

We prove the equivalence of two fundamental properties of algebraic stacks: being a quotient stack in a strong sense, and the resolution property, which says that every coherent sheaf is a quotient of some vector bundle. Moreover, we prove these properties in the important special case of orbifolds whose associated algebraic space is a scheme.

H. R. Sadjadpour, N. J. A. Sloane, M. Salehi, G. Nebe

The performance of a Turbo code with short block length depends critically on the interleaver design. There are two major criteria in the design of an interleaver: the distance spectrum of the code and the correlation between the information input data and the soft output of each decoder corresponding to its parity bits. This paper describes a new interleave

A. Roger Hammons,, P. Vijay Kumar, A. R. Calderbank, N. J. A. Sloane

Certain notorious nonlinear binary codes contain more codewords than any known linear code. These include the codes constructed by Nordstrom-Robinson, Kerdock, Preparata, Goethals, and Delsarte-Goethals. It is shown here that all these codes can be very simply constructed as binary images under the Gray map of linear codes over Z_4, the integers mod 4 (altho

David De Wit

We present and prove in detail a Poincare--Birkhoff--Witt commutator lemma for the quantum superalgebra U_q[gl(m|n)].

L. El Kaoutit, J. Gomez-Torrecillas

In order to extrincate the structure of corings with a finitely generated and projective generator we give the notion of a comatrix coring. As consequences we give generalizations of the main characterizations of faithfully flat Galois corings and extensions which work for corings without grouplike elements, as well as a generalization of the Descent Theorem

T. Mansour, J. West

Let B_n be the hyperoctahedral group; that is, the set of all signed permutations on n letters, and let B_n(T) be the set of all signed permutations in B_n which avoids a set T of signed patterns. In this paper, we find all the cardinalities of the sets B_n(T) where $T \subseteq B_2$. This allow us to express these cardinalities via inverse of binomial coeff

Masakazu Teragaito

The crosscap number of a knot in the 3-sphere is the minimal genus of non-orientable surface bounded by the knot. We determine the crosscap numbers of torus knots.

W. A. Zuniga-Galindo

Let K be a p-adic field, R the valuation ring of K, and P the maximal ideal of R. Let $Y subseteq R^{2}$ be a non-singular closed curve, and Y_{m} its image in R/P^{m} times R/P^{m}, i.e. the reduction modulo P^{m} of Y. We denote by Psi an standard additive character on K. In this paper we discuss the estimation of exponential sums of type S_{m}(z,Psi,Y,g):

Olivier Biquard, Philip Boalch

On a complex curve, we establish a correspondence between integrable connections with irregular singularities, and Higgs bundles such that the Higgs field is meromorphic with poles of any order. The moduli spaces of these objects are obtained by fixing at each singularity the polar part of the connection. We prove that they carry hyperKahler metrics, which a

K. A. Bronnikov, J. C. Fabris

Exact cosmological solutions for effective actions in D dimensions inspired by the tree-level superstring action are studied. For a certain range of free parameters existing in the model, nonsingular bouncing solutions are found. Among them, of particular interest can be open hyperbolic models, in which, without any fine tuning, the internal scale factor and

A. Y. Segal

We construct gauge theory of interacting symmetric traceless tensor fields of all ranks s=0,1,2,3, ... which generalizes Weyl-invariant dilaton gravity to the higher spin case, in any dimension d>2. The action is given by the trace of the projector to the subspace with positive eigenvalues of an arbitrary hermitian differential operator H, the symmetric tens

Michael A. Ivanov

A field model of two-component fermions is described, the consequences of which coincide in the main with primary postulates of the standard model. Such a model can be constructed for 4 generations at the minimum. Peculiarities of the relative coordinate space, determining in general an internal symmetry group, are considered. Analogues of the Higgs fields a

Shozo Uehara, Satoshi Yamada

We study the behavior of matrix string theory in the strong coupling region, where matrix strings reduce to discrete light-cone type IIA superstrings except at the usual string-interaction points. In the large N limit, this reduction corresponds to the double-dimensional reduction from wrapped supermembranes on R^{10} x S^1 to type IIA superstrings on R^{10}

T. Fischbacher, H. Nicolai, H. Samtleben

We analyze the scalar potentials of maximal gauged three-dimensional supergravities which reveal a surprisingly rich structure. In contrast to maximal supergravities in dimensions D>3, all these theories admit a maximally supersymmetric (N=16) ground state with negative cosmological constant Lambda<0, except for the gauge group SO(4,4)^2, for which Lambda=0.

Andrew J. Tolley, Neil Turok

We consider the quantization of the massless minimally coupled scalar field in de Sitter spacetime. The no-boundary Euclidean prescription naturally picks out the de Sitter invariant vacuum state of Kirsten and Garriga. We extend Strominger&#39;s dS/CFT correspondence to this case which allows us to interpret the massless field in terms of a Euclidean CFT. T

Zack Sullivan

We present the fully differential production and decay of a W&#39; boson, with arbitrary vector and axial-vector couplings, to any final state at next-to-leading order in QCD. We demonstrate a complete factorization of couplings at next-to-leading order in both the partial width of the W&#39; boson, and in the full two-to-two cross section. We provide numeri

K. S. Babu, Jogesh C. Pati

The Extended Supersymmetric Standard Model (ESSM), motivated on several grounds, introduces two vectorlike families (16 + 16-bar) of SO(10)) with masses of order one TeV. It is noted that the successful predictions of prior work on fermion masses and mixings, based on MSSM embedded in SO(10), can be retained rather simply within the ESSM extension. These inc

A. I. Shoshi, F. D. Steffen, H. G. Dosch, H. J. Pirner

We present the perturbative and non-perturbative QCD structure of the dipole-dipole scattering amplitude in momentum space. The perturbative contribution is described by two-gluon exchange and the non-perturbative contribution by the stochastic vacuum model which leads to confinement of the quark and antiquark in the dipole via a string of color fields. This

Nathan F. Lepora

We examine whether the analysis of quantum corrections for the kink soliton carries over to the &#39;t Hooft-Polyakov monopole. For the kink, it is central that the quantum fluctuations are eigenmodes of a Hermitian operator. For the monopole, we show the analogous operator is not Hermitian. This property raises some questions about the quantization procedur

Christopher Smith

A simple matching procedure is proposed to extract constraints on effective meson theories. In this way, a QCD prediction for the pion decay constant is found, F(pi)=2 m(pi)/pi, i.e. approximately 90MeV. The same procedure also determines other mesonic observables, like the decay width of the sigma meson to two photons. Finally, some information which can be

A. C. Melissinos

If the gravitational interaction is unified with the electroweak and strong interactions at a mass M=10^15 GeV, the evolution of Newton&#39;s constant must differ from its classical (general relativistic) form. We can model such behavior by introducing an ad hoc dependence on ln(s/4m^2) where s is the usual cm energy between two protons. We can then predict

H. Fritzsch

The QCD anomaly leads to an abnormal mixing and mass pattern for the pseudoscalar mesons. Furthermore it is responsible for the quality of isospin symmetry in the meson spectrum. Similarities between the large mixing angles among the neutral 0^-+ mesons and the large mixing angles observed in neutrino oscillations are pointed out.

A. Brandenburg, M. Maniatis, M. M. Weber

Supersymmetry predicts that gauge couplings are equal to the corresponding gaugino-sfermion-fermion Yukawa couplings. This prediction can be tested for the QCD sector of the MSSM by studying the processes eplus+eminus -> squark+antisquark+gluon and eplus+eminus -> squark+antiquark+gluino at a future linear collider. We present results for these processes at

A. V. Kotikov, G. Parente

Using an analytical parameterization for the behavior of the x slope of the structure function F_2 at small x in perturbative QCD, at the leading twist approximation of the Wilson operator product expansion, and applying a flat initial condition in the DGLAP evolution equations, we found very good agreement with new precise deep inelastic scattering experime

Carla Carvalho, Martin Bucher

We compute the probability distribution of the invariant separation between nucleation centers of colliding true vacuum bubbles arising from the decay of a false de Sitter space vacuum. We find that even in the limit of a very small nucleation rate per unit Hubble volume the production of widely separated bubble pairs is suppressed. This distribution is of p

Miroslav Pardy

After the clasical approach to acceleration of a charged particle by delta-form impulsive force, we consider the corresponding quantum theory based on the Volkov solution of the Dirac equation. We determine the modified Compton formula for frequency of photons generated by the scattering of the delta-form laser pulse on the electron in a rest.

E. Martynov, E. Predazzi, A. Prokudin

Exclusive photoproduction of all vector mesons by real and virtual photons is considered in the Soft Dipole Pomeron model. It is emphasized that being the Pomeron in this model a double Regge pole with intercept equal to one, we are led to rising cross-sections but the unitarity bounds are not violated. It is shown that all available data for rho, omega, phi

Emmanuel A. Paschos, Olga Lalakulich

The \bar{nu}e^- --> pi^- pi^0 and nu e^+ --> pi^+ pi^0 reaction have a resonant structure whenever the energy of the s--channel equals the mass of a J^P=1^- vector meson. The resonant cross sections are of the order 10^{-38} cm^2 and correspond to cosmic ray antineutrino energies in the range 0.2 to 2 TeV. A similar structure occurs in the annihilation of co

ALEPH Collaboration

A search for charged Higgs bosons produced in pairs is performed with data collected at centre-of-mass energies ranging from 189 to 209 GeV by ALEPH at LEP, corresponding to a total luminosity of 629 invpb. The three final states taunutaunu, taunucs and cscs are considered. No evidence for a signal is found and lower limits are set on the mass M_H+ as a func

B. Aubert, The BABAR Collaboration

We report on the evidence for the decays B0 -> Ds+ pi- and B0 -> Ds- K+ and the results of a search for the decays B0 -> Ds*+ pi- and B0 -> Ds*-K+ from a sample of 84 million Upsilon(4S) decays into B meson pairs collected with the BABAR detector at the PEP II asymmetric-energy e^{+}e^{-} collider. The measured B0 -> Ds+ pi- yield has a probability of less t

Henk van Elst, Reza Tavakol

The second of the annual BritGrav meetings on current research in Gravitational Physics in Britain took place at the School of Mathematical Sciences of Queen Mary, University of London on June 10/11, 2002. 47 plenary talks of 12min duration were given. We make available the abstracts of the talks and the references to the electronic preprints at arXiv.org wh

D. Grigoriev

Public-key cryptosystems are suggested based on invariants of groups. We give also an overview of the known cryptosystems which involve groups.

Andras Benczur, David R. Karger

We improve on random sampling techniques for approximately solving problems that involve cuts and flows in graphs. We give a near-linear-time construction that transforms any graph on n vertices into an O(n\log n)-edge graph on the same vertices whose cuts have approximately the same value as the original graph&#39;s. In this new graph, for example, we can r

Gavriel Segre

Giorgio Parisi&#39;s recent speculations on the concept of continuous dimension (cond-mat/0207334) are compared with Von Neumann&#39;s serious work.

J. Wang, G. A. Khodaparast, J. Kono, T. Slupinski

We have performed a two-color time-resolved magneto-optical Kerr effect (MOKE) study of a ferromagnetic InMnAs/GaSb heterostructure. We observed ultrafast photo-induced changes in the MOKE signal induced by a large density of spin-polarized transient carriers created only within the InMnAs layer using intense 140 fs mid-infrared pulses. Our data clearly demo

Arun Paramekanti, Mohit Randeria

We construct a phenomenological superfluid Fermi liquid theory for a two-dimensional d-wave superconductor on a square lattice, and study the effect of quasiparticle interactions on the superfluid density. Using simple models for the dispersion and the Landau interaction function, we illustrate the deviation of these results from those for the isotropic supe

Matej Komelj, Claude Ederer, James W. Davenport, Manfred Faehnle

A systematic ab-initio study within the framework of the local-spin-density approximation including spin-orbit coupling and an orbital-polarization term is performed for the spin and orbital moments and for the X-ray magnetic circular dichroism (XMCD) spectra in hcp Co, in a Pt supported and a free standing Co monolayer, and in a Pt supported and a free stan

A. Gurevich, V. M. Vinokur

We predict a new dynamic state in current-carrying superconductors with multicomponent order parameter. If the current density J exceeds a critical value J_t, an interband breakdown caused by charge imbalance of nonequilibrium quasiparticles occurs. For J > J_t, the electric field penetrating from current leads gives rise to various static and dynamic solito

Alexander J. Wagner

Stationary droplets simulated by multi-phase lattice Boltzmann methods lead to spurious velocities around them. In this article I report the origin of these spurious velocities for one example and show how they can be avoided.

P. Monthoux, G. G. Lonzarich

We compare predictions of the mean-field theory of superconductivity for nearly antiferromagnetic and nearly ferromagnetic metals for cubic and tetragonal lattices. The calculations are based on the parametrization of an effective interaction arising from the exchange of magnetic fluctuations and assume that a single band is relevant for superconductivity. T

Dirk Tasche

The consultative papers for the Basel II Accord require rating systems to provide a ranking of obligors in the sense that the rating categories indicate the creditworthiness in terms of default probabilities. As a consequence, the default probabilities ought to present a monotonous function of the ordered rating categories. This requirement appears quite int

Felipe Valencia, Aldo H. Romero, Miguel Kiwi, Ricardo Ramirez

DFT calculations performed on Si_2H_6, Si_2F_6, Si_2Cl_6, and Si_2Br_6 are reported. The evolution of the energy, the chemical potential and the molecular hardness, as a function of torsion angle, is studied. Results at the DFT-B3LYP/6-311++G** level show that the molecules always favor the stable staggered conformations, with low but significant energy barr

Raul Toral, Claudio Mirasso, James D. Gunton

We show the existence of a system size coherence resonance effect for an ensemble of globally coupled excitable systems. Namely, we demonstrate numerically that the regularity in the signal emitted by an ensemble of globally coupled Fitzhugh-Nagumo systems, under excitation by independent noise sources, is optimal for a particular value of the number of coup

Jose Rogan, Ricardo Ramirez, Aldo H. Romero, Miguel Kiwi

Collision processes between two gold clusters are investigated using classical molecular dynamics in combination with embedded atom (EA) potentials, after checking the reliability of EA results by contrasting them with first principles calculations. The Au projectiles considered are both single atoms (N=1) and clusters of N=2, 12, 13 and 14 atoms. The target

D. Y. Vodolazov, F. M. Peeters

Applying the time-dependent Ginzburg-Landau equations, transitions between metastable states of a superconducting ring are investigated in the presence of an external magnetic field. It is shown that if the ring exhibits several metastable states at a particular magnetic field, the transition from one metastable state to another one is governed by both the r

E. Anglada, J. Soler, J. Junquera, E. Artacho

Basis sets of atomic orbitals are very efficient for density functional calculations but lack a systematic variational convergence. We present a variational method to optimize numerical atomic orbitals using a single parameter to control their range. The efficiency of the basis generation scheme is tested and compared with other schemes for multiple zeta bas

T. D. Doan, D. B. Tran Thoai

The relaxation kinetics of cavity polaritons by scattering with thermal acoustic phonons is studied within the rate equation approximation. Numerical results show that a suppression of the bottleneck of lower polariton states occurs at high polariton densities. We have found that the long decay time of the photon-like polaritons, the thin width of the embedd

H. W. Schumacher, C. Chappert, P. Crozat, R. C. Sousa

We study the precessional switching of the magnetization in microscopic spin valve cells induced by ultra short in-plane hard axis magnetic field pulses. Stable and highly efficient switching is monitored following pulses as short as 140 ps with energies down to 15 pJ. Multiple application of identical pulses reversibly toggles the cell&#39;s magnetization b

Kazuyuki Matsuhira, Zenji Hiroi, Takashi Tayama, Seishi Takagi

The low temperature magnetic properties of pyrochlore compound Dy2Ti2O7 in magnetic fields applied along the [111] direction are reported. Below 1 K, a clear plateau has been observed in the magnetization process in the field range 2~9 kOe, followed by a sharp moment jump at around 10 kOe that corresponds to a breaking of the spin ice state. We found that th

Huan-Qiang Zhou, Jon Links, Ross H. McKenzie

We study the exact solution for a two-mode model describing coherent coupling between atomic and molecular Bose-Einstein condensates (BEC), in the context of the Bethe ansatz. By combining an asymptotic and numerical analysis, we identify the scaling behaviour of the model and determine the zero temperature expectation value for the coherence and average ato

N. Goncharuk, L. Smrcka, J. Kucera

The far-infrared absorption in two-dimensional electron layers subject to magnetic field of general orientation was studied theoretically. The Kubo formula was employed to derive diagonal components of the magneto-conductivity tensor of two-dimensional electron single-layers and double-layers. A parabolic quantum well was used to model single-layer systems.

A. Sudbo, F. S. Nogueira, J. Hove

Paper withdrawn; see comments

M. Levanda, V. Fleurov

We consider the role of the third dimension in the conductivity of a quasi 2D electron gas. If the transverse correlation radius of the scattering potential is smaller than the width of the channel, i.e. the width of the transverse electron density distribution, then scattering to higher levels of the confinement potential becomes important, which causes a b

Cesar Briceno, Kevin Luhman, Lee Hartmann, John Stauffer

We present the results of a deep, optical/IR wide field imaging survey of selected fields in the nearby (d ~ 140 pc) Taurus star-forming region. We report the discovery of 9 new members with spectral types M5.75-M9.5. We derive an Initial Mass Function encompassing 54% of the known members in Taurus. Comparison with dense regions like the Trapezium Cluster i

Adam Burrows, David Sudarsky

We review some of the characteristics of irradiated extrasolar giant planets (EGPs), in anticipation of their direct detection from the ground and from space. Spectral measurements are the key to unlocking their structural and atmospheric characteristics and to determining the true differences between giant planets and brown dwarfs. In this spirit, the theor

F. D. A. Hartwick

The velocity ellipsoid for 38 globular clusters with [Fe/H] <= -1.0 is derived and shown to be significantly anisotropic with major axis directed towards low Galactic latitude. Principal axes of the spatial distribution of different groups of clusters are derived and compared with the velocity ellipsoid. The metal poor cluster spatial distribution is signifi

Thomas P. Greene, Charles J. Lada

We present the first spectrum of a highly veiled, strongly accreting protostar which shows photospheric absorption features and demonstrates the stellar nature of its central core. We find the spectrum of the luminous (L_bol = 10 L_sun) protostellar source, YLW 15, to be stellar-like with numerous atomic and molecular absorption features, indicative of a K5

Moshe Elitzur, Zeljko Ivezic, Dejan Vinkovic

Most dusty winds are described by a set of similarity functions of a single independent variable that can be chosen as the overall optical depth at visual. The self-similarity implies general scaling relations among the system parameters, in agreement with observations. Dust drift through the gas has a major impact on the structure of most winds.

M. Endl, M. Kuerster, S. Els, A. P. Hatzes

We present the complete results of the planet search program carried out at the ESO Coude Echelle Spectrometer (CES) on La Silla, using the Long Camera from Nov. 1992 to April 1998. The CES survey has monitored 37 late-type (F8V - M5V) stars in the southern hemisphere for variations in their differential radial velocities (RV) in order to detect Doppler refl

A. G. Sanchez, N. D. Padilla, D. G. Lambas

We develop a new method to determine the linear mass power spectrum using the mass function of galaxy clusters. We obtain the rms mass fluctuation sigma (M) using the expression for the mass function in the Press & Schechter (1974), Sheth, Mo & Tormen (2001) and Jenkins et al. (2001) formalisms. We apply different techniques to recover the adimensional power

Deidre A. Hunter, Vera C. Rubin, Rob A. Swaters, Linda S. Sparke

We present long-slit spectra of three irregular galaxies from which we determinethe stellar kinematics in two of the galaxies (NGC 1156 and NGC 4449) and ionized-gas kinematics in all three (including NGC 2366). We compare this to the optical morphology and to the HI kinematics of the galaxies. In the ionized gas, we see a linear velocity gradient in all thr

T. Musil, V. Karas

Time evolution of an advection-dominated accretion flow is explored in terms of relativistic fluid equations. An axially symmetric, vertically averaged mean flow is constructed and then perturbed. An axisymmetric pattern is followed as it propagates in the form of a wave towards the horizon of a rotating (Kerr) black hole. Several assumptions are relaxed in

Christopher W. Mauche

Using data obtained in 1994 June/July with the Extreme Ultraviolet Explorer deep survey photometer and in 2001 January with the Chandra X-ray Observatory Low Energy Transmission Grating Spectrograph, we investigate the extreme-ultraviolet (EUV) and soft X-ray oscillations of the dwarf nova SS Cyg in outburst. We find quasi-periodic oscillations (QPOs) at nu_

Sebastien Lepine, Michael M. Shara, R. Michael Rich

We have conducted a systematic search for high proper motion stars in the Digitized Sky Survey, in the area of the sky north of -2.8 degrees in declination and within 25 degrees of the galactic plane. Using the SUPERBLINK software, a powerful automated blink comparator developed by us, we have identified 601 stars in the magnitude range 9<r<20 with proper mo

D. Petry, I. H. Bond, S. M. Bradbury, J. H. Buckley

The BL Lac object H1426+428 was recently detected as a high energy gamma-ray source by the VERITAS collaboration (Horan et al. 2002). We have reanalyzed the 2001 portion of the data used in the detection in order to examine the spectrum of H1426+428 above 250 GeV. We find that the time-averaged spectrum agrees with a power law of the shape dF/dE = 10^(-7.31

R. Bowen, P. G. Ferreira

We consider the most general parametrization of flat topologically compact universes, complementing the work of Scannapieco, Levin and Silk to include non-trivial shapes. We find that modifications in shape of the fundamental domain will lead to distinct signatures in the anisotropy of the cosmic microwave radiation. We make a preliminary assessment of the e

Harald Kuntschner, Russell J. Smith, Matthew Colless, Roger L. Davies

We describe the construction and study of an objectively-defined sample of early-type galaxies in low-density environments. The sample galaxies are selected from a recently-completed redshift survey using uniform and readily-quantified isolation criteria, and are drawn from a sky area of ~700 deg^2, to a depth of 7000 k/ms and an apparent magnitude limit of

R. F. Butler, A. Golden, A. Shearer

There remain several definitive gamma-ray pulsars that are as yet undetected in the optical regime. A classic case is the pulsar PSR B1951+32, associated with the complex CTB 80 SNR. Previous ground based high speed 2-d optical studies have ruled out candidates to V ~ 24. Hester (2000a) has reported an analysis of archival HST/WFPC2 observations of the CTB 8

Grazyna Stasinska

The methods of abundance determinations in HII regions and planetary nebulae are described, with emphasis on the underlying assumptions and inherent problems. Recent results on abundances in Galactic HII regions and in Galactic and extragalactic Planetary Nebulae are reviewed.

L. Clewley, S. J. Warren, P. C. Hewett, John E. Norris

This is the first in a series of three papers presenting a new calculation of the mass of the Galaxy based on radial velocities and distances measured for a sample of some 100 faint 16 < B < 20 field blue horizontal-branch (BHB) stars. This study aims to reduce the uncertainty in the measured mass of the Galaxy by increasing the number of halo objects at Gal

J. R. Goicoechea, J. Cernicharo

We present Infrared Space Observatory (ISO) observations of 16OH and 18OH toward Sgr B2 with a spectral resolution of 35 km/s. The OH J=5/2-3/2 and J=3/2-1/2 rotational lines of the 2Pi1/2 ladder are seen in emission while the cross-ladder transitions (from the 2Pi3/2 J=3/2 to the J=1/2, 3/2 and 5/2 levels of the 2Pi1/2ladder), and the 2Pi3/2 J=5/2-3/2 and J

A. Tzioumis, E. King, R. Morganti, D. Dallacasa

A small sample of 7 southern Compact Steep Spectrum (CSS) radio sources has been selected as part of the study of a larger flux-limited complete sample of radio sources. High resolution images, using the VLBI network in the southern hemisphere and the high resolution MERLIN array, are presented for all sources in the CSS sample. The overall morphology of eac

E. Paunzen, G. Handler, W. W. Weiss, N. Nesvacil

The group of lambda Bootis type stars comprises late B- to early F-type, Population I objects which are basically metal weak, in particular the Fe group elements, but with the clear exception of C, N, O and S. The present work is a continuation of the studies by Paunzen et al. (1998, A&A, 335, 533), who presented first results on the pulsational characterist

Arne Rau, Jochen Greiner

We analyzed 139 chi-state observations of GRS 1915+105 with RXTE from 1997 to 2000 and found i) that the observations fall into two groups with different Comptonization behavior, ii) that the slope of the hard X-ray component correlates with the radio flux, thus revealing the interaction of jet and corona, and iii) a 590 days long term periodicity in the har

A. Ford, R. D. Jeffries, B. Smalley, S. G. Ryan

We have obtained echelle spectroscopy of 14 Population II objects selected from those previously observed by Bonifacio & Molaro (1997). For one object, HD 140283, we obtained exquisite data with the High Dispersion Spectrograph on the Subaru Telescope, with S/N exceeding 1000 per 0.018A pixel. Li abundances have been determined by spectral synthesis from bot

Ernst Paunzen, Ilian Kh. Iliev, Inga Kamp, Ina S. Barzova

The lambda Bootis stars are Population I, late B to early F-type stars, with moderate to extreme (up to a factor 100) surface underabundances of most Fe-peak elements and solar abundances of lighter elements (C, N, O, and S). To put constraints on the various existing theories that try to explain these peculiar stars, we investigate the observational propert

Stefan Gottloeber, Ewa Lokas, Anatoly Klypin

Using numerical simulations and the Sheth-Tormen approximation we study the mass function of dark matter halos in voids. We find that the void mass function is significantly lower and its shape is different than that of the field halos. We predict that in the standard LCDM model a void with radius 10 h^-1 Mpc should have 50 halos with circular velocity v_c >

H. Meusinger, R. -D. Scholz, M. Irwin, H. Lehmann

We present results of the spectroscopical follow-up observations of QSO candidates from a combined variability and proper motion (VPM) survey in a ~10 square degrees region centered on the globular cluster M3. The search is based on a large number of digitised Schmidt plates with a time-baseline of three decades. This paper reviews the candidate selection, t

T. R. Bedding, A. A. Zijlstra, A. Jones, F. Marang

The nearby Mira-like variable L2 Pup is shown to be undergoing an unprecedented dimming episode. The stability of the period rules out intrinsic changes to the star, leaving dust formation along the line of sight as the most likely explanation. Episodic dust obscuration events are fairly common in carbon stars but have not been seen in oxygen-rich stars. We

T. Kato, P. A. Dubovsky, R. Stubbings, M. Simonsen

GZ Cnc was discovered as a variable star by Takamizawa (Tmz V34), which turned out to a cataclysmic variable (CV). Past studies have shown that this object is a good candidate for a rarely outbursting, long-period dwarf nova. Only three outbursts were recorded between 1999 and 2001. In 2002 March-May, the object suddenly showed a dramatic increase of the out

M. Nagashima, Y. Yoshii, T. Totani, N. Gouda

Number counts of galaxies are re-analyzed using a semi-analytic model (SAM) of galaxy formation based on the hierarchical clustering scenario. Faint galaxies in the Subaru Deep Field (SDF) and the Hubble Deep Field (HDF) are compared with our model galaxies. We have determined the astrophysical parameters in the SAM that reproduce observations of nearby gala