October 2002 arXiv papers — page 3

A. Marinov, S. Gelberg, D. Kolb, R. Brandt

A consistent interpretation is given to some previously unexplained phenomena seen in nature in terms of the recently discovered long-lived high spin super- and hyper-deformed isomeric states. The Po halos seen in mica are interpreted as due to the existence of such isomeric states in corresponding Po or nearby nuclei which eventually decay by gamma- or beta

Karol Zyczkowski, Artur Lozinski

In this work we propose a definition of an Euroattractor: an attracting invariant measure of a certain iterated functions system (IFS). An IFS is defined by specifying a set of functions, defined in subsets of R^N or in a classical phase space, which act randomly on the initial point, so it may be considered as a generalization of the notion of classical dyn

Sanjay Jain, Sandeep Krishna

We give a self-contained introduction to the theory of directed graphs, leading up to the relationship between the Perron-Frobenius eigenvectors of a graph and its autocatalytic sets. Then we discuss a particular dynamical system on a fixed but arbitrary graph, that describes the population dynamics of species whose interactions are determined by the graph.

Heide Narnhofer, Walter Thirring

The entanglement of clouds of atoms recently experimentally verified is expressed in terms of the fluctuation algebra introduced by Goderis, Verbeure and Vets. A mean field Hamiltonian describing the coupling to a laser beam leads to different time evolutions if considered on microscopic or mesoscopic operators. Only the latter creates non trivial correlatio

J. P. Keating, N. Linden, Z. Rudnick

There has recently been interest in relating properties of matrices drawn at random from the classical compact groups to statistical characteristics of number-theoretical L-functions. One example is the relationship conjectured to hold between the value distributions of the characteristic polynomials of such matrices and value distributions within families o

S. Baskal, Y. S. Kim

It is shown that the one-lens system in para-axial optics can serve as an optical computer for contraction of Wigner's little groups and an analogue computer which transforms analytically computations on a spherical surface to those on a hyperbolic surface. It is shown possible to construct a set of Lorentz transformations which leads to a two-by-two mat

Andrej Zlatos

We construct non-random bounded discrete half-line Schr\" odinger operators which have purely singular continuous spectral measures with fractional Hausdorff dimension (in some interval of energies). To do this we use suitable sparse potentials. Our results also apply to whole line operators, as well as to certain random operators. In the latter case we

Andrej Zlatos

A Jacobi matrix with $a_n\to 1$, $b_n\to 0$ and spectral measure $ν'(x)dx + dν_{sing}(x)$ satisfies the Szeg\H o condition if $\int_{0}^π\ln \bigl[ ν'(2\cosθ) \bigr] dθ$ is finite. We prove that if $a_n = 1 + \frac α{n} + O(n^{-1-\eps})$ and $b_n = \frac β{n} + O(n^{-1-\eps})$ with $2α\ge |β|$ and $\eps>0$, then the corresponding matrix is Szeg\H o.

F. Hiroshima, H. Spohn

We consider an electron, spin 1/2, minimally coupled to the quantized radiation field in the nonrelativistic approximation, a situation defined by the Pauli-Fierz Hamiltonian $H$. There is no external potential and $H$ fibers as $\int^\oplus H_p dp$ according to the total momentum $p$. We prove that the ground state subspace of $H_p$ is two-fold degenerate p

Volker Bach, Frederic Klopp, Heribert Zenk

We study the photoelectric effect on the example of a simplified model of an atom with a single bound state, coupled to the quantized electromagnetic field. For this model, we show that Einstein's prediction for the photoelectric effect is qualitatively and quantitatively correct to leading order in the coupling parameter. More specifically, considering

Alexei F. Cheviakov

In this paper we establish Bäcklund transformations between solutions of several cases of classical isotropic MHD and plasma equilibria and corresponding anisotropic equilibria. The transformations appear to be infinite-dimensional and allow building solutions with variety of physical properties. We also present a new infinite-dimensional Lie group of intrin

David Bruce Wilson

We extend a technique for lower-bounding the mixing time of card-shuffling Markov chains, and use it to bound the mixing time of the Rudvalis Markov chain, as well as two variants considered by Diaconis and Saloff-Coste. We show that in each case Theta(n^3 log n) shuffles are required for the permutation to randomize, which matches (up to constants) previous

Sorin Popa

We present here a shorter version of the proof of a result from our paper ``On a class of type II$_1$ factors with Betti numbers invariants'', showing that the von Neumann factor associated with the group $\Bbb Z^2 \rtimes SL(2, \Bbb Z)$ has trivial fundamental group.

Andrey N. Tyurin

In the abelian case (the subject of several beautiful books) fixing some combinatorial structure (so called theta structure of level k) one obtains a special basis in the space of sections of canonical polarization powers over the jacobians. These sections can be presented as holomorphic functions on the "abelian Schottky space". This fact provides v

Elisabetta Colombo, Bert van Geemen

Naruki gave an explicit construction of the moduli space of marked cubic surfaces, starting from a toric variety and proceeding with blow ups and contractions. Using his result, we compute the Chow groups and the Chern classes of this moduli space.As an application we relate a recent result of Freitag on the Hilbert polynomial of a certain ring of modular fo

Werner Muller

In this paper we study the absolute convergence of the spectral side of the Arthur trace formula. We reduce the problem of the absolute convergence to a problem about local components of automorphic representations. The latter problem can be settled for GL(n).

Ruedi Suter

Let g be a complex simple Lie algebra and b a fixed Borel subalgebra of g. We shall describe the abelian ideals of b in a uniform way, that is, independent of the classification of complex simple Lie algebras.

A. Mutlu, T. Porter

Crossed squares and 2-crossed modules are both algebraic models for 3-types. This paper explores the interrelationships between these two models.

S. Caenepeel, T. Guédénon

Let $k$ be a field, and $H$ a Hopf algebra with bijective antipode. If $H$ is commutative, noetherian, semisimple and cosemisimple, then the category ${}_{H}{\mathcal {YD}}^H$ of Yetter-Drinfeld modules is semisimple. We also prove a similar statement for the category of Long dimodules, without the assumption that $H$ is commutative.

S. Caenepeel, Dingguo Wang, Yanxin Wang

Let $H$ be a Hopf algebra. Ju and Cai introduced the notion of twisting of an $H$-module coalgebra. In this note, we study the relationship between twistings, crossed coproducts and Hopf-Galois coextensions. In particular, we show that a twisting of an $H$-Galois coextension remains $H$-Galois if the twisting is invertible.

Alexei F. Cheviakov

In this paper we perform Lie group analysis of systems of partial differential equations which describe different cases of classical plasma equilibria, and find groups of transformations admitted by those equations in several important cases. We also give a recipe how to apply Lie formalism to look for Bäcklund transformations between systems of partial diff

Frederic Chapoton

A nice factorization is given for the characteristic polynomials of intervals in some posets of leaf-labeled forests of rooted binary trees.

Marc Chardin

This article first presents two examples of algorithms that extracts information on scheme out of its defining equations. We also give a review on the notion of Castelnuovo-Mumford regularity, its main properties (in particular its relation to computational issues) and different ways that were used to estimate it.

Priska Jahnke, Ivo Radloff

The consequences of the splitting of higher jet sequences of vector bundles on a compact complex (Kaehler) manifold are studied, proving an infinitesimal convers to a result of I.Biswas.

Long Wang

For any two n-th order polynomials a(s) and b(s), the Hurwitz stability of their convex combination is necessary and sufficient for the existence of a polynomial c(s) such that c(s)/a(s) and c(s)/b(s) are both strictly positive real.

M. Khoshnevisan, Florentin Smarandache, Sukanto Bhattacharya

In this paper we take a look at a simple portfolio insurance strategy using a protective put and computationally derive the investor's governing utility structures underlying such a strategy under alternative market scenarios. Investor utility is deemed to increase with an increase in the excess equity generated by the portfolio insurance strategy over a

Konrad Schmuedgen

Let $K_f$ be a closed semi-algebraic set in $\dR^d$ such that there exist bounded real polynomials $h_1,{...},h_n$ on $K_f$. It is proved that the moment problem for $K_f$ is solvable provided it is for all sets $K_f\cap C_λ$, where $C_λ=\{x:h_1(x)=λ_1,{...},h_n(x)=λ_n\}$ and $\inf\{h_j(x); x\in K_f\}\leλ_j\le\sup\{h_j(x);x\in K_f\}$. New classes of non-comp

Simon Gindikin, Bernhard Kroetz, Gestur Olafsson

Let $G/H$ be a semisimple symmetric space. Then the space $L^2(G/H)$ can be decomposed into a finite sum of series representations induced from parabolic subgroups of $G$. The most continuous part of the spectrum of $L^2(G/H)$ is the part induced from the smallest possible parabolic subgroup. In this paper we introduce Hardy spaces canonically related to thi

Ernesto Lupercio, Bernardo Uribe

The purpose of this paper is to introduce the notion of loop groupoid associated to a groupoid. After studying the general properties of the loop groupoid, we show how this notion provides a very natural geometric interpretation for the twisted sectors of an orbifold, and for the inner local systems introduced by Ruan by means of a natural generalization of

F. Quevedo

An overview is presented of some cosmological aspects of string theory. Recent developments are emphasised, especially the attempts to derive inflation or alternatives to inflation from the dynamics of branes in string theory. Time dependent backgrounds with potential cosmological implications, such as those provided by negative tension branes and S-branes a

M. Trapletti

We apply the well-known Scherk-Schwarz supersymmetry breaking mechanism in an open string context. We construct a new Z_3\times Z_3^\prime model, containing only D9-branes, and rederive from a more geometric perspective the known Z_6^\prime\times Z_2^\prime model, containing D9, D5 and \bar D 5 branes. We show recent results about the study of quantum instab

Vladimir Dzhunushaliev, Douglas Singleton

The dual superconductor picture of the QCD vacuum is thought to describe various aspects of the strong interaction including confinement. Ordinary superconductivity is described by the Ginzburg-Landau (GL) equation. In the present work we show that it is possible to arrive at a GL-like equation from pure SU(2) gauge theory. This is accomplished by using Abel

Miloslav Znojil

Witten's supersymmetric quantum mechanics may incorporate potentials with strong singularities after their appropriate regularization. This was proposed by Das and Pernice [Nucl. Phys. B 561 (1999) 357 and arXiv: hep-th/0207112]. We suggest that one of the most natural recipes of this type is generated by an infinitesimal complex shift of coordinates. Th

Abdou M. Abdel-Rehim, Deirdre Black, Amir H. Fariborz, Joseph Schechter

We study the role of a possible nonet of light scalar mesons in the still interesting $η\to 3π$ decay process, with the primary motivation of learning more about the scalars themselves. The framework is a conventional non-linear chiral Lagrangian of pseudoscalars and vectors, extended to include the scalars. The parameters involving the scalars were previous

Xiangdong Ji, Jian-Ping Ma, Feng Yuan

We study the three-quark light-cone amplitudes of the proton including quarks' transverse momenta. We classify these amplitudes using a newly-developed method in which light-cone wave functions are constructed from a class of light-cone matrix elements. We derive the constraints on the amplitudes from parity and time-reversal symmetries. We use the ampli

E. Gardi, R. G. Roberts

We claim that factorization implies that the evolution kernel, defined by the logarithmic derivative of the N-th moment of the structure function d ln F_2^N / d ln Q^2, receives logarithmically enhanced contributions (Sudakov logs) from a single source, namely the constrained invariant mass of the jet. Available results from fixed-order calculations facilita

Michael Klasen

The Feynman diagram generator FeynArts and the computer algebra program FormCalc allow for an automatic computation of 2->2 and 2->3 scattering processes in High Energy Physics. We have extended this package by four new kinematical routines and adapted one existing routine in order to accomodate also two- and three-body decays of massive particles. This make

R. M. Godbole

Decays of the lightest neutralino are studied in $R_p$-violating models, with operators $λ^\prime L Q D^c$ and $λL L E^c$ involving third-generation matter fields and with dominant $λ^\prime$ and $λ$ couplings. Decays with the top-quark among the particles produced are considered, in addition to those with an almost massless final state. Phenomenological ana

Andrew Akeroyd, Abdesslam Arhrib

We study the associated production of the $A^0$ neutral CP--odd Higgs boson with a neutral gauge boson $Z$ as well as single production of $A^0$ via $e^+e^- \to ν_e {\barν}_e A^0$ at the one loop level in the Minimal Supersymmetric Standard Model (MSSM). We show that the MSSM cross--section may be enhanced by light SUSY particles. Then we study the productio

Svjetlana Fajfer, Anita Prapotnik, Paul Singer

The radiative decays D^0 -> K^0(bar) P^0 gamma with nonresonant K^0(bar) P^0 (P^0 = pi^0, eta, eta') are considered within the framework which combines heavy quark effective theory and the chiral Lagrangian. Due to neutral mesons the amplitudes do not have bremsstrahlung contributions. We assume factorization for the weak matrix elements. Light (virtual)

I. N. Mishustin, M. Hanauske, A. Bhattacharyya, L. M. Satarov

We study properties of compact stars with the deconfinement phase transition in their interiors. The equation of state of cold baryon-rich matter is constructed by combining a relativistic mean-field model for the hadronic phase and the MIT Bag model for the deconfined phase. In a narrow parameter range two sequences of compact stars (twin stars), which diff

C. Avila, J. Magnin, J. C. Sanabria

In a model of hadrons in which the hadron wave function at low $Q^2$ is represented by a hadron-like Fock state expansion, we calculate the $π$ and $K$ parton distribution functions by comparing to experimental data. We show that the model gives an accurate description of available data and, in addition, gives a clear prediction of the initial flavors to be

Stefan Berge, Michael Klasen

In the Minimal Supersymmetric Standard Model (MSSM), the process e+ e- -> gluino gluino is mediated by quark/squark loops, dominantly of the third generation, where the mixing of left- and right-handed states can become large. Taking into account realistic beam polarization effects, photon and Z0-boson exchange, and current mass exclusion limits, we scan the

Gerald V. Dunne, Christian Schubert

We present explicit closed-form expressions for the two-loop Euler-Heisenberg Lagrangians in a constant self-dual field, for both spinor and scalar QED. The simplicity of these representations allows us to examine in detail the asymptotic properties of these Lagrangians, and to construct their imaginary part using Borel dispersion relations. In particular, f

O. V. Selyugin

With relation to the RHIC spin program we research the polarization effects in elastic proton-proton scattering at small momentum transfer and in the diffraction dip region. The calculations take into account the Coulomb-hadron interference effects including the additional Coulomb-hadron phase. In particular we show the impact of the form of the hadron poten

Wojciech Krolikowski

Operating with the bilarge neutrino mixing, we show that in the option of Dirac neutrinos the fermion universality -- expressed by the proportionality of neutrino masses to charged-lepton masses -- predicts $Δm_{21}^2$ of the order $10^{-5} {\rm eV}^2$, consistently with the LMA MSW solar solution. In contrast, in the option of Majorana neutrinos the fermion

Werner Porod

We demonstrate how the fundamental supersymmetric theory at high energy scales can be reconstructed using precision data expected at future high energy collider experiments. We have studied a set of representative examples in this context: minimal supergravity; gauge mediated supersymmetry breaking; and superstring effective field theories.

Martin Schmaltz

Little Higgs theories are an exciting new possibility for physics at TeV energies. In the Standard Model the Higgs mass suffers from an instability under radiative corrections. This ``hierarchy problem'' motivates much of current physics beyond the Standard Model research. Little Higgs theories offer a new and very promising solution to this problem

Ilya L. Shapiro, Joan Sola

We present a model of inflation based on the anomaly-induced effective action of gravity in the presence of a conformally invariant Hilbert-Einstein term. Our approach is based on the conformal representation of the fields action and on the integration of the corresponding conformal anomaly. In contradistinction to the original Starobinsky's model, infla

Brian T. Meadows

Among the many unresolved questions in light quark spectroscopy, the underlying structure of the scalar mesons and the identification of states with a gluonic content rank high. Recently, new information has come from $ϕ$ radiative decays, $J/ψ$, $τ$, $D$ and $D_s$ meson decays. Other papers in this conference review radiative transitions of $ϕ$ and $J/ψ$. T

V. A. De Lorenci, R. Klippert, Yu. N. Obukhov

We study the optical paths of the light rays propagating inside a nonlinear moving dielectric media. For the rapidly moving dielectrics we show the existence of a distinguished surface which resembles, as far as the light propagation is concerned, the event horizon of a black hole. Our analysis clarifies the physical conditions under which electromagnetic an

J. A. K. Suykens, J. Vandewalle, B. De Moor

We show how coupling of local optimization processes can lead to better solutions than multi-start local optimization consisting of independent runs. This is achieved by minimizing the average energy cost of the ensemble, subject to synchronization constraints between the state vectors of the individual local minimizers. From an augmented Lagrangian which in

Sara Cohen, Werner Nutt, Yehoshua Sagiv

Query equivalence is investigated for disjunctive aggregate queries with negated subgoals, constants and comparisons. A full characterization of equivalence is given for the aggregation functions count, max, sum, prod, toptwo and parity. A related problem is that of determining, for a given natural number N, whether two given queries are equivalent over all

L. Kondic, R. R. Hartley, S. G. K. Tennakoon, B. Painter

Granular materials are known to separate by size under a variety of circumstances. Experiments presented here and elucidated by modeling and MD simulation document a new segregation mechanism, namely segregation by friction. The experiments are carried out by placing steel spheres on a horizontal plane enclosed by rectangular sidewalls, and subjecting them t

R. N. Bhowmik, R. Nagarajan, R. Ranganathan

We report the particle size dependent magnetic behaviour in the antiferromagnetic spinel CoRh2O4. The nanoparticles were obtained by mechanical milling of bulk material, prepared under sintering method. The XRD spectra show that the samples are retaining the spinel structure. The particle size decreases from 70 nm to 16 nm as the milling time increases from

S. Yi, L. You

We discuss the expansion of an initially trapped dipolar condensate. When the nominal isotropic s-wave interaction strength becomes tunable through a Feshbach resonance, anisotropic dipolar effects are shown to be detectable under current experimental conditions [E. A. Donley {\it et al.}, Nature {\bf 412}, 295 (2001)].

Ondrej Sipr, Antonin Simunek, Sergey Bocharov, Gunther Drager

Polarized x-ray absorption near edge structure (XANES) spectra at both the Cu and the Ge K-edges of CuGeO3 are measured and calculated relying on the real-space multiple-scattering formalism within a one-electron approach. The polarization components are resolved not only in the unit cell coordinate system but also in a local frame attached to the nearest ne

J. Tempere, I. F. Silvera, J. T. Devreese

The stability of multielectron bubbles (MEBs) in liquid helium is investigated using the liquid-drop model for fissioning nuclei. Whereas a critical positive pressure can make the bubble unstable against fissioning, a small negative pressure suffices to introduce a restoring force preventing any small deformation of the bubble to grow. We also find that ther

M. E. Simon, C. M. Varma

A proposal to test the proposed time-reversal and inversion breaking phase in the Pseudogap region of the Cuprate compounds through the variation of Second-harmonic generation intensity with temperature and polarization and angle of incidence is presented.

Alexander Buehler, Ute Loew, Kai P. Schmidt, Goetz S. Uhrig

By high temperature series expansion and exact complete diagonalization the magnetic susceptibility chi(T) and the specific heat C(T) of a two-leg S=1/2 ladder with cyclic (4-spin) exchange are computed. Both methods yield convincing results for not too small temperatures. We find that a small amount of cyclic exchange influences the thermodynamical properti

A. I. Olemskoi

Within Tsallis statistics, a picture is elaborated to address self--similar time series as a thermodynamic system. Thermodynamic--type characteristics relevant to temperature, pressure, entropy, internal and free energies are introduced and tested. Predictability conditions of time series analysis are discussed in details on the basis of Van der Waals model.

Javier Junquera, Magali Zimmer, Pablo Ordejon, Philippe Ghosez

We report first-principles density-functional pseudopotential calculations on the atomic structures, electronic properties, and band offsets of BaO/BaTiO$_3$ and SrO/SrTiO$_3$ nanosized heterojunctions grown on top of a silicon substrate. The density of states at the junction does not reveal any electronic induced interface states. A dominant perovskite char

Andrea Cavagna, Irene Giardina, Giorgio Parisi, Marc Mezard

We revisit two classic Thouless-Anderson-Palmer (TAP) studies of the Sherrington-Kirkpatrick model [Bray A J and Moore M A 1980 J. Phys. C 13, L469; De Dominicis C and Young A P, 1983 J. Phys. A 16, 2063]. By using the Becchi-Rouet-Stora-Tyutin (BRST) supersymmetry, we prove the general equivalence of TAP and replica partition functions, and show that the an

B. Davoudi, R. Asgari, M. Polini, M. P. Tosi

We use a density functional theoretical approach to calculate the pair distribution function and the effective interactions in homogeneous fluids of spinless charged bosons. The scheme involves the self-consistent solution of a two-particle scattering problem with an effective scattering potential which embodies many-body effects and is adjusted to the compr

Paul Maragakis, Ryan Lee Barnett, Efthimios Kaxiras, Marcus Elstner

Minuscule molecular forces can transform DNA into a structure that is elongated by more than half its original length. We demonstrate that this pronounced conformational transition is of relevance to ongoing experimental and theoretical efforts to characterize the conducting properties of DNA wires. We present quantum mechanical calculations for acidic, dry,

Y. Morita, V. P. S. Awana, H. Yamauchi, M. Karppinen

Here results of a systematic study on oxygen stoichiometry are reported for the first three members of the novel CoSr2(Y,Ce)sCu2O5+2s or Co-12s2 homologous series, i.e. Co-1212, Co-1222 and Co-1232 phases with a SrO-CoO1-SrO-CuO2-(Y,Ce)-[O2-(Y,Ce)]s-1-CuO2 layered structure. The oxygen content was precisely determined by two independent chemical techniques:

Wan Ahmad Tajuddin Wan Abdullah

Economic ensembles can be modeled as networks of interacting agents whose be-haviors are described in terms of game theory. The evolutionary paradigm has been applied to two-person games to discover strategies in this context. Subse-quently, many-player games, and specifically global games (where payoffs depend collectively on all the rest of the players) as

R. Lopez-Sandoval, G. M. Pastor

The dimerized one-dimensional Hubbard model is studied in the framework of lattice density-functional theory (LDFT). The single-particle density matrix gamma_{ij} with respect to the lattice sites is considered as basic variable. The corresponding interaction-energy functional W[gamma_{ij}] is defined by Levy's constrained search. Exact numerical results

H. W. F. Sung, C. Rudowicz

This article describes various misconceptions and misinterpretations concerning presentation of the hysteresis loop for ferromagnets occurring in undergraduate textbooks. These problems originate from our teaching a solid state / condensed matter physics (SSP/CMP) course. A closer look at the definition of the 'coercivity' reveals two distinct notion

N. -C. Yeh

Recent experimental and theoretical developments in high-temperature superconductivity are reviewed, and the empirically asymmetric behavior between hole-doped and electron-doped cuprates is contrasted. A number of phenomena previously considered as essential for the formation of cuprate superconductivity, such as the pairing symmetry, pseudogap phenomenon,

Q. A. Wang, S. Salaun, A. Bulou

The pressure influence on the lattice vibration of $CaZnF_4$ has been studied by Raman diffusion up to 17 GPa. Most Raman frequencies increase with increasing pressure. Three singularities in the pressure induced frequency evolution are observed around 1.5 GPa, 10 GPa and 17 GPa. The samples pressurized to 17 GPa or higher do not revert to the ambient pressu

Suzanne Fielding, Peter Sollich

We study the non-equilibrium version of the fluctuation dissipation (FD) relation in the glass phase of a trap model that is driven into a non-equilibrium steady state by external ``shear''. This extends our recent study of ageing FD relations in the same model, where we found limiting, observable independent FD relations for ``neutral'' obse

Maxim Lyutikov, Roger Blandford

We study the dynamics of relativistic electromagnetic explosions as a possible mechanism for the production of Gamma-Ray Bursts. We propose that a rotating relativistic stellar-mass progenitor loses much of its spin energy in the form of an electromagnetically-dominated outflow. After the flow becomes optically thin, it forms a relativistically expanding, no

A. G. Elfimov, R. M. O. Galvao, V. Jatenco-Pereira, R. Opher

Excitation of a Global Alfven wave (GAW) is proposed as a viable mechanism to explain plasma heating in the magnetosphere of young stars. The wave and basic plasma parameters are compatible with the requirement that the dissipation length of GAWs be comparable to the distance between the shocked region at the star's surface and the truncation region in t

Jacco Vink, J. Martin Laming

We investigate the non-thermal X-ray emission from Cas A. For the hard X-ray continuum we test the model proposed by Laming, which invokes bremsstrahlung from electrons accelerated by lower hybrid plasma waves. The justification for this model comes from our determination of a lower limit to the average magnetic field of B > 0.5 mG, which suggest that most o

Herman L. Marshall, Rick A. Edelson, Simon Vaughan, Mathew A. Malkan

An observation of Mrk 478 using the Chandra Low Energy Transmission Grating Spectrometer is presented. The source exhibited 30-40% flux variations on timescales of order 10000 s together with a slow decline in the spectral softness over the full 80 ks observation. The 0.15--3.0 keV spectrum is well fitted by a single power law with photon index of Gamma = 2.

T. Fang, K. R. Sembach, C. R. Canizares

With the Chandra X-ray Telescope we have detected a zero-redshift OVII He-alpha absorption line along the sight line toward 3C 273. This line detection is highly significant, with a signal-to-noise ratio (S/N) of 6.4. We explore two models, which associate this line with (1) the intragroup gas in the Local Group, and (2) the hot halo gas in the vicinity of o

S. M. Kahn, J. R. Peterson, F. B. S. Paerels, H. Xu

In many clusters of galaxies, the cooling time at the core of the intracluster medium is much less than the age of the system, suggesting that the the gas should continually lose energy by radiation. Simple thermodynamic arguments then require that the expected "cooling flow" should exhibit a specific spectroscopic signature, characterized by a diffe

J. R. Peterson, J. G. Jernigan, S. M. Kahn

We discuss multivariate Monte Carlo methods appropriate for X-ray dispersive spectrometers. Dispersive spectrometers have many advantages for high resolution spectroscopy in the X-ray band. Analysis of data from these instruments is complicated by the fact that the instrument response functions are multi-dimensional and relatively few X-ray photons are detec

J. R. Peterson, S. M. Kahn, F. B. S. Paerels, J. S. Kaastra

We present high resolution X-ray spectra of 14 putative cooling-flow clusters of galaxies obtained with the Reflection Grating Spectrometer on XMM-Newton. The clusters in the sample span a large range of temperatures and mass deposition rates. Various of these spectra exhibit line emission from O VIII, Ne X, Mg XII & XI, Al XIII & XII, Si XIV & XIII, N VII,

Walter Brisken

Very long baseline interferometry (VLBI) provides the resolution needed to make precision measurements of a pulsar's parallax and proper motion. In making these measurements, the astronomer is faced with difficult calibration problems and a paucity of strong point-like calibrators that ultimately limit the accuracy of parallax measurements of even the br

M. Zoccali, A. Renzini, S. Ortolani, L. Greggio

We present a new determination of the metallicity distribution, age, and luminosity function of the Galactic bulge stellar population. By combining near-IR data from the 2MASS survey, from the SOFI imager at ESO NTT and the NICMOS camera on board HST we were able to construct color-magnitude diagrams (CMD) and luminosity functions (LF) with large statistics

L. J. Goicoechea, D. Alcalde, V. N. Shalyapin

We review some techniques to study the nature and size of the optical continuum sources in multiple QSOs. We focus on the source originating the events with several months timescale (the rapid variability source) as well as the source that is responsible for the non-variable background component (the background source). The techniques are used to study both

J. I. Read, G. Gilmore

We present some simple models to determine whether or not the accretion of cold dark matter by supermassive black holes is astrophysically important. Contrary to some claims in the literature, we show that supermassive black holes cannot significantly alter a power law density cusp via accretion, whether during mergers or in the steady state.

D. Pierini, K. J. Leech, H. J. Voelk

We study the relationship between gas cooling via the [C II] (158 micron) line emission and dust cooling via the far-IR continuum emission on the global scale of a galaxy in normal (i.e. non-AGN dominated and non-starburst) late-type systems. It is known that the luminosity ratio of total gas and dust cooling, L(C II)/L(FIR), shows a non-linear behaviour wit

J. B. Feng, Y. F. Huang, Z. G. Dai, T. Lu

In previous works, a generic dynamical model has been suggested by Huang et al., which is shown to be correct for both adiabatic and radiative blastwaves, and in both ultra-relativistic and non-relativistic phases. In deriving their equations, Huang et al. have assumed that the radiative efficiency of the fireball is constant. They then applied their model d

R. Oechslin, G. Poghosyan, K. Uryu

Binary neutron star mergers are expected to be one of the most promising source of gravitational waves (GW) for the network of laser interferometric and bar detectors becoming operational in the next few years. The merger wave signal is expected to be sensitive to the interior structure of the neutron star (NS). The structure of high density phases of matter

P. Møller, J. P. U. Fynbo, J. Hjorth, B. Thomsen

We report on a 3600 s spectrum of GRB 021004 obtained with the Nordic Optical Telecope on La Palma 10.71 hours after the burst. We identify absorption lines from five systems at redshifts 1.3806, 1.6039, 2.2983, 2.3230, and 2.3292. In addition we find an emission line which, if due to Ly-alpha from the host galaxy, gives a redshift of 2.3351. The nearest abs

Juan Fabregat

We present a photometric survey aimed to characterize the Be star population of young open clusters. It is found that in these clusters early-type Be stars are more frequent than in the galactic field, and late-type Be stars are scarce or inexistent. We interpret this result as evidence for an evolutionary enhancement of the Be phenomenon towards the end of

J. Sanz-Forcada, N. S. Brickhouse, A. K. Dupree

A survey of 28 stars using EUV spectra has been conducted to establish the structure of stellar coronae in active binary systems from the EMD, electron densities, and scale sizes. Observations obtained by the EUVE during 9 years of operation are included for the stars in the sample. EUVE data allow a continuous EMD to be constructed in the range log T~5.6-7.

E. Piconcelli, L. Bassani, M. Cappi, F. Fiore

We briefly report on an on-going spectroscopic study of hard X-ray sources selected serendipitously in 12 XMM-Newton fields. Results for the analysis of the 41 sources from the first seven EPIC observations have been discussed in a previous paper (Piconcelli et al. 2002, Paper I) where we found an absolute fraction of X-ray absorbed sources (~30%) lower than

M. Monelli, G. Andreuzzi, G. Bono, R. Buonanno

We present accurate multiwavelength UBVI time series data of the LMC cluster Reticulum. Data cover a time interval of ~ 6 yr and have been collected with SUSI1/2 and SOFI at NTT/ESO. For each band we collected approximately 30 short/long exposures and the total exposure times range from roughly 3500 (U, B), 6000s (V) to 8300s (I). The observing strategy and

G. Woan

The GEO600 laser-interferometric gravitational wave detector near Hannover, Germany, is one of six such interferometers now close to operation worldwide. The UK/German GEO collaboration uses advanced technologies, including monolithic silica suspensions and signal recycling, to deliver a sensitivity comparable with much larger detectors in their initial conf

R. Ruffini, C. L. Bianco, P. Chardonnet, F. Fraschetti

Using GRB 991216 as a prototype, it is shown that the intensity substructures observed in what is generally called the "prompt emission" in gamma ray bursts (GRBs) do originate in the collision between the accelerated baryonic matter (ABM) pulse with inhomogeneities in the interstellar medium (ISM). The initial phase of such process occurs at a Loren

D. Steeghs, M. Perryman, A. Reynolds, J. H. J. de Bruijne

We present high time-resolution photometry of the dwarf nova IY UMa using the S-Cam2 super-conducting tunnel junction device attached to the 4.2m William Herschel Telescope on La Palma. Exploiting the well-defined white dwarf and hot spot eclipse features, we derive an updated orbital ephemeris for IY UMa and an orbital period of 0.07390897(5) days. A white

L. Binette, D. Gonzalez-Gomez, Y. D. Mayya

The ionization structure of the Orion nebula can be described as a skin-like ionization structure on the surface of a dense cloud. We propose that a steep density stratification, increasing as a powerlaw ($n \propto x^{-2}$) function of distance x from the ionization front, exhibits properties which agree with our long-slit spectrum of the Orion nebula. For

L. Gabora

Fundamental approaches bypass the problem of getting consciousness from non-conscious components by positing that consciousness is a universal primitive. For example, the double aspect theory of information holds that information has a phenomenal aspect. How then do you get from phenomenal information to human consciousness? This paper proposes that an entit

L. Miller, A. M. Lopes, R. J. Smith, S. M. Croom

We report the possible discovery of multiple gravitationally-lensed images of QSOs with angular separations on arcminute scales. The QSOs were selected from the completed 2dF QSO survey as having redshifts and optical colours which are statistically consistent. In this paper we present higher-quality optical spectra of the candidates and discuss the likeliho

D. -H. Lee, F. Y. Wu

We consider discrete spin models on arbitrary planar graphs and lattices with frustrated interactions. We first analyze the Ising model with frustrated plaquettes. We use an algebraic approach to derive the result that an Ising model with some of its plaquettes frustrated has a dual which is an Ising model with an external field $iπ/2$ applied to the dual si

Carl P. Dettmann

Recent advances in the periodic orbit theory of stochastically perturbed systems have permitted a calculation of the escape rate of a noisy chaotic map to order 64 in the noise strength. Comparison with the usual asymptotic expansions obtained from integrals and with a previous calculation of the electrostatic potential of exactly selfsimilar fractal charge