January 2001 arXiv papers — page 8

Nobuhisa Fujita, Komajiro Niizeki

The one-electron properties of a certain class of one-dimensional ternary quasicrystals are investigated. In particular, we show in detail the presence of a special kind of critical states called marginal critical states in these QCs. By the use of a real-space renormalization-group method, it is shown that the scaling properties of marginal critical states

Valerio Scarani, Nicolas Gisin

We consider a family of quantum communication protocols involving $N$ partners. We demonstrate the existence of a link between the security of these protocols against individual attacks by the eavesdropper, and the violation of some Bell's inequalities, generalizing the link that was noticed some years ago for two-partners quantum cryptography. The argum

H. M. Wiseman, L. K. Thomsen

A continuous atom laser will almost certainly have a linewidth dominated by the effect of the atomic interaction energy, which turns fluctuations in the condensate atom number into fluctuations in the condensate frequency. These correlated fluctuations mean that information about the atom number could be used to reduce the frequency fluctuations, by controll

Ts. Dankova, G. Rosensteel

The irreducible representations of the Lie algebra ${\frak su}$(3) describe rotational bands in the context of the nuclear shell and interacting boson models. The density matrices associated with ${\frak su}$(3) provide an alternative theoretical framework for obtaining these bands. The ${\frak su}$(3) density matrix formulation is mathematically simpler tha

V. Avila-Reese, E. Vázquez-Semadeni

We discuss the dissipation of turbulent kinetic energy Ek in the global ISM by means of 2-D, MHD, non-isothermal simulations in the presence of model radiative heating and cooling. We argue that dissipation in 2D is representative of that in three dimensions as long as it is dominated by shocks rather than by a turbulent cascade. Energy is injected at a few

Tom Hadfield

Motivated by the search for new examples of "noncommutative manifolds", we study the noncommutative geometry of the group C*-algebras of various discrete groups. The examples we consier are the infinite dihedral group ${\bf Z} \times_σ {\bf Z}_2$ and the semidirect product ${\bf Z} \times_σ {\bf Z}$. We present a unified treatment of the K-homology a

A. Bashir, R. Delbourgo, M. L. Roberts

We derive expressions for the phase-space of a particle of momentum $p$ decaying into $N$ particles, that are valid for any number of dimensions. These are the imaginary parts of so-called `sunset' diagrams, which we also obtain. The results are given as a series of hypergeometric functions, which terminate for odd dimensions and are also well-suited for

Henry P. Stapp

Orthodox Copenhagen quantum theory renounces the quest to understand the reality in which we are imbedded, and settles for practical rules that describe connections between our observations. Many physicist have believed that this renunciation of the attempt describe nature herself was premature, and John von Neumann, in a major work, reformulated quantum the

G. Bowen

Classical communication through quantum channels may be enhanced by sharing entanglement. Superdense coding allows the encoding, and transmission, of up to two classical bits of information in a single qubit. In this paper, the maximum classical channel capacity for states that are not maximally entangled is derived. Particular schemes are then shown to atta

Marc-Thierry Jaekel, Serge Reynaud

We analyze the quantum fluctuations of vacuum stress tensors and spacetime curvatures, using the framework of linear response theory which connects these fluctuations to dissipation mechanisms arising when stress tensors and spacetime metric are coupled. Vacuum fluctuations of spacetime curvatures are shown to be a sum of two contributions at lowest orders;

Marc-Thierry Jaekel, Serge Reynaud

A mirror scattering vacuum fields is submitted to a quantum fluctuating radiation pressure. It also experiences a motional force, related to force fluctuations through fluctuation-dissipation relations. The resulting position fluctuations of the coupled mirror are related to the dissipative part of the mechanical admittance. We compute the time dependent pos

Patrick Navez, Alessandra Gatti, Luigi A. Lugiato

By analogy to classical cryptography, we develop a "quantum public key" based cryptographic scheme in which the two public and private keys consist in each of two entangled beams of squeezed light. An analog message is encrypted by modulating the phase of the beam sent in public. The knowledge of the degree of non classical correlation between the be

Sergey P. Roshchupkin, Oleg B. Lysenko

We theoretically investigate nonresonant spontaneous bremsstrahlung in the scattering of an electron by a nucleus in the field of two linearly polarized light waves propagating in the same direction in the general relativistic case. It is demonstrated that there are two substantially different kinematic ranges: the noninterference range, where the Bunkin-Fed

W. Dür, G. Vidal, J. I. Cirac

We analyze the problem of quantum data compression of commuting density operators in the visible case. We show that the lower bound for the compression factor given by the Levitin--Holevo function is reached by providing an explicit protocol.

Boris P. Lavrov

UV continua observed in multi-bubble and single-bubble sonoluminescence spectra of hydrogen-containing liquids have the same physical nature - radiative dissociation of electronically excited hydrogen molecules (and possibly hydrides of heavy rare gases like ArH). In the case of SBSL of "air bubble in water" the oscillating bubble actually consists o

S. Przybyl, P. Pieranski

Closely packed conformations of helices formed on the ideal rope are considered. The pitch versus radius relations which define a closely packed helix are determined. The relations stem from the turn-to-turn distance and curvature limiting conditions. Plots of the relations are shown to cross each other. The physical sense of the crossing point is discussed.

B. Militzer, D. M. Ceperley

Restricted path integral Monte Carlo simulations are used to calculate the equilibrium properties of hydrogen in the density and temperature range of $9.83 \times 10^{-4}\rm \leq ρ\leq 0.153 \rm gcm^{-3}$ and $5000 \leq T \leq 250 000 \rm K$. We test the accuracy of the pair density matrix and analyze the dependence on the system size, on the time step of th

Angels Ramos, Jurgen Schaffner-Bielich, Jochen Wambach

We discuss the kaon-nucleon interaction and its consequences for the change of the properties of the kaon in the medium. The onset of kaon condensation in neutron stars under various scenarios as well its effects for neutron star properties are reviewed.

Y. G. Ma

The emission of clusters in the nuclear disassembly is investigated within the framework of isospin dependent lattice gas model and classical molecular dynamics model. As observed in the recent experimental data, it is found that the emission of individual cluster is poissonian and thermal scaling is observed in the linear Arrhenius plots made from the avera

E917 Collaboration, B. B. Back, R. R. Betts, J. Chang

We present results from Experiment E917 for antilambda and antiproton production in Au+Au collisions at 11.7 A GeV. We have measured invariant spectra and yields for both species in central and peripheral collisions. We find that the antilambda/antiproton ratio near mid-rapidity increases from 0.26+0.19-0.15 in peripheral collisions to 3.6+4.7-1.8 in central

R. Gonzalez-Cinca, L. Ramirez-Piscina, J. Casademunt, A. Hernandez-Machado

We have studied sidebranching induced by fluctuations in dendritic growth. The amplitude of sidebranching induced by internal (equilibrium) concentration fluctuations in the case of solidification with solutal diffusion is computed. This amplitude turns out to be significantly smaller than values reported in previous experiments.The effects of other possible

Chris Ray, Giulio Ruffini

In applying the stationary phase approximation to coherent state path integrals a difficulty occurs; there are no classical paths that satisfy the boundary conditions of the path integral. Others have gotten around this problem by reevaluating the action. In this work it is shown that it is not necessary to reevaluate the action because the stationary phase

M. A. Man'ko, V. I. Man'ko, R. Vilela Mendes

A general framework is presented which unifies the treatment of wavelet-like, quasidistribution, and tomographic transforms. Explicit formulas relating the three types of transforms are obtained. The case of transforms associated to the symplectic and affine groups is treated in some detail. Special emphasis is given to the properties of the scale-time and s

Vladislav Kravchenko, Hector Oviedo

The Maxwell equations for chiral media are treated with the aid of quaternionic analysis methods. Besides the possibility of simplification of the form of such basic facts like the Stratton-Chu formulas we obtain a criterion for the extendability of the electromagnetic field from a sufficiently smooth closed surface to its interior or exterior domain.

Michael Thaddeus

The space of complete collineations is a compactification of the space of matrices of fixed dimension and rank, whose boundary is a divisor with normal crossings. It was introduced in the 19th century and has been used to solve many enumerative problems. We show that this venerable space can be understood using the latest quotient constructions in algebraic

S. Console, A. Fino

Let $M= G/Γ$ be a compact nilmanifold endowed with an invariant complex structure. We prove that, on an open set of any connected component of the moduli space ${\cal C} ({\frak g})$ of invariant complex structures on $M$, the Dolbeault cohomology of $M$ is isomorphic to the one of the differential bigraded algebra associated to the complexification $\cg^\C$

Aaron Bertram, Michael Thaddeus

The dth symmetric product of a curve of genus g is a smooth projective variety. This paper is concerned with the little quantum cohomology ring of this variety, that is, the ring having its 3-point Gromov-Witten invariants as structure constants. This is of considerable interest, for example as the base ring of the quantum category in Seiberg-Witten theory.

Nets Hawk Katz, Terence Tao

In this paper we investigate three unsolved conjectures in geometric combinatorics, namely Falconer's distance set conjecture, the dimension of Furstenburg sets, and Erdos's ring conjecture. We formulate natural $δ$-discretized versions of these conjectures and show that in a certain sense that these discretized versions are equivalent. In particular

Hélène Esnault, Claus Hertling

Bolibruch's examples of representations of pi_1(P^1-finitely many points) which are not realizable by Fuchsian differential systems are adapted to curves of higher genus.

Deepak Parashar

Duality between the coloured quantum group and the coloured quantum algebra corresponding to GL(2) is established. The coloured L^{\pm} functionals are constructed and the dual algebra is derived explicitly. These functionals are then employed to give a coloured generalisation of the differential calculus on quantum GL(2) within the framework of the R-matrix

W. Van Assche, S. B. Yakubovich

We consider multiple orthogonal polynomials corresponding to two Macdonald functions (modified Bessel functions of the second kind), with emphasis on the polynomials on the diagonal of the Hermite-Padé table. We give some properties of these polynomials: differential properties, a Rodrigues type formula and explicit formulas for the third order linear recurr

Walter Van Assche

We show how one can obtain rational approximants for $q$-extensions of the harmonic series and the logarithm (and many other similar quantities) by Padé approximation using little $q$-Legendre polynomials and we show that properties of these orthogonal polynomials indeed prove the irrationality, with an upper bound of the measure of irrationality which is as

Ely Kerman

We construct a new aperiodic symplectic plug and hence new smooth counterexamples to the Hamiltonian Seifert conjecture in R^{2n} for n>2. In other words, we develop an alternative procedure, to those of V. L. Ginzburg and M. Herman, for constructing smooth Hamiltonian flows, on the standard symplectic R^{2n} for n>2, which have compact regular level sets th

Lin WENG

New local and global non-abelian zeta functions for elliptic curves are studied using certain refined Brill-Noether loci in moduli spaces of semi-stable bundles. Examples of these zeta functions and a justification of using only semi-stable bundles are given too. We end this paper with an appendix on the so-called Weierstrass Groups for general curves, which

Antun Milas

The $\mathbb{Z}/2\mathbb{Z}$--graded intertwining operators are introduced. We study these operators in the case of ``degenerate'' N=1 minimal models, with the central charge $c=3/2$. The corresponding fusion ring is isomorphic to the Grothendieck ring for the Lie superalgebra ${\mathfrak osp}(1|2)$. We also discus multiplicity--2 fusion rules and lo

Alan Weinstein

The main result of this paper is a convexity theorem for momentum mappings of certain hamiltonian actions of noncompact semisimple Lie groups. The image is required to fall within a certain open subset D of the (dual of the) Lie algebra, and the momentum map itself is required to be proper as a map to D. The set D corresponds roughly, via the orbit method, t

Michael Thaddeus

By normalizing the space of commuting pairs of elements in a reductive Lie group G, and the corresponding space for the Langlands dual group, we construct pairs of hyperkahler orbifolds which satisfy the conditions to be mirror partners in the sense of Strominger-Yau-Zaslow. The same holds true for commuting quadruples in a compact Lie group. The Hodge numbe

Michael Thaddeus

We study moduli spaces of parabolic Higgs bundles on a curve and their dependence on the choice of weights. We describe the chamber structure on the space of weights and show that, when a wall is crossed, the moduli space undergoes an elementary transformation in the sense of Mukai.

A. Zamolodchikov, Al. Zamolodchikov

Liouville field theory is considered with boundary conditions corresponding to a quantization of the classical Lobachevskiy plane (i.e. euclidean version of $AdS_2$). We solve the bootstrap equations for the out-vacuum wave function and find an infinite set of solutions. This solutions are in one to one correspondence with the degenerate representations of t

T. A. Ivanova, A. D. Popov

Topological Chern-Simons (CS) and BF theories and their holomorphic analogues are discussed in terms of de Rham and Dolbeault cohomologies. We show that Cech cohomology provides another useful description of the above topological and holomorphic field theories. In particular, all hidden (nonlocal) symmetries of non-Abelian CS and BF theories can be most clea

Jae-Suk Park

It is known that the Seiberg-Witten invariants, derived from supersymmetric Yang-Mill theories in four-dimensions, do not distinguish smooth structure of certain non-simply-connected four manifolds. We propose generalizations of Donaldson-Witten and Vafa-Witten theories on a Kähler manifold based on Higgs Bundles. We showed, in particular, that the partition

A. Denner, S. Dittmaier, M. Roth, D. Wackeroth

We describe the salient features of precise predictions for the processes e+ e- -> WW -> 4f(gamma) as obtained with the Monte Carlo generator RacoonWW, including the complete O(alpha) electroweak radiative corrections in the double-pole approximation. Numerical results for some distributions are given at the typical linear-collider energy \sqrt{s}=500 GeV. M

Loyal Durand, Phuoc Ha, Gregory Jaczko

We analyze the connections between the quark model (QM) and the description of hadrons in the low-momentum limit of heavy-baryon effective field theory in QCD. By using a three-flavor-index representation for the effective baryon fields, we show that the ``nonrelativistic'' constituent QM for baryon masses and moments is completely equivalent through

P. S. Cherzor, V. A. Ilyin, A. E. Pukhov

We present a method for symbolic evaluation of Feynman amplitudes. We construct special polarization basis for spinor particles which produces compact expressions for tensor products of basis spinors.

Gilberto Colangelo, Gino Isidori

These lectures provide an elementary introduction to Chiral Perturbation Theory, focused on the sector of pseudoscalar meson interactions. Basic concepts and technical methods of this approach are discussed on general grounds and with the help of a few specific examples.

M. M. Muhlleitner

Future $γγ$ colliders allow the production of the heavy neutral MSSM Higgs bosons $H$ and $A$ as single resonances. The prospects of finding these particles in the $b\bar{b}$ and the neutralino-pair final states have been analysed. The $H,A$ bosons can be discovered for medium values of $\tanβ$ with masses up to 70--80% of the initial $e^\pm e^-$ c.m. energy

M. M. Muhlleitner

In order to verify the Higgs mechanism experimentally, the Higgs self-couplings have to be probed. These couplings allow the reconstruction of the characteristic Higgs potential responsible for the electroweak symmetry breaking. The couplings are accessible in a variety of multiple Higgs production processes. The theoretical analysis including the most relev

B. F. L. Ward, S. Jadach, W. Płaczek, M. Skrzypek

We present precision calculations of the processes e+ e- -> 4-fermions in which the double resonant W+ W- and ZZ intermediate states occur. Referring to these latter intermediate states as the 'signal processes', we show that, by using the YFS Monte Carlo event generators YFSWW3-1.14 and KoralW-1.42 in an appropriate combination, we achieve a physica

A. Freitas, S. Heinemeyer, W. Hollik, W. Walter

A review is given on the quantum correction $Δr$ in the $W$--$Z$ mass correlation at the electroweak two-loop level, as derived from the calculation of the muon lifetime in the Standard Model. Exact results for $Δr$ and the $W$-mass prediction including ${\mathcal{O}}(α^2)$ corrections with fermion loops are presented and compared with previous results of a

K. Fialkowski, R. Wit

Charge fluctuations as a possible signal of quark - gluon plasma (QGP) were recently suggested. A short summary of comments presented on this subject is given and supplemented by a discussion of the coexistence of pions produced "directly" and through a QGP phase. Such a coexistence may obscure the expected plasma signal similarly to the effects cons

A. Denner, S. Dittmaier, M. Roth, D. Wackeroth

Electroweak radiative corrections to e+e- scattering processes typically amount to O(10%) at LEP energies. Their logarithmic increase with energy renders them even more important at future colliders. Although the bulk of these corrections is due to universal process-independent effects, the remaining non-universal corrections are nevertheless phenomenologica

Saeed Ahmad, Riazuddin

We compute the branching ratios for the radiative rare decays of B into K-Meson states and compare them to the experimentally determined branching ratio for inclusive decay b -> s gamma using non relativistic quark model, and form factor definitions consistent with HQET covariant trace formalism. Such calculations necessarily involve a potential model. In or

D. V. Shirkov

We analyze the effect of $π^2$-terms in the QCD perturbative expansions for the s-channel effective coupling and observables, the effect known from the 80s. We remind that these terms can be collected into specific functions -- strong s-channel coupling $\tildaα_s$ and its effective powers ${\mathfrak A}(s)$ free of ghost singularities. Further on, we study

Jiri Bicak

The work on black holes immersed in external fields is reviewed in both test-field approximation and within exact solutions. In particular we pay attention to the effect of the expulsion of the flux of external fields across charged and rotating black holes which are approaching extremal states. Recently this effect has been shown to occur for black hole sol

H. Lichtenegger, W. Hausleitner, F. Gronwald, B. Mashhoon

As a consequence of gravitomagnetism, which is a fundamental weak-field prediction of general relativity and ubiquitous in gravitational phenomena, clocks show a difference in their proper periods when moving along identical orbits in opposite directions about a spinning mass. This time shift is induced by the rotation of the source and may be used to verify

Carlo Rovelli

I sketch the main lines of development of the research in quantum gravity, from the first explorations in the early thirties to nowadays.

Enea Zaffanella, Patricia M. Hill, Roberto Bagnara

Complementation, the inverse of the reduced product operation, is a technique for systematically finding minimal decompositions of abstract domains. File' and Ranzato advanced the state of the art by introducing a simple method for computing a complement. As an application, they considered the extraction by complementation of the pair-sharing domain PS f

Annalisa Bossi, Sandro Etalle, Sabina Rossi

We study the properties of input-consuming derivations of moded logic programs. Input-consuming derivations can be used to model the behavior of logic programs using dynamic scheduling and employing constructs such as delay declarations. We consider the class of nicely-moded programs and queries. We show that for these programs a weak version of the well-kno

Annalisa Bossi, Sandro Etalle, Sabina Rossi, Jan-Georg Smaus

In logic programming, dynamic scheduling refers to a situation where the selection of the atom in each resolution (computation) step is determined at runtime, as opposed to a fixed selection rule such as the left-to-right one of Prolog. This has applications e.g. in parallel programming. A mechanism to control dynamic scheduling is provided in existing langu

Xin He, Ming-Yang Kao, Hsueh-I Lu

We propose a fast methodology for encoding graphs with information-theoretically minimum numbers of bits. Specifically, a graph with property pi is called a pi-graph. If pi satisfies certain properties, then an n-node m-edge pi-graph G can be encoded by a binary string X such that (1) G and X can be obtained from each other in O(n log n) time, and (2) X has

M. Ducasse

Over the past decades automated debugging has seen major achievements. However, as debugging is by necessity attached to particular programming paradigms, the results are scattered. The aims of the workshop are to gather common themes and solutions across programming communities, and to cross-fertilize ideas. AADEBUG 2000 in Munich follows AADEBUG'93 in

J. J. Palacios, A. J. Perez-Jimenez, E. Louis, J. A. Verges

Building upon traditional quantum chemistry calculations, we have implemented an {\em ab-initio} method to study the electrical transport in nanocontacts. We illustrate our technique calculating the conductance of C$_{60}$ molecules connected in various ways to Al electrodes characterized at the atomic level. Central to a correct estimate of the electrical c

Romualdo Pastor-Satorras, Alessandro Vespignani

We describe the construction of a conserved reaction-diffusion system that exhibits self-organized critical (avalanche-like) behavior under the action of a slow addition of particles. The model provides an illustration of the general mechanism to generate self-organized criticality in conserving systems. Extensive simulations in d=2 and 3 reveal critical exp

L. Bureau, T. Baumberger, C. Caroli

We measure the displacement response of a frictional multicontact interface between identical polymer glasses to a biased shear force oscillation. We evidence the existence, for maximum forces close below the nominal static threshold, of a jamming creep regime governed by an ageing-rejuvenation competition acting within the micrometer-sized contacting asperi

William B. Black, Michael D. Graham

Recent experiments suggest that shear-enhanced growth of concentration fluctuations in polymer solutions is strongly influenced by solid boundaries. We analyze the dynamics of a model of a sheared polymer solution, accounting for the effect of stress variations on mass flux and for wall-slip. If (and only if) these effects are present, the flow exhibits a bo

Yiing-Rei Chen, Philip B. Allen

CaMnO3 is a simple bi-partite antiferromagnet(AF) which can be continuously electron-doped up to LaMnO3. Electrons enter the doubly degenerate E_g subshell with spins aligned to the S=3/2 core of Mn^4+ (T_2g^3)$. We take the Hubbard and Hund energies to be effectively infinite. Our model Hamiltonian has two E_g orbitals per Mn atom, nearest neighbor hopping,

Sergei G. Sharapov, Hans Beck, Vadim M. Loktev

We derive a finite temperature time-dependent effective theory for the phase $θ$ of the pairing field, which is appropriate for a 2D conducting electron system with non-retarded d-wave attraction. As for s-wave pairing the effective action contains terms with Landau damping, but their structure appears to be different from the s-wave case due to the fact tha

Gregory C. Psaltakis

The phase fluctuations of the condensate in doped antiferromagnets, described by a t-t'-J model and a suitable 1/N expansion, provide a mechanism for a Kosterlitz-Thouless (KT) type of transition to a superconducting state below T_{c}. In this paper, we present a Monte Carlo study of the corresponding superfluid weight D_{s}(T) in the classical (large-N)

Johannes Berg, Matteo Marsili, Aldo Rustichini, Riccardo Zecchina

Traders in a market typically have widely different, private information on the return of an asset. The equilibrium price of the asset may reflect this information more accurately if the number of traders is large enough compared to the number of the states of the world that determine the return of the asset. We study the transition from markets where prices

Luca Salasnich

In a recent paper [Int. J. Mod. Phys. B {\bf 14}, 405 (2000)] we discussed the Bose-Einstein condensation (BEC) in the framework of Tsallis's nonextensive statistical mechanics. In particular, we studied an ideal gas of bosons in a confining harmonic potential. In this memoir we generalize our previous analysis by investigating an ideal Bose gas in a gen

Oscar Iglesias, Amilcar Labarta

Finite-size and surface effects in fine particle systems are investigated by Monte Carlo simulation of a model of a $γ$-Fe$_2$O$_3$ (maghemite) single particle. Periodic boundary conditions have been used to simulate the bulk properties and the results compared with those for a spherical shaped particle with free boundaries to evidence the role played by the

C. Laforge, D. Passerone, A. B. Harris, Ph. Lambin

We propose a two-stage mechanism for the rotational surface disordering phase transition of a molecular crystal, as realized in C$_{60}$ fullerite. Our study, based on Monte Carlo simulations, uncovers the existence of a new intermediate regime, between a low temperature ordered $(2 \times 2)$ state, and a high temperature $(1 \times 1)$ disordered phase. In

Mikio Eto

Electronic states and transport phenomena in semiconductor quantum dots are studied theoretically. Taking account of the electron-electron Coulomb interaction by the exact diagonalization method, the ground state and low-lying excited states are calculated as functions of magnetic field. Using the obtained many-body states, we discuss the temperature depende

A. S. Wilson, A. J. Young, P. L. Shopbell

We describe observations of the two nearest, powerful radio galaxies with the Chandra X-ray Observatory: Cygnus A (z = 0.0562) and Pictor A (z = 0.035). Since the early results from these observations are published elsewhere (Wilson, Young & Shopbell 2000, 2001), we here confine ourselves to a summary of the main conclusions and a few remarks about other asp

F. Govoni, T. A. Ensslin, L. Feretti, G. Giovannini

Clusters of galaxies may contain cluster-wide, centrally located, diffuse radio sources, called halos. They have been found to show morphologies similar to those of the X-ray emission. To quantify this qualitative statement we performed a point-to-point comparison of the radio and the X-ray emission for four clusters of galaxies containing radio halos: Coma,

Martin Still, Kieran O'Brien, Keith Horne, Bram Boroson

We present RXTE observations of the eclipsing X-ray binary Hercules X-1 conducted during an anomalous low state. Data reduction reveals a light curve over 2.7 orbital cycles remarkably similar to optical and UV light curves which are dominated by the companion star. Count rates are modulated close to the orbital period, attaining a maximum when the inner fac

Alessandro Baldi, Sandro Bardelli, Elena Zucca

We present the results of a study of the spectral properties of galaxies in the central part of the Shapley Concentration, covering an extremely wide range of densities, from the rich cluster cores to the underlying supercluster environment. Our sample is homogeneous, in a well defined magnitude range (17=<b_J=<18.8) and contains ~1300 spectra of galaxies at

P. Molaro, P. Bonifacio, M. Centurion, G. Vladilo

UVES observations at ESO/VLT of the DLA at z=3.39 towards QSO 0000-2621 provided refined abundances for Fe, Si, N, Ni, and new abundances for O, Ar, P, Zn, Cr, H2. These determinations confirm that the system has remarkable properties with the lowest metallicity, a very low H2 molecular fraction and it has no detectable presence of dust. The [alpha/Fe-peak]

P. Bonifacio, P. Molaro

The 8m class telescopes allow for the first time to study stars of external galaxies with the same resolution and S/N ratio which has been so far used for Galactic stars. It is quite likely that this study will shake some of our current beliefs. In this poster we highlight some of the results which have been obtained for two giants in the Sgr dSph thanks to

J. Nevalainen, J. Kaastra, A. N. Parmar, M. Markevitch

We present BeppoSAX results of a spatially resolved spectral analysis of A3571, a relaxed nearby cluster of galaxies. In the central 2&#39; (130/h_50 kpc) radius the metal abundance is 0.49 +- 0.08 solar and the absorption (1.13 +-0.28) x 10^21 atom/cm^2 whereas elsewhere within an 8&#39;(520/h_50 kpc) radius the abundance is 0.32 \+- 0.05 solar and the abso

M. Ramella, W. Boschin, D. Fadda, M. Nonino

We present an objective and automated procedure for detecting clusters of galaxies in imaging galaxy surveys. Our Voronoi Galaxy Cluster Finder (VGCF) uses galaxy positions and magnitudes to find clusters and determine their main features: size, richness and contrast above the background. The VGCF uses the Voronoi tessellation to evaluate the local density a

D. Grupe, H. -C. Thomas, K. M. Leighly

We report the discovery of a highly X-ray variable AGN, RX J2217.9-5941. This object was bright during the ROSAT All-Sky Survey (RASS), during which a decrease in the count rate by a factor of 12 was observed. It was found to be much fainter in follow-up HRI observations and is therefore an X-ray transient AGN candidate. On long time scales of years, its cou

C. D. Mackay, R. N. Tubbs, R. Bell, D. Burt

A radically new CCD development by Marconi Applied Technologies has enabled substantial internal gain within the CCD before the signal reaches the output amplifier. With reasonably high gain, sub-electron readout noise levels are achieved even at MHz pixel rates. This paper reports a detailed assessment of these devices, including novel methods of measuring

J. E. Baldwin, R. N. Tubbs, G. C. Cox, C. D. Mackay

A quantitative assessment is presented of diffraction-limited stellar images with Strehl ratios of 0.25-0.30 obtained by selection of short-exposure CCD images of stars brighter than +6m at 810nm with the Nordic Optical Telescope.

U. Fritze-v. Alvensleben

The first part of this paper deals with the impact of nonsolar and - for late-type, dwarf, and high redshift galaxies - generally subsolar abundances on the interpretation of observational data for starburst galaxies. It points out the differences in colors, luminosities, emission lines, etc. obtained from a model using low metallicity input physics for a st

Ari Laor

Analysis of PG quasar observations suggests a nonlinear relation between the black hole mass, M_BH, and the bulge mass, M_bulge, although a linear relation, as proposed for nearby galaxies, cannot be ruled out. New M_BH values for nearby galaxies from Gebhardt et al., and L_bulge measurements for Seyfert 1 galaxies from Virani et al., are used here to obtain

Marc A. W. Verheijen, Renzo Sancisi

In this data paper we present the results of an extensive 21cm-line synthesis imaging survey of 43 spiral galaxies in the nearby Ursa Major cluster using the Westerbork Synthesis Radio Telescope. Detailed kinematic information in the form of position-velocity diagrams and rotation curves is presented in an atlas together with HI channel maps, 21cm continuum

Bahram Mobasher, Jose Afonso, Lawrence Cram

The Infrared Space Observatory (ISO) is used to carry out mid-IR (7 and 15 micron) and far-IR (90 micron) observations of a sample of star-forming sub-mJy radio sources. By selecting the sample at radio wavelengths, one avoids biases due to dust obscuration. It is found that the mid-IR luminosities, covering the PAH features, measure the star formation rate

Nissim Kanekar, Jayaram N. Chengalur

We report Giant Metrewave Radio Telescope (GMRT) 21cm observations of two confirmed and one candidate low redshift damped Lyman-alpha systems (DLAS). HI absorption was detected in the two confirmed systems, at z=0.2378 and z=0.5247, with spin temperatures (Ts) of 2050 +- 200 K and 330 +- 70 K respectively. The non-detection of absorption in the third (candid

Kenneth F. Nicholson

Extreme speed profiles, that are impossible to anayze correctly using the usual methods, are shown to be easily handled using the methods developed previously by Nicholson (astro-ph/0006330). These profiles are constant orbital speeds with sharp and smooth ramps at the origin, and constant angular velocity with speeds increasing linearly to the galaxy rim. A

S. W. Bruenn, K. R. De Nisco, A. Mezzacappa

We apply our recently developed code for spherically symmetric, fully general relativistic (GR) Lagrangian hydrodynamics and multigroup flux-limited diffusion neutrino transport to examine the effects of GR on the hydrodynamics and transport during collapse, bounce, and the critical shock reheating phase of core collapse supernovae. Comparisons of models com

C A Jackson, D M Londish

We have analysed the 2dF spectra of a sample of galaxies common to the 2dF galaxy redshift survey (2dFGRS, Colless 1999) and the NRAO VLA sky survey (NVSS, Condon et al. 1998). Our sample comprises 88 galaxies selected by Sadler et al. (1999) from 30 2dFGRS fields observed in 1998. In this paper we discuss how this and future, much larger, samples of 2dFGRS-

C A Jackson, J V Wall

In this paper we discuss the demographics of the radio blazar population: (i) what are their parent (`unbeamed&#39;) sources and (ii) what magnitude and/or type of evolution have they undergone ? The discussion is based on models of radio source evolution and beaming based on a `dual population&#39; unification paradigm. These models, developed from radio bl

John Quenby, Athina Meli

Numerical modelling is performed for extreme relativistic parallel shocks with upstream Lorentz factor $Γ=50$. Assuming the scattering is either large angle or over pitch angles $\sim Γ^{-1}$, spectral flattening and shock aaceleration speed-up is found. The energy gain for the first shock cycle is $\sim Γ^{2}$. The likely output from relativistic shocks due

Athina Meli, John Quenby

Numerical Monte Carlo simulations of the diffusive shock acceleration in the test particle limit are investigated. We simulate high relativistic flow astrophysical plasmas for upstream $γ$ $\sim5$ and up to $γ$ $\sim1000$. These gamma values are relevant to the diffusive shock acceleration models of Active Galactic Nuclei (AGN) and Gamma Ray Bursts (GRBs). T

Max Tegmark

We argue for a ``parametrized post-Friedmanian&#39;&#39; approach to linear cosmology, where the history of expansion and perturbation growth is measured without assuming that the Einstein Field Equations hold. As an illustration, a model-independent analysis of 92 type Ia supernovae demonstrates that the curve giving the expansion history has the wrong shap

Adan Cabello

A recent proof of Bell&#39;s theorem without inequalities [A. Cabello, Phys. Rev. Lett. 86, 1911 (2001)] is formulated as a Greenberger-Horne-Zeilinger-like proof involving just two observers. On one hand, this new approach allows us to derive an experimentally testable Bell inequality which is violated by quantum mechanics. On the other hand, it leads to a

Daniel F. Carvalho, Mario E. Gomez, Shaaban Khalil

We study the lepton-flavor violation processes tau ->mu gamma and mu->e gamma in two different examples of models with non-universal soft breaking terms derived from strings. We show that the predictions are quite different from those of universal scenarios. Non-universal A-terms provide an interesting framework to enhance the supersymmetric contributions to

Ben Craps, Matthias R. Gaberdiel

The consistency of the orbifold action on open strings between D-branes in orbifold theories with and without discrete torsion is analysed carefully. For the example of the C^3/Z_2 x Z_2 theory, it is found that the consistency of the orbifold action requires that the D-brane spectrum contains branes that give rise to a conventional representation of the orb

S. J. Huber, P. John, M. G. Schmidt

We discuss the generation of the baryon asymmetry by a strong first order electroweak phase transition in the early universe, particularly in the context of the MSSM. This requires a thorough numerical treatment of the bubble wall profile in the case of two Higgs fields. CP violating complex particle masses varying with the Higgs field in the wall are essent