February 2002 arXiv papers — page 20

Jan-e Alam

The productions of real photons from quark gluon plasma and hot hadronic matter formed after the nucleus - nucleus collisions at ultra-relativistic energies are discussed. The effects of the spectral shift of the hadrons at finite temperature on the production of photons are investigated. On the basis of the present analysis it is shown that the photon spect

Nguyen Dinh Dang, Vuong Kim Au, Toshio Suzuki, Akito Arima

In this report we've shown that the arguments, which the author of the Comment presents to prove his case, are either wrong or irrelevant.

Sven Soff, Steffen A. Bass, David H. Hardtke, Sergey Y. Panitkin

We make predictions for the kaon interferometry measurements in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC). A first order phase transition from a thermalized Quark-Gluon-Plasma (QGP) to a gas of hadrons is assumed for the transport calculations. The fraction of kaons that are directly emitted from the phase boundary is considerably enhanc

G. Penner, U. Mosel

The pi^- p -> omega n threshold cross section measured in the seventies resisted up to now a consistent theoretical description in line with experiment, mainly caused by too large Born contributions. This led to a discussion in the literature about the correctness of the extraction of these data points. We show that the extraction method used in these refere

M. de Leon, J. C. Marrero, D. Martin de Diego

A new geometrical setting for classical field theories is introduced. This description is strongly inspired in the one due to Skinner and Rusk for singular lagrangians systems. For a singular field theory a constraint algorithm is developed that gives a final constraint submanifold where a well-defined dynamics exists. The main advantage of this algorithm is

Taku Matsui

We present a proof of the central limit theorem for a pair of mutually non-commuting operators in mixing quantum spin chains. The operators are not necessarily strictly local but quasi-local. As a corollary we obtain a direct construction of the time evolution of the algebra of normal fluctuation for Gibbs states of finite range interactions on a one-dimensi

Joe Harris, Mike Roth, Jason Starr

We describe the Hilbert schemes parametrizing curves on a cubic threefold of degree at most 5. In a forthcoming paper, we use this description to give a new proof and extension of a theorem of Iliev, Markushevich and Tikhimirov.

Stéphane Fischler

The problem we consider is to define families of n-dimensional integrals, endowed with group actions as in Rhin-Viola's work on irrationality measures of $ζ(2)$ and $ζ(3)$, the values of which are linear forms, over the rationals, in multiple zeta values of weight at most n. We generalize Vasilyev's and Sorokin's approaches, and give a change of

Yu. Baryshnikov, J. E. Yukich

Consider sequential packing of unit balls in a large cube, as in the Renyi car-parking model, but in any dimension and with Poisson input. We show after suitable rescaling that the spatial distribution of packed balls tends to that of a Gaussian field in the thermodynamic limit. We prove analogous results for related applied models, including ballistic depos

Estelle Basor, Yang Chen

The continuous analogue of a Toeplitz determinant identity for Wiener-Hopf operators is proved. An example which arises from random matrix theory is studied and an error term for the asymptotics of the determinant is computed.

Florin Radulescu

Let $F_n$, $n\geq2$, be the free group with $n$ generators, denoted by $U_1,U_2,...,U_n$. Let $C*(F_n)$ be the full $C^*$-algebra of $F_n$. Let $\mathcal{X}$ be the vector subspace of the algebraic tensor product $C^*(F_n) \otimes C^*(F_n)$, spanned by $1\otimes1,U_1\otimes1,...,U_n\otimes1,1\otimes U_1,...,1\otimes U_n$. Let $|| \cdot ||_{\min}$ and $|| \cd

S. V. Shadrin

For any connected component $H_0$ of the space of real meromorphic functions we build a compactification $N(H_0)$ of the space $H_0$. Then we express the Euler characteristics of the spaces $H_0$ and $N(H_0)$ in terms of topological invariants of functions from $H_0$.

Bertfried Fauser

Quantum Clifford Algebras (QCA), i.e. Clifford Hopf gebras based on bilinear forms of arbitrary symmetry, are treated in a broad sense. Five alternative constructions of QCAs are exhibited. Grade free Hopf gebraic product formulas are derived for meet and join of Grassmann-Cayley algebras including co-meet and co-join for Grassmann-Cayley co-gebras which are

Pawel Felcyn

In this paper we will prove that for a compact, symplectic manifold $(M, ω)$ and for $ω$-compatible almost-complex structure J any properly perturbed J-holomorphic curve has a non-negative symplectic area. This non-negative property provides us with a new obstruction to the bubbling off phenomenon and thus allows us to redefine the Floer symplectic homology.

Ilya Zakharevich

The most useful and interesting line bundles over algebraic curves of a very high genus have the ratio δof the degree to the genus close to half-integer values, usually δ\approx 0, δ\approx 1/2, or δ\approx 1; the numeric properties are very different in these three cases. This leads to three different theories for curves of infinite genus. For analytic curv

S. Bundfuss, T. Krueger, S. Troubetzkoy

We consider an Axiom A diffeomorphism and the invariant set $Ω$ of orbits which never falls into a fixed hole. We study various aspects of the complexity of the symbolic representation of $Ω$. Our main result are that each topologically transitive component of $Ω$ is coded and that typically $Ω$ is of finite type.

Jean Alexandre, Nick E. Mavromatos, Sarben Sarkar

Starting from a N=1 scalar supermultiplet in 2+1 dimensions, we demonstrate explicitly the appearance of induced N=1 vector and scalar supermultiplets of composite operators made out of the fundamental supersymmetric constituents. We discuss an extension to a N=2 superalgebra with central extension, due to the existence of topological currents in 2+1 dimensi

A. de Souza Dutra, V. G. C. S. dos Santos, A. M. Stuchi

In this work we develop an approach to obtain analytical expressions for potentials in an impenetrable box. It is illustrated through the particular cases of the harmonic oscillator and the Coulomb potential. In this kind of system the energy expression respect the correct quantum limits, which is a very important quality. The similarity of this kind of prob

J. Kluson

In this paper we present two solutions of open bosonic string field theory defined on D0-brane background that correspond to the change of the D0-brane position in the transverse space.

Changrim Ahn, Chaiho Rim, Marian Stanishkov

In this paper, exact one-point functions of N=1 super-Liouville field theory in two-dimensional space-time with appropriate boundary conditions are presented. Exact results are derived both for the theory defined on a pseudosphere with discrete (NS) boundary conditions and for the theory with explicit boundary actions which preserves super conformal symmetri

A. Davidson, B. F. Toner, R. R. Volkas, K. C. Wali

If our 3+1-dimensional universe is a brane or domain wall embedded in a higher dimensional space, then a phenomenon we term the ``clash of symmetries'' provides a new method of breaking some continuous symmetries. A global $G_{\text{cts}} \otimes G_{\text{discrete}}$ symmetry is spontaneously broken to $H_{\text{cts}} \otimes H_{\text{discrete}}$, wh

Iliana Carrillo-Ibarra, Hugo Garcia-Compean

We survey geometric quantization of finite dimensional affine Kahler manifolds. Its corresponding prequantization and the Berezin's deformation quantization formulation, as proposed by Cahen et al., is used to quantize their corresponding Kahler quotients. Equivariant formalism greatly facilitates the description.

Sergei V. Ketov, Thorsten Leonhardt, Werner Rühl

We search for a possible bosonic (i.e. non-supersymmetric) string/gauge theory correspondence by using IIB and 0B strings as a guide. Our construction is based on the low-energy bosonic string effective action modified by an extra form flux. The closed string tachyon can be stabilyzed if the AdS scale L does not exceed certain critical value, L<L_c. We argue

P. F. Harrison, D. H. Perkins, W. G. Scott

Following recent results from the SNO solar neutrino experiment and the K2K long-baseline neutrino experiment, the combined existing data on neutrino oscillations now point strongly to a specific form for the lepton mixing matrix, with effective bimaximal mixing of $\nu_{\mu}$ and $\nu_{\tau}$ at the atmospheric scale and effective trimaximal mixing for $\nu

F. Becattini

An analysis of hadron abundances in heavy ion collisions from SPS to RHIC energy within the statistical-thermal model is presented. Pb--Pb collisions at 40 A GeV are analysed for the first time here. Unlike stated in similar recent studies, the data analysis rules out a complete strange chemical equilibrium in full phase space. In fact, the use of multiplici

A. S. Dighe, T. Hurth, C. S. Kim, T. Yoshikawa

We estimate ΔGamma_d/Γ_d, including 1/m_b contributions and part of the next-to-leading order QCD corrections, and find it to be around 0.3%. We show the methods to measure ΔGamma_d/Γ_d by using at least two different final states on the untagged B_d decay. The nonzero width difference can also be used to identify new physics effects and to resolve a twofold

Don Colladay, Patrick McDonald

An analysis of spinor redefinitions in the context of the Lorentz-violating QED extension is performed. Certain parameters that apparently violate Lorentz invariance are found to be physically irrelevant as they can be removed from the lagrangian using an appropriate redefinition of the spinor field components. It is shown that conserved currents may be defi

S. I. Klimushin, E. V. Bugaev, I. A. Sokalski

We present the formula for angular distribution of integral flux of conventional ($π, K$) muons deep under water taking into account the sphericity of the atmosphere and fluctuations of muon energy losses.The accuracy of this formula for various sea level muon spectra is discussed. The possibility of reconstructing two parameters of sea level spectrum by fit

Anjan S. Joshipura, Saurabh D. Rindani

The solar and atmospheric data and possibly large value for the effective neutrino mass in neutrinoless double beta decay experiment together indicate that all the three neutrinos are nearly degenerate. A verifiable texture for the neutrino mass matrix is proposed to accommodate these results. This texture allows almost degenerate neutrino masses two of whic

C. Giunti

Using an analogy with the well-known double-slit experiment, we show that the standard phase of neutrino oscillations is correct, refuting recent claims of a factor of two correction. We also improve the wave packet treatment of neutrino oscillations taking into account explicitly the finite coherence time of the detection process.

Monika Randhawa, Manmohan Gupta

The unitarity based analysis carried out in hep-ph/0106161, involving the evaluation of Jarlskog&#39;s rephasing invariant parameter J and the angles of the unitarity triangle is extended to include the effects of K^0-\bar K^0 and B^0-\bar B^0 mixings. The present analysis attempts to evaluate CP violating phase δ, V_{td} and the angles of the unitarity tria

I. Ajinenko, S. Akimenko, G. Britvich, I. Britvich

The decay $K^{-} \to μ^{-} \barν π^{0}$ has been studied using in-flight decays detected with ``ISTRA+&#39;&#39; setup operating in the 25 GeV negative secondary beam of the U-70 PS. About 112K events were used for the analysis. The $λ_{+}$ and $λ_{0}$ slope parameters of the decay formfactors $f_{+}(t)$, $f_{0}(t)$ have been measured : $λ_{+}= 0.0321 \pm 0.

Wojciech Broniowski, Wojciech Florkowski

Predictions of the single-freeze-out model for the particle spectra at RHIC are presented. The model assumes that the chemical and thermal freeze-outs occur simultaneously, and incorporates in simple terms the longitudinal and transverse flow. All resonance decays are included. The model predictions and the data are in striking agreement in the whole availab

F. D. R. Bonnet, D. B. Leinweber, A. G. Williams, J. M. Zanotti

Using mean--field improved gauge field configurations, we compare the results obtained for the quark propagator from Wilson fermions and Overlap fermions on a $\3$ lattice at a spacing of $a=0.125(2)$ fm.

A. G. Williams

The standard techniques of gauge-fixing, such as covariant gauge fixing, are entirely adequate for the purposes of studies of perturbative QCD. However, they fail in the nonperturbative regime due to the presence of Gribov copies. These copies arise because standard local gauge fixing methods do not completely fix the gauge. Known Gribov-copy-free gauges, su

Christof Gattringer, P. E. L. Rakow, Andreas Schaefer, Wolfgang Soeldner

Quenched SU(3) lattice gauge theory shows three phase transitions, namely the chiral, the deconfinement and the Z3 phase transition. Knowing whether or not the chiral and the deconfinement phase transition occur at the same temperature for all Z3 sectors could be crucial to understand the underlying microscopic dynamics. We use the existence of a gap in the

A. Bornheim, CLEO Collaboration

We report a new measurement of the CKM parameter V_ub made with a sample of 9.7 million B B-bar events collected with the CLEO II detector. Using Heavy Quark theory, we combine the observed yield of leptons from semileptonic B decay in the end-point momentum interval 2.2-2.6 GeV/c with recent CLEO II data on B --> X_s gamma to find |V_ub| = (4.08 +/- 0.34 +/

K. Abe, The Belle Collaboration

We report the observation of the decay mode $B^{\pm}\to p \bar{p} K^{\pm}$ based on an analysis of 29.4 fb$^{-1}$ of data collected by the Belle detector at KEKB. This is the first example of a $b\to s$ transition with baryons in the final state. The $p \bar{p}$ mass spectrum in this decay is inconsistent with phase space and is peaked at low mass. The branc

A. Mikovic

We describe how a spin-foam state sum model can be reformulated as a quantum field theory of spin networks, such that the Feynman diagrams of that field theory are the spin-foam amplitudes. In the case of open spin networks, we obtain a new type of state-sum models, which we call the matter spin foam models. In this type of state-sum models, one labels both

G. M. Kremer, F. P. Devecchi

A kinetic theory of relativistic gases in a two-dimensional space is developed in order to obtain the equilibrium distribution function and the expressions for the fields of energy per particle, pressure, entropy per particle and heat capacities in equilibrium. Furthermore, by using the method of Chapman and Enskog for a kinetic model of the Boltzmann equati

Remo Garattini

A simple model of spacetime foam, made by $N$ Reissner-Nordström wormholes with a magnetic and electric charge in a semiclassical approximation, is taken under examination. The Casimir-like energy of the quantum fluctuation of such a model is computed and compared with that one obtained with a foamy space modeled by $N$ Schwarzschild wormholes. The compariso

L. C. Garcia de Andrade

Metric perturbations the stability of solution of Einstein-Cartan cosmology (ECC) are given. The first addresses the stability of solutions of Einstein-Cartan (EC) cosmological model against Einstein static universe background. In this solution we show that the metric is stable against first-order perturbations and correspond to acoustic oscillations. The se

Lorenzo Iorio

In this paper the possibility of measuring some general relativistic effects in the gravitational field of the Moon via selenodetic missions, with particular emphasis to the future Japanese SELENE mission, is investigated. For a typical selenodetic orbital configuration the post-Newtonian Lense-Thirring gravitomagnetic and the Einstein&#39;s gravitoelectric

Slawomir J. Nasuto, Mark J. Bishop

This article presents the long-term behaviour analysis of Stochastic Diffusion Search (SDS), a distributed agent-based system for best-fit pattern matching. SDS operates by allocating simple agents into different regions of the search space. Agents independently pose hypotheses about the presence of the pattern in the search space and its potential distortio

D. Ravi, R. K. Shyamasundar

One of the most important problems in hybrid systems is the {\em reachability problem}. The reachability problem has been shown to be undecidable even for a subclass of {\em linear} hybrid systems. In view of this, the main focus in the area of hybrid systems has been to find {\em effective} semi-decision procedures for this problem. Such an algorithmic appr

Wei Li, Shilong Ma, Yuefei Sui, Ke Xu

Classical computations can not capture the essence of infinite computations very well. This paper will focus on a class of infinite computations called convergent infinite computations}. A logic for convergent infinite computations is proposed by extending first order theories using Cauchy sequences, which has stronger expressive power than the first order l

Shilong Ma, Yuefei Sui, Ke Xu

Given a sequence $\{Π_n\}$ of Horn logic programs, the limit $Π$ of $\{Π_n\}$ is the set of the clauses such that every clause in $Π$ belongs to almost every $Π_n$ and every clause in infinitely many $Π_n$&#39;s belongs to $Π$ also. The limit program $Π$ is still Horn but may be infinite. In this paper, we consider if the least Herbrand model of the limit of

Anup Mishra, Michael Ma, Fu-Chun Zhang

We use fermion mean field theory to study possible plaquette ordering in the antiferromagnetic SU(4) Heisenberg model. We find the ground state for both the square and triangular lattices to be the disconnected plaquette state. Our mean field theory gives a first order transition for plaquette ordering for the triangular lattice. Our results suggest a large

J. D. Albrecht, D. L. Smith

We investigate theoretically electrical spin injection at a Schottky contact between a spin-polarized electrode and a non-magnetic semiconductor. Current and electron density spin-polarizations are discussed as functions of barrier energy and semiconductor doping density. The effect of a spin-dependent interface resistance that results from a tunneling regio

Hoang K. Nguyen

We establish the existence of a hidden degree of freedom and the critical states of a spinless electron system in a spatially-correlated random magnetic field with vanishing mean. Whereas the critical states are carried by the zero-field contours of the field landscape, the hidden degree of freedom is recognized as being associated with the formation of vort

Greg A. Voth, B. Bigger, M. R. Buckley, W. Losert

Fluid-mediated interactions between particles in a vibrating fluid lead to both long range attraction and short range repulsion. The resulting patterns include hexagonally ordered micro-crystallites, time-periodic structures, and chaotic fluctuating patterns with complex dynamics. A model based on streaming flow gives a good quantitative account of the attra

E. L. Nagaev, A. I. Podel&#39;shchikov, V. E. Zil&#39;bervarg

A version of the magnetoimpurity theory of the colossal magnetoresistance materials suitable for the double exchange ferromagnetic nondegenerate semiconductors is presented. It provides an explanation of the nonmonotonic temperature dependence for the charge carrier density in them when it displays first a maximum and then a minimum, on increase in temperatu

D. S. Dean, R. R. Horgan

A field theory to describe electrostatic interactions in soap films, described by electric multi-layers with a generalized thermodynamic surface-charging mechanism, is studied. In the limit where the electrostatic interactions are weak this theory is exactly soluble. The theory incorporates in a consistent way, the surface-charging mechanism and the fluctuat

P. Allegrini, V. Benci, P. Grigolini, P. Hamilton

The adoption of the Kolmogorov-Sinai (KS) entropy is becoming a popular research tool among physicists, especially when applied to a dynamical system fitting the conditions of validity of the Pesin theorem. The study of time series that are a manifestation of system dynamics whose rules are either unknown or too complex for a mathematical treatment, is still

S. Mossa, G. Ruocco, M. Sampoli

The depolarized light scattering spectra of the glass forming liquid ortho-terphenyl have been calculated in the low frequency region using molecular dynamics simulation. Realistic system&#39;s configurations are produced by using a recent flexible molecular model and combined with two limiting polarizability schemes, both of them using the dipole-induced-di

Jacco H. Snoeijer, J. M. J. van Leeuwen

We study force correlations in the q-model for granular media at infinite depth, for general q-distributions. We show that there are no 2-point force correlations as long as q-values at different sites are uncorrelated. However, higher order correlations can persist, and if they do, they only decay with a power of the distance. Furthermore, we find the entir

E. A. Jagla

We study the appearance and evolution of an array of parallel cracks in a thin slab of material that is directionally dried, and show that the cracks penetrate the material uniformly if the drying front is sufficiently sharp. We also show that cracks have a tendency to become evenly spaced during the penetration. The typical distance between cracks is mainly

Min Sik Park, S. K. Kwon, B. I. Min

We have investigated electronic structures of a room temperature diluted magnetic semiconductor : Co-doped anatase $\rm TiO_{2}$. We have obtained the half-metallic ground state in the local-spin-density approximation(LSDA) but the insulating ground state in the LSDA+$U$+SO incorporating the spin-orbit interaction. In the stoichiometric case, the low spin st

Akito Kobayashi, Atsushi Tsuruta, Tamifusa Matsuura, Yoshihiro Kuroda

We investigate the phase diagram of the electron-doped systems in high-Tc cuprates. We calculate the superconducting transition temperature Tc, the antiferromagnetic transition temperature TN, the NMR relaxation rate 1/T1 with the antiferromagnetic fluctuations in the fluctuation-exchange (FLEX) approximation and with the superconducting fluctuations in the

A. Kalvová, B. Velický

We study theoretically electron transients in semiconductor alloys excited by light pulses shorter than 100 femtoseconds and tuned above the absorption edge during and shortly after the pulse, when disorder scattering is dominant. We use non-equilibrium Green functions employing the field-dependent self-consistent Born approximation. The propagators and the

I. Kanter, W. Kinzel, E. Kanter

A connection between the theory of neural networks and cryptography is presented. A new phenomenon, namely synchronization of neural networks is leading to a new method of exchange of secret messages. Numerical simulations show that two artificial networks being trained by Hebbian learning rule on their mutual outputs develop an antiparallel state of their s

G. Bouzerar, T. P. Pareek

We present a theory for carrier induced ferromagnetism in diluted magnetic semi-conductor (DMS). Our approach treats on equal footing quantum fluctuations within the RPA approximation and disorder within CPA. This method allows for the calculation of $T_c$, magnetization and magnon spectrum as a function of hole, impurity concentration and temperature. It is

Hikaru Kawamura

Recent studies on the chiral order of regularly frustrated XY magnets are reviewed both in classical and quantum cases. In the classical case, chiral transition is a thermal one, while in the quantum case, it is a quantum phase transition. Importance of spatial dimensionality on the chiral order is clarified. Particular attention is paid to the possible ``sp

Nurit Avraham, Boris Khaykovich, Yuri Myasoedov, Michael Rappaport

Vortex matter phase transitions in the high-temperature superconductor Bi2Sr2CaCu2O8 were studied using local magnetization measurements combined with a vortex &#39;shaking&#39; technique. The measurements revealed thermodynamic evidence of a first-order transition along the second magnetization peak line, at temperatures below the apparent critical point Tc

Miyuki K. Shimamura, Tetsuo Deguchi

Several nontrivial properties are shown for the mean square radius of gyration $R_K^2$ of ring polymers with a fixed knot type K. Through computer simulation, we discuss both finite-size and asymptotic behaviors of the gyration radius under the topological constraint for self-avoiding polygons consisting of N cylindrical segments with radius r. We find that

Takanobu Jujo

The renormalization of the magnetic field penetration depth $λ$ owing to the electron-electron correlation is discussed with its application to high-$T_{\rm c}$ cuprates. The formula for the current carried by quasiparticle with the Umklapp scattering is derived, on the basis of which we investigate how the value of $λ^{-2}$ deviates from that of $n/m^*$ whe

R. J. Baxter

We discuss some of the difficulties that have been mentioned in the literature in connection with the Bethe ansatz for the six-vertex model and XXZ chain, and for the eight-vertex model. In particular we discuss the ``beyond the equator&#39;&#39;, infinite momenta and exact complete string problems. We show how they can be overcome and conclude that the coor

F. J. Lu, Q. D. Wang, B. Aschenbach, Ph. Durouchoux

We present a {\it Chandra} ACIS observation of SNR G54.1+0.3. This supernova remnant is resolved into several distinct X-ray emitting components: a central bright point-like source (CXOU J193030.13+185214.1), a surrounding ring, bipolar elongations, plus low surface brightness diffuse emission. The spectra of these components are all well described by power-

Nicole M. Lloyd-Ronning

We discuss the prompt emission of Gamma-Ray Bursts in different spectral energy bands. First, we suggest that a three-part synchrotron emission model is a good description of the ~20 keV - 1 MeV gamma-ray emission of GRBs. We show that this model provides excellent fits to the data and naturally explains the observed global correlations between spectral para

Falk Herwig, Sachiko Amari, Maria Lugaro, Ernst Zinner

The carbon and nitrogen isotopic ratios of pre-solar SiC grains of type A+B suggest a proton-limited nucleosynthetic process as encountered, for instance, during the very late thermal pulse of post-AGB stars. We study the nuclear processes during this phase and find carbon and nitrogen isotopic ratios which can reproduce those of A+B grains. These results ar

Daniel Thomas, Claudia Maraston, Ralf Bender

We compute new population synthesis models of Lick absorption line indices with variable alpha/Fe ratios and use them to derive average ages, metallicities, and alpha/Fe element enhancements for a sample of 126 field and cluster early-type galaxies. Calibrating the models on galactic globular clusters, we show that any population synthesis model being based

Antoinette Songaila, Lennox L. Cowie

We analyze the Ly alpha forest properties of a sample of 15 high redshift quasars lying between z = 4.42 and z = 5.75, using high signal-to-noise spectra obtained with ESI on the Keck II 10 m telescope. The distribution of transmissions in the Ly alpha region in this redshift range is shown to be consistent with that found in lambda cold dark matter simulati

H. W. W. Spoon, J. V. Keane, A. G. G. M. Tielens, D. Lutz

Mid infrared spectra provide a powerful probe of the conditions in dusty galactic nuclei. They variously contain emission features associated with star forming regions and absorptions by circumnuclear silicate dust plus ices in cold molecular cloud material. Here we report the detection of 6-8um water ice absorption in 18 galaxies observed by ISO. While the

J. B. Hutchings, A. W. Fullerton, A. P. Cowley, P. C. Schmidtke

Spectra of the magnetic white dwarf binary AM Her were obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) during three consecutive spacecraft orbits. These observations were split into 19 spectra of about 5 min duration (0.025P binary phase) partially covering the binary orbit. We report the phase-related changes in the far ultraviolet continuum

M. Meixner, T. Ueta, M. Bobrowsky, A. K. Speck

We use detailed radiative transfer models to investigate the differences between the Star-Obvious Low-level-Elongated proto-planetary nebulae (SOLE PPNs) and DUst-Prominent Longitudinally-EXtended proto-planetary nebulae (DUPLEX PPNs) which are two subclasses of PPNs suggested by Ueta, Meixner, & Bobrowsky (2000). We select one SOLE PPN, HD 161796, and one D

P. B. Tissera, R. Dominguez-Tenreiro, C. Scannapieco, A. Saiz

We use cosmological SPH simulations to study the effects of mergers in the star formation history of galactic objects in hierarchical clustering scenarios. We find that during some merger events, gaseous discs can experience two starbursts: the first one during the orbital decay phase, due to gas inflows driven as the satellite approaches, and the second one

S. P. Swordy, L. F. Fortson, J. Hinton, J. Horandel

The observation of a small change in spectral slope, or &#39;knee&#39; in the fluxes of cosmic rays near energies 10^15 eV has caused much speculation since its discovery over 40 years ago. The origin of this feature remains unknown. A small workshop to review some modern experimental measurements of this region was held at the Adler Planetarium in Chicago,

Natalia A. Drake, Ramiro de la Reza, Licio da Silva, David L. Lambert

PDS365 is a newly detected rapidly rotating (vsin i = 20 km/s) single low mass giant star which with HD233517 and HD219025 forms a remarkable ensemble of single K giants with the unique properties of rapid rotation, very strong Li lines, an asymmetrical Halpha profile, and a large far infrared excess. Their vsin i values are between 18 and 23 km/s, and LTE L

Martin Eriksson, Rahman Amanullah

We investigate the possibility of using the proposed SNAP satellite in combination with low-z supernova searches to distinguish between different inverse power-law quintessence models. If the true model is that of a cosmological constant, we determine the prospects of ruling out the inverse power-law potential. We show that SNAP combined with e.g. the SNfact

M. Lopez-Corredoira, J. Betancort-Rijo, J. E. Beckman

A new method is developed to calculate the amplitude of the galactic warps generated by a torque due to external forces. This takes into account that the warp is produced as a reorientation of the different rings which constitute the disc in order to compensate the differential precession generated by the external force, yielding a uniform asymptotic precess

G. Handler, R. R. Shobbrook

We searched for Delta Scuti-type pulsations amongst known and candidate Gamma Doradus stars. We acquired 270 h of observations and monitored a total of 26 stars. One target, HD 209295, turned out to be a member of both classes of pulsating star. We classify six of our targets as new bona fide Gamma Doradus stars, nine more as good Gamma Doradus candidates, a

R. Della Ceca, T. Maccacaro, A. Caccianiga, P. Severgnini

The XMM-Newton Survey Science Center is constructing a large (~1000 sources) and complete sample of bright serendipitous XMM-Newton sources at high galactic latitude, so as to allow both the discovery of sources of high individual interest as well as statistical population studies. The sample, known as ``The XMM-Newton Bright Serendipitous Source Sample&#34;

Deidre A. Hunter, Eric M. Wilcots

We present radio interferometric observations of two irregular galaxies that were candidates for having unusually extended HI emission. The galaxies, UGC 199 and DDO 26, otherwise appeared to be normal, low-luminosity systems with modest star-formation rates. To a detection limit of 2--3E19 /cm^2 at a resolution of about 50&#34;, however, the HI around neith

M. R. Zapatero Osorio, V. J. S. Bejar, Ya. Pavlenko, R. Rebolo

We present intermediate- and low-resolution optical spectra around Halpha and LiI 6708 A for a sample of 25 low mass stars and 2 brown dwarfs with confirmed membership in the pre-main sequence stellar sigma Orionis cluster. Our observations are intended to investigate the age of the cluster. The spectral types derived for our target sample are found to be in

M. Contini, S. M. Viegas, M. A. Prieto

The multiwavelength emission spectrum and associated velocity field of the Seyfert prototype NGC 4151 is modeled. HST data has impressively revealed the existence of a large range of velocities (100 - 1500 \kms) dominating the emitting clouds in the extended emission line region of the galaxy. Following this observational result, a revision of the photoioniz

Lyman Page

The study of the Cosmic Microwave Background (CMB) is a rapidly maturing field. In remarkable advances in the past two years, experiments have begun to probe the detailed structure of the CMB angular spectrum thereby providing insight into the contents of the universe. We briefly review the BOOMERanG and DASI results with an emphasis on what the data tell us

G. J. Mathews, K. Ichiki, T. Kajino, M. Orito

A generic feature of cosmic quintessence models is the possibility of significant energy density in the scalar field during the radiation dominated epoch. This possibility is even greater if the quintessence field begins in a kinetic-dominated regime, for example as might be generated at the end of &#34;quintessential inflation.&#34; As such, these models ca

Falk Herwig, Maria Lugaro, Klaus Werner

H-deficient post-AGB objects, e.g. PG1159 type star K1-16 and born-again AGB star Sakurai&#39;s object, have been reported to be significantly iron-deficient. We find that the iron deficiencies expected due to neutron-capture nucleosynthesis during either the progenitor AGB evolution and/or the neutron burst that occurs as a result of the rapid burning of pr

Jounghun Lee, Ue-Li Pen

We report the first direct observational evidence for alignment of galaxy spin axes with the local tidal shear field. We measure quantitatively the strength of this directional correlation of disk galaxies from the Tully catalog with the local shear field reconstructed from PSCz galaxies. We demonstrate that the null hypothesis of random galaxy alignments re

Taejoon Kouh, J. M. Valles,

We have fabricated quasi-two-dimensional arrays of nano-scale Pb grains coupled by an overlayer of Ag grains. Their temperature dependent resistive transitions follow predictions for an array of mesoscopic superconductor-normal-superconductor junctions. The decrease of their transition temperatures with Ag overlayer thickness systematically deviates from the

Cyril Proust, Etienne Boaknin, R. W. Hill, Louis Taillefer

The transport of heat and charge in the overdoped cuprate superconductor Tl_2Ba_2CuO_(6+delta) was measured down to low temperature. In the normal state, obtained by applying a magnetic field greater than the upper critical field, the Wiedemann-Franz law is verified to hold perfectly. In the superconducting state, a large residual linear term is observed in

Joel H. Kastner, Jingqiang Li, Saeqa D. Vrtilek, Ian Gatley

Chandra X-ray Observatory (CXO) images have revealed that the X-ray emitting regions of the molecule-rich young planetary nebulae (PNs) BD+30 3639 (BD+30) and NGC 7027 are much more asymmetric than their optical nebulosities. To evaluate the potential origins of these X-ray asymmetries, we analyze X-ray images of BD+30, NGC 7027, and another planetary nebula

Q. H. Zhang, V. Topor Pop, S. Jeon, C. Gale

We study the event-by-event fluctuations of the charged particles and compare the results of different Monte-Carlo Generators (MCG): VNIb, HIJING, HIJING/B${\bar B}$ and RQMD. We find that the $D$-measure can be used to distinguish between the different gluon populations that are present in the MCG models. On the other hand, the value of the $D$-measure show

Yosef Ashkenazy, Don R. Baker, Hezi Gildor, Shlomo Havlin

Evidence of past climate variations are stored in ice and indicate glacial-interglacial cycles characterized by three dominant time periods of 20kyr, 40kyr, and 100kyr. We study the scaling properties of temperature proxy records of four ice cores from Antarctica and Greenland. These series are long-range correlated in the time scales of 1-100kyr. We show th

Pengjie Zhang, Ue-Li Pen

We explore the intergalactic medium (IGM) as a potential source of the unresolved soft X-ray background (XRB) and the feasibility to extract the IGM state and evolution from XRB observations. We build two analytical models, the continuum field model and the halo model, to calculate the IGM XRB mean flux, angular auto correlation and cross correlation with ga

Harry Westfahl, Joerg Schmalian, Peter G Wolynes

We present a many body approach for non-equilibrium behavior and self-generated glassiness in strongly correlated quantum systems. It combines the dynamical mean field theory of equilibrium systems with the replica theory for classical glasses without quenched disorder. We apply this approach to study a quantized version of the Brazovskii model and find a se

John C. Baez, J. Daniel Christensen, Thomas R. Halford, David C. Tsang

Using numerical calculations, we compare three versions of the Barrett-Crane model of 4-dimensional Riemannian quantum gravity. In the version with face and edge amplitudes as described by De Pietri, Freidel, Krasnov, and Rovelli, we show the partition function diverges very rapidly for many triangulated 4-manifolds. In the version with modified face and edg

D. H. Correa, G. S. Lozano, E. F. Moreno, F. A. Schaposnik

We study chiral symmetries of fermionic non commutative dipole theories. By using Fujikawa&#39;s approach we obtain explicit expressions of the anomalies for Dirac and chiral fermions in 2 and 4 dimensions.

Edwin Langmann, Richard J. Szabo

We describe a novel duality symmetry of Phi(4)-theory defined on noncommutative Euclidean space and with noncommuting momentum coordinates. This duality acts on the fields by Fourier transformation and scaling. It is an extension, to interactions defined with a star-product, of that which arises in quantum field theories of non-interacting scalar particles c

M. Eschrig, M. R. Norman

We explain recent experimental results on the superconducting state spectral function as obtained by angle resolved photoemission, as well as by tunneling, in high Tc cuprates. In our model, electrons are coupled to the resonant spin fluctuation mode observed in inelastic neutron scattering experiments, as well as to a gapped continuum. We show that, althoug