October 2000 arXiv papers — page 13

Melanie Bertelson

A regular Poisson manifold can be described as a foliated space carrying a tangentially symplectic form. Examples of foliations are produced here that are not induced by any Poisson structure although all the basic obstructions vanish.

A. P. Isaev, O. Ogievetsky

We suggest a formula for quantum universal $R$-matrices corresponding to quasitriangular classical $r$-matrices classified by Belavin and Drinfeld for all simple Lie algebras. The $R$-matrices are obtained by twisting the standard universal $R$-matrix.

Kieran G. O'Grady

By results of the author there exists a projective (holomorphic) symplectic desingularization of the moduli space of rank-two torsion-free sheaves on a genus-two Jacobian with $c_1=0$ and $c_2=2$. This desingularization has a natural map to the self-product of the Jacobian. We show that the fiber over $(0,0)$ is a 6-dimensional projective irreducible symplec

Radu Pantilie, John C. Wood

Let $M^m$ be a compact oriented smooth manifold which admits a smooth circle action with isolated fixed points which are isolated as singularities as well. Then all the Pontryagin numbers of $M^m$ are zero and its Euler number is nonnegative and even. In particular, $M^m$ has signature zero. Since a non-constant harmonic morphism with one-dimensional fibres

T. Harmark, N. A. Obers

We examine the Hagedorn behavior of little string theory using its conjectured duality with near-horizon NS5-branes. In particular, by studying the string-corrected NS5-brane supergravity solution, it is shown that tree-level corrections to the temperature vanish, while the leading one-loop string correction generates the correct temperature dependence of th

Vikram Vyas

In the world line representation of the fermionic effective action for QCD the interaction between Fermions and the gauge field is contained in the fermionic Wilson loop, namely the Wilson loop for a spin-half particle. It is argued that a string representation of the fermionic Wilson loop can provide a link connecting QCD with a dual description of a meson

Giuseppe Mussardo

The scaling form of the free--energy near a critical point allows for the definition of various universal ratios of thermodynamical amplitudes. Together with the critical exponents they characterize the universality classes and may be useful experimental quantities. We show how these universal quantities can be computed for a particular class of universality

Chung-Chieh Lee, Choon-Lin Ho

In this paper we derive the general expression of a one-loop effective potential of the nonintegrable phases of Wilson lines for an SU(N) gauge theory with a massless adjoint fermion defined on the spactime manifold $R^{1,d-3}\times T^2$ at finite temperature and fermion density. The Phase structure of the vacuum is presented for the case with $d=4$ and N=2

A. Kizilersu, A. W. Schreiber, A. G. Williams

We propose a regularization-independent method for studying a renormalizable field theory nonperturbatively through its Dyson-Schwinger equations. Using QED_4 as an example, we show how the coupled equations determining the nonperturbative fermion and photon propagators can be written entirely in terms of renormalized quantities, which renders the equations

M. S. Goes-Negrao, J. A. Helayel-Neto, M. R. Negrao

Following a previous work on Abelian (2,0)-gauge theories, one reassesses here the task of coupling (2,0) relaxed Yang-Mills super-potentials to a (2,0)-nonlinear Sigma-model, by gauging the isotropy or the isometry group of the latter. One pays special attention to the extra "chiral-like" component-field gauge potential that comes out from the relax

E. Pallante, A. Pich, I. Scimemi

The Standard Model prediction for epsilon'/epsilon is updated, taking into account the chiral loop corrections induced by final state interactions. The resulting value, epsilon'/epsilon = (17\pm 6)\times 10^{-4}, is in good agreement with present measurements.

Sonja Kabana

The kaon number density in nucleus+nucleus and p+p reactions is investigated for the first time as a function of the initial energy density $ε$ and is found to exhibit a discontinuity around $ε$=1.3 GeV/fm$^3$. This suggests a higher degree of chemical equilibrium for $ε>$ 1.3 GeV/fm$^3$. It can also be interpreted as reflection of the same discontinuity, ap

A Donnachie, H G Dosch

Predictions for deep Virtual Compton Scattering are obtained in a two-component dipole model of diffraction. The model automatically includes hard and soft components and implicitly allows for ``hadronic'' contributions via large dipoles. It is also applicable to real Compton Scattering, which provides an important constraint.

Yu. A. Kubyshin, P. G. Tinyakov

The propagator in the instanton background in the $(- λϕ^{4})$ scalar model in four dimensions is studied.Leading and sub-leading terms of its asymptotics for large momenta and its on-shell double residue are calculated analytically. These results are applied to the analysis of the initial-state and initial-final-state corrections and the calculation of the

A. Rajantie

It has recently been suggested that the baryon washout problem of the standard electroweak baryogenesis scenario could be avoided if inflation ends with a period of parametric resonance at a low enough energy density. I present results of numerical simulations in which this process was studied in the Abelian Higgs model. Our results show that because of the

I. N. Mishustin, L. M. Satarov, H. Stoecker, W. Greiner

Equation of state of baryon rich quark matter is studied within the SU(3) Nambu-Jona-Lasinio model with flavour mixing interaction. Possible bound states (strangelets) and chiral phase transitions in this matter are investigated at various values of strangeness fraction S/3B. The model predictions are very sensitive to the ratio of vector (Gv) and scalar (Gs

Achille Stocchi

A review of the results on B^0- \bar {\rm B^0} mixing and b-lifetimes obtained by CDF, LEP and SLD collaborations is presented with special emphasis on B^0_s- \bar {{\rm B}^0_s} mixing.

F. Becattini, L. Bellucci, G. Passaleva

A detailed analysis is performed of transverse momentum spectra of several identified hadrons in high energy collisions within the framework of the statistical model of hadronisation. The effect of the decay chain following hadron generation is accurately taken into account. The considered centre-of-mass energies range from ~ 10 to 30 GeV in hadronic collisi

D. Winder

We use an optimized hopping parameter expansion (linear δexpansion) for the free energy to study the phase transitions at finite temperature and finite charge density in a global U(1) scalar Higgs sector in the continuum and on the lattice at large couplings. We are able to plot out phase diagrams in lattice parameter space and find that the standard second-

R. D. Kenway

This review concentrates on progress in lattice QCD during the last two years and, particularly, its impact on phenomenology. The two main technical developments have been successful implementations of lattice actions with exact chiral symmetry, and results from simulations with two light dynamical flavours which provide quantitative estimates of quenching e

T. Fuchs, B. Pasquini, C. Unkmeir, S. Scherer

We present a calculation of the virtual Compton scattering amplitude for the pseudoscalar meson octet in the framework of chiral perturbation theory at ${\cal O}(p^4)$. We calculate the electromagnetic generalized polarizabilities and compare the results in the real Compton scattering limit to available experimental values. Finally, we give predictions for t

Stefan Wolf

Non-relativistic QCD (NRQCD) predicts colour octet contributions to be significant not only in many production processes of heavy quarkonia but also in their radiative decays. We investigate the photon energy distributions in these processes in the endpoint region. There the velocity expansion of NRQCD breaks down which requires a resummation of an infinite

German Rodrigo, Marcello Ciafaloni

We further analyze the definition and the calculation of the heavy quark impact factor at next-to-leading (NL) $\log s$ level, and we provide its analytical expression in a previously proposed k-factorization scheme. Our results indicate that k-factorization holds at NL level with a properly chosen energy scale, and with the same gluonic Green's function pre

Leonard S. Kisslinger, Wei-hsing Ma, Pengnian Shen

The Pomeron, which dominates high energy elastic and diffractive hadronic processes, must be largely gluonic in nature. We use a recent picture of a scalar glueball/sigma system with coupling of the sigma to glue determined from experiment to predict strong peripheral sigma production seen in the p p $π^oπ^o$ final state.

Sourendu Gupta

I describe results on screening masses in hot gauge theories. Wilsonian effective long distance theories called dimensionally reduced (DR) theories describe very well the longest screening length in pure gauge theories. In the presence of fermions, meson-like screening lengths dominate the long-distance physics for 3T_c/2 < T < 3 T_c, and thus obstruct pertu

M. B. Johnson, B. Z. Kopeliovich, I. K. Potashnikova, P. L. McGaughey

We report an analysis of the nuclear dependence of the yield of Drell-Yan dimuons from the 800 GeV/c proton bombardment of $^2H$, C, Ca, Fe, and W targets. Employing a new formulation of the Drell-Yan process in the rest frame of the nucleus, this analysis examines the effect of initial-state energy loss and shadowing on the nuclear-dependence ratios versus

Don Hochman

Photoproduction of $D_s^{\pm}$ mesons has been measured in the ZEUS detector at HERA and compared with predictions of NLO pQCD calculations. The ratio of $D_s^{*\pm}$ to $D^{*\pm}$ cross sections has been compared to results from $e^{+}e^{-}$ experiments. Orbitally excited P-wave charm mesons have been observed in the $D^{*\pm}π^{\mp}$ final state. The fract

Laurent Serin

The large amount of data accumulated at LEP2 by the ALEPH experiment has been used to search for supersymmetric particles. No signal has been found therefore limits have been determined. Within the Constrained Minimal Supersymmetric Standard Model, the constraints from direct SUSY searches of charginos, sleptons and neutralinos, are combined to extract a low

J. -F. Pascual-Sánchez

The acceleration of the cosmic expansion has been discovered as a consequence of redshift Supernovae data. In the usual way, this cosmic acceleration is explained by the presence of a positive cosmological constant or quantum vacuum energy, in the background of standard Friedmann models. Recently, looking for an alternative explanation, I have considered an

Donato Bini, Robert T. Jantzen

Revised version to be published in the Proceedings of the Encuentros Relativistas Españoles, September, 2000 [ http://hades.eis.uva.es/EREs2000 ]

S. S. Xulu

The energy distribution in the most general nonstatic spherically symmetric space-time is obtained using Møller&#39;s energy-momentum complex. This result is compared with the energy expression obtained by using the energy-momentum complex of Einstein. Some examples of energy distributions in different prescriptions are discussed.

O. Sarbach, M. Heusler, O. Brodbeck

It is shown that the dynamical evolution of linear perturbations on a static space-time is governed by a constrained wave equation for the extrinsic curvature tensor. The spatial part of the wave operator is manifestly elliptic and self-adjoint. In contrast to metric formulations, the curvature-based approach to gravitational perturbation theory generalizes

L. Herrera, A. Di Prisco, J. Martinez

We describe the departure from equilibrium of matter distributions representing sources for a class of Weyl metric. It is shown that, for extremely high gravitational fields, slight deviations from spherical symmetry may enhance the stability of the system weakening thereby its tendency to a catastrophic collapse. For critical values of surface gravitational

R. D. M. De Paola, N. F. Svaiter

In this work we consider a quantum analog of Newton&#39;s bucket experiment in a flat spacetime: we take an Unruh-DeWitt detector in interaction with a real massless scalar field. We calculate the detector&#39;s excitation rate when it is uniformly rotating around some fixed point and the field is prepared in the Minkowski vacuum and also when the detector i

Israel Quiros

The issue of the transformations of units is treated, mainly, in a geometrical context. It is shown that Weyl-integrable geometry is a consistent framework for the formulation of the gravitational laws since the basic law on which this geometry rests is invariant under point-dependent transformations of units. Riemann geometry does not fulfill this requireme

Baudouin Le Charlier, Sabina Rossi, Pascal Van Hentenryck

Many abstract interpretation frameworks and analyses for Prolog have been proposed, which seek to extract information useful for program optimization. Although motivated by practical considerations, notably making Prolog competitive with imperative languages, such frameworks fail to capture some of the control structures of existing implementations of the la

H. Diamant, D. Andelman

The interaction between a flexible polymer in good solvent and smaller associating solute molecules such as amphiphiles (surfactants) is considered theoretically. Attractive correlations, induced in the polymer because of the interaction, compete with intra-chain repulsion and eventually drive a joint self-assembly of the two species, accompanied by partial

Jairo Sinova, Geoff Canright, Horacio E. Castillo, Allan H. MacDonald

We study the nature of the broken ergodicity in the low temperature phase of Ising spin glass systems, using as a diagnostic tool the spectrum of eigenvalues of the spin-spin correlation function. We show that multiple extensive eigenvalues of the correlation matrix $C_{ij}\equiv< S_i S_j>$ occur if and only if there is replica symmetry breaking. We support

R. Moessner

A non-technical introduction to the theory of magnets with strong geometric frustration is given, concentrating on magnets on corner-sharing (kagome, pyrochlore, SCGO and GGG) lattices. Their rich behaviour is traced back to a large ground-state degeneracy in model systems, which renders them highly unstable towards perturbations. A systematic classification

M. R. Norman

Recent neutron scattering experiments in the superconducting state of YBCO have been interpreted in terms of a magnetic collective mode whose dispersion relative to the commensurate wavevector has a curvature opposite in sign to a conventional magnon dispersion. The purpose of this article is to demonstrate that simple linear response calculations are in sup

Cawley D. Vaccarella, C. A. R Sa de Melo

Assuming that the order parameter corresponds to an equal spin triplet pairing state, we calculate the angular dependence of the upper critical field in triplet quasi-one-dimensional superconductors at high magnetic fields applied alongthe yz plane

A. Gandolfi, C. M. Newman, D. L. Stein

We study zero-temperature, stochastic Ising models sigma(t) on a d-dimensional cubic lattice with (disordered) nearest-neighbor couplings independently chosen from a distribution mu on R and an initial spin configuration chosen uniformly at random. Given d, call mu type I (resp., type F) if, for every x in the lattice, sigma(x,t) flips infinitely (resp., onl

Roland Faller, Florian Mueller-Plathe

Atomistic (atom-scale) and coarse-grained (meso-scale) simulations of structure and dynamics of poly-isoprene melts are compared. The local structure and chain packing is mainly determined by the atomistic details of the polymer architecture. The large-time dynamics encountered in NMR experiments can be explained by meso-scale simulations including stiffness

Xiao-Hong Wang, Shlomo Havlin, Moshe Schwartz

We find numerically that the sample to sample fluctuation of the entropy, $ΔS$, is a tool more sensitive in distinguishing how from high temperature behaviors, than the corresponding fluctuation in the free energy. In 1+1 dimensions we find a single phase for all temperatures since $(ΔS)^{2}$ is always extensive. In 2+1 dimensions we find a behavior may look

P. Dolby, R. Seviour, C. J. Lambert

In this letter, we examine the effect of Coulomb interactions in the normal region of a normal-superconducting (N/S) mesoscopic structure, here the change from an attractive to a repulsive coulombic interaction, at the N/S interface, causes a shift in the order parameter phase. We show that this shift has a pronounced effect on Andreev bound states and demon

Cristian Micheletti, Flavio Seno, Amos Maritan

A novel scheme is introduced to capture the spatial correlations of consecutive amino acids in naturally occurring proteins. This knowledge-based strategy is able to carry out optimally automated subdivisions of protein fragments into classes of similarity. The goal is to provide the minimal set of protein oligomers (termed ``oligons&#39;&#39; for brevity) t

Jun Wang, Wei Wang

Based on the concept of energy landscape a picture of the mismatch between the reduced interaction matrix of residues and the matrix of statistical contact potentials is presented. For the Miyazawa and Jernigan (MJ) matrix, rational groupings of 20 kinds of residues with minimal mismatches under the consideration of local minima and statistics on correlation

Erik Aurell, Stanley Brown, Johan Johanson, Kim Sneppen

The lysogeny maintenance switch in phage lambda is one of the simplest examples on the molecular level of computation, command and control in a living system. If, following infection of the bacterium E. coli, the virus enters the lysogenic pathway, it represses its developmental functions, and integrates its DNA into the host chromosome. In this state the pr

Thomas Vojta

Phase transitions which occur at zero temperature when some non-thermal parameter like pressure, chemical composition or magnetic field is changed are called quantum phase transitions. They are caused by quantum fluctuations which are a consequence of Heisenberg&#39;s uncertainty principle. These lecture notes give a pedagogical introduction to quantum phase

F. Trudu, V. Fiorentini, P. Ruggerone, U. Hansen

An upper bound to the roughening temperature of a close-packed singular surface, fcc Al (111), is obtained via free energy calculations based on thermodynamic integration using the embedded-atom interaction model. Roughening of Al (111) is predicted to occur at around 890 K, well below bulk melting (933 K), and it should therefore be observable, save for pos

T. Hikihara, M. Kaburagi, H. Kawamura

The ground-state phase diagram of the frustrated spin-S XXZ chain with the competing nearest- and next-nearest-neighbor antiferromagnetic couplings is studied numerically by using the density-matrix renormalization-group method for the cases of S = 1/2, 3/2, and 2. We are paricularly interested in the possible gapless and gapped chiral phases, in which the c

Youichi Yanase, Takanobu Jujo, Kosaku Yamada

The anomalous properties of High-$T_{\rm c}$ cuprates are investigated both in the normal state and in the superconducting state. In particular, we pay atte ntion to the pseudogap in the normal state and the phase transition from the pse udogap state to the superconducting state. The pseudogap phenomena observed in cuprates are naturally understood as a prec

Lorenzo Matassini, Fabio Franci

Starting from the observation of the real trading activity, we propose a model of a stockmarket simulating all the typical phases taking place in a stock exchange. We show that there is no need of several classes of agents once one has introduced realistic constraints in order to confine money, time, gain and loss within an appropriate range. The main ingred

H. Jeong, B. Tombor, R. Albert, Z. N. Oltvai

In a cell or microorganism the processes that generate mass, energy, information transfer, and cell fate specification are seamlessly integrated through a complex network of various cellular constituents and reactions. However, despite the key role these networks play in sustaining various cellular functions, their large-scale structure is essentially unknow

Peter Kostaedt, Mario Liu

This paper examines the mathematical properties of the relativistic diffusion equation. The peculiar solution which Hiscock and Lindblom identified as an instability is shown to emerge from an ill-posed initial value problem. These do not meet the mathematical conditions required for realistic physical problems and can not serve as an argument against the re

A. Sherman, M. Schreiber

We use the diagram technique for spin operators to calculate Green&#39;s functions and observables of the spin-1/2 quantum Heisenberg antiferromagnet on a square lattice. The first corrections to the self-energy and interaction are taken into account in the chain diagrams. The approximation reproduces main results of Takahashi&#39;s modified spin-wave theory

Mun-Seog Kim, C. U. Jung, Sung-Ik Lee, A. Iyo

The magnetization of the four-layer superconductor CuBa_{2}Ca_{3}Cu_4O_{12-δ} with T_c\simeq117 K is presented. The high-field magnetization around T_c(H) follows the exact two-dimensional scaling function given by Tešanović and Andreev. This feature is contrary to the inference that the interlayer coupling becomes strong if the number of CuO_2 planes in a u

Ken&#39;ichi Takano

We study a period-4 antiferromagnetic mixed quantum spin chain consisting of three kinds of spins. When the ground state is singlet, the spin magnitudes in a unit cell are arrayed as (s-t, s, s+t, s) with integer or half-odd integer s and t (0 <= t < s). The spin Hamiltonian is mapped onto a nonlinear sigma model (NLSM) in a previously developed method. The

James L. Crooks, James O. Dunn, Paul H. Frampton, Y. Jack Ng

A particular kind of quintessence is considered, with equation of motion $p_Q/ρ_Q = -1$, corresponding to a cosmological term with time-dependence $Λ(t) = Λ(t_0) (R(t_0)/R(t))^{P}$ which we examine initially for $0 \leq P < 3$. Energy conservation is imposed, as is consistency with big-bang nucleosynthesis, and the range of allowed $P$ is thereby much restri

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

Using FORS2, mounted on Kueyen (UT2 of the VLT), we have obtained the redshift of the lensing galaxy in the gravitational lens system HE1104-1805. We measure z=0.729, in good agreement with previous estimates based on the time delay and the position of the lens on the fundamental plane. It also coincides with one of the metal line absorption systems that are

Tanya Taidakova, Leonid M. Ozernoy, Nick N. Gorkavyi

Our numerical simulations of the Edgeworth-Kuiper belt objects gravitationally scattered by the four giant planets accounting for mean motion resonances reveal numerous resonant gaps in the distribution of the scattered population.

Richard S. Ellis, Roberto G. Abraham, Mark Dickinson

Hierarchical galaxy formation models make specific predictions concerning the relative assembly rates and star formation histories of spiral bulges and field ellipticals. Independently of the cosmological model and initial power spectrum of fluctuations, at all epochs the stellar populations in spiral bulges should be older and redder than those in typical e

Matthew G. Baring, Alice K. Harding

The absence of radio pulsars with long periods has lead to the popular notion of a high P ``death line.&#39;&#39; In the standard picture, beyond this boundary, pulsars with low spin rates cannot accelerate particles above the stellar surface to high enough energies to initiate pair cascades, and the pair creation needed for radio emission is strongly suppre

K. J. Brooks, J. B. Whiteoak

We have made observations of the four hyperfine transitions of the 2Pi(3/2), J=3/2 ground state of OH at 1612, 1665, 1667 and 1720 MHz and the related 1.6-GHz continuum emission, towards NGC 6334 using the Australia Telescope Compact Array. The observations covered all the major radio continuum concentrations aligned along the axis of NGC 6334 (V, A to F). W

A. P. Smale, M. J. Church, M. Balucinska-Church

We present striking results from Rossi X-ray Timing Explorer (RXTE) observations of the 21-hr low mass X-ray binary X1624-490, showing five complex dips in unprecedented detail. For the first time, dipping is detected up to 15 keV. Prominent flares are also observed in the light curves, limited to energies above 8 keV. Spectra selected by intensity during di

G. Tosti, S. Ciprini, E. Massaro, M. Maesano

We report the main results of our six year long intensive optical monitoring on blazars ON 231 (W Com), BL Lac, and 3C 273. Intensive optical monitoring is an indispensable tool to obtain well sampled light curves and thus to understand the correlation with the variability in other bands and to discriminate among the proposed emission models. The curves base

H. B. Sandvik, J. Magueijo

We extend a previous bispectrum analysis of the COBE-DMR 4 year maps, allowing for the presence of correlations between all possible angular scales. We find that the non-Gaussian signal found earlier for bispectrum components including adjacent modes does not extend to triplets of modes with larger separations. Indeed for all separations $Δ\ell >1$ we find t

J. E. Howe, M. L. N. Ashby, E. A. Bergin, G. Chin

We mapped a 13 by 22 pc region in emission from 492 GHz [C I] and, for the first time, 551 GHz ^{13}CO(5-4) in the giant molecular cloud M17SW, using the Submillimeter Wave Astronomy Satellite. The morphologies of the [C I] and ^{13}CO emission are strikingly similar. The extent and intensity of the [C I] and ^{13}CO(5-4) emission is explained as arising fro

R. L. Snell, J. E. Howe, M. L. N. Ashby, E. A. Bergin

We present Submillimeter Wave Astronomy Satellite (SWAS) observations of the 1_{10}-1_{01} transition of ortho-water at 557 GHz toward 12 molecular cloud cores. The water emission was detected in NGC 7538, Rho Oph A, NGC 2024, CRL 2591, W3, W3(OH), Mon R2, and W33, and was not detected in TMC-1, L134N, and B335. We also present a small map of the water emiss

R. L. Snell, J. E. Howe, M. L. N. Ashby, E. A. Bergin

We present a 17-point map of the M17SW cloud core in the 1_{10}-1_{01} transition of ortho-water at 557 GHz obtained with the Submillimeter Wave Astronomy Satellite. Water emission was detected in 11 of the 17 observed positions. The line widths of the water emission vary between 4 and 9 km s^{-1}, and are similar to other emission lines that arise in the M1

R. L. Snell, J. E. Howe, M. L. N. Ashby, E. A. Bergin

We have used the Submillimeter Wave Astronomy Satellite to map the ground-state 1_{10}-1_{01} transition of ortho-water at 557 GHz in the Orion molecular cloud. Water emission was detected in Orion over an angular extent of about 20 arcmin, or nearly 3 pc. The water emission is relatively weak, with line widths (3-6 km s^{-1}) and V_{LSR} velocities (9-11 km

D. Kiselman, R. J. Rutten, B. Plez

Assuming LTE, we synthesise solar G band spectra from the semiempirical flux-tube model of Briand Solanki (1995). The results agree with observed G-band bright-point contrasts within the uncertainty set by the amount of scattered light. We find that it is the weakening of spectral lines within the flux tube that makes the bright-point contrast in the G band

Francesca Matteucci

We discuss the main ingredients necessary to build models of chemical evolution of spiral galaxies and in particular the Milky Way galaxy. These ingredients include: the star formation rate, the initial mass function, the stellar yields and the gas flows. Then we discuss models for the chemical evolution of galaxy disks and compare their predictions with the

S. L. Bridle, M. P. Hobson, Richard Saunders, A. N. Lasenby

We demonstrate that the maximum-entropy method for gravitational lens reconstruction presented in Bridle et al. (1998) may be applied even when only shear \emph{or} magnification information is present. We also demonstrate that the method can easily handle irregularly shaped observing fields and, because shear is a non-local function of the lensing mass, rec

P. T. O&#39;Brien, J. N. Reeves, M. J. L. Turner, K. A. Pounds

We present XMM-Newton observations of the bright quasar PKS0558-504. The 0.2-10 keV spectrum is dominated by a large, variable soft X-ray excess. The fastest flux variations imply accretion onto a Kerr black hole. The XMM-Newton data suggest the presence of a `big blue bump&#39; in PKS0558-504 extending from the optical band to ~3 keV. The soft X-ray spectru

My Ha Vuong, Bernard H. Foing

We present a model for the hydrogenation states of Polycyclic Aromatic Hydrocarbons (PAHs) in the diffuse interstellar medium. First, we study the abundance of hydrogenation and charge states of PAHs due to photo-ionization, photo-dissociation in the interstellar UV field, electron recombination and chemical reactions between PAH cations and H or H_2. For PA

L. Gregorini, I. Prandoni, H. R. de Ruiter, P. Parma

The emergence of a new population of radio galaxies at mJy and sub-mJy levels is responsible for the change in the slope of the radio source counts. This population seems to include both star forming galaxies and classical (AGN-powered) radio sources, but the relative importance of the two classes is still debated. We present results from the ATESP radio sur

Daniel Huber

Real physical systems are often maintained off equilibrium by energy or matter flows. If these systems are far from equilibrium then the thermodynamical branch become unstable and fluctuations can lead them to other more stable states. These new states are often endowed with higher degrees of organization. In order to explore whether an energy-flow in combin

T. Maeno, S. Orito, H. Matsunaga, BESS Collaboration

The energy spectrum of cosmic-ray antiprotons has been measured by BESS successively in 1993, 1995, 1997 and 1998. In total, 848 antiprotons were clearly identified in energy range 0.18 to 4.20 GeV. From these successive measurements of the antiproton spectrum at various solar activity, we discuss about the effect of the solar modulation and the origin of co

R. Shibata, K. Matsushita, N. Y. Yamasaki, T. Ohashi

The temperature distribution of the intracluster medium (ICM) in the Virgo cluster of galaxies has been derived from extensive mapping observations with ASCA covering an area of 19 deg^2. In the spectral analysis, the inner region within a radius of ~60&#39; from M87 is characterized by an ICM temperature of kT \~2.5 keV with little variation. On the other h

Witold Maciejewski, James Binney

We consider long-slit emission-line spectra of galactic nuclei when the slit is wider than the instrumental PSF, and the target has large velocity gradients. The finite width of the slit generates complex distributions of brightness at a given spatial point in the measured spectrum, which can be misinterpreted as coming from additional physically distinct nu

Beth A. Brown, Joel N. Bregman

Hot gas dominates the emission in X-ray luminous early-type galaxies, but in relatively X-ray faint systems, integrated X-ray emission from discrete stellar-like sources is thought to be considerable, although the amount of the contribution is controversial. To help resolve this issue, we examine the radial X-ray surface brightness distribution of 17 X-ray f

J. L. Rosenberg, S. E. Schneider

We present the Arecibo Dual-Beam Survey (ADBS), a &#34;blind&#34; 21cm survey for galaxies. The ADBS is the largest to date with the Arecibo radio telescope. We were able to achieve an rms sensitivity of 3-4 mJy in only 7 seconds. The ADBS covers substantially more volume than the Spitzak & Schneider (1998) and the Zwaan et al. (1997) surveys. It is surpasse

S. E. Schneider, J. L. Rosenberg

The contribution of extragalactic objects with HI masses below $10^8 M_\odot$ to the HI mass function remains uncertain. Several aspects of the detection of low-mass sources in HI surveys are not always considered, and as a result different analysis techniques yield widely different estimates for their number density. It is suggested at one extreme that the

P. C. van der Kruit

The presence of radial truncations in stellar disks is reviewed. There is ample evidence that many disk galaxies have relatively shaprt truncations in their disks. These often are symmetric and independent of the wavelength band of the observations. The ratio of the truncation radius R_{max} to the disk scalelength h appears often less then 4.5, as expected

Naohisa Takesue, Yasuhiko Fujii, Hoydoo You

Ionic-pair equal-time displacement correlations in relaxor lead magnesium niobate, $Pb(Mg_{1/3}Nb_{2/3})O_{3}$, have been investigated at room temperature in terms of an x-ray diffuse scattering technique. Functions of the distinct correlations have been determined quantitatively. The results show the significantly strong rhombohedral-polar correlations rega

Michael Stay

By allowing measurements of observables other than the state of the qubits in a quantum computer, one can find eigenvectors very quickly. If a unitary operation U is implemented as a time-independent Hamiltonian, for instance, one can collapse the state of the computer to a nearby eigenvector of U with a measurement of the energy. We examine some recent prop

Z. Idziaszek, L. Santos, M. Lewenstein

We study the collective Raman cooling of a polarized trapped Fermi gas in the Festina Lente regime, when the heating effects associated with photon reabsorptions are suppressed. We predict that by adjusting the spontaneous Raman emission rates and using appropriately designed anharmonic traps, temperatures of the order of 2.7% of the Fermi temperature can be

Ethan T. Vishniac, Jungyeon Cho

We construct a magnetic helicity conserving dynamo theory which incorporates a calculated magnetic helicity current. In this model the fluid helicity plays a small role in large scale magnetic field generation. Instead, the dynamo process is dominated by a new quantity, derived from asymmetries in the second derivative of the velocity correlation function, c

Stoytcho Yazadjiev

We present solution generating techniques which permit to construct exact inhomogeneous and anisotropic cosmological solutions to a four-dimensional low energy limit of string theory containing non-minimally interacting electromagnetic and dilaton fields. Some explicit homogeneous and inhomogeneous cosmological solutions are constructed. For example, inhomog

Cheng-Wei Chiang, Lincoln Wolfenstein

A qualitative understanding of the day-night asymmetry for solar neutrinos is provided. The greater night flux in nu_e is seen to be a consequence of the fact that the matter effect in the sun and that in the earth have the same sign. It is shown in the adiabatic approximation for the sun that for all values of the mixing angle theta_V between 0 and pi/2, th

C. Anastasiou, E. W. N. Glover, C. Oleari, M. E. Tejeda-Yeomans

We present the two-loop virtual QCD corrections to the scattering of massless distinct quarks in conventional dimensional regularisation. The structure of the infrared divergences agrees with that predicted by Catani while expressions for the finite remainder are given for each of the s-, t- and u-channels in terms of polylogarithms. The results presented he

Pawel Ciecielag, Michal Chodorowski, Marcin Kiraga, Michael Strauss

We present a numerical study of the relation between the cosmic peculiar velocity field and the gravitational acceleration field. We show that on mildly non-linear scales (4-10 Mpc Gaussian smoothing), the distribution of the Cartesian coordinates of each of these fields is well approximated by a Gaussian. In particular, their kurtoses and negentropies are s

Ludovic Berthier, Leticia F. Cugliandolo, Jose Luis Iguain

We study the dynamics of a glassy model with infinite range interactions externally driven by an oscillatory force. We find a well-defined transition in the (Temperature-Amplitude-Frequency) phase diagram between (i) a `glassy&#39; state characterized by the slow relaxation of one-time quantities, aging in two-time quantities and a modification of the equili

D. R. Stinebring, M. A. McLaughlin, J. M. Cordes, K. M. Becker

We have made high-resolution, high-sensitivity dynamic spectra of a sample of strong pulsars at 430 MHz with the Arecibo radiotelescope. For 4 pulsars we find faint but sharply delineated features in the secondary spectra. These are examples of the previously observed ``crisscross&#39;&#39; or ``multiple drift slope&#39;&#39; phenomenon presumed to be due to

Vasilis Niarchos

In this note we reexamine the possibility of constructing stable non-supersymmetric theories that exhibit an exponential density of states. For weakly coupled closed strings there is a general theorem, according to which stable theories with an exponential density of states must exhibit an almost exact cancellation of spacetime bosons and fermions (not neces

S. Fernando, F. Mansouri

We show that an $SL(2,R)_L \times SL(2,R)_R$ Chern-Simons theory coupled to a source on a manifold with the topology of a disk correctly describes the entropy of the AdS$_3$ black hole. The resulting boundary WZNW theory leads to two copies of a twisted Kac-Moody algebra, for which the respective Virasoro algebras have the same central charge $c$ as the corr

C. L. Carilli, K. M. Menten, J. T. Stocke, E. Perlman

We present measurements of absorption by the 21cm hyperfine transition of neutral hydrogen toward radio sources at substantial look-back times. These data are used in combination with observations of rotational transitions of common interstellar molecules, to set limits on the evolution of the fine structure constant: (dot alpha)/alpha < 3.5e-15/yr to a look

Alexei A. Oblomkov, Alexei V. Penskoi

A generalized inverse problem for a two-dimensional difference operator is introduced. A new construction of the algebro-geometric difference operators of two types first considered by I.M.Krichever and S.P.Novikov is proposed

Masayasu Harada, Koichi Yamawaki

We propose ``vector manifestation (VM)&#39;&#39; of the Wigner realization of the chiral symmetry in which the symmetry is restored at the critical point by the massless degenerate pion (and its flavor partners) and rho meson (and its flavor partners) as the chiral partner, in sharp contrast to the traditional manifestation á la linear sigma model where the