February 1998 arXiv papers — page 17

D. Alloin, Y. Mellier, J. -P. Kneib

We present a new investigation of the Cloverleaf (z$=$2.56) based on the HST/WFPC2, IRAM and CFHT/FOCAM images data. The WFPC2 data shows a significant overdensity of galaxies around the Cloverleaf that we interpret as the presence of a distant cluster of galaxies along the line of sight. The Cloverleaf is probably the result of the lensing effects which inc

C. Porcel, F. Garzon, J. Jimenez-Vicente, E. Battaner

Observations of the Local Arm have been carried out in the near-infrared with the 1.5 m ``Carlos Sánchez'' telescope in Tenerife. A model of the disc with adjustable parameters fitted to reproduce the DIRBE-COBE survey, has been subtracted from the observational data in order to obtain a clean map of the Local Arm, uncontaminated by other components

E. Xanthopoulos, I. W. A. Browne, L. J. King, L. V. E. Koopmans

We report the discovery of a new double image gravitational lens system B1030+074 which was found during the Jodrell Bank - VLA Astrometric Survey (JVAS). We have collected extensive radio data on the system using the VLA, MERLIN, the EVN and the VLBA and optical observations using WFPC2 on the HST. The lensed images are separated by 1.56 arcseconds and thei

A. Fontana, S. D'Odorico, E. Giallongo, S. Cristiani

We present here the spectrum of the galaxy companion to the z=4.7 quasar BR1202-0725, in the optical range 6000-9000 A, corresponding to 1050-1580 A rest-frame. We detect a strong Lya emission line at z=4.702, with an integrated flux of 2x10^{-16} ergs/cm^2/s, and a UV continuum longward of the Lya emission at a flux level of 3x10^{-19}ergs/cm^2/s/A. We fail

Jeffrey R. Weeks

If the universe is multiply-connected and sufficiently small, then the last scattering surface wraps around the universe and intersects itself. Each circle of intersection appears as two distinct circles on the microwave sky. The present article shows how to use the matched circles to explicitly reconstruct the global topology of space.

E. Battaner, H. Lesch, E. Florido

We present a simplified model in which we suggest that two important galactic problems -the magnetic field configuration at large scales and the flat rotation curve- may be simultaneously explained. A highly convective disc produces a high turbulent magnetic diffusion in the vertical direction, stablishing a merging of extragalactic and galactic magnetic fie

E. Battaner, E. Florido

The distribution of superclusters in the Local Supercluster neighbourhood presents such a remarkable periodicity that some kind of network must fit the observed large scale structure. A three dimension chessboard has been suggested$^{1}$. The existence of this network is really a challenge for currently-suggested theoretical models. For instance, CDM models

G. S. Da Costa, D. Hatzidimitriou

We have obtained spectra at the Ca II triplet of individual red giants in seven SMC star clusters whose ages range from ~4 to 12 Gyr. The spectra have been used to determine mean abundances for six of the star clusters to a typical precision of 0.12 dex. When combined with existing data for other objects, the resulting SMC age-metallicity relation is general

Yu. N. Morokov

Thirty years ago, H.Schwarz has attempted to modulate an electron beam with optical frequency. When a 50-keV electron beam crossed a thin crystalline dielectric film illuminated with laser light, electrons produced the electron-diffraction pattern not only at a fluorescent target but also at a nonfluorescent target. In the latter case the pattern was of the

V. V. Flambaum, A. A. Gribakina, G. F. Gribakin

Using a configuration interaction approach we study statistics of the dipole matrix elements (E1 amplitudes) between the 14 lower odd states with J=4 and 21st to 100th even states with J=4 in the Ce atom (1120 lines). We show that the distribution of the matrix elements is close to Gaussian, although the width of the Gaussian distribution, i.e. the root-mean

David A. Kessler, Zvi Ner, Leonard M. Sander

We discuss the problem of fronts propagating into metastable and unstable states. We examine the time development of the leading edge, discovering a precursor which in the metastable case propagates out ahead of the front at a velocity more than double that of the front and establishes the characteristic exponential behavior of the steady-state leading edge.

Philip Foth

Given a compact Kaehler manifold, we consider the complement U of a divisor with normal crossings and a unitary local system V on it. We consider a differential graded Lie algebra (DGLA) of forms with holomorphic logarithmic singularities and vanishing residues. We construct a spectral sequence corresponding to the anti-holomorphic filtration of this algebra

Peter Filip

Specific results of the computer simulation of dilepton production from expanding pion gas created in Pb+Pb 160 GeV/n collisions are presented. Azimuthal asymmetry of dilepton pairs in non-central collisions and interesting shape of the rapidity distribution of dilepton pairs are predicted. These results are understood on theoretical level as a consequence o

Ruy Exel, Marcelo Laca

Given an arbitrary infinite 0--1 matrix A having no identically zero rows, we define an algebra OA as the universal C*-algebra generated by partial isometries subject to conditions that generalize, to the infinite case, those introduced by Cuntz and Krieger for finite matrices. We realize OA as the crossed product algebra for a partial dynamical system and,

George I. Kamberov

This paper presents results on the extent to which mean curvature data can be used to determine a surface in space or its shape. The emphasis is on Bonnet's problem: classify and study the surface immersions in $\R^3$ whose shape is not uniquely determined by the first fundamental form and the mean curvature function. The properties of immersions with um

Nikolai V. Brilliantov, Thorsten Poeschel

A first-principle continuum-mechanics expression for the rolling friction coefficient is obtained for the rolling motion of a viscoelastic sphere on a hard plane. It relates the friction coefficient to the viscous and elastic constants of the sphere material. The relation obtained refers to the case when the deformation of the sphere $ξ$ is small, the veloci

R. Balian, H. Flocard, M. Veneroni

Generalized BCS equations which consistently include the projection on the particle-number parity are derived from a systematic variational method. Numerical solutions are given that are illustrative of ultra-small metallic grains. Compared to the BCS approximation, the pairing is slightly enhanced in even and noticeably inhibited in odd systems. In the latt

M. Krusius, T. Vachaspati, G. E. Volovik

It is now well-recognized that the Universe may behave like a condensed matter system in which several phase transitions have taken place. Superconductors and the superfluid phases of 3He are condensed matter systems with useful similarities to the Universe: they both contain Bose fields (order parameter) and Fermions (quasiparticles) which interact in a way

R. Sadat

X-ray clusters are powerful tools for the determination of cosmological parameters. More specifically, the combined knowledge of the redshift distribution of X-ray clusters together with the luminosity-temperature correlation, $L_X-T_X$ provides us a new test for constraining the mean density of the universe ${Ω_{0}}$. After a brief description of this test,

B. Fort, Y. Mellier

The case for a flat Cold Dark Matter model with a positive cosmological constant $Λ$ has been recently strongly advocated by some theoreticians. In this paper we give the observers point of view to the light of the most recent observations with a special emphasis on lensing tests. We confirm the apparent cosmic concordance for a flat Universe with $Ω_Λ$ clos

Y. Mellier, F. Bernardeau, L. van Waerbeke

The last decade has shown a considerable development of gravitational lensing for cosmology because it probes the amount and the nature of dark matter, and provides information on the density parameter $Ω$, the cosmological constant $Λ$ and the Hubble constant $H_{o}$. Therefore, gravitational lensing can constrain the cosmological scenario which gave birth

D. V. Bisikalo, A. A. Boyarchuk, O. A. Kuznetsov, V. M. Chechetkin

Results of numerical simulations of matter flows in a semidetached binary system similar to the low-mass X-ray binary X1822--371 are presented. Three-dimensional modeling of the mass transfer gas dynamics makes it possible to investigate gas streams in the system and to study the influence of a common envelope. The presence of the common envelope leads to th