Measurement of the Mass Profile of Abell 1689

In this letter we present calibrated mass and light profiles of the rich cluster of galaxies Abell 1689 out to 1 $h^{-1}$ Mpc from the center. The high surface density of faint blue galaxies at high redshift, selected by their low surface brightness, are unique tools for mapping the projected mass distribution of foreground mass concentrations. The systematic gravitational lens distortions of $10^4$ of these background galaxies in 15\arcmin\ fields reveal detailed mass profiles for intervening clusters of galaxies, and are a direct measure of the growth of mass inhomogeneity. The mass is measured directly, avoiding uncertainties encountered in velocity or X-ray derived mass estimates. Mass in the rich cluster Abell 1689 follows smoothed light, outside 100 h$^{-1}$ kpc, with a rest-frame V band mass-to-light ratio of $400 \pm 60$ $h^{-1} (M/L_V)_\odot$. Near the cluster center, mass appears to be more smoothly distributed than light. Out to a radius of 1 $h^{-1}$ Mpc the total mass follows a steeper than isothermal profile. Comparing with preliminary high resolution N-body clustering simulations for various cosmogonies on these scales, these data are incompatible with hot dark matter, a poor fit to most mixed dark matter models, and favor open or $\Lambda > 0$ cold dark matter. Substructure is seen in both the mass and the light, but detailed correspondence is erased on scales less than 100 $h^{-1}$ kpc.Comment: 13 pages, uuencoded, compressed postscript file, 2 figures included additional 1Mbyte figure available on request. Only change is that in original errorbars on Fig. 5 were a factor of 2 too big

BASEL - The base language for an extensible language facility

Basic language for extensible language facilit

Real-Time Vector Automata

We study the computational power of real-time finite automata that have been augmented with a vector of dimension k, and programmed to multiply this vector at each step by an appropriately selected $k \times k$ matrix. Only one entry of the vector can be tested for equality to 1 at any time. Classes of languages recognized by deterministic, nondeterministic, and "blind" versions of these machines are studied and compared with each other, and the associated classes for multicounter automata, automata with multiplication, and generalized finite automata.Comment: 14 page

Characterization of the domain chaos convection state by the largest Lyapunov exponent

Using numerical integrations of the Boussinesq equations in rotating cylindrical domains with realistic boundary conditions, we have computed the value of the largest Lyapunov exponent lambda1 for a variety of aspect ratios and driving strengths. We study in particular the domain chaos state, which bifurcates supercritically from the conducting fluid state and involves extended propagating fronts as well as point defects. We compare our results with those from Egolf et al., [Nature 404, 733 (2000)], who suggested that the value of lambda1 for the spiral defect chaos state of a convecting fluid was determined primarily by bursts of instability arising from short-lived, spatially localized dislocation nucleation events. We also show that the quantity lambda1 is not intensive for aspect ratios Gamma over the range 20<Gamma<40 and that the scaling exponent of lambda1 near onset is consistent with the value predicted by the amplitude equation formalism