Simulations of dual morphology in spiral galaxies

Gas and stars in spiral galaxies are modelled with the DUAL code, using hydrodynamic and N-body techniques. The simulations reveal morphological differences mirroring the dual morphologies seen in B and K' band observations of many spiral galaxies. In particular, the gaseous images are more flocculent with lower pitch angles than the stellar images, and the stellar arm-interarm contrast correlates with the degree of morphological decoupling.Comment: 4 pages, 4 figures, to appear in Disk of Galaxies: Kinematics, Dynamics and Perturbations, ASP Conf. Series, 200

Particle-fluid interactions for flow measurements

Study has been made of the motion of single particle and of group of particles, emphasizing solid particles in gaseous fluid. Velocities of fluid and particle are compared for several conditions of physical interest. Mean velocity and velocity fluctuations are calculated for single particle, and some consideration is given to multiparticle systems

Aspects of holography and rotating AdS black holes

A comparison is made between the thermodynamics of weakly and strongly coupled Yang-Mills with fixed angular momentum. The free energy of the strongly coupled Yang-Mills is calculated by using a dual supergravity description corresponding to a rotating black hole in an Anti de Sitter (AdS) background. All thermodynamic quantities are shown have the same ratio of 3/4 (independent of angular momentum) between strong and weak coupling.Comment: 6 pages latex, Talk given at the TMR conference ``Quantum aspects of gauge theories, supersymmetry and unification", Paris Sept. 199

Natural Entropy Production in an Inflationary Model for a Polarized Vacuum

Though entropy production is forbidden in standard FRW Cosmology, Berman and Som presented a simple inflationary model where entropy production by bulk viscosity, during standard inflation without ad hoc pressure terms can be accommodated with Robertson-Walker's metric, so the requirement that the early Universe be anisotropic is not essential in order to have entropy growth during inflationary phase, as we show. Entropy also grows due to shear viscosity, for the anisotropic case. The intrinsically inflationary metric that we propose can be thought of as defining a polarized vacuum, and leads directly to the desired effects without the need of introducing extra pressure terms.Comment: 7 pages including front one. Accepted to publication, Astrophysics and Space Science, subjected to a minor correction, already submitte