Jorge L. Cervantes-Cota

The influence of numerical parameters on tidally triggered bar formation

The joint influence of numerical parameters such as the number of particlesxa0 N , the gravitational softening lengthxa0 e and the time-step

Bianchi V inflation in the Brans-Dicke theory?

Delta t

Isotropization of Bianchi Models and a New FRW Solution in Brans–Dicke Theory

is investigated in the context of galaxy simulations. For isolated galaxy models we have performed a convergence study and estimated the numerical parameters ranges for which the relaxed models do not deviate significantly from its initial configuration. By fixingxa0 N , we calculate the range of the mean interparticle separationxa0

The Influence of Scalar Fields in Protogalactic Interactions

lambda(r)

A Newtonian Approach to the Cosmological Dark Fluids

along the disc radius. Uniformly spaced values ofxa0 λ are used asxa0 e in numerical tests of disc heating. We have found that in the simulations with

Fluids in Cosmology

N=1,310,720

New Solutions of Bianchi Models in Scalar-Tensor Theories

particlesxa0 λ varies by a factor ofxa06, and the corresponding final Toomres parameters Q change by only aboutxa05xa0perxa0cent. By decreasingxa0 N , the λ and Q ranges broaden. Largexa0 e and smallxa0 N cause an earlier bar formation. In addition, the numerical experiments indicate, that for a given set of parameters the disc heating is smaller with the Plummer softening than with the spline softening. For galaxy collision models we have studied the influence of the selected numerical parameters on the formation of tidally triggered bars in galactic discs and their properties, such as their dimensions, shape, amplitude and rotational velocity. Numerical simulations indicate that the properties of the formed bars strongly depend upon the selection ofxa0 N andxa0 e . Large values of the gravitational softening parameter and a small number of particles result in the rapid formation of a well defined, slowly rotating bar. On the other hand, small values ofxa0 e produce a small, rapidly rotating disc with tightly wound spiral arms, and subsequently a weak bar emerges. We have found that by increasingxa0 N , the bar properties converge and the effect of the softening parameter diminishes. Finally, in some cases short spiral arms are observed at the ends of the bar that change periodically from trailing to leading and vice-versa – the wiggle.

Symplectic Symmetry and the Ab Initio No-Core Shell Model

It is shown some exact solutions in the Brans-Dicke (BD) theory for a Bianchi V metric having the property of inflationary expansion, graceful exit, and asymptotic evolution to a Friedmann-Robertson-Walker (FRW) open model. It is remarkable that an inflationary behaviour can occur, even without a cosmological potential or constant. However, the horizon and flatness problems cannot be solve within the standard BD theory because the inflationary period is severely restricted by the value of the BD parameter

The influence of non-minimally coupled scalar fields on the dynamics of interacting galaxies

omega

On the stability of cosmological solutions in Brans-Dicke theory

.Some exact solutions in the Brans-Dicke (BD) theory are shown for a Bianchi V metric having the properties of inflationary expansion, graceful exit and asymptotic evolution to a Friedmann-Robertson-Walker open model. It is remarkable that inflationary behaviour can occur, even without a cosmological potential or constant. However, the horizon and flatness problems cannot be solved within the standard BD theory because the inflationary period is severely restricted by the value of the BD parameter .