Gravitación y Teoría de Campos

# Matter-dominated models with bulk viscosity driving the accelerated expansion of the Universe

Thursday, 23 June 2011 from to (America/Mexico_City)
at Ulises Nucamendi ( Salon Grande )
Uni. Michoacana San Nicolas de Hidalgo
 Description In this talk, we will explore the viability of a bulk viscous matter-dominated Universe to explain the present accelerated expansion of the Universe. The model is composed by a pressureless fluid with bulk viscosity proportiontal the Hubble parameter. The pressureless fluid characterizes both the baryon and dark matter components. We will study the behavior of the Universe according to this model analyzing the scale factor as well as some curvature scalars and the matter density. We compute the best estimated values of the viscous parameters using the type Ia Supernovae (SNe Ia) probe. We find that from all the possible scenarios for the Universe, the preferred one by the best estimated values is that of an expanding Universe beginning with a Big-Bang, followed by a decelerated expansion at early times, and with a smooth transition in recent times to an accelerated expansion epoch that is going to continue forever. The predicted age of the Universe is a little smaller than the mean value of the observational constraint coming from the oldest globular clusters but it is still inside of the confidence interval of this constraint. A drawback of the model is the violation of the local second law of thermodynamics in redshifts z > 1. However, when we assume a constant viscous parameter, the best estimated value satisfies the local second law of thermodynamics, the age of the Universe is in perfect agreement with the constraint of globular clusters, and it also has a Big-Bang, followed by a decelerated expansion with the smooth transition to an accelerated expansion epoch in late times, that is going to continue forever.  Organised by Wolfgang Bietenholz