Accelerated Expansion

Astrophysics preprint Chasing Lambda

Recent astronomical observations of SNIa, CMB, as well as BAO in the Sloan Digital Sky Survey suggest that the current Universe has entered a stage of an accelerated expansion with the redshift transition at about z=0.5. While the simplest candidates for explanation of this fact is cosmological constant/vacuum energy there exist a serious problem of coincidence. In the theoretical cosmology we can find many possible approaches alleviating this problem by applying new physics or other conception of dark energy. We consider state of art candidates for the description of accelerating Universe in the framework of the Bayesian model selection. We point out advantages as well as troubles of this approach. We find that the combination of four data bases gives a stringent posterior probability of the LambdaCDM model which is 74%. This fact is a quantitative exemplification of a turmoil in modern cosmology over the Lambda problem.