Ajustes dos parâmetros cosmológicos de um modelo de unificação de matéria escura e energia escura

Abstract

We propose a phenomenological unified model for dark matter and dark energy based on an equation of state parameter w that scales with the arc tangent of the redshift. The free parameters of the model are three constants: Ωb0, α and β. Parameter α dictates the transition rate between the matter dominated era and the accelerated expansion period. The ratio β/α gives the redshift of the equivalence between both regimes. Cosmological parameters are fixed by observational data from Primordial Nucleosynthesis, Supernovae of the type Ia, Gamma-Ray Bursts and Baryon Acoustic Oscillations. The various sets of data are used in different combinations to constraint the parameters through statistical analysis. The unified model is compared to the ΛCDM model and their differences are emphasized. The analysis performed on the background seems to indicate that our dynamical unified model is slightly preferable to the concordance ΛCDM model. However, by developing the perturbation theory for our unified model, we conclude that it is unable to produce the power spectrum of density fluctuation observed today. This is a possibly fatal drawback of our model, at least in the parameterization of w.