Toy models unifying dark energy and dark matter

Abstract

It is very common to find numerical studies of dark energy and dark matter. Among these, one can find the interesting proposal of unifying dark matter and dark energy with the use of a single component with an 'exotic' equation of state. However, there is a certain shortage of analyses involving exact analytic models following this proposal. Therefore, here are presented examples of simple exact cosmological models which can reproduce some of the desired properties of an unified dark matter/energy fluid.

A mathematical analysis of the evolution of perturbations in a modified Chaplygin gas model

“…where x = 1/ [2 (1 + µ)], which can be inverted easily to yield a = a (t) only for µ = 0 and µ = −1/2, while for spaces with any curvature, explicit solutions for a (t) for the particular choices µ = −1/2, γ = 2/3 and γ = 4/3 are given by Costa [38]. It is usual to choose µ > 0, but here we will restrict the analysis to the particular choice µ = −1/2, when one has explicitly,…”

“…In the main section of the article the evolution of perturbations for a modified Chaplygin gas model [38] is obtained, with conclusions being presented in the last section. Throughout the text natural units are used, where c = G =h = k B = 1, unless stated otherwise.…”