On 1 + 3 covariant perturbation with chaplygin-stiff fluid system in modified Gauss-Bonnet gravity

Abstract

The early stage of the evolution of the universe, when taken along with the recent observations that the current universe is dominated by dark energy, leads to at least a potential problem that modern cosmology must address. Cosmology still lacks a model to deal with the observed current cosmic acceleration. In this paper, a framework is proposed to address the current accelerated expansion of the universe via large scale structure formation. In this regards, we investigate cosmological perturbations of modified Gauss-Bonnet (f (G)) gravity in the presence of a stiff fluid and two different forms of chaplygin gas model, using the 1 + 3 covariant formalism. Gradient variables of respective fluids were defined to obtain the energy overdensity perturbation equations in redshift space, responsible for large scale structure formation. Using a particular functional form of f (G) model, together with two different forms of chaplygin gas, the perturbation equations were solved separately to study the growth of energy overdensity contrast with redshift. The numerical results for both considered forms of chaplygin gas models show that the energy overdensity contrast decays with redshift which might enhance the large structure formation scenario.