ACCELERATING UNIVERSE WITH MODIFIED FRIEDMANN EQUATION

Abstract

In this paper we propose a specific modification for Friedmann equation which leads during the matter-dominated era to a Cardassian type model, with the usual two undetermined parameters but with an important difference however, the usual parameter B which is constant in the Cardassian model becomes a function of time in this model. We found that although the model leads to acceleration at recent epoch. The acceleration values are more moderate than in the usual Cardassian model because B(t) is a reducing function of time. The model further leads to an increase in the abundance of light element during nucleosynthesis. We use the difference between the predicted and measured values of big bang nucleosynthesis of helium to obtain a value for n and B(t).