Derivation of Friedman Equations

Abstract

In this report we make a detailed derivation of Friedman Equations, which are the dy- namical equations of a homogeneous and isotropic universe. First, we derive them in the framework of the General Relativity keeping the relativistic expressions as a reference for the rest of the report. Then, using the Newtonian formalism and solving some fundamental problems, we reach some dy- namical equations for the universe and compare the results with the relativistic ones, focusing our attention on the meaning of the expressions and on the cosmological constant.