A Study of some Cosmological Parameters at Different Eras of the Universe

This work deals with the implication of the concept of the energy density at three different eras (radiation, matter and dark energy dominated eras) through the evolution of the universe. The solution of the Einstein's equations (Friedmann Robertson Walker equations, FRW), yields two explicit forms of the scale factor R(t): one is the power-law solution for both radiation and matter dominated eras and other is the exponential solution for the dark energy dominated era.
In the present work an equation for the three parameters has been derived, Hubble (H), redshift (z) and deceleration (q), in three different eras, with a thorough discussion.