Browsing by Author "Bewketu, Asnakew"

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    Dynamics in A Maximally Symmetric Universe
    (Addis Ababa University, 2012-03) Bewketu, Asnakew; Wotro, Legesse (PhD)
    Our present understanding of the evolution of the universe relies upon the Friedmann- Robertson- Walker cosmological models. This model is so successful that it is now being considered as the Standard Model of Cosmology. So in this work we derive the Friedmann equations using the Friedmann-Robertson-Walker metric together with Einstein eld equation and then we give a simple method to reduce Friedmann equations to a second order linear di erential equation when it is supplemented with a time dependent equation of state. Furthermore, as illustrative examples, we solve this equation for some speci c time dependent equation of states. And also by using the Friedmann equations with some time dependent equation of state we try to determine the cosmic scale factor(the rate at which the universe expands) and age of the Friedmann universe, for the matter dominated era, radiation dominated era and for both matter and radiation dominated era by considering di erent cases. We have nally discussed the observable quantities that can be evidences for the accelerated expansion of the Friedmann universe