Dark energy cosmological models in certain theories of gravitation

This thesis entitled "Dark Energy Cosmological Models in Certain Theories of Gravitation" is devoted to studying dark energy cosmological models in Einstein's theory of gravity and other alternative theories of gravitations namely, Lyra Manifold (1951), Saez-Ballester (1986) and f(R, T) (Harko et al. 2011) theories of gravitation. It mainly focuses on the investigation of certain dark energy cosmological models in specific alternative theories of gravitation that allowed us to map the whole history of cosmic evolution from early times to the late stages of the universe and also these models will indicate the current accelerated expansion of the universe. In order to introduce the reader to these concepts, we will now provide a brief overview of what will be discussed.