Cosmological Consequences of Some New Versions of Dark Energy Models

Abstract

it is observed that the universe expanding with repulsive force. Dark en ergy is an unknown force and responsible for current cosmic acceleration. Generally, in order to find the best-fit model to discuss the cosmic accel eration and dark energy phenomenon, there are two directions that are dynamical dark energy models and modified theories of gravity. One of the dynamical model is holographic dark energy which is also modified in different forms such as modified, generalized, Tsallis, Renyi, Sharma Mittal holographic dark energy models, etc. The modified theories include fractal cosmology, Dvali-Gabadadze-Porrati braneworld, second Randall Sundrum braneworld, loop quantum cosmology, dynamical Chern-Simons gravity, f(R), f(T), f(R,T) theories of gravity etc. Taking some of these models and theories, researchers established different cosmological parame ters.In this thesis, we use Tsallis holographic dark energy model with gen eralized ghost pilgrim dark energy as infra-red cutoff for modified theo ries of gravity such as cyclic universe, Dvali-Gabadadze-Porrati braneworld, Randal-Sundrum II braneworld and dynamical Chern-Simons theory in the fat Friedmann-Robertson-Walker universe. In these directions, we study some cosmological parameters like equation of state, deceleration parame ter, squared sound speed and Om (combination of Hubble and cosmos red shift parameter) parameter. We also establish some cosmic planes such as ω −ω and r−s on the basis of present day observational data.