Investigation of dynamics of the universe by using interacting models

In this thesis, three problems are discussed. In the first study, by considering the quadratic contributions of inhomogeneous dark energy, dark energy and dark matter interactions were examined in holographic model and EoS parameters for these interactions and energy densities were obtained. The results were compared with the observational data. In the second study, the interaction between the dark sector was considered the inhomogeneous dark energy. Entropy changes under these interactions were investigated by choosing different interaction parameters. In this study, Chaplygin gas was considered as the source of dark energy and holographic model was considered. EoS parameters were obtained and entropy changes were obtained by using these new EoS parameters. It is also discussed whether the results provide the generalized second law of thermodynamics (GSL) or not . In the third study, anisotropic Bianchi V universe model was taken into consideration, unlike the other two studies. In this universe model, the effects of the interaction between the dark sectors, which are considered as two fluids, on the important cosmological parameters are examined. In addition, continuity equation containing anisotropic additives was obtained. By using this continuity equation, the new EoS parameter of dark energy was obtained and the results were compared with the observational results. As a result, the effects of the interaction between the components in the dark sector on the physical quantities and dynamics of the universe were shown to be important, the results were discussed and compared with the observational data.