Böcker av Molla Mengesha Nigus

This thesis titled "Impact of anisotropy on dark energy cosmologicalmodels in theories of gravitation" consists of nine chapters and dealswith the investigation of some spatially homogeneous and anisotropicdark energy cosmological models in the framework of Einstein's generaltheory of gravitation, and also in some other theories of gravitation likeBrans-Dicke (1961) and Saez-Ballester (1986) scalar-tensor theories ofgravitation, which are viable alternatives to Einstein theory of gravitation.Cosmology is the study of the universe as a whole. It mainly deals withthe mechanism of the evolution of the universe and its components. Itseeks to answer the oldest questions of mankind: How did the universecome into existence? What is the universe made of? What will happen tous in the future? There are still many unanswered questions which remainsubject to further scientific investigation and philosophical debate.According to the modern cosmology, the universe begins with a BigBang, and through the evolution of the universe, different fields split fromeach other and the components (fluids) of the universe evolve. While theuniverse expands, different structures (such as galaxies, black holes, starsand planets) emerge. In order to study the universe we need to knowits space-time geometry, and the fluids as its components and how theyinteract with each other and with space-time. This has been done usingEinstein's theory of gravitation by constructing cosmological models.