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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 50701 (04)
- University: Sharif University of Technology
- Department: Physics
- Advisor(s): Baghram, Shant; Khosravi, Nima
- Abstract:
- The observations of the cosmic background radiation and large-scale structures show that the standard cosmological model is in good agreement with observational data. The standard model is based on the cosmological constant, dark matter, and Gaussian, nearly scale-invariant, adiabatic, and isotropic initial conditions. Although this model has been phenomenologically successful, but the problems of dark energy, dark matter, missing baryons and early universe remain unresolved. One of the most important theoretical questions in cosmology is whether the cosmological constant is the reason for accelerated cosmic expansion. In other words, is Einsteinian gravity the correct theory on the cosmic scale or does it need to be modified? The purpose of this thesis is to theoretically examine modified gravity models that satisfy local gravity constraints, have background solutions with accelerated expasion. We then examine the perturbation theory of these models and, in particular, models that add extra degrees of freedom. As a specific example, we study uLCDM which is a cosmological model inspired from the lately proposed ensemble theory of gravity. We have calculated the cosmic perturbations, and specifically the growth function and growth rate for this new model
- Keywords:
- Cosmology ; Generalized Gravity ; Universe Large-Scale Structure ; Accelerated Expansion
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