Nonlocal Gravity and It’s Local Limit in Cosmology

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Tabatabaei Yazdi, Mohammad Javad | 2022

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Type of Document: M.Sc. Thesis
Language: Farsi
Document No: 55703 (04)
University: Sharif University of Technology
Department: Physics
Advisor(s): Baghram, Shant
Abstract:
The theory of nonlocal gravity is a classical modification of Einstein’s general relativity, that explores nonlocal effects of gravity by putting aside the locality postulate, or the assumption that the non-inertial observer is equivalent to an inertial observer with the same speed at each instant of time. In this research we explore the local limit of this theory, or in other words, we consider nonlocality with only a short-term memory, with the goal of calculating the effects of nonlocality on cosmology in mind. We calculate these effects that are formulated inspired by the effects of materials in electrodynamics, on a homogenous universe in the local limit. We also reproduce the theory of cosmological perturbations in the presence of these effects. We show that the corrections to the equations governing the dynamics of homogenous universe and the perturbations are determined only by an unknown function of time which acts like the dielectric permittivity in electrodynamics. Numerical evaluation of this function, to explain some recent observational tensions in cosmology, is the prospective goal of this research
Keywords:
Cosmology ; General Relativity Theory ; Non-Local Gravity ; Locality Limit ; Cosmic Perturbation Theory