Modified Newtonian dynamics (MOND) is a phenomenological theory which aims to explain dark matter. However, the theory is criticized for not being a good fit to observations at multiple scales and with lack of fundamental motivations. Bimetric MOND (BIMOND) is a theory with a fundamental relativistic action including two copies of Eintein-Hilbert terms (each equiped with a separate dynamical...
General theory of relativity, which is currently the widely accepted theory of gravity, directly predicts the existence of gravitational waves. This phenomenon was directly measured only in 2015 and in 2017 observational data confirmed the prediction that gravitational waves propagate at the speed of light. However, there are phenomena that general relativity cannot satisfactorily explain...
We investigate the regularization of the Euclidean gravitational action in the teleparallel equivalent of general relativity (TEGR), where the action is dynamically equivalent to that of GR but depends on both the tetrad and an undetermined spin connection. We evaluate the action using both bulk and quasi-local surface integrals across three frames: proper, canonical, and a newly introduced...
Due to GR's age as a theory, many coordinate systems have been developed for it, each of which is specialized for some particular application. However, extensions of GR often lack these coordinate systems, as the GR ones are not trivially generalizable. In this thesis, we seek to develop such coordinate systems for New General Relativity (NGR), specifically in the context of black hole...
