On Covariant Emergent Gravity

Abstract

This Bachelor thesis is on Covariant Emergent Gravity (CEG): a covariant formulation by Sabine Hossenfelder of the ideas of Erik Verlinde on gravity as an emergent force. In this work, the ideas of Erik Verlinde are presented as well as the field equations of CEG. The aim of this thesis is to find experimentally verifiable results for CEG. From the field equations we derive a general gravitational lensing formalism for CEG that is applicable to general lensing systems. This thesis also includes an attempt at an expanding universe model for a vacuum or matter dominated universe. Subsequently, a numerical algorithm is presented to solve for the non-linear differential equations in CEG and MOND in Newtonian regimes for general matter distributions using Fourier transformations. A faster version of this algorithm for cylindrical symmetric matter distributions using Fourier-Bessel transformations is also presented. This algorithm is tested on both the Sun and galaxy NGC6503. Next, the rotation curves as predicted by CEG and MOND of 132 galaxies are compared to the observed velocities using the SPARC data set. The velocities are fitted using three fit parameters and a Markov Chain Monte Carlo algorithm. Both theories show good fits to the observed velocities. We conclude that no differences between the predictions of CEG and MOND can be made on the basis of rotation curves, but that covariant features (such as gravitational lensing) might be used to distinguish between the two theories. An important test for both theories can be provided by a comparison between strong lensing measurements and rotation curves for a single galaxies.