Exploring alternative theories of gravity : tests and new solutions

Abstract

In this thesis alternatives theories of gravity are considered in the astrophysical context. The first part of the thesis is based around extending the number of solutions in one particular kind of alternative theory of gravity, namely conformal gravity. This involves finding two new solutions in the cylindrical topology, principally the static case and the charged case. The next part of thesis is dedicated to exploring phenomena in the conformal model. This is performed for the spherical case since astrophysical phenomena are spherical in nature. Constraints on the characteristic constant of the spherical symmetric metric are then obtained in each case. The second theory of gravity investigated is f (R) gravity in its Palatini form. This part of the work has more of a theoretical consequence and involves the study of the fate of black holes in the limit as their mass decreases to zero. Of particular interest, the eventual fate of the entropy content of such a black hole is considered. This investigation was conducted at the beginning of the project and can be found in Appendix B. The investigation in Appendix A was also conducted in the initial phases of the project, however in this case the topic of study was the collisional energy product of pairs of counter-rotating particles in cylindrical spacetimes in general relativity.