Infinite Derivative Gravity: A Ghost and Singularityfree Theory
Abstract
The objective of this thesis is to present a viable extension of general relativity free from cosmological singularities. A viable cosmology, in this sense, is one that is free from ghosts, tachyons or exotic matter, while staying true to the theoretical foundations of General Relativity such as general covariance, as well as observed phenomenon such as the accelerated expansion of the universe and inflationary behaviour at later times. To this end, an infinite derivative extension of relativity is introduced, with the gravitational action derived and the nonlinear field equations calculated, before being linearised around both Minkowski space and de Sitter space. The theory is then constrained so as to avoid ghosts and tachyons by appealing to the modified propagator, which is also derived. Finally, the Raychaudhuri Equation is employed in order to describe the ghostfree, defocusing behaviour around both Minkowski and de Sitter spacetimes, in the linearised regime.
 Publication:

arXiv eprints
 Pub Date:
 April 2017
 DOI:
 10.48550/arXiv.1704.07211
 arXiv:
 arXiv:1704.07211
 Bibcode:
 2017arXiv170407211C
 Keywords:

 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 PhD Thesis, April 2017, Lancaster University Physics Department, 146 pages, 5 figures