Infinite Derivative Gravity: A Ghost and Singularity-free 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 non-linear 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 ghost-free, defocusing behaviour around both Minkowski and de Sitter spacetimes, in the linearised regime.

PhD Thesis, April 2017, Lancaster University Physics Department, 146 pages, 5 figures

Cited by in corpus (6)

• Parity-Violating Gravity and GW170817 in Non-Riemannian Cosmology
• Constraints on Spatially Oscillating Sub-mm Forces from the Stanford Levitated Microsphere Experiment Data
• Revealing Infinite Derivative Gravity's true potential: The weak-field limit around de Sitter backgrounds
• Conditions for defocusing around more general metrics in Infinite Derivative Gravity
• Criteria for resolving the cosmological singularity in Infinite Derivative Gravity around expanding backgrounds
• Gravitational radiation in Infinite Derivative Gravity and connections to Effective Quantum Gravity