New Mechanisms in Inflationary Cosmology

Abstract

Cosmological Collider Physics (CCP), a mechanism in which heavy particles produced dur- ing inflation leave an observable footprint in primordial non-Gaussianities, carries the prospect of probing physics at scales far higher than any terrestrial collider. In this thesis supersymmetric (SUSY) orbifold grand unified theories (GUTs) are identified as a natural candidate predicting new particles which could be detected in CCP. The high scale of unification naively places SUSY orbifold GUTs out of reach, but there exists a “chemical potential" extension of CCP that increases the observable mass range.

A chemical potential mechanism is developed for spin-1 particles coupled to inflation, and allows for the possible detection of heavy gauge bosons from orbifold SUSY GUTs in future large scale structure surveys, and in 21-cm tomography. The mechanism requires a complex vector that is neutral under the standard model, eliminating the minimal SU(5) and SO(10) GUTs, while leaving open the classic trinification scenario. The chemical potential mechanism is thenextended to a pair of charged scalars appearing in a loop. The spectral decomposition is utilised to make the loop process analytically calculable, and is then applied to the detection of heavy Higgs triplets in the SU(5) scenario.

In the final chapter a perturbative model of warm inflation is developed. Warm inflation is a variant of inflation in which primordial fluctuations are thermal, providing a foil to the standard lore that the origin of structure in our universe is due to quantum fluctuations. The chemical potential models, suitably modified, are the key to maintaining theoretical control in this framework, something which has long been a problem. The fluctuation-dissipation theorem, an important theorem in warm inflation, is modified by the chemical potential, and many of the results in the literature must be modified to take this change into account. The predictions of warm inflation are consistent with the CMB power spectrum, and primordial NGs are again the key to obtaining more information about the dynamics of inflation.