Observable predictions of generalised inflationary scenarios.
Abstract
Inflation is an early period of accelerated cosmic expansion, thought to be sourced
by high energy physics. A key task today is to use the influx of increasingly precise
observational data to constrain the plethora of inflationary models suggested by
fundamental theories of interactions. This requires a robust theoretical framework
for quantifying the predictions of such models; helping to develop such a framework
is the aim of this thesis.
We begin by providing the first complete quantization of subhorizon perturbations
for the well-motivated class of multi-field inflationary models that possess a
non-trivial field metric. In particular, the implications for the bispectrum of the
Cosmic Microwave Background (cmb) are potentially very exciting. The subsequent
evolution of perturbations in the superhorizon epoch is then considered, via a
covariant extension of the transport formalism. We demonstrate appropriate matching
between the subhorizon and superhorizon calculations.
With the aim of developing intuition about the relation between inflationary dynamics
and the evolution of cosmic observables, we investigate analytic approximations
of superhorizon perturbation evolution. The validity of these analytic results
is contingent on reaching a state of adiabaticity which we discuss and illustrate in
depth. We then apply our analytic methods to elucidate the types of inflationary
dynamics that lead to an enhanced cmb non-Gaussianity, both in its bispectrum and
trispectrum. In addition to deriving a number of new simple relations between the
non-Gaussianity parameters, we explain dynamically how and why different shapes
of inflationary potential lead to particular observational signals.
In addition to multiple scalar fields, candidate theories of high energy physics
include many possible modifications to the Einstein{Hilbert action. We consider
the observational viability of single field chaotic inflation with additional corrections
as motivated by low energy effective string theory. These new ingredients allow
for consistency of chaotic inflationary models that are otherwise in tension with
observational data.
Authors
Elliston, JosephCollections
- Theses [3704]