Peter Adshead

Modern cosmology seeks to find new ways in which gravity and quantum field theory can lead to new, consistent models of the early universe while also designing tests and experiments to distinguish between them. This thesis presents work toward these goals.

In the first part of this thesis, I explore the statistical consequences of parameterizing the likelihood surface of Cosmic Microwave Background (CMB) data directly in terms of the slow roll parameters, thus encoding the slow roll prior into the likelihood.

In the second part of this thesis, I present progress toward the understanding of the generation and interaction of the perturbations generated during inflation. The lowest order results, the tree level correlation functions, are already well understood.

However, beyond tree level, the full implications of the quantum nature of the perturbations are not fully appreciated. I build on existing results, and explore the consequences of a very large number of light scalar degrees of freedom in the early universe.

In the final part of this thesis, I consider the theoretical and observational aspects of the three point function for stochastic backgrounds of gravitational waves. I point out that higher order correlation functions of gravitational waves may provide a way to verify the inflationary origin of any positive detection of a stochastic gravitational wave background