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Inflation is an early period of accelerated cosmic expansion, thought to besourced by high energy physics. A key task today is to use the influx ofincreasingly precise observational data to constrain the plethora ofinflationary models suggested by fundamental theories of interactions. Thisrequires a robust theoretical framework for quantifying the predictions of suchmodels; helping to develop such a framework is the aim of this thesis. Weprovide the first complete quantization of subhorizon perturbations for thewell-motivated class of multi-field inflationary models with a non-trivialfield metric, which we show may yield interesting signatures in the bispectrumof the Cosmic Microwave Background (CMB). The subsequent evolution ofperturbations in the superhorizon epoch is then considered, via a covariantextension of the transport formalism. To develop intuition about therelationship between inflationary dynamics and the evolution of cosmicobservables, we investigate analytic approximations of superhorizonperturbation evolution. The validity of these analytic results is contingent onreaching a state of adiabaticity which we discuss and illustrate in depth. Wethen apply our analytic methods to elucidate the types of inflationary dynamicsthat lead to an enhanced CMB non-Gaussianity, both in its bispectrum andtrispectrum. In addition to deriving a number of new simple relations betweenthe non-Gaussianity parameters, we explain dynamically how and why differentshapes of inflationary potential lead to particular observational signatures.Candidate theories of high energy physics such as low energy effective stringtheory also motivate single-field modifications to the Einstein-Hilbert action.We show how a range of such corrections allow for consistency of single-fieldchaotic inflationary models that are otherwise in tension with observationaldata.

Observable predictions of generalised inflationary scenarios