A new slow-roll paradigm in multifield inflation

Abstract

Increasing effort has been put over the past few years to understand the consequences of the presence of several scalar fields in an early inflationary phase, since theories beyond the Standard Model generically predict such scenarios. The wealth of experimental information that can be obtained from the Cosmic Microwave Background is not yet conclusive about whether cosmic inflation was driven by one or by many scalar fields. Nevertheless, multifield inflationary models produce a great diversity of features that will potentially be measurable in the foreseeable future. In this thesis we wonder about the following elemental question regarding the widely used slow-roll approximation in multifield models: what are the conditions for multifield inflation? As surprising as it might seem, that question, which could be considered as a prior to further developments, did not have a closed answer in the literature on the subject. In this work we give the correct interpretation of the slow-roll approximation in multifield models of inflation and present some interesting new phenomena that arise from this improved understanding.