Gravity seminar - Hiranya Peiris Seminar

The recent Planck 2015 results, in combination with BICEP/Keck data, appear to disfavour the very simplest inflationary model while continuing to support the inflationary paradigm. This indicates that a successful inflation model may need to encode interesting and nontrivial physics. In recent years, an intensive international effort has gone into embedding inflation into fundamental particle physics. As a result, several generic features of inflation within this fundamental context have emerged. These indicate that, while “single-field” inflationary models are simple, they are not necessarily natural. For example, proposed fundamental particle physics scenarios have many (even hundreds) of scalar degrees of freedom, not just one, and these fields are expected to interact through a complex potential. I will focus on several examples of how to test models of inflation motivated by fundamental physics, and distinguish them from simple toy-model descriptions of inflation.