Multiple Field Inflation and Signatures of Heavy Physics in the CMB

Abstract

In this thesis we present our research in the context of multiple field inflation. Current precision measurements of the cosmic microwave background radiation (CMB) provide compelling evidence for the paradigm of inflation. Simple single field inflation can fit the data well, but the precise microphysical origin of inflation remains unknown. We are interested in the case that single field inflation is an effective description of a more fundamental theory containing multiple scalar fields. Even if these extra degrees of freedom are all very heavy compared to the Hubble scale of inflation they still might influence the dynamics of the inflaton. This leads to features in the statistical properties of the temperature fluctuations in the CMB. We study what the possible effects are and how future data might be able to detect physics beyond single field inflation. In this thesis we will first introduce inflation and its current observational status. Then we discuss the master's research, which consists of two projects. The first project is to provide an overview of studies of multiple field inflation in the literature. We translate between the different notations and definitions used in various papers and study the different approximation schemes and their regime of validity. The second project is a numerical study of concrete models of multi-field inflation from recent papers in the literature. We study if the current and future experiments might be able to detect the presence of the additional fields in these models.