CMB Non-Gaussianities from Inflation Models

Agashe, Anish Ninad and Roy, Shubho Ranjan (2017) CMB Non-Gaussianities from Inflation Models. Masters thesis, Indian Institute of Technology.

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Abstract

nflation [1, 2] offers solutions to several open questions in standard cosmology. It proposes a period of extremely rapid (exponential) expansion of the universe prior to the gradual Big Bang expansion. During Inflation, the energy density of the universe was dominated by a cosmological constant-type of vacuum energy which later decayed to produce the matter and radiation that fills the universe today. The simplest model of inflation involves a single scalar field, say, φ , dubbed as the inflaton [3]. Inflationary models are defined by a particular inflaton action (kinetic and potential terms) and its coupling to gravity. The dynamics (self coupling) of the inflaton field depend on the inflationary potential, V ( φ ). The different possibilities for V ( φ ) can lead to different models of inflation. Some well studied models [4] are small field inflation , large field inflation , axion monodromy inflation etc. There also are models with multiple inflaton fields [4, 5], e.g. N inflation . Thus, inflation is not a unique theory and still remains as a paradigm since the possibilities for getting inflationary expansion are (frustratingly) varied. In addition, we would like to distinguish inflation from other alternatives. To break the degeneracies among models, we need higher order correlation functions [6] of the CMB spectrum, namely non-Gaussianities . The ultimate goal of the project was to see how to filter out some inflation models based on the CMB non-Gaussianities. This is a very apt time to work on this as there are huge amounts of data available from experiments like Planck , BICEP 2 and BICEP 3

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