On Natural Inflation with an Extra Scalar Field

Abstract

The goal of this work is to study an extra feature of an inflationary model, the so-called Natural Inflation (NI) model, that could possibly describe the early stages of evolution of the universe. We will study the consequence of an additional coupling of the inflaton φ with a second scalar field χ, that respects the shift symmetry of NI for φ. To study the system we first present some preliminary theoretical concepts about classical field theory and about deriving the equations of motion from action principles in general relativity. Then, we will show that χ has exponentially growing solutions, such that that the inflationary period is shortened, for a given range of parameters. This could modify the observable predictions of NI