A Celestial Story of Supersymmetry: Inflation and Reheating in the Early Universe

Abstract

The Standard Model of particle physics and Big Bang cosmology have been successfully used to describe the evolution and current state of the Universe. However, they are known to be incomplete as they leave several unanswered questions, including inflation, dark matter, dark energy, the baryon asymmetry of the universe, and neutrino masses. This thesis presents several models that aim to answer these questions within the framework of supersymmetry and supergravity. We begin by constructing scalar potentials that support slow roll inflation using a single chiral superfield and discuss how to satisfy cosmic microwave background constraints. We then consider how to incorporate supersymmetry breaking effects into account, which leads to a bound on the supersymmetry breaking scale and the inflation scale. After finishing this simple model, we turn to consider how to apply modular symmetry in inflation. Modular symmetry is a strong constraint as well as a useful handle in understanding the dynamics of inflation. In particular, we consider how to construct scalar potentials that resolve the flavor puzzles and simultaneously give rise to inflation. This combination naturally provides the necessary channels for reheating and predicts that the inflaton primarily decays to heavy right-handed neutrinos. By explicit calculation, we show that if the inflaton mass is high enough, this process can be used to produce the baryon asymmetry of the universe. In the end, we discuss a mechanism that produces dark matter at the end of inflation, known as gravitational particle production. We compare the relic abundance of dark matter in supergravity models and non-supersymmetric models, identifying the parameter space that generates sufficient dark matter.