A tale of two particles

Abstract

It was the earliest of times, it was the latest of times, it was the age of inflation, it was the age of collapse, it was the epoch of perturbation growth, it was the epoch of perturbation damping, it was the CMB of light, it was the dwarf galaxy of darkness, it was the largest of cosmic scales, it was the smallest of Milky Way subhalos, we had multiple nonminimally coupled inflatons before us, we had inelastically selfinteracting dark matter before us, we were all going direct to the Planck scale, we were all going direct the other way. Motivated by apparent discrepancies between the standard theory and observation, we analyze two astrophysical systems in the context of new particle physics. Taking a phenomenological approach, we calculate observable consequences of novel particle models during two different stages in the development of our universe. First, we explore the possibility that nonminimally coupled multifield inflation can generate a large primordial isocurvature fraction and account for the "low-multipole anomaly" in the Cosmic Microwave Background. Second, we consider the effects of dark matter that inelastically self-interacts to determine the effect on the structure and abundance of Milky Way satellites and dwarf galaxies. The disparity of time and energy scales examined in this thesis serves to highlight the range of ways to use observables in the sky as a probe of new particle physics that may be elusive at current experiments on the ground.