UC Irvine

Many mysteries in particle physics have hinted at physics beyond the standard model. The microscopic identity of dark matter and the origin of the matter-antimatter asymmetry have been elusive, despite the efforts throughout the years in probing the rich space of theories and models. To be able to map out the possibilities thoroughly, it is important to understand and revisit assumptions that have been made before. The primary aim of this work is to reconsider and relax a few of these assumptions in theories of dark matter and baryogenesis, exploring alternatives to standard lore. In chapter 2, we introduce a novel solution to the strong CP problem. We revisit the assumption that the strong CP problem exists everywhere in the universe, and propose a mechanism in which the $\overline{\theta}$ term in QCD can be dynamically cancelled as a result of the local environment of dark matter. In chapter 3, we examine the current-day constraints on a well-studied WIMP DM model, while abandoning the assumption that its abundance today was produced via freezeout in a standard cosmology. Finally, in chapter 4, we explore a novel interplay between the roles of decay and annihilation in generating the baryon asymmetry. Typically, either decay or annihilation dominate the processes that drive the baryon asymmetry. However, we show that both decay and annihilation can operate together, leading to an interesting path to baryogenesis.