Topics in Cosmology and Quantum Mechanics

This dissertation explores two topics located in the intersection of quantum mechanics and cosmology. Entanglement harvesting is a phenomenon in which quantum entanglement can develop between the states of two Unruh-DeWitt detectors travelling through spacetime by way of mutual interaction with a scalar quantum field. I numerically explore entanglement harvesting of Unruh-DeWitt detectors in Minkowski space travelling with constant acceleration, generalizing previous analytical results which held only in a limiting case. Cosmic bubble collisions arise in inflationary cosmology as a mechanism to begin reheating at the end of inflation. I extend the previously proposed theory of boom and bust inflation which relies on the existence of a large extra dimension by exploring particular inflationary models in which reheating need not begin the first time that two bubble walls collide. This allows for a smaller lower bound on the size of the compact extra dimension in the boom and bust proposal.