UC Santa Cruz

A physical understanding of the high energy interactions between black holes and stars, coupled with the context of their galactic birthplaces, will allow us to use these systems as tools to better understand black holes at all masses, the lives and deaths of stars, and the dynamics in galactic centers. This dissertation is concerned with interactions at different physical scales: At the solar radius scale, we present the first simulations of successful common envelope ejection leading to binary neutron star formation in 3D hydrodynamics. At the AU scale, we discuss the tidal disruption of a star by a supermassive black hole. We construct the "tidal disruption menu" of objects and black holes that lead to observable tidal disruption flares. We use an analytic framework to calculate the composition of the fallback material onto the supermassive black hole as a function of time. We present the first simulations of tidal disruptions of stars with realistic structures and compositions, which predict abundance anomalies at the peak timescale. We present the STARS library, a grid of simulations interpolated to provide the mass fallback rate to the black hole for a main-sequence star of any mass, age, and impact parameter. We show that all of our simulations can be reduced to a single relationship. Connecting these phenomena to kpc-scale galaxy physics, we present a systematic study of tidal disruption event host galaxies in the context of the local galaxy population, and in particular our finding that they are highly centrally concentrated. Finally, at cosmological scales, we present a study on the obstacles to constructing de Sitter space in theories of quantum gravity. We find that, within controlled approximations, one lacks the tools to construct de Sitter space in string theory.