Abstract

A physical understanding of the high-energy interactions between stars, black holes, and neutron stars, combined with the context of their galactic birthplaces, will allow us to use these events as tools to better understand black holes at all masses, the lives and deaths of stars, and the dynamics in galactic centers.  With these goals in mind, I will discuss stellar interactions at different physical scales, using a combination of computational hydrodynamics, analytic modeling, and galaxy-matching techniques. At the solar radius scale, I will present the formation of a binary neutron star that will merge via gravitational wave emission. The theoretical framework developed with this work will allow for the modeling of virtually any binary star system. At the AU scale, I will discuss the tidal disruption of a star by a supermassive black hole. I will present the STARS library of tidal disruption event simulations and will show that all of our simulations can be reduced to a single relationship. At the pc scale, I will introduce a self-consistent model of the structure of AGN disks with embedded stars, accounting for energy and momentum feedback from stars, supernovae, and compact objects. Connecting these phenomena to kpc-scale physics, I will present a systematic study of the host galaxies of tidal disruption events, and in particular our finding that these galaxies are highly centrally concentrated. Finally, at cosmological scales, I will discuss de Sitter space in the context of dark energy and quantum gravity. Our understanding of stellar interactions and our ability to use these interactions as tools to answer fundamental questions in astrophysics and physics will be revolutionized with the >1 million annual events we expect from gravitational-wave observatories and electromagnetic surveys in the next few years.