Strong Gravity

Dr. Avery Broderick will provide a highly accessible and interesting lecture on the Event Horizon Telescope (EHT) and international efforts to interpret horizon-resolving images of numerous supermassive black holes. Black holes are among the most powerful and mysterious phenomena in the universe. Almost every galaxy has at its core a supermassive black hole, millions or even billions of times more massive than our sun. Despite composing a small fraction of the galactic mass budgets, they set the stage for astrophysical dramas that dictate the fates of their hosts. Though black holes are in theory the ultimate manifestation of strong gravity’s impact on the visible universe, placing these exotic phenomena on concrete empirical footing has been impossible - until now.

This talk will explore the applications of the computing power of numerical relativity to gravitational theories beyond general relativity. Specifically, I will consider dynamical Chern-Simons gravity, which has roots in string theory and loop quantum gravity. I will discuss our  formalism and efforts to simulate binary black holes in this theory to generate waveforms LIGO and LISA. Additionally, I will discuss the generation of numerical black hole solutions in this theory, and applications to probing black hole shadows with the Event Horizon Telescope. 

Black-hole recoils are arguably the strong-gravity phenomena with the most striking astrophysical consequences. In the late inspiral and final coalescence of black-hole binaries, anisotropic emission of gravitational waves causes significant linear momentum loss. The remnant black hole, therefore, recoils in the opposite direction. These final kicks can reach magnitudes up to 5000 km/s (“superkicks”), larger than the escape speed of even the most massive galaxies, thus opening the possibility of black hole ejections. In this talk, I summarize recent advances in modeling black-hole recoils and their astrophysical environments. I will address the relevance of disk-assisted spin alignment, new approaches to model black-hole recoils with waveform approximants, and prospects to directly detect superkicks with gravitational-wave detectors.