Princeton University Gravity Initiative Seminar Series

Abstract: Gravitational waves have uncovered a treasure trove of nearly 90 merging black holes and neutron stars, each with its own unique story to tell. In the first part of the talk, our focus will center on black hole spins, seeking to decipher the secrets hidden within, including their origins, hometowns, and the forces driving their mergers. We will challenge the belief that isolated binary black holes should have spins aligned with orbital angular momentum. We will explore the mechanisms influencing these spins, from their origins to the forces driving their mergers.  In the second part of the talk, we will ask "Do black holes play overtones?". Black holes produce a range of tones, known as quasinormal modes, which can be used for "black hole spectroscopy" similar to identifying elements through spectral lines. Among these modes are "overtones," short-lived tones. Recent studies have suggested that black hole mergers produce many overtones, but we argue that this is not the case. We discuss the implications for data analysis and the evidence for quadratic modes, sourced by first-order counterparts.