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Explore the complex dynamics of stellar discs around supermassive black holes through this 56-minute astrophysics seminar from the Institute for Advanced Study. Delve into the process of resonant relaxation, which governs how angular-momentum vectors of stellar orbits evolve around supermassive black holes like the one at our Galactic centre. Learn about the dual responses that stellar discs can exhibit when encountering perturbers such as intermediate-mass black holes: either torquing the perturber until alignment occurs, or breaking up under specific conditions. Discover the mechanism of 'resonant dynamical friction' responsible for the alignment process, and understand the critical conditions that determine when disc disruption occurs, drawing parallels to Hill radius concepts in tidal interactions. Examine how dense solitonic cores, potentially formed from axion-like dark matter, could disrupt the Milky Way's nuclear disc, demonstrating how observations of this disc can reveal its evolutionary history, detect nearby perturbers, and probe dark matter models in previously unconstrained mass ranges.
