Collisions of hairy BHs

"Black holes surrounded by long-term stable, fundamental fields act ""in some aspects"" like astrophysical black holes surrounded by accretion disks. As such, these systems can be used to understand possible modified gravitational-wave emission and other dynamical effects. We will perform collisions of black holes surrounded by scalar clouds. The initial data for this problem can be set using previous work by team members. The alignment of black hole spin with accretion disks is a robust prediction of basically all models, but it has yet to be verified though nonlinear evolutions. We will perform such evolutions in a carefully selected setup with bosonic clouds. We will further explore scenarios where matter is allowed to couple to bosonic fields. There, objects orbiting around supermassive black holes may ""float"" on a fixed circular geodesic for long timescales, energy being drawn from the hole's rotational energy. Floating orbits are observationally interesting, producing potentially observable effects such as the halting of inspirals (perhaps even producing gaps in accretions disks), and giving rise to nearly monochromatic waves. Detection of these orbits is tantamount to searching for resonances, as routinely performed at particle accelerators. We will study floating in detail by understanding the evolution of eccentric orbits or spinning objects, finite-size and finite mass effects, and nonlinear simulations of extreme-mass-ratio inspirals."