Dynamical Friction From Ultralight Dark Matter
  We simulate the gravitational dynamics of a massive object interacting with
Ultralight / Fuzzy Dark Matter (ULDM/FDM), non-relativistic quantum matter
described by the Schrodinger-Poisson equation. We first consider a point mass
moving in a uniform background, and then a supermassive black hole (SMBH)
moving within a ULDM soliton. After replicating simple dynamical friction
scenarios to verify our numerical strategies, we demonstrate that the wake
induced by a moving mass in a uniform medium may undergo gravitational collapse
that dramatically increases the drag force, albeit in a scenario unlikely to be
encountered astrophysically. We broadly confirm simple estimates of dynamical
friction timescales for a black hole at the center of a halo but see that a
large moving point mass excites coherent "breathing modes" in a ULDM soliton.
These can lead to "stone skipping" trajectories for point masses which do not
sink uniformly toward the center of the soliton, as well as stochastic motion
near the center itself. These effects will add complexity to SMBH-ULDM
interactions and to SMBH mergers in a ULDM universe.
