Effective Cross Section of Fuzzy Dark Matter Halos
  We numerically study the movement of two colliding fuzzy dark matter solitons
without explicit self-interaction and find the effective cross section of
dissipative change in velocity. The cross section turns out to be inversely
proportional to the velocity cubed, and we present its analytic interpretation.
Using the result we roughly estimate spatial offsets during head-on collisions
of two fuzzy dark matter halos, which can be related to the spatial offsets
between stars and dark matter in collisions of some galaxy clusters. We also
show that the gravitational cooling plays an important role during the
collisions.
