Superradiance from BEC vortices: a numerical study
  The scattering of sound wave perturbations from vortex excitations of Bose-Einstein condensates(BEC) is investigated by numerical integration of the associated Klein-Gordon equation. It is found that, at sufficiently high angular speeds, sound wave-packets can extract a sizeable fraction of the vortex energy through a mechanism of superradiant scattering. It is conjectured that this superradiant regime may be detectable in BEC experiments. 
F. Federici, C. Cherubini, S. Succi, and M. P. Tosi