Quasinormal modes, superradiance and area spectrum for 2+1 acoustic black holes

We present an exact expression for the quasinormal modes of acoustic disturbances in a rotating (2+1)-dimensional sonic black hole (draining bathtub fluid flow) in the low frequency limit and evaluate the adiabatic invariant proposed by Kunstatter. We also compute, via Bohr-Sommerfeld quantization rule the equivalent area spectrum for this acoustic black hole, and we compute the superradiance phenomena for pure spinning 2+1 black holes.