Instabilities of wave function monopoles in Bose-Einstein condensates
  We present analytic and numerical results for a class of monopole solutions to the two-component Gross-Pitaevski equation for a two-species Bose condensate in an effectively two-dimensional trap. We exhibit dynamical instabilities involving vortex production as one species pours through another, from which we conclude that the sub-optical sharpness of potentials exerted by matter waves makes condensates ideal tools for manipulating condensates. We also show that there are two equally valid but drastically different hydrodynamic descriptions of a two-component condensate, and illustrate how different phenomena may appear simpler in each. 
Th. Busch and J.R. Anglin