Split Instability of a Vortex in an Attractive Bose-Einstein Condensate
  An attractive Bose-Einstein condensate with a vortex splits into two pieces via the quadrupole dynamical instability, which arises at a weaker strength of interaction than the monopole and the dipole instabilities. The split pieces subsequently unite to restore the original vortex or collapse. 
Hiroki Saito and Masahito Ueda