Vortex-lattice formation and melting in a nonrotating Bose-Einstein   condensate
  Numerical simulations of the interference of a three-way segmented nonrotating Bose-Einstein condensate reveal the production of a honeycomb vortex lattice containing significant numbers of vortices and antivortices. If confined within a trap, the lattice subsequently melts, exhibiting a rich assortment of vortex-antivortex interactions. In contrast with nonlinear vortex production mechanisms previously described for Bose-Einstein condensates, the process here is shown to be primarily one of linear superposition, with initial vortex locations approximately described by a linear theory of wave packet interference. 
Gary Ruben, David M. Paganin, and Michael J. Morgan (School of   Physics, Monash University)