Generation and evolution of vortex-antivortex pairs in Bose-Einstein   condensates
  We propose a method for generating and controlling a spatially separated vortex--antivortex pair in a Bose-Einstein condensate trapped in a toroidal potential. Our simulations of the time dependent Gross-Pitaevskii equation show that in toroidal condensates vortex dynamics are different from the dynamics in the homogeneous case. Our numerical results agree well with analytical calculations using the image method. Our proposal offers an effective example of coherent generation and control of vortex dynamics in atomic condensates. 
J.-P. Martikainen, K.-A. Suominen, L. Santos, T. Schulte, and A.   Sanpera