The possibility of vortices in a superfluid led to an intense search for vortices in a trapped Bose gas. The first observations by the JILA group were less than spectacular; the single vortex that could be produced and images had a ghostly existence, but the experiment demonstrated that such excited states do indeed exist. Since that time, vortices in trapped gases have been produced in a number of laboratories using a variety of experimental techniques. Of particular interest to us were the recent JILA experiments which achieved a vortex array by first spinning up a normal cloud and then cooling the spinning gas through the BEC transition temperature. In the paper cited below, we describe a scenario which can account for the formation of vortices in this particular experimental arrangement.
*J.E. Williams, E. Zaremba, B. Jackson, T. Nikuni and A. Griffin, Phys. Rev. Lett. 88, 070401 (2002).