title: Velocity of vortices in inhomogeneous Bose-Einstein condensates.
abstract: We derive, from the Gross-Pitaevskii equation, an exact expression for the velocity of any vortex in a Bose-Einstein condensate, in equilibrium or not, in terms of the condensate wave function at the center of the vortex. In general, the vortex velocity is a sum of the local superfluid velocity, plus a correction related to the density gradient near the vortex. A consequence is that in rapidly rotating, harmonically trapped Bose-Einstein condensates, unlike in the usual situation in slowly rotating condensates and in hydrodynamics, vortices do not move with the local fluid velocity. We indicate how Kelvin's conservation of circulation theorem is compatible with the velocity of the vortex center being different from the local fluid velocity. Finally, we derive an exact wave function for a single vortex near the rotation axis in a weakly interacting system, from which we derive the vortex precession rate.
authors.affiliation: Center of Mathematics for Applications, University of Oslo, P.O. Box 1053, Blindern, NO-0316 Oslo, Norway.
authors.forename: Halvor M
authors.initials: HM
authors.lastname: Nilsen
authors.forename: Gordon
authors.initials: G
authors.lastname: Baym
authors.forename: C J
authors.initials: CJ
authors.lastname: Pethick
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D008956:Models, Chemical; D015233:Models, Statistical; D017711:Nonlinear Dynamics; D010825:Physics / Q000379:methods*