Hydrodynamic approach to vortex stability in trapped Bose condensates

We study a vortex in a two-dimensional, harmonically trapped Bose-Einstein condensate at zero temperature. Through a variational calculation using a trial condensate wave function and a nonlinear Schrodinger (or Gross-Pitaevskii) Lagrangian, we obtain the effective potential experienced by a vortex at an arbitrary position in the condensate, and find that an off-center vortex will move in a circular trajectory around the trap center. The frequency of this precession is too small to excite any modes in the cloud, and thus the vortex appears dynamically more stable than predicted by a classical continuous model. The lifetime of a vortex in a trapping potential which is not perfectly cylindrically symmetric is also considered. (C) 2000 Elsevier Science B.V. All rights reserved.