Normal modes of a vortex in a trapped Bose-Einstein condensate

A hydrodynamic description is: used to study the normal modes of a vortex in a zero-temperature Bose-Einstein condensate. In the Thomas-Fermi limit, the circulating superfluid velocity far from the vortex core provides a small perturbation that splits the originally degenerate normal modes of a vortex-free condensate. The relative frequency shifts are small in all cases considered (they vanish for the lowest dipole mode with /m/ = 1), suggesting that the vortex is stable. The Bogoliubov equations serve to verify the existence of helical waves, similar to those of a vortex line in an unbounded weakly interacting Bose gas. In the large-condensate (small-core) limit, the condensate wave function reduces to that of a straight vortex in an unbounded condensate the corresponding Bogoliubov equations have no bound-state solutions that are uniform along the sym metry axis and that decay exponentially far from the vortex core. [S1050-2947(98)04010-4].