Manipulating Bose-Einstein condensed atoms in toroidal traps

We consider Bose-Einstein condensed atoms confined in a toroidal trap. We demonstrate that under conditions of one-dimensional behavior, the density distribution of the atoms may be exponentially localized/delocalized, even for very small variations in the trapping potential along the torus. This observation allows one to control the atom density externally via slight modifications of the trapping potential. For similar reasons, small irregularities of the trap may also have a very pronounced effect on the density of the cloud.