Collective motion of a Bose-Einstein condensate has been a system of interest since the discovery of BEC. Boltzmann proved that the monopole mode of a thermal gas in an isotropic, harmonic and 3D trap is undamped.
BECs are not classical gases and their weakly interacting nature causes damping in a 3D monopole mode. However, experimental limitations have precluded studies of this behavior in very spherical traps.
When confined to lower dimensions, quantum gases exhibit remarkable physical properties such as the Berezkinskii-Kosterlitz-Thouless transition or the Tonks-Girardeau gas. Confinement effects in a quasi-2D condensate are predicted to shift the frequency of the monopole mode.
One effect in particular connects a small frequency shift with certain quantum corrections.