Collective Excitations in Quasi-2D Condensates*

Quantum gases confined to lower dimensions 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 certain collective excitations, in particular the monopole mode. In our experiment, quasi-2D condensates are created by loading a 3D condensate into a 1D optical lattice, collective modes are then parametrically driven by modulating the strength of the trap. We have characterized a potential source of systematic error associated with a cross dimensional anharmonicity in the trap. This so called ``anharmonic shear'' also allows us to separate and simultaneously image each individual layer in the lattice.