Tuning Interactions in Two and Three Dimensions

We present recent work on a Bose gas with tuneable interactions in two very different geometries. In three dimensions, we study the stability of a thermal 39K Bose gas across a broad Feshbach resonance, focusing on the unitary regime. We measure the general scaling laws relating the particle-loss and heating rates to the temperature, scattering length, and atom number. As a consequence of species-specific Efimov physics, we find 39K to be particularly promising for studies of many-body physics in a unitary Bose gas. We also present more recent work on a two-dimensional trapping configuration. Such a setup permits investigation of the subtle interplay between interactions and condensation in this regime, in particular the crossover between BEC and BKT physics.