Modelling the thermodynamics of ultracold atomic bubbles in space

With the recent observation of ultracold atomic bubbles in microgravity using the NASA Cold Atom Lab (CAL) aboard the International Space Station, we discuss modelling the thermodynamic properties of shell-shaped quantum fluids and directly compare to the data obtained from the experiment. We calculate the critical temperature required to achieve Bose-Einstein condensation (BEC) in the novel hollowed-out bubble geometries generated on CAL and, in line with experiment, model how the temperature evolves as an initially condensed gas is inflated into a bubble adiabatically. Using a simplified isotropic `bubble-trap' potential, we show that standard semiclassical methods overestimate the BEC critical temperature for atoms confined in quasi-2D thin shells and with this insight carry out our analysis of the anisotropic CAL trap using a hybrid spectral and semiclassical approach. We conclude by discussing the near-future possibility of achieving large condensed bubbles on CAL.