TRAPPED BOSE-EINSTEIN CONDENSATES AT FINITE-TEMPERATURE - A 2-GAS MODEL

A simple picture describes the results of recent treatments of partial ly-condensed, dilute, trapped Bose gases at temperature T > 0. The con densate wave function is nearly identical to that of a T = 0 condensat e with the same number of condensate atoms, No. The cloud of non-conde nsed atoms is described by the statistical mechanics of an ideal Bose gas in the combined potentials of the magnetic trap and the cloud-cond ensate interaction. We provide a physical motivation for this result, show how it emerges in the Hartree-Fock-Bogoliubov-Popov approximation , and explore some of its implications for future experiments.