Abstract
An analytical property is pointed out for the universal differential equation first derived by Dalfovo, Pitaevskii, and Stringari for the condensate wave function at the boundary of a trapped Bose gas. Specifically, the constant multiplying the Airy function of the solution asymptotically outside the trap is 2. Accordingly, the Wentzel-Kramers-Brillouin approximation is determined in the case of a spherically symmetric harmonic potential. This calculation is related to Josephson-type currents flowing between well-separated traps.