Dark matter axions and other highly degenerate bosonic fluids are commonly
described by classical field equations. In a recent paper \cite{BECprop} we
calculated the duration of classicality of homogeneous condensates with
attractive contact interactions and of self-gravitating homogeneous condensates
in critical expansion. According to their classical equations of motion, such
condensates persist forever. In their quantum evolution parametric resonance
causes quanta to jump in pairs out of the condensate into all modes with
wavevector less than some critical value. We estimated in each case the time
scale over which the condensate is depleted and after which a classical
description is invalid.Comment: 5 pages, no figures, contributed to the 13th Patras Workshop on
Axions, WIMPs and WISPs, Thessaloniki, May 15 to 19, 201
