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.

Chakrabarty, Sankha "Duration of Classicality of Homogeneous Condensateswith Attractive Interactions" in Proceedings of the 13th "Patras" Workshop on Axions, WIMPs and WISPs, PATRAS 2017 / Maroudas, Marios (eds.), Verlag Deutsches Elektronen-Synchrotron : 2018 ; Patras 2017 : 13th Patras Workshop on Axions, WIMPs and WISPs, 2017-05-15 - 2017-05-19, Thessaloniki 13th Patras Workshop on Axions, WIMPs and WISPs, AXION-WIMP 2017, Thessaloniki, Greece, 15 May 2017 - 19 May 2017; Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-PROC, 231-235 (2018). doi:10.3204/DESY-PROC-2017-02/sikivie_pierre

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