2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/186022It is shown that the the quantum phase space distributions corresponding to a density operator $ρ$ can be expressed, in thermofield dynamics, as overlaps between the state $\mid ρ>$ and "thermal" coherent states. The usefulness of this approach is brought out in the context of a master equation describing a nonlinear oscillator for which exact expressions for the quantum phase distributions for an arbitrary initial condition are derived.17 pages, revtex, no figures. number of pages were incorrectly stated as 3 instead of 17. No other correctionsQuantum Physicstext