The dynamics of unstable-state decay

We consider a Fokker-Planck equation in the "order parameter" space and present an asymptotic method to obtain in the low-noise limit the time-dependent probability density, its moments and the first-passage time distribution. We apply the general results to the Ginzburg-Landau potential and its extention for a laser model with saturation. Special attention is paid to the stable equilibrium point and the macroscopically unaccessible region beyond it not studied before. We demonstrate that some of our results (e.g. mean first-passage time) coincide with those yielded by exact expressions in the appropriate limit.