A self-consistent treatment of the dynamics of stable and unstable collective modes

We address the dynamics of damped collective modes in terms of first and second moments. The modes are introduced in a self-consistent fashion with the help of a suitable application of linear response theory. Quantum effects in the fluctuations are governed by diffusion coefficients D_{\mu\nu}. The latter are obtained through a fluctuation dissipation theorem generalized to allow for a treatment of unstable modes. Numerical evaluations of the D_{\mu\nu} are presented. We discuss briefly how this picture may be used to describe global motion within a locally harmonic approximation.