  A method is presented which allows one to introduce collective coordinates
self-consistently, in distinction to the Caldeira-Leggett model. It is
demonstrated how the partition function Z for the total nuclear system can be
calculated to deduce information both on its level density as well as on the
decay rate of unstable modes. For the evaluation of Z different approximations
are discussed. A recently developed variational approach turns out superior to
the conventional methods that include quantum effects on the level of local
RPA. Dissipation is taken into account by applying energy smearing, simulating
in this way the coupling to more complicated states. In principle, such a
coupling must depend on temperature. Previous calculations along another
microscopic approach show this fact to imply an intriguing variation of the
transport coefficients of collective motion with T. The relevance of this
feature is demonstrated for the thermal fission rate and for the formation
probability of super-heavy elements.
