Damped collective motion of many body systems: A variational approach to   the quantal decay rate
  We address the problem of collective motion across a barrier like encountered in fission. A formula for the quantal decay rate is derived which bases on a recently developed variational approach for functional integrals. This formula can be applied to low temperatures that have not been accessible within the former PSPA type approach. To account for damping of collective motion one particle Green functions are dressed with appropriate self-energies. 
Christian Rummel and Helmut Hofmann