  We use the full multiple scattering expansion of the retarded self-energy to
obtain the gain and loss rates present in the Kadanoff-Baym relativistic
transport equation. The rates we obtain include processes with any number of
particles. As a first approximation, we only consider central cuts in the
self-energies, but otherwise our results are general. We specialize to the case
of scalar field theory to compare with lowest order results. The main
application of this work is relativistic transport theory of very dense
systems, such as the quark-gluon plasma or the early universe, where
multi-particle interactions are important.
