  Hirsch's dynamic Hubbard model describes the effect of orbital expansion with
occupancy by coupling the doublon operator to an auxiliary boson. We use the
nonequilibrium dynamical mean field method to study the properties of doublon
and hole carriers in this model in the strongly correlated regime. In
particular, we discuss how photodoping leads to doublon and hole populations
with different effective temperatures, and we analyze the relaxation behavior
as a function of the boson coupling and boson energy. In the polaronic regime,
the nontrivial energy exchange between doublons, holes and bosons can result in
a negative temperature distribution for the holes.
