Kubo cumulant expansion

There are several ways of proceeding from here to arrive at the master equation for the reduced density matrix. The Zwanzig projection operator technique in Liouville space or the Kubo cumulant expansion may be used and both methods have recently been applied to study optical dephasing in solids. 

Kubo R. Generalized cumulant expansion method. J. Phys. Soc. Japan. 

---