In non-equilibrium statistical mechanics, there is this formidable formalism, called the Schwinger-Keldysh formalism. I have read about it, and I understand what it is.

However, what I what to know is if there are any concrete applications of this formalism that give answers that cannot be obtained by other techniques? For example, in calculating transport coefficients, are there problems that can be solved by Schwinger-Keldysh that cannot be solved by using the Boltzmann equation or the Kubo formula?

This post imported from StackExchange Physics at 2017-07-02 10:56 (UTC), posted by SE-user Raghu Mahajan