Keldysh nonequilibrium Green function technique is used very widely to describe transport phenomena in mesoscopic systems.
The technique is somewhat subtle, and a rigorous treatment would require much more than we have at our disposal, see, for example, the text-bookk by Haug and Jauho .
The goal of these lectures is to give a rough idea of how the technique works,
and illustrate it with a few simple examples.
Our main applicaton is to calculate the current through a resonant-tunnelling diod; this calculation can be done in a number of different ways, such as the Landauer-Buttiker formalism, or by a Master Equation approach, and our hope is that studying this exactly solvable problem by different methods will give insight to the different formalisms.
Researchers should cite this work as follows: