Landauer formula for the current through an interacting electron region

A Landauer formula for the current through a region of interacting electrons is derived using the nonequilibrium Keldysh formalism. The case of proportionate coupling to the left and right leads, where the formula takes an especially simple form, is studied in more detail. Two particular examples where interactions give rise to novel effects in the current are discussed: In the Kondo regime, an enhanced conductance is predicted, while a suppressed conductance is predicted for tunneling through a quantum dot in the fractional quantum Hall regime.