  The Landauer transport formulation is generalized to the case of a dynamic
scatterer with an arbitrary energy level structure, weakly coupled to a long
ideal noninteracting wire.
  The two-terminal linear conductance of the device is expressed in terms of
the (in general inelastic) scattering cross sections of the electrons off the
scatterer, using a Fermi-liquid picture for the scattering states of the whole
system. Assuming unitarity, i.e. the optical theorem, we obtain the same
results from a Kubo linear response treatment and from a Keldysh technique
approach.
