Optical conductance fluctuations: Diagrammatic analysis in the Landauer approach and nonuniversal effects

The optical conductance of a multiple scattering medium is defined as the total transmitted light of a normalized diffuse incoming beam. This quantity, analogous to electronic conductance, exhibits universal conductance fluctuations. We perform a detailed diagrammatic analysis of these fluctuations. With a Kadanoff-Baym technique all the leading diagrams are systematically generated. A cancellation of the short distance divergencies occurs that yields a well behaved theory. The analytical form of the fluctuations is calculated and the theory is applied to optical systems. Absorption and internal reflections, which are taken into account, reduce the fluctuations significantly.