Statistics of radiation in a disordered medium: from ballistic to   diffusive regime
  The distribution function for the intensity of radiation propagating in a random medium is analyzed for arbitrary multiplicity of scattering (for arbitrary relation between the distance of propagation and mean free path), including as limiting cases purely ballistic and purely diffusive regimes. The calculation is fulfilled in the framework of diagram techniques and is based on the topological analysis of diagram. 
Eugene Kogan and Moshe Kaveh (Jack and Pearl Resnick Institute of   Advanced Technology, Department of Physics, Bar-Ilan Uni...