Induced dipole-dipole interactions in light diffusion from point dipoles
  We develop a perturbative treatment of induced dipole-dipole interactions in the diffusive transport of electromagnetic waves through disordered atomic clouds. The approach is exact at order two in the atomic density and accounts for the vector character of light. It is applied to the calculation of the electromagnetic energy stored in the atomic cloud - which modifies the energy transport velocity - and of the light scattering and transport mean free paths. Results are compared to those obtained from a purely scalar model for light. 
Nicolas Cherroret, Dominique Delande, Bart A. van Tiggelen
cond-mat.dis-nn physics.atom-ph