Diffusion of classical waves in random media with microstructure resonances

The diffusion constant of classical waves propagating in random media with microstructure resonances is obtained. Renormalizations of D that are due to expansions in transferred momentum q and frequency ω in the Bethe–Salpeter equation are taken into account. The diffusion constant is estimated for scalar waves propagating in the medium with randomly distributed dielectric spheres with the use of the nondiagonal off-shell transition matrix for penetrable scatterers. A detailed comparison of different sources of renormalization is made. Differences between previous calculations based on the on-shell scattering matrix and new results implementing the off-shell scattering matrix are discussed.