Singularities of Diffuse Wave Fields in Scattering Media with Refractive Index Gradients

The subject of this paper is the radiative transfer in media with refractive index gradients. Asymptotic expressions of the intensity distributions in the vicinity of singular directions are derived. Critical conditions for the occurrence of singular intensity distributions in fields of scattered radiation in a medium are formulated. It is shown that singular radiation fields in such media can be generated, among other things, by nonsingular configurations of radiation sources. The obtained results are verified by direct comparison with the results of numerical calculations using the Monte Carlo statistical modelling method.