Persistent random walk model for transport through thin slabs

We present a model for transport in multiply scattering media based on a th ree-dimensional generalization of the persistent random walk. The model ass umes that photons move along directions that are parallel to the axes. Alth ough this hypothesis is not realistic, it allows us to solve exactly the pr oblem of multiple scattering propagation in a thin slab. Among other quanti ties, the transmission probability and the mean transmission time can be ca lculated exactly. Besides being completely solvable, the model could be use d as a benchmark for approximation schemes to multiple light scattering. [S 1063-651X(99)10006-0].