Transport through waveguides with surface disorder

We show that the distribution of the conductance in quasi-one-dimensional systems with surface disorder is correctly described by the Dorokhov-Mello-Pereyra-Kumar equation if one includes direct processes in the scattering matrix S through Poisson's kernel. Although our formulation is valid for any arbitrary number of channels, we present explicit calculations in the one channel case. Ours result is compared with solutions of the Schroedinger equation for waveguides with surface disorder calculated numerically using the R-matrix method.