Using K-branch entropy solutions for multiphase geometric optics computations

This paper is devoted to a numerical simulation of the classical WKB system arising in geometric optics expansions. It contains the nonlinear eikonal equation and a linear conservation law whose coefficient can be discontinuous. We address the problem of treating it in such a way superimposed signals can be reproduced by means of the kinetic formulation of ``multibranch solutions'' originally due to Brenier and Corrias. Some existence and uniqueness results are given together with computational test-cases of increasing difficulty displaying up to five multivaluations.