Ondes semi-linéaires conormales par rapport à deux hypersurfaces transverses. (Conormal semilinear waves with respect to two transversal hypersurfaces) (Q1263732)

The authors consider a first order semilinear system in dimension two or a second order scalar equation on an open set in the Euclidean space and study the symbols and the asymptotic developments of a conormal solution with respect to the union of two characteristic surfaces. Such solutions were studied and constructed by \textit{J. Rauch} and \textit{M. Reed} [Indiana Univ. Math. J. 34, 337-353 (1985; Zbl 0537.35057)] and others. Applications of the authors' results to the Cauchy problem with classical initial data will be given in a later paper.