Propagation of singularities for hyperbolic operators with multiple involutive characteristics (Q5905550)

The authors give a generalization to the case \(m\geq 2\) of a preceding result of \textit{R. Lascar} [Propagation des singularités des solutions d'équations pseudo-différentielles à caractéristiques de multiplicités variables (Lect. Notes Math. 856) (1981; Zbl 0482.58031), Ch. III] on the propagation of \(C^ \infty\) singularities for an hyperbolic pseudodifferential operator whose principal symbol vanishes of order \(m=2\) on an involutive manifold.