Boundary propagation of singularities for nonlinear second order Dirichlet problems (Q1813940)

For the Dirichlet problem for second-order nonlinear PDE of real principal type in an \(n\)-dimensional domain with smooth noncharacteristic boundary the author proves the propagation of \(H^{s'}\)-singularities of real-valued \(H^ s\)-solutions along bicharacteristic curves for \(s>5+{n\over 2}\) and \(s'<2s-{n\over 2} -{9\over 2}\).