Interactions of conormal waves for fully semilinear wave equations (Q803810)

The author proves an existence theorem for the continuation form of the Cauchy problem \(Pu=f(x,u(x)\), \(\nabla u(x))\) where P is a second order strictly hyperbolic differential operator, with initial data strongly conormal to three characteristic hypersurfaces intersecting at the origin and the light cone for P over 0. With suitable assumptions, the author also gives some estimates of the conormal energy for the linear equation with vanishing initial data.