Interaction of conormal waves with strong and weak singularities for semi-linear equations

We first define a kind of new function space, called the space of twice conormal distributions. With some estimates on these function spaces, we can prove that if there exist two characteristic hypersurfaces bearing strong and weak singularities respectively intersect transversally, then some new singularities will take place and their strength will be no more than the original weak one. Wang Weike: born in Jan. 1955. Professor. Current research interest is in hyperbolic partial diffrential equation theory Supported by the National Natural Science Foundation of China