SEMILINEAR CAUCHY-PROBLEM WITH CONORMAL I NITIAL DATA - REGULARITY ATTHE WEDGE AND PRINCIPLE SYMBOL

We consider the semi-linear Cauchy problem for a first order strictly hyperbolic system with any size, any number of variables and (sufficie ntly regular) conormal initial data with respect to an hypersurface. W e precise the conormal structure of the solution and we prove, thanks to a suitable paradifferential calculus, that the principal symbol of the solution coincides, outside the wedge, with the solution of the st andard transport equation corresponding formally to the linearized pro blem.