In this paper some aspects concerning the finite element solution of t
he electromagnetic propagation in nonlinear media are studied through
complementary formulations of the Maxwell equations. Nonlinear hyperbo
lic equations generate discontinuous solutions even if the initial and
boundary conditions are regular. The numerical solution definitively
breaks and the Galerkin method does not converge any more after the ti
me at which a sharp discontinuity is developed. The sharpening of the
solution is related to the loss of its uniqueness.