Ill-posedness of the Cauchy problem for totally degenerate system of conservation laws.
Initial Value Problems in Lp for Systems with Variable Coefficients.
Intégrabilité d'une classe de systèmes de lois de conservation.
Involutivity and Symple Waves in R^2
A strictly hyperbolic quasi-linear 2×2 system in two independent variables with C2 coefficients is considered. The existence of a simple wave solution in the sense that the solution is a 2-dimensional vector-valued function of the so called Riemann invariant is discussed. It is shown, through a purely geometrical approach, that there always exists simple wave solution for the general system when the coefficients are arbitrary C^2 functions depending on both, dependent and independent variables.