Characteristic initial boundary value problems for symmetric hyperbolic systems (Q1268683)

The authors consider the initial boundary value problems for symmetric hyperbolic systems of first-order. In this paper, they treat the case where the rank of boundary matrix is not constant. Therefore ``maximal positive'' boundary condition is not sufficient for the well-posedness of the above problems. In this paper, assuming that the initial data are zero, the authors give sufficient conditions so that the above initial boundary value problem admits a weak solution, and also give some estimates for the weak solutions.