Symmetric hyperbolic systems with boundary conditions that do not satisfy the Kreiss–Sakamoto condition
Symmetric hyperbolic systems with a class of non-homogeneous boundary conditions that do not satisfy the Kreiss–Sakamoto condition (or uniform Lopatinskii condition) are discussed. The boundary conditions are of conservative type. An energy estimate which provides interior and boundary regularity for weak solutions to the system is proved. The results are valid for operators with rough coefficients. As an example the anisotropic Maxwell system is considered.