Morrey-Campanato estimates for Helmholtz equations with two unbounded   media
  We prove uniform Morrey-Campanato estimates for Helmholtz equations in the case of two unbounded inhomogeneous media separated by an interface. They imply weighted $L^2$-estimates for the solution. We prove also a uniform $L^2$-estimate {\em without weight} for the trace of the solution on the interface 
Elise Fouassier (IRMAR)