On the Solvability of Systems of Pseudodifferential Operators
We study the solvability for a system of pseudodifferential operators. We will assume that the systems is of principal type, i.e., the principal symbol vanishes of first order on the kernel, and that the eigenvalue close to zero has constant multiplicity. We prove that local solvability is to condition (PSI) on the eigenvalues as in the scalar case. This condition rules out any sign changes from -
