Remarks on Pseudodifferential Operators Related to the Time Harmonic Maxwell Equations

The class of pseudodifferential operators is essentially the smallest algebra of operators which contains all differential operators, all fundamental solutions of elliptic differential operators and all integral operators with pseudohomogeneous kernel expansions. The linear pseudodifferential operators can be characterized by generalized Fourier multipliers, known as symbols. The development of the theory of pseudodifferential operators has made it possible to provide a unified treatment of differential and integral operators.