On wave propagation in inhomogeneous systems

We present a theory of electron, electromagnetic, and elastic wave propagat ion in systems consisting of nonoverlapping scatterers in a host medium. Th e theory provides a framework for a unified description of wave propagation in three-dimensional periodic structures, finite slabs of layered structur es, and systems with impurities: isolated impurities. impurity aggregates, or randomly distributed impurities. We point out the similarities and diffe rences between the different cases considered, and discuss the numerical im plementation of the formalism. (C) 2001 Elsevier Science B.V. All rights re served.