  Casimir-Polder interactions are considered in an inhomogeneous, dispersive
background. We consider both the interaction between a polarizable atom and a
perfectly conducting wall, and between such an atom and a plane interface
between two different inhomogeneous dielectric media. Renormalization is
achieved by subtracting the interaction with the local inhomogeneous medium by
itself. The results are expressed in general form, and generalize the
Dzyaloshinskii-Lifshitz-Pitaevskii interaction between a spatially homogeneous
dielectric interface and a polarizable atom.
