Adrian Parsegian


Bethesda, MD 20892 U.S.A.

Rudi Podgornik


Univ. Ljubljana, Slovenia

Most materials are not ideal conductors; interfaces are not step functions. The Lifshitz formulation liberated Casimir theory from its ideal-conductor assumption. This talk will consider interfaces with spatially graded dielectric response in the direction perpendicular to the parallel faces of interacting planar bodies. We have recently followed earlier work with Jim Kiefer & George Weiss to extend the Lifshitz result for any spatial variation of dielectric response normal to the faces of interacting half-spaces. Working in a macroscopic-continuum limit, we are able to include the consequences of retardation and finite temperature. Noisome contact divergences in the interaction free energy can be made to disappear. New facility emerges to formulate interactions involving spatially inhomogeneous systems.