SPECTRUM OF THE CASIMIR EFFECT AND THE LIFSHITZ THEORY

Recent work has revealed that the frequency spectrum of the Casimir force is a function with discontinuities and large oscillations. This spectrum is derived from the Lifshitz theory, using a form of the theory that does not assume analyticity of the dielectric function. In the case of a perfect conductor, these oscillations almost exactly cancel. This leads to the possibility that one could upset this cancellation, and have the force between two slabs of material larger in magnitude than the Casimir force and possibly repulsive. In an approximation in which evanescent modes are ignored, it is shown that the force between two slabs may be expressed directly in terms of the reflection coefficients for light to be reflected from a single slab. This allows the force to be computed directly from empirical optical data.