Repulsive Casimir force as a result of vacuum radiation pressure

We study the Casimir force between a perfectly conducting and an infinitely permeable plate with the radiation pressure approach, used by earlier authors for the case of two perfectly conducting plates. This method illustrates in a very simple context how a repulsive force arises as a consequence of the redistribution of the vacuum-field modes corresponding to specific boundary conditions. We show that the result is independent of the cutoff function used for regularization.