QED vacuum between a conducting and a permeable plate

We consider the photon field between an unusual configuration of infinite p arallel plates, namely: a perfectly conducting plate (epsilon --> infinity) and an infinitely permeable one (mu --> infinity). After quantizing the ve ctor potential in the coulomb gauge, we obtain explicit expressions for the vacuum expectation values of field operators of the form [EiEj](0) and [Bi Bj](0). These field correlators allow us to re-obtain the Casimir effect fo r this set-up and to discuss the light velocity shift caused by the presenc e of plates (Scharnhorst effect: Scharnhorst (1990 Phys. Lett. B 236 354), Barton (1990 Phys. Lett. B 237 559), Barton and Scharnhorst (1993 J. Phys. A: Math. Gen. 26 2037)) for both scalar and spinor QED.