Casimir effect in dielectrics: Surface area contribution

TL;DR

This paper analyzes the Casimir effect in dielectric materials, focusing on surface area contributions and finite-volume corrections, providing explicit formulas and discussing implications for phenomena like sonoluminescence.

Contribution

It extends previous work by explicitly calculating surface area contributions to the Casimir energy in dielectrics, including finite-volume effects and their dependence on material properties.

Findings

Surface area correction is proportional to the dielectric interface surface.

Volume effects dominate for large bubbles.

Explicit formulas for surface contributions as a function of refractive index.

Abstract

In this paper we take a deeper look at the technically elementary but physically robust viewpoint in which the Casimir energy in dielectric media is interpreted as the change in the total zero point energy of the electromagnetic vacuum summed over all states. Extending results presented in previous papers [hep-th/9609195; hep-th/9702007] we approximate the sum over states by an integral over the density of states including finite volume corrections. For an arbitrarily-shaped finite dielectric, the first finite-volume correction to the density of states is shown to be proportional to the surface area of the dielectric interface and is explicitly evaluated as a function of the permeability and permitivity. Since these calculations are founded in an elementary and straightforward way on the underlying physics of the Casimir effect they serve as an important consistency check on field-theoretic calculations. As a concrete example we discuss Schwinger's suggestion that the Casimir effect might be the underlying physical basis behind sonoluminescence}. The recent controversy concerning the relative importance of volume and surface contributions is discussed. For sufficiently large bubbles the volume effect is always dominant. Furthermore we can explicitly calculate the surface area contribution as a function of refractive index.