Electromagnetic zero-point energy and radiation pressure for a rectangular cavity

Abstract

The presence of the conducting walls of a closed cavity changes the energy of the zero-point fluctuations of the electromagnetic field in free space. This electromagnetic zero-point energy (difference) Δ E is calculated for a rectangular cavity. From Δ E the pressures exerted on the cavity walls are derived, which are the differences of the radiation pressures of the electromagnetic zero-point fluctuations inside and outside the cavity, respectively. The pressures on the different walls of a non-cubic cavity are not equal and may even differ in sign. For a cubic cavity of length L, ΔE == 0.0916 c ̵ /L . The zero-point radiation pressure tends to expand the cubic cavity. The implication of this result for Casimir's model of the electron is discussed.