Casimir energy in spherical cavities

TL;DR

This paper calculates the Casimir energy in spherical cavities with dispersive, lossy dielectric materials, accounting for incoherent radiation to ensure thermodynamic equilibrium, and evaluates the finite energy change for an atom at the cavity center.

Contribution

It introduces a method to compute Casimir energy in lossy, dispersive spherical cavities considering incoherent radiation for thermodynamic consistency.

Findings

The cavity energy contribution diverges due to atom-atom interactions.

The energy change for an atom at the cavity center is finite.

A specific case evaluation demonstrates the method's application.

Abstract

We calculate the Casimir energy at spherical cavities within a host made up of an arbitrary material described by a possibly dispersive and lossy dielectric response. To that end, we add to the coherent optical response a contribution that takes account of the incoherent radiation emitted by the host in order to guarantee the detailed balance required to keep the system at thermodynamic equilibrium in the presence of dissipation. The resulting boundary conditions allow a conventional quantum mechanical treatment of the radiation within the cavity from which we obtain the contribution of the cavity walls to the density of states, and from it, the thermodynamic properties of the system. The contribution of the cavity to the energy diverges as it incorporates the interaction energy between neighbor atoms in a continuum description. The change in the energy of an atom situated at the center of the cavity due to its interaction with the fluctuating cavity field is however finite. We evaluate the latter for a simple case.