CASIMIR FREE-ENERGY OF A SPHERICAL CAVITY IN A DIELECTRIC MEDIUM

An expression is derived for the Casimir free energy of a spherical ca vity in a polar dielectric medium at finite temperature. In the proces s of the derivation the general problem of infinities and their renorm alization in calculations of Casimir forces is analyzed. It is shown t hat the renormalized Casimir free energy has a minimum at a finite mes oscopic value of the cavity radius R=R-Min(Cas), with the repulsion fo r R <R-Min(Cas) and the attraction for R greater than or equal to R-Mi n(Cas). The implications of this result for the explanation of cavitat ion effects are discussed. (C) 1997 American Institute of Physics.