Thermodynamic Issues Related to Casimir Forces from a Classical Physics Perspective

Daniel C. Cole

Dept. of Manufacturing Engineering

15 St. Mary's Street

Boston University

Brookline, MA 02446

Using our present knowledge of Casimir forces, it is interesting to return to early thermodynamic blackbody radiation analyses and examine how they would be modified if these ideas were taken into account. The first part of this talk dwells on the conventional analysis entering into the Wien displacement law, as often still reported in conventional textbooks in thermodynamics, statistical mechanics, and quantum mechanics. A number of subtle, but critical, assumptions are conventionally made that are clearly invalid when one takes into account the presence of Casimir-type forces. If these assumptions are not imposed, but the analysis is carried out in more generality by properly accounting for the change in the normal modes of the radiation as cavity changes are made, then a generalized Wien displacement law can be derived that holds with Casimir forces being present. In addition, however, a far more surprising result is also obtained, namely, a derivation falls out for the appropriate spectrum of classical electromagnetic zero-point radiation, in order for this analysis to hold at temperature T=0.

This talk then reviews related work where this similar analysis has been applied to other systems, including N harmonic electric dipole oscillators, and cavities of arbitrary shape that are composed of perfectly conducting walls, all bathed in blackbody radiation. There are both practical as well as purely theoretical possible consequences of this work, as will be discussed here.