THE PRESSURE IN POLARIZED SYSTEMS

Controversies concerning notation rather than physics have consumed a great amount of attention, and time, of those working on the thermodynamics of polarized systems. This pertains especially to the definition of the pressure and to the question of what is "material" and what "field" in an interacting system. For all measurable quantities, recently definite expressions were derived. In this paper, the observable facts are interpreted in terms of familiar concepts. We identify the different observables associated with the notion of pressure and show that, in a polarized system, "the pressure" does not exist. We propose definitions of the field and the material momentum, of the field and the internal energy, the field Stress tensor, the pressure, and the force. None of these quantities has any precise meaning nor is independently measurable. Our scheme of definitions is fully consistent, from covariant language to irreversible thermodynamics and hydrodynamics. We discuss alternatives and point out the extent of arbitrariness between common usage on one side and convenience on the other. © 1993 Academic Press, Inc.