Internal variables in the local-equilibrium approximation
The author introduces in this, one of his last papers, two classes of variables: (a) Extensive variables which can have values in non- equilibrium. They are represented in a Gibbs phase space. (b) Intensive variables which ``appear in physical space''. Now entropy and temperature in physical space \((\bar S,\bar T)\) are approximated by the values of \(S\) and \(T\) in Gibbsian phase space by what the author calls ``the principle of the local state''. The trick is to formulate the Gibbs equation for the reversible process ``accompanying'' in phase space the process of interest, and hence to get a grip on the entropy production. A short quote from Bridgman's ``Nature of Thermodynamics'' (1941, 1961) does unfortunately not carry the appropriate page number.
scientific article; zbMATH DE number 519553