ENTROPY AND IRREVERSIBILITY IN MACROSCOPIC SYSTEMS

The main purpose of this paper is to present a critical discussion of the concept of entropy with the aim of characterizing the non-equilibrium states of a closed many-body system. The essential point of the argument is, in the first place, to point out that the idea of coarse graining as proposed by Ehrenfest may be uniquely defined in terms of the macroscopic information available to the observer. Second, it is shown how to define an entropy function solely in these terms with the same meaning as the H-function as conceived by Boltzmann.