Time Evolution In Macroscopic Systems. II: The Entropy

TL;DR

This paper explores the concept of entropy in nonequilibrium macroscopic systems, emphasizing the role of entropy production and providing a foundation for nonequilibrium thermodynamics.

Contribution

It introduces an unambiguous definition of time-dependent information entropy and highlights the importance of entropy production in nonequilibrium systems.

Findings

Time-dependent entropy can be defined unambiguously.

Entropy production governs ongoing processes.

Differences between equilibrium and nonequilibrium entropy are clarified.

Abstract

The concept of entropy in nonequilibrium macroscopic systems is investigated in the light of an extended equation of motion for the density matrix obtained in a previous study. It is found that a time-dependent information entropy can be defined unambiguously, but it is the time derivative or entropy production that governs ongoing processes in these systems. The differences in physical interpretation and thermodynamic role of entropy in equilibrium and nonequilibrium systems is emphasized and the observable aspects of entropy production are noted. A basis for nonequilibrium thermodynamics is also outlined