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Updated: Apr 27, 2026

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Entropy meters and the entropy of non-extensive systems
Elliott H Lieb1, Jakob Yngvason2
1Departments of Mathematics and Physics , Princeton University , Princeton, NJ 08544, USA.
Abstract:
In our derivation of the second law of thermodynamics from the relation of adiabatic accessibility of equilibrium states, we stressed the importance of being able to scale a system's size without changing its intrinsic properties. This leaves open the question of defining the entropy of macroscopic, but unscalable systems, such as gravitating bodies or systems where surface effects are important. We show here how the problem can be overcome, in principle, with the aid of an 'entropy meter'. An entropy meter can also be used to determine entropy functions for non-equilibrium states and mesoscopic systems.
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