Entropy meters and the entropy of non-extensive systems

Elliott H. Lieb, Jakob Yngvason

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


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 'entropymeter'. An entropymeter can also be used to determine entropy functions for non-equilibrium states and mesoscopic systems.

Original languageEnglish (US)
Article number20140192
JournalProceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
Issue number2167
StatePublished - Jul 8 2014

All Science Journal Classification (ASJC) codes

  • General Engineering
  • General Physics and Astronomy
  • General Mathematics


  • Entropy meters
  • Non-extensive systems
  • Second law of thermodynamics


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