Physics of negative absolute temperatures

Eitan Abraham and Oliver Penrose
Phys. Rev. E 95, 012125 – Published 17 January 2017

Abstract

Negative absolute temperatures were introduced into experimental physics by Purcell and Pound, who successfully applied this concept to nuclear spins; nevertheless, the concept has proved controversial: a recent article aroused considerable interest by its claim, based on a classical entropy formula (the “volume entropy”) due to Gibbs, that negative temperatures violated basic principles of statistical thermodynamics. Here we give a thermodynamic analysis that confirms the negative-temperature interpretation of the Purcell-Pound experiments. We also examine the principal arguments that have been advanced against the negative temperature concept; we find that these arguments are not logically compelling, and moreover that the underlying “volume” entropy formula leads to predictions inconsistent with existing experimental results on nuclear spins. We conclude that, despite the counterarguments, negative absolute temperatures make good theoretical sense and did occur in the experiments designed to produce them.

  • Figure
  • Received 13 October 2016

DOI:https://doi.org/10.1103/PhysRevE.95.012125

©2017 American Physical Society

Physics Subject Headings (PhySH)

Statistical Physics & Thermodynamics

Authors & Affiliations

Eitan Abraham*

  • Institute of Biological Chemistry, Biophysics, and Bioengineering, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom

Oliver Penrose

  • Department of Mathematics and the Maxwell Institute for Mathematical Sciences, Colin Maclaurin Building, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom

  • *E.Abraham@hw.ac.uk
  • O.Penrose@hw.ac.uk

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Issue

Vol. 95, Iss. 1 — January 2017

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