Negative Temperature: Further Extensions
Abstract
This work is motivated by the recent paper [M. Baldovin, S. Iubini, R. Livi, and A. Vulpiani, Statistical mechanics of systems with negative temperature, arXiv:2103.12572]. The authors suggest that negative absolute temperatures are consistent with equilibrium thermodynamics. This is correct, if the environment also has negative temperature. Otherwise, such states represent the transient though maybe longlived metastable effects. Here, we consider the extension of the negative temperatures to the relativistic systems. We show that the states with negative temperature are possible in the Dirac vacuum, which is obtained by the PT symmetry transformation from the conventional Dirac sea. If such vacuum with inverse population fills the whole Universe, its thermodynamics determined by negative temperatures becomes equilibrium.
 Publication:

Soviet Journal of Experimental and Theoretical Physics Letters
 Pub Date:
 May 2021
 DOI:
 10.1134/S0021364021090058
 arXiv:
 arXiv:2104.01013
 Bibcode:
 2021JETPL.113..602V
 Keywords:

 General Relativity and Quantum Cosmology;
 Condensed Matter  Other Condensed Matter;
 High Energy Physics  Phenomenology
 EPrint:
 3 pages, no figures, accepted in JETP letters