Entropy as an adiabatic invariant

TL;DR

This paper critically examines the concept of entropy as an adiabatic invariant and offers a brief critique of a prior work on negative absolute temperatures, emphasizing the importance of rigorous thermodynamic definitions.

Contribution

It provides a concise critique of Dunkel and Hilbert's work on negative temperatures, highlighting issues in their thermodynamic approach.

Findings

Raises questions about the validity of negative absolute temperatures

Highlights the importance of consistent thermodynamic definitions

Calls for further discussion and clarification in the field

Abstract

This short article was submitted to Nature Physics as a Correspondence. The intention was to provide a brief albeit significant criticism of the work of J. Dunkel and S. Hilbert, \textit{Consistent Thermostatistics Forbids Negative Absolute Temperatures}, Nature Physics \textbf{10}, (2014). The respected editor decided not to publish the Correspondence. We have therefore decided to submit the paper to arXiv. Comments/criticisms are welcomed, particularly from the authors of the mentioned paper.