Uniqueness of Gibbs entropy within the microcanonical formalism

Michele Campisis

Published 2014-11-10Version 1

It is a well known fact that, within the classical microcanonical formalism, the Gibbs entropy (alias volume entropy) is a thermodynamically consistent expression of entropy. Building on the concept of uniqueness of Clausius integrating factor for the inexact heat differential (i.e., the existence of a universal temperature scale) here we show that Gibbs entropy is the unique consistent expression. As a consequence negative temperatures are inadmissible within the classical microcanonical formalism.