System-size scaling of Boltzmann and alternate Gibbs entropies

Abstract

It has recurrently been proposed that the Boltzmann textbook definition of entropy $S(E)=k\ln \Omega (E)$ in terms of the number of microstates $\Omega (E)$ with energy $E$ should be replaced by the expression $S_G(E)=k\ln {\sum }_{E^{\prime }<E}\Omega (E^{\prime })$ examined by Gibbs. Here, we show that $S_G$ either is equivalent to $S$ in the macroscopic limit or becomes independent of the energy exponentially fast as the system size increases. The resulting exponential scaling makes the realistic use of $S_G$ unfeasible and leads in general to temperatures that are inconsistent with the notions of hot and cold.

7 pages, 3 figures

References in corpus (3)

• Negative Absolute Temperature for Motional Degrees of Freedom
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• Equilibration rates and negative absolute temperatures for ultracold atoms in optical lattices

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