Ensemble equivalence for general many-body systems

Abstract: It has been proved for a class of mean-field and long-range systems that the concavity of the thermodynamic entropy determines whether the microcanonical and canonical ensembles are equivalent at the level of their equilibrium states, i.e., whether they give rise to the same equilibrium states. Here we show that this correspondence is actually a general result of statistical mechanics: it holds for any many-body system for which equilibrium states can be defined and in principle calculated. The same correspondence applies for other dual statistical ensembles, such as the canonical and grand-canonical ensembles.