Simple spin models with non-concave entropies
arXiv:cond-mat/0504020 · doi:10.1119/1.2794350
Abstract
Two simple spin models are studied to show that the microcanonical entropy can be a non-concave function of the energy, and that the microcanonical and canonical ensembles can give non-equivalent descriptions of the same system in the thermodynamic limit. The two models are simple variations of the classical paramagnetic spin model of non-interacting spins and are solved as easily as the latter model.
v1: 11 pages, 5 figures. v2: Short, published version of v1, 6 pages, 3 figures. See v1 for the solutions of some of the problems listed in v2