Statistical mechanics of systems with long-range interactions and negative absolute temperature
Abstract
A Hamiltonian model living in a bounded phase space and with long-range interactions is studied. It is shown, by analytical computations, that there exists an energy interval in which the microcanonical entropy is a decreasing convex function of the total energy, meaning that ensemble equivalence is violated in a negative-temperature regime. The equilibrium properties of the model are then investigated by molecular dynamics simulations: first, the caloric curve is reconstructed for the microcanonical ensemble and compared to the analytical prediction, and a generalized Maxwell-Boltzmann distribution for the momenta is observed; then, the nonequivalence between the microcanonical and canonical descriptions is explicitly shown. Moreover, the validity of Fluctuation-Dissipation Theorem is verified through a numerical study, also at negative temperature and in the region where the two ensembles are nonequivalent.
Keywords
Cite
@article{arxiv.1904.13249,
title = {Statistical mechanics of systems with long-range interactions and negative absolute temperature},
author = {Fabio Miceli and Marco Baldovin and Angelo Vulpiani},
journal= {arXiv preprint arXiv:1904.13249},
year = {2019}
}