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First-order microcanonical transitions in finite mean-field models

Mickael Antoni·Stefano Ruffo·Alessandro Torcini
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Abstract

A microcanonical first order transition, connecting a clustered to a homogeneous phase, is studied from both the thermodynamic and dynamical point of view for a N-body Hamiltonian system with infinite-range couplings. In the microcanonical ensemble specific heat can be negative, but besides that, a microcanonical first order transition displays a temperature discontinuity as the energy is varied continuously (a dual phenomenon to the latent heat in the canonical ensemble). In the transition region, the entropy per particle exhibits, as a function of the order parameter, two relative maxima separated by a minimum. The relaxation of the metastable state is shown to be ruled by an activation process induced by intrinsic finite N fluctuations. In particular, numerical evidences are given that the escape time diverges exponentially with N, with a growth rate given by the entropy barrier.

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Mickael Antoni, Stefano Ruffo, Alessandro Torcini. 2004-01-12. First-order microcanonical transitions in finite mean-field models. https://doi.org/10.1209/epl%2Fi2004-10028-6

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