First-order microcanonical transitions in finite mean-field models

Year: 2004

Authors: Antoni M., Ruffo S., Torcini A.

Autors Affiliation: UMR-CNRS 6171 – Université d’Aix Marseille III, Av. Esc. Normandie-Niemen 13397 Marseille Cedex 20, France;
Dipartimento d’Energetica “S. Stecco” and CSDC Università di Firenze and INFN and INFM, V. S. Marta 3, 50139 Firenze, Italy;
Istituto Nazionale di Ottica Applicata, Largo E. Fermi 6, 50125 Firenze, Italy

Abstract: A microcanonical first-order transition, connecting a clustered to a homogeneous phase, is studied from both the thermodynamic and the dynamical point of view for an 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.

Journal/Review: EUROPHYSICS LETTERS

Volume: 66 (5)      Pages from: 645  to: 651

KeyWords: Metastable States; Relaxation; System
DOI: 10.1209/epl/i2004-10028-6

ImpactFactor: 2.229
Citations: 31
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