Volume 75, Number 4, August 2006
|Page(s)||528 - 534|
|Published online||19 July 2006|
Metastability in specific-heat measurements: Simulations with the FPU model
Department of Mathematics, Università di Milano Via Saldini 50, 20133 Milano, Italy
Accepted: 3 July 2006
In this letter we report numerical results giving, as a function of time, the energy fluctuation of a Fermi-Pasta-Ulam system in dynamical contact with a heat bath, the initial data of the FPU system being extracted from a Gibbs distribution at the same temperature of the bath. The aim is to get information on the specific heat of the FPU system in the spirit of the fluctuation-dissipation theorem. While the standard equilibrium result is recovered at high temperatures, there exists a critical temperature below which the energy fluctuation as a function of time tends to an asymptotic value sensibly lower than the one expected at equilibrium. This fact appears to exhibit the existence of a metastable state for generic initial conditions. An analogous phenomenon of metastability was up to now observed in FPU systems only for exceptional initial data having vanishing Gibbs measure, namely excitations of a few low-frequency modes (as in the original FPU work).
PACS: 05.45.-a – Nonlinear dynamics and chaos / 05.20.-y – Classical statistical mechanics
© EDP Sciences, 2006
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