2026/07/15 by Matteo Razza, Andrea Carati, Luigi Galgani
Physics and Astronomy · #cond-mat.stat-mech #physics.class-ph
In this work, we numerically studied the cooling process of a Fermi--Pasta--Ulam system, which occurs when the FPU system is placed in contact with a gas whose temperature T is reduced with a certain cooling rate ξ. It was found that the existence of a weak stochastic threshold has a significant impact on the cooling process, because below such a stochastic threshold the specific FPU energy is larger than its temperature, i.e., the FPU system falls out of equilibrium. The difference remains finite in the limit T → 0, so that the FPU system maintains a residual amount of energy E0 at vanishing temperature. Our numerical simulations reveal that this energy exhibits a power--law dependence on both the system size and the cooling rate, scaling approximately as E0 ∼ (ξN)2/3.