Macroscopic transformation of irreversible processes in coupled many-mode systems off equilibrium

Abstract

With the aid of machine computation, we investigated the time evolution of nonlinearly coupled Langevin equations with 20 modes as a specific example of nonlinear systems off equilibrium. If the strength of an external excitation, which is restricted to a few particular modes, is sufficiently small, the asymptotic motion observed in the phase space of 20 modes approaches a fixed point while undergoing fluctuations. As the strength exceeds a certain critical value, the motion transits to a limit-cycle-like motion in the phase space. The rate of orbit separation between an arbitrary pair of modes participating in the limit-cycle-like motion is much greater than the similar rate observed in the fixed-point-like motion. The irreversible decay rate of the asymptotic structure decreases as the intensity of random forces decreases, confirming that the most stable structure realized in the asymptotic time limit of a nonlinear system off equilibrium is the one with the least irreversible decay rate.