Fluctuations in the relaxation dynamics of mixed chaotic systems

The relaxation dynamics in mixed chaotic systems are believed to decay algebraically with a universal decay exponent that emerges from the hierarchical structure of the phase space. Numerical studies, however, yield a variety of values for this exponent. In order to reconcile these results, we consider an ensemble of mixed chaotic systems approximated by rate equations and analyze the fluctuations in the distribution of Poincaré recurrence times. Our analysis shows that the behavior of these fluctuations, as a function of time, implies a very slow convergence of the decay exponent of the relaxation.