Kinetics of structural relaxation in a constrained dynamics system

The relaxation kinetics of complex systems is discussed in terms of two models. The first one describes the process as a series of parallel reactions, while the second one considers it as a chain of sequential reactions. It is demonstrated that the first model predicts, according to the experimental observations, that the time dependence of the thermodynamic functions follows a stretched exponential law. A discussion is given on whether the effective time, tau(eff), that controls the rate of the relaxation process is to be determined: through the average of the jump frequency, 1/[nu], or by the average of the jump time, [tau].