EN
A new probabilistic representation of the multichannel relaxation mechanism, which generates the universal two power-law relaxation response with the stretched exponential and the classical exponential decays as special cases, is presented. The consideration of irreversible stochastic transitions of complex systems is based on a general probabilistic formalism applied to the analysis of the first passage of a system. By means of limit theorems the origins of the universality of relaxation responses are indicated. This approach, without referring to the conventional stochastic transition description, allows us to derive explicitly the intensity of transition from an initial state for a complex system in the most general case of parallel channel relaxation with a random number of transition channels, each characterized by an individual relaxation rate. The nonexponential relaxation is shown to result from general properties of transition channels only, namely, from the asymptotical self-similar behavior of their relaxation rate distributions. For the reader’s convenience a survey of limit theorems of probability theory is included in the Appendix.