Recent progress in understanding relaxation in complex systems

Abstract The evolution of dynamics with time in complex interacting systems is shown to be general. The caged dynamics exemplified by the nearly constant loss (NCL), is followed in time and terminated by the primitive relaxation, which is called the Johari–Goldstein β-relaxation in the case of glass-forming substances. The latter is the precursor of the many-body relaxation process which increases in length-scale with time until the terminal relaxation is reached to determine the transport coefficient. Using experimental data, we show these three ubiquitous features in the dynamics are inter-related as shown by correlations in their properties, and hence all must be considered together. The dynamics of hydrated proteins are chosen here as an example for detailed discussion. These three major processes and their inter-relations are found in hydrated proteins. An interpretation of the data follows along the line of other complex systems exhibiting similar dynamics.