  We examine structural relaxation in a supercooled glass-forming liquid
simulated by NVE molecular dynamics. Time correlations of the total kinetic
energy fluctuations are used as a comprehensive measure of the system's
approach to the ergodic equilibrium. We find that, under cooling, the total
structural relaxation becomes delayed as compared with the decay of the
component of the intermediate scattering function corresponding to the main
peak of the structure factor. This observation can be explained by collective
movements of particles preserving many-body structural correlations within
compact 3D cooperatively rearranging regions.
