The mode coupling theory of structural relaxations
Already Maxwell assumed that there are slow, strongly temperature dependent re laxation processes in liquids. Upon supercooling the time scale rQ of these processes can become of macroscopic size. This means that rQ becomes comparable to the time scale iexp, characterizing the experiment which is designed to probe the sys tem ’s dynamics. The origin of the mentioned processes is anticipated to be the cooperative motion of large clusters of molecules, and these processes are therefore referred to as structural relaxation. The slowest of these is called the a - relaxation process.