Microscopic theory of heterogeneity and nonexponential relaxations in supercooled liquids.

Recent experiments show that supercooled liquids around the glass transition temperature are "dynamically heterogeneous" [H. Sillescu, J. Non-Cryst. Solids 243, 81 (1999)]. Such heterogeneity is expected from the random first order transition theory of the glass transition. Using a microscopic approach based on this theory, we derive a relation between the departure from Debye relaxation as characterized by the beta value of a stretched exponential response function, phi(t) = e(-(t/tau(KWW))beta), and the fragility of the liquid. The beta value is also predicted to depend on temperature and to vanish as the ideal glass transition is approached at the Kauzmann temperature.