Why diffusion decouples from viscosity near the glass transition

Near $T_g$ in molecular liquids such as o-terphenyl, $D\eta/T$ exceeds its high-temperature value by roughly two to three orders of magnitude (approximate), and $D\sim \tau_{\alpha}^{-\xi}$ with a fractional exponent reported near 0.75 to 0.85. Predict the magnitude, temperature dependence and exponent $\xi$ from a theory of dynamic heterogeneity, and explain why rotational diffusion follows viscosity more closely than translational diffusion.

A theory that predicts $D(T)$, $\eta(T)$ and the decoupling exponent for a model liquid and agrees with simulations and with measurements on molecular glass formers.