Geometry of Empty Space is the Key to Near-Arrest Dynamics
  We study several examples of kinetically constrained lattice models using dynamically accessible volume as an order parameter. Thereby we identify two distinct regimes exhibiting dynamical slowing, with a sharp threshold between them. These regimes are identified both by a new response function in dynamically available volume, as well as directly in the dynamics. Results for the selfdiffusion constant in terms of the connected hole density are presented, and some evidence is given for scaling in the limit of dynamical arrest. 
Aonghus Lawlor, Paolo De Gregorio, Phil Bradley, Mauro Sellitto, and   Kenneth A. Dawson