Dynamical arrest, tracer diffusion and Kinetically Constrained Lattice   Gases
  We analyze the tagged particle diffusion for kinetically constrained models for glassy systems. We present a method, focusing on the Kob-Andersen model as an example, which allows to prove lower and upper bounds for the self diffusion coefficient $D_S$. This method leads to the exact density dependence of $D_{S}$, at high density, for models with finite defects and to prove diffusivity, $D_{S}>0$, at any finite density for highly cooperative models. A more general outcome is that under very general assumptions one can exclude that a dynamical transition, like the one predicted by the Mode-Coupling-Theory of glasses, takes place at a finite temperature/chemical potential for systems of interacting particles on a lattice. 
Cristina Toninelli, Giulio Biroli