  We investigate via Monte Carlo simulations the kinetically constrained
Kob-Andersen lattice glass model showing that, contrary to current
expectations, the relaxation process and the dynamical heterogeneities seems to
be characterized by different time scales. Indeed, we found that the relaxation
time is related to a reverse percolation transition, whereas the time of
maximum heterogeneity is related to the spatial correlation between particles.
This investigation leads to a geometrical interpretation of the relaxation
processes and of the different observed time scales.
