  We prove the emergence of spatially correlated dynamics in slowly compacting
dense granular media by analyzing analytically and numerically multi-point
correlation functions in a simple particle model characterized by slow
non-equilibrium dynamics. We show that the logarithmically slow dynamics at
large times is accompanied by spatially extended dynamic structures that
resemble the ones observed in glass-forming liquids and dense colloidal
suspensions. This suggests that dynamic heterogeneity is another key common
feature present in very different jamming materials.
