  In this paper, we derived a critical condition for matter equilibration in
heavy ion collisions using a holographic approach. A gravitational shock waves
with infinite transverse extension is used to model infinite nucleus. We
constructed the trapped surface in the collision of two asymmetric planar shock
waves with sources at different depth in the bulk AdS and formulated a critical
condition for matter equilibration in collision of "nucleus" in the dual gauge
theory. We found the critical condition is insensitive to the depth of the
source closer to the AdS boundary. To understand the origin of the critical
condition, we computed the Next to Leading Order stress tensor in the boundary
field theory due to the interaction of the nucleus and found the critical
condition corresponds to the breaking down of the perturbative expansion. We
indeed expect non-perturbative effects be needed to describe black hole
formation.
