Entropy production in collisions of gravitational shock waves and of heavy ions

We calculate the area of a marginally trapped surface formed by a head-on collision of gravitational shock waves in AdS_D. We use this to obtain a lower bound on the entropy produced after the collision. A comparison to entropy production in heavy ion collisions is included. We also discuss an O(D-2) remnant of conformal symmetry which is present in a class of gravitational shock wave collisions in AdS_D and which might be approximately realized (with D=5) in central heavy-ion collisions.