  In the flat space, non-spherical shells collapse to give globular cluster
after many oscillations. We show that in anti de sitter space, they form black
holes in one dynamical time. We propose that this is the mechanism of early
thermalization in strong quark-gluon plasma in gravity dual. This is traced
back to the a remarkable property of AdS : the period in radial motion is
amplitude independent in spite of the NON-linearity of the equation of motion.
We investigate the interaction effect numerically and observe the same
qualitative behavior for the attractive forces. For repulsive interactions,
particles halt at a small but finite radius for long time due to the specific
structure of the bulk AdS propagator. It helps hair creation in the AdS black
hole.
