A Modified "Bottom-up" Thermalization in Heavy Ion Collisions
  In the initial stage of the bottom-up picture of thermalization in heavy ion collisions, the gluon distribution is highly anisotropic which can give rise to plasma instability. This has not been taken account in the original paper. It is shown that in the presence of instability there are scaling solutions, which depend on one parameter, that match smoothly onto the late stage of bottom-up when thermalization takes place. 
A.H. Mueller, A.I. Shoshi and S.M.H. Wong