Exponential growth of space-like gluon distribution functions

The ordinary damping processes that drive gluon distribution functions to their equilibrium form can produce exponential growth in frames where the plasma has a non-zero flow velocity. This occurs when kμ is space-like and k . u is negative. For propagation from space-time point yα to zα the exponential growth is in the center of mass coordinate xα (yα + zα)/2 projected along the space-like momentum. Thus f(k, x) grows exponentially in the variable kαxα/k2. (orig.)