  The hot and dense matter created in the early stage of a relativistic heavy
ion collision is composed mainly of gluons. Radiative processes can play an
important role for the thermalization of such partonic systems. The simplest
parton number changing processes are commonly described by the Gunion-Bertsch
formula. We show that the cross section from the exact matrix element for the
lowest order radiative process could be significantly smaller than that based
on the Gunion-Bertsch formula. In light of this, we discuss the role of
radiative processes on the equilibrium and equilibration of a gluon plasma.
