  We consider the evolution of a parton plasma created in Au+Au collisions at
LHC and at RHIC energies. Using Boltzmann equation, relaxation time
approximation and perturbative QCD, we show the physics of both thermal and
chemical equilibration in a transparent manner. In particular, we show
inelastic processes are, contrary to common assumption, more important than
elastic processes, the state of equilibration of the system can compensate for
some powers of $\a_s$ for the purpose of equilibration, the two-stage
equilibration scenario is, barring any unknown non-perturbative effects,
inevitable and is an intrinsic feature of perturbative QCD, and gluon
multiplication is the leading process for entropy generation.
