Shear Viscosity in a Gluon Gas

The relation of the shear viscosity coefficient to the recently introduced transport rate is derived within relativistic kinetic theory. We calculate the shear viscosity over entropy ratio \eta/s for a gluon gas, which involves elastic gg-> gg perturbative QCD (PQCD) scatterings as well as inelastic gg<->ggg PQCD bremsstrahlung. For \alpha_s=0.3 we find \eta/s=0.13 and for \alpha_s=0.6, \eta/s=0.076. The small \eta/s values, which suggest strongly coupled systems, are due to the gluon bremsstrahlung incorporated.