Shear viscosity in weakly coupled N=4 super Yang-Mills theory compared to QCD

We compute the shear viscosity of weakly coupled N = 4 supersymmetric Yang-Mills theory. Our result for eta/s, the viscosity to entropy-density ratio, is many times smaller than the corresponding weak-coupling result in QCD. This suggests that eta/s of QCD near the transition point is several times larger than the viscosity bound, eta/s >= 1/4 pi.