  Employing a perturbative QCD based parton cascade we calculate the elliptic
flow $v_2$ and its transverse momentum dependence $v_2(p_T)$ for the gluon
matter created in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. To make
comparisons with the experimental data at the BNL Relativistic Heavy Ion
Collider (RHIC), parton-hadron duality is assumed. We find that whereas the
integrated $v_2$ matches the experimental data, the gluon (or pion) $v_2(p_T)$
is about 20-50% smaller than the experimental data. Hadronization via gluon
fragmentation and quark recombination seems to be the key to explaining the
necessary jump of $v_2(p_T)$ from the partonic to the hadronic phase. We also
show that the elliptic flow values moderately depend on the chosen freezeout
condition, which will thus constrain the shear viscosity to the entropy density
ratio of the quark gluon plasma created at RHIC.
