Hints of incomplete thermalization in RHIC data

The large elliptic flow observed in Au- Au collisions at RHIC is often put forward as a compelling evidence for the formation of a strongly interacting quark-gluon plasma. The main argument is that the measured elliptic flow is as large as the value given by fluid dynamics models that assume complete thermalization. It is argued that this claim may not be justified, since a detailed examination of experimental data rather suggests that the system created is not fully equilibrated at the time when anisotropic flow develops.