Abstract: Do we need viscous hydrodynamics at RHIC?

The evolution of bulk properties of matter in transport models provides insight into the equation of state and thermalization of hot and dense nuclear matter produced in relativistic heavy ion collisions. This can help understand the success of ideal hydrodynamic models and transport models for the description of experimental data at RHIC. The evolution is studied in the framework of the AMPT model. The most thermalized matter is in the central cell in central collisions. The bulk properties of matter in the central cell indicate that non-equilibrium dynamics, hadronization scheme, scattering cross section all contribute to thermalization. Even though the isotropy crosses one briefly during the evolution, it never stays at one for any significant period of time. The crossing comes from the influence of the transverse flow. As a result of the fast expansion of the produced matter, only partial thermalization is achieved. Thus a careful study with viscous hydrodynamics needs to be performed for relativistic heavy ion collisions.