Shear viscosity to entropy density ratio of Hagedorn states

The fireball concept of Hagedorn, developed in the 1960s, is an alternative description of hadronic matter. Using a recently derived description yielding the mass spectrum and the dynamics, we use the transport model GiBUU to calculate the shear viscosity of a gas of such Hagedorn states, applying the Green-Kubo method to Monte Carlo calculations. Since the entropy density is rising ad infinitum near T-H, this leads to a very low shear viscosity to entropy density ratio near T-H. Further, by comparing our results with analytic expressions, we find a nice extrapolation behavior, indicating that a gas of Hagedorn states comes close to or even goes below the boundary 1/4 pi from AdS/CFT.