QCD at High Temperature : Results from Lattice Simulations with an   Imaginary mu
  We summarize our results on the phase diagram of QCD with emphasis on the high temperature regime. For $T \ge 1.5 T_c$ the results are compatible with a free field behavior, while for $T \simeq 1.1 T_c$ this is not the case, clearly exposing the strongly interacting nature of QCD in this region 
Massimo D'Elia, Francesco Di Renzo, Maria Paola Lombardo