Electrical Conductivity of Hot QCD Matter

We study the electric conductivity of hot QCD matter at various temperatures T within the off-shell parton-hadron-string dynamics transport approach for interacting partonic, hadronic or mixed systems in a finite box with periodic boundary conditions. The response of the strongly interacting system in equilibrium to an external electric field defines the electric conductivity σ(0). We find a sizable temperature dependence of the ratio σ(0)/T well in line with calculations in a relaxation time approach for T(c)<T<2.5T(c). The ratio drops in the hadronic phase with T, shows a minimum close to T(c), and becomes approximately constant (~0.3) above ~5T(c). Our findings imply that the QCD matter even at T ≈ T(c) is a much better electric conductor than Cu or Ag (at room temperature).