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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 sigma_0. We find a sizable temperature dependence of the ratio sigma_0/T well in line with calculations in a relaxation time approach for Tc<T<2.5Tc. The ratio drops in the hadronic phase with T, shows a minimum close to Tc, and becomes approximately constant (~0.3) above ~5Tc. Our findings imply that the QCD matter even at T=Tc is a much better electric conductor than Cu or Ag (at room temperature).