Electric and magnetic response of hot QCD matter

We study the electric conductivity as well as the magnetic response of hot QCD matter at various temperatures T and chemical potentials mu(q) within the off-shell parton-hadron-string dynamics transport approach for interacting partonic 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), whereas the response to a moderate external magnetic field defines the induced diamagnetic moment mu(L) (T, mu(q)) as well as the spin susceptibility chi(S)(T ,mu(q)). We find a sizable temperature dependence of the dimensionless ratio sigma(0)/T well in linewith calculations in a relaxation time approach for T-c < T < 2.5T(c) as well as an increase of sigma(0) with mu(2)(q)/T (2). Furthermore, the frequency dependence of the electric conductivity sigma(Omega) shows a simple functional form well in line with results from the dynamical quasiparticle model. The spin susceptibility chi(S)(T , mu(q)) is found to increase with temperature T and to rise similar to mu(2)(q)/T (2) too. The actual values for the magnetic response of the QGP in the temperature range below 250 MeV show that the QGP should respond diamagnetically in actual ultrarelativistic heavy-ion collisions since the maximal magnetic fields created in these collisions are smaller than B-c(T), which defines a boundary between diamagnetism and paramagnetism.