Frankfurt 2014 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 33: Schwerionenkollisionen und QCD Phasen

HK 33.8: Vortrag

Mittwoch, 19. März 2014, 18:30–18:45, HZ 6

Electric and magnetic response of hot QCD matter — •Thorsten Steinert and Wolfgang Cassing — Institut für Theoretische Physik, Universität Giessen, 35392 Giessen, Germany

We study the electric conductivity as well as the magnetic response of hot QCD matter at various temperatures T and chemical potentials µ_q within the off-shell Parton-Hadron-String Dynamics (PHSD) 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 σ₀ whereas the response to a moderate external magnetic field defines the induced diamagnetic moment µ_L (T, µ_q) as well as the spin susceptibility χ_S(T, µ_q). We find a sizeable temperature dependence of the dimensionless ratio σ₀/T well in line with calculations in a relaxation time approach for T_c < T < 2.5   T_c as well as an increase of σ₀ with µ_q²/T². Furthermore, the frequency dependence of the electric conductivity σ(Ω) shows a simple functional form well in line with results from the Dynamical QuasiParticle Model (DQPM). The spin susceptibility χ_S(T,µ_q) is found to increase with temperature T and to rise ∼ µ_q²/T², 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 ultra-relativistic 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.