Title: Magnetic susceptibility of QCD matter

Speaker: Prof. Gunnar Bali, University of Regensburg, Germany

Abstract: While magnetic field strengths created in solid state physics laboratory experiments do not exceed 10^6 Gauss, corresponding to (40 eV)^2, much stronger fields can be present in compact astrophysical objects like magnetars or during neutron star mergers as well as in heavy ion collisions. These fields are so strong that in their presence the properties of strongly interacting matter will change, possibly with observable consequences. I will describe theoretical expectations relating to matter in such environments. These have mostly been obtained by lattice QCD simulations. QCD matter turns out to be paramagnetic at zero temperature, diamagnetic at low temperatures and again paramagnetic at high temperatures. The magnetic susceptibility can be decomposed into Pauli spin and angular momentum related Landau contributions. Most intriguingly and contrary to conventional solid state materials, it is the Pauli term which is responsible for the diamagnetism at low temperatures.