Magnetic catalysis (and inverse catalysis) at finite temperature in two-color lattice QCD

Two-color lattice QCD with N-f = 4 staggered fermion degrees of freedom (no rooting trick is applied) with equal electric charge q is studied in a homogeneous magnetic background field B and at nonzero temperature T. In order to circumvent renormalization as a function of the bare coupling, we apply a fixed-scale approach. We study the influence of the magnetic field on the critical temperature. At rather small pseudoscalar meson mass [m(pi) approximate to 175 MeV approximate to T-c(B = 0)] we confirm a monotonic rise of the quark condensate <(psi) over bar psi > with increasing magnetic field strength, i.e., magnetic catalysis, as long as one is staying within the confinement or deconfinement phase. In the transition region we find indications for a nonmonotonic behavior of Tc(B) at low magnetic field strength (qB < 0.8 GeV2) and a clear rise at stronger magnetic field. The conjectured existence of a minimum value T-c(B*) < Tc(B = 0) would leave a temperature window for a decrease of <(psi) over bar psi > with rising B (inverse magnetic catalysis) also in the present model.