The QCD phase diagram for external magnetic fields
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- Bali, G.S., Bruckmann, F., Endrődi, G. et al. J. High Energ. Phys. (2012) 2012: 44. doi:10.1007/JHEP02(2012)044
The effect of an external (electro)magnetic field on the finite temperature transition of QCD is studied. We generate configurations at various values of the quantized magnetic flux with Nf = 2 + 1 flavors of stout smeared staggered quarks, with physical masses. Thermodynamic observables including the chiral condensate and susceptibility, and the strange quark number susceptibility are measured as functions of the field strength. We perform the renormalization of the studied observables and extrapolate the results to the continuum limit using Nt = 6, 8 and 10 lattices. We also check for finite volume effects using various lattice volumes. We find from all of our observables that the transition temperature Tc significantly decreases with increasing magnetic field. This is in conflict with various model calculations that predict an increasing Tc(B). From a finite volume scaling analysis we find that the analytic crossover that is present at B = 0 persists up to our largest magnetic fields eB ≈ 1 GeV2, and that the transition strength increases mildly up to this eB ≈ 1 GeV2.