Niklas Mueller (University of Heidelberg, Germany)
Magnetic catalysis and inverse magnetic catalysis in QCD
We investigate the effects of strong magnetic fields on the QCD phase structure at vanishing density by solving the gluon and quark
gap equations. The chiral crossover temperature as well as the
chiral condensate is computed. For asymptotically large
magnetic fields we find magnetic catalysis, while we find inverse
magnetic catalysis for intermediate magnetic fields. Moreover, for
large magnetic fields the chiral phase transition for massless
quarks turns into a crossover.
The underlying mechanisms are then investigated analytically within
a few simplifications of the full numerical analysis. We find that a
combination of gluon screening effects and the weakening of the
strong coupling is responsible for the phenomenon of inverse
catalysis seen in lattice studies. In turn, the magnetic catalysis
at large magnetic field is already indicated by simple arguments
based on dimensionality.