Inverse magnetic catalysis in the soft-wall model of AdS/QCD

Magnetic effects on chiral phase transition have been investigated in a modified soft-wall AdS/QCD model, in which the dilaton field is taken to be negative at the ultraviolet region and positive at the infrared region as in Phys. Rev. D 93 (2016) 101901 and JHEP 04 (2016) 036. The magnetic field is introduced into the background geometry by solving the Einstein-Maxwell system. After embedding the magnetized background geometry into the modified soft-wall model, the magnetic field dependent behavior of chiral condensate is worked out numerically. It is found that, in the chiral limit, the chiral phase transition remains as a second order at finite magnetic field B, while the symmetry restoration temperature and chiral condensate decrease with the increasing of magnetic field in small B region. When including finite quark mass effect, the phase transition turns to be a crossover one, and the transition temperature still decreases with increasing magnetic field B when B is not very large. In this sense, inverse magnetic catalysis effect is observed in this modified soft-wall AdS/QCD model.