The chiral transition in a magnetic background: Finite density effects and the functional renormalization group

We compute the phase diagram of the quark-meson model at finite temperature, finite baryon chemical potential μ B = 3 μ and constant external magnetic field B, using the functional renormalization group. Our results show that the critical temperature increases as a function of B at μ = 0, but for values μ larger than about 210 − 225 MeV, the opposite behavior is realized. As the magnetic field increases, the critical point (T * , μ *) moves from large μ, small T towards small μ, larger T in the μ-T phase diagram