The RG flow of Nambu–Jona-Lasinio model at finite temperature and density

We study the Nambu–Jona-Lasinio model at finite temperature and finite density by using the functional renormalization group. The RG flows of the four-Fermi coupling constant in the NJL model are investigated. We obtain the chiral phase boundary in cases of the large-[Formula: see text] leading approximation and an improved approximation. The large-[Formula: see text] nonleading term at the vanishing temperature has a singularity at the Fermi surface. We show that the quantum corrections by the large-[Formula: see text] nonleading term largely influence the phase boundary at low temperature and high density region.