Application of the Non-Perturbative Renormalization Group to the Nambu-Jona-Lasinio/Gross-Neveu Model at Finite Temperature and Chemical Potential

The chiral phase structure of the Nambu-Jona-Lasinio/Gross-Neveu model at finite temperature T and finite chemical potential µ is investigated using the (Wilsonian) nonperturbative renormalization group (NPRG).In the large N c limit, the solutions of NPRG with various cutoff schemes are given.For a sufficiently large ultraviolet cutoff, the NPRG results coincide with those of the Schwinger-Dyson equation and have little cutoff scheme dependence.Next, to improve the approximation, we incorporate the mesonic fluctuations.We introduce the auxiliary fields for mesons and then derive NPRG equation for finite N c .The chiral phase structure on the (T, µ) plane beyond the leading order of the 1/N c expansion is investigated in the sharp cutoff limit.The N c dependence of the chiral phase diagram is obtained.