Effects of vector coupling on chiral and color-superconducting phase transitions - interplay among the scalar, pairing and vector interaction Original Research Article

We investigate effects of the vector interaction appearing in chiral effective Lagrangians on the chiral and color superconducting (CSC) phase transitions using Nambu-Jona-Lasinio model. It is shown that the repulsive density-density interaction coming from the vector term enhances competition between the chiral symmetry breaking (κSB) and CSC phase transition: When the vector coupling is increased, the first order transition between the κSB and CSC phase becomes weaker, and the coexisting phase in which both the chiral and color-gauge symmetries are dynamically broken comes to exisit in a wider region in the T-μ plane. We find that the critical line of the first order transition can have two endpoints for an intermediate range of the vector coupling.