Studies On The Chiral Transition At Finite Isospin Chemical Potential

The flavor mixing induced by the mismatched vector-isoscalar and vector-isovector interactions at finite baryon chemical potential μ and isospin chemical potential μI a is demonstrated in the Nambu-Jona-Lasinio(NJL) model of QCD. The influence of this nonanomaly flavor mixing on the possible separate chiral transitions at nonzero μI is studied under the assumption of the effective restoration of the U(1)A symmetry. We find that for the weak isospin asymmetry, the two separate phase boundaries found previously can be converted into one only if the vector-isovector coupling gvv is significantly stronger than the vector-isoscalar one gvs without the axial anomaly. When the weak Kabayashi-Maskawa-’t Hooft(KMT) interaction is included, we find that the separation of the chiral transition with two critical end points for the relatively strong isospin asymmetry can still be removed, owing to the vector interactions. In this case, it is not the vector coupling difference but the strength of gvv which is crucial for the only phase boundary. We also point out that, in the NJL-type model with mismatched vector interactions, the recently proposed equivalence for chiral transitions at finite μ and μI does not hold, even at the mean field approximation.Additionally, we study the properties of quark number and isovector susceptibilities along the phase boundary at nonzero μ and μI in NJL. We find that not only the quark number susceptibility, the isovector susceptibility also diverges at the tricritical point (TCP). However, the sigularity of the isovector susceptibility at TCP is quite mild compared to that of the quark number susceptibility since μI is small in heavy ion collisions.