  Following our recenty proposed self-consistent mean-field approximation
approach, we have done some researches on the chiral phase transition of strong
interaction matter within the framework of Nambu-Jona-Lasinio (NJL) model. The
chiral susceptibility and equation of state (EOS) are computed in this work for
both two-flavor and three-flavor quark matter for contrast. The Pauli-Villars
scheme, which can preserve gauge invariance, is used in this paper. Moreover,
whether the three-flavor quark matter is more stable than the two-flavor quark
matter or not in quark stars is discussed in this work. In our model, when the
bag constant are the same, the two-flavor quark matter has a higher pressure
than the three-flavor quark matter, which is different from what Witten
proposed in his pioneering work.
