Search

The structure of light quark star is studied within a new two-flavor NJL model. By retaining the contribution from the vector term in the Fierz-transformed Lagrangian, a two-solar-mass pure quark star is achieved. To overcome the disadvantage of three-momentum truncation in the regularisation procedure, we introduce the proper-time regularisation. We also employ the newly proposed definition of vacuum pressure, in which the quasi-Wigner vacuum (corresponding to the quasi-Winger solution of the gap equation) is used as the reference ground state. Free parameter includes only a mixing constant $\alpha$ which weighs contribution from Fierz-transformed Lagrangian. We constrain $\alpha$ to be around $0.9$ by the observed mass of pulsars $PSR J0348+0432$ and $PSR J1614-2230$. We find the calculated surface energy density meets the requirement ($> 2.80\times10^{14}$g/cm$^3 $). Besides, for a 1.4 solar mass star, the tidal Love number $k_2$ and deformability $\Lambda$ are calculated which satisfies the constrain $200 < \Lambda < 800$.

Based on the two flavor NJL model with a proper time regularization, we used stationary wave condition (SWC) for the first time to study the influence of the finite volume effects on the chiral phase transition of quark matter at finite temperature. It is found that when the cubic volume size L is large than LSWC = 500 fm, the chiral quark condensate is indistinguishable from that max at L = $\infinity$,Here it should be noted that 500 fm is far greater than the size of QGP produced at laboratory and the lattice QCD simulation space size. It is also much larger than the previous limit size LAPBC = 5 fm estimated by the commonly used anti-periodic boundary condition (APBC). max We also found that when the space size L is less than LSWC = 0.25 fm, the spontaneous symmetry min breaking concept is no longer valid. In addition, we first introduce the spatial susceptibility, and through the study of the spatial susceptibility, it was revealed for the first time that the chiral phase transition caused by the finite volume effects in the nonchiral limit is a crossover.