Nonstrange quark stars from an NJL model with proper-time regularization

摘要

The structure of a light quark star is studied within a new two-flavor Nambu-Jona-Lasinio 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 regularization procedure, we introduce the proper-time regularization. We also employ the newly proposed definition of vacuum pressure [J. Phys. G 45, 105001 (2018)], in which the quasi-Wigner vacuum (corresponding to the quasi-Wigner solution of the gap equation) is used as the reference ground state. The free parameters include only a mixing constant α which weighs the contribution from the Fierz-transformed Lagrangian. We constrain α to be around 0.9 by the observed mass of pulsars PSR J0348 + 0432 and PSR J1614-2230. We find that the calculated surface energy density meets the requirement (>2.80 × 10~(14) g/cm~3) [Phys. Rev. D 99, 043001 (2019)]. Besides, for a 1.4-solar-mass star, the deformability Λ is calculated, which is consistent with a recent analysis on the binary neutron star merger GW170817 with Λ in (0,630) for large component spins and 300 +420 -230 when restricting the magnitude of the component spins [Phys. Rev. X 9, 011001 (2019)], and satisfies the constraints 200 < Λ < 800 of early works.