Strange quark stars within proper time regularized (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>2</mml:mn><mml:mo>+</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math>)-flavor NJL model
Cheng-Ming Li, Shu-Yu Zuo, Yan Yan, Ya-Peng Zhao, Fei Wang, Yong-Feng Huang, Hong-Shi Zong
Abstract
In this work, we use the equation of state (EOS) of the ($2+1$)-flavor Nambu-Jona-Lasinio (NJL) model to study the structure of the strange quark star. With a new free parameter $\ensuremath{\alpha}$, the Lagrangian is constructed by two parts, the original NJL Lagrangian and the Fierz transformation of it, as $\mathcal{L}=(1\ensuremath{-}\ensuremath{\alpha}){\mathcal{L}}_{\mathrm{NJL}}+\ensuremath{\alpha}{\mathcal{L}}_{\text{Fierz}}$. To determine the range of $\ensuremath{\alpha}$, we compare the binding energies in the two-flavor and ($2+1$)-flavor cases. We also consider the constraints of chemical equilibrium and electric charge neutrality in the strange quark star and choose six representative EOSs with different $\ensuremath{\alpha}$ and $B$ (bag constant) to study their influence on the structure of the strange quark star. As a result, we find that a larger $\ensuremath{\alpha}$ and a smaller $B$ correspond to a heavier star with a stiffer EOS. Furthermore, the heaviest strange quark star is in agreement with not only the recent mass observation of PSR $\mathrm{J}0740+6620$ and the x-ray observations on radius measurements, but also the constraint on the tidal deformability of GW170817.