Equation of state for hyperonic neutron-star matter in SU(3) flavor symmetry

Abstract

Using a relativistic mean-field model calibrated to finite-nucleus observables and bulk properties of dense nuclear matter, we investigate hyperonic neutron-star matter within an SU(3) flavor-symmetry scheme. To retain SU(6)-based couplings within SU(3) flavor symmetry, we add a quartic $\varphi$ self-interaction and $\varphi$-$\rho$ mixing. We demonstrate the roles of ${\alpha }_v$ ($F/(F+D)$ ratio), ${\theta }_v$ (mixing angle), and $z_v$ (singlet-to-octet coupling ratio) in SU(3)-invariant vector-meson couplings. It is found that $z_v$ predominantly controls the maximum mass of a neutron star, and $2M_{\odot }$ neutron stars can be supported for $z_v\le 0.15$. The ${\alpha }_v$ also helps sustain large masses, whereas ${\theta }_v$ has a smaller effect on neutron-star properties. This SU(3) framework reconciles nuclear and astrophysical constraints, and offers a plausible resolution to the hyperon puzzle.

Comments: 15 pages, 7 figures, 3 tables