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 $\phi$ self-interaction and $\phi$-$\rho$ 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 $z_{v}\le0.15$. 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.