Hyperon-mixed neutron star with universal many-body repulsion

TL;DR

This paper introduces a universal many-body repulsion model via multi-pomeron exchange to stiffen the equation of state of hyperon-rich neutron star matter, enabling neutron stars to reach observed high masses.

Contribution

The study develops a new multi-pomeron exchange potential model that maintains a stiff equation of state in hyperon-rich neutron star matter, consistent with experimental data.

Findings

Maximum neutron star mass reaches 2 solar masses with hyperon mixing.

The model's interactions align with experimental hyperon-nucleon data.

The equation of state remains sufficiently stiff despite hyperon presence.

Abstract

Neutron stars with large masses $\sim 2M_{\odot}$ require the hard stiffness of equation of state (EoS) of neutron-star matter. On the other hand, hyperon mixing brings about remarkable softening of EoS. In order to solve this problem, a multi-pomeron exchange potential (MPP) is introduced as a model for the universal many-body repulsion in baryonic systems on the basis of the Extended Soft Core (ESC) baryon-baryon interaction. The strength of MPP is determined by analyzing the nucleus-nucleus scattering with the G-matrix folding model. The interactions in $\Lambda\!N$, $\Sigma\!N$ and $\Xi\!N$ channels are shown to be consistent with experimental indications. The EoS in neutron-star matter with hyperon mixing is obtained from ESC in addition of MPP, and mass-radius relations of neutron stars are derived. The maximum mass is shown to reach $2M_{\odot}$ even in the case of including hyperon mixing on the basis of model-parameters determined by terrestrial experiments.