Hyperon puzzle and the RMF model with scaled hadron masses and coupling constants

TL;DR

This paper explores a relativistic mean-field model with density-dependent hadron masses and couplings, demonstrating a mechanism to stiffen the equation of state of dense matter and potentially resolve the hyperon puzzle in neutron stars.

Contribution

It introduces a novel approach where nucleon mass stabilization at high densities stiffens the EoS, addressing the hyperon puzzle in neutron star modeling.

Findings

Stiffening of the EoS at high densities increases maximum neutron star mass.

Inclusion of hyperons and phi meson mass reduction maintains a stiff EoS.

Mechanism for nucleon mass stabilization can be realized through a scalar field term.

Abstract

The equation of state of cold baryonic matter is studied within a relativistic mean-field model with hadron masses and coupling constants depending on a scalar field. We demonstrate that if the effective nucleon mass stops to decrease with a density increase at densities $n>n_*>n_0$, where $n_0$ is the nuclear saturation density, the equation of state stiffens for these densities and the limiting neutron star mass increases. The stabilization of the nucleon mass can be realised if in the equation of motion for the scalar mean-field there appear a term sharply varying in a narrow vicinity of the field value corresponding to the density $n_*$. We show several possible realizations of this mechanism getting sufficiently stiff equations of state. The appearance of hyperons in dense neutron star interiors is accounted for. The obtained equations of state remain sufficiently stiff if the reduction of the $\phi$ meson mass is incorporated. Thereby, the hyperon puzzle can be resolved.