Quark-quark interaction and quark matter in neutron stars

TL;DR

This paper investigates the impact of quark interactions and phase transitions on neutron star properties, demonstrating that incorporating quark matter can produce maximum neutron star masses consistent with recent astronomical observations.

Contribution

It introduces a unified framework handling hyperon mixing and quark deconfinement effects using Brueckner-Bethe-Goldstone theory, achieving realistic neutron star mass predictions.

Findings

Maximum neutron star masses exceed 2 solar masses.

Quark matter inclusion stiffens the EoS, aligning with observational data.

Phase transitions do not reduce maximum mass below 2 solar masses.

Abstract

Hyperon ($Y$) mixing in neutron-star matter brings about a remarkable softening of the equation of state (EoS) and the maximum mass is reduced to a value far less than $2M_{\odot}$. One idea to avoid this "hyperon puzzle in neutron stars" is to assume that the many-body repulsions work universally for every kind of baryons. The other is to take into account the quark deconfinement phase transitions from a hadronic EoS to a sufficiently stiff quark-matter EoS. In the present approach, both effects are handled in a common framework. As well as the hadronic matter, the quark matter with the two-body quark-quark interactions are treated within the Brueckner-Bethe-Goldstone theory beyond the mean field frameworks, where interaction parameters are based on the terrestrial data. The derived mass-radius relations of neutron stars show that maximum masses reach over $2M_{\odot}$ even in the cases of including hadron-quark phase transitions, being consistent with the recent observations for maximum masses and radii of neutron stars by the NICER measurements and the other multimessenger data.