Quantum van der Waals quarkyonic matter at non-zero isospin asymmetry

TL;DR

This paper extends quantum van der Waals quarkyonic matter models to include isospin asymmetry, analyzing the phase transition, neutron star properties, and the impact of isospin-dependent interactions.

Contribution

It introduces a two-component van der Waals model with isospin dependence, providing new insights into the equation of state and neutron star characteristics under asymmetric conditions.

Findings

Speed of sound peaks indicate quarkyonic transition.

Quarkyonic onset density varies mildly with isospin asymmetry.

Heavy neutron stars with masses ≥ 2.6 solar masses are supported.

Abstract

We extend the recently developed quantum van der Waals quarkyonic matter to non-zero isospin asymmetries by utilizing the two-component van der Waals equation with a generalized excluded volume prescription. The isospin dependence of van der Waals interaction parameters is determined by constraints on the symmetry energy, slope of the symmetry energy, and nuclear ground state properties. We find that the speed of sound has a peak for all values of the asymmetry parameter, signifying a transition to quarkyonic matter. The quarkyonic matter onset density is found to have a mild dependence on isospin asymmetry, with specific details influenced by the isospin dependence of the repulsive interactions. We also incorporate leptonic degrees of freedom and explore the neutron star matter equation of state, calculating mass-radius relations and tidal properties of neutron stars. We find that quarkyonic matter supports heavy neutron stars with a maximum mass of at least 2.6 solar masses. We observe quantitatively different behavior for the excluded volume cases of isospin-blind ($b_{n}=b_{pn}$) and isospin-dependent ($b_{n} \neq b_{pn}$) repulsion, the latter being preferred by observational constraints.