The van der Waals Hexaquark Chemical Potential in Dense Stellar Matter

TL;DR

This paper models the chemical potential of hexaquarks using a van der Waals approach within dense stellar matter, revealing critical temperatures, metastability regions, and implications for neutron star properties.

Contribution

It introduces a QCD-motivated van der Waals model for hexaquark chemical potential and explores its effects on dense stellar matter and neutron star characteristics.

Findings

Critical temperature near 163 MeV for color-singlet states.

Identification of metastability regions in chemical potential isotherms.

Maximum mass and radius bounds for neutron stars with hexaquark layers.

Abstract

We explore the chemical potential of a QCD-motivated van der Waals (VDW) phase change model for the six-quark color-singlet, strangeness S=-2 particle known as the hexaquark with quark content (uuddss). The hexaquark may have internal structure, indicated by short range correlations, that allow for non-color-singlet diquark and triquark configurations whose interactions will change the magnitude of the chemical potential. In the multicomponent VDW Equation of State (EoS), the quark-quark particle interaction terms are sensitive to the QCD color factor, causing the pairing of these terms to give different interaction strengths for their respective contributions to the chemical potential. This results in a critical temperature near 163 MeV for the color-singlet states and tens of MeV below this for various diquark and triquark states. The VDW chemical potential is also sensitive to the number density, leading to chemical potential isotherms that exhibit spinodal extrema, which also depend on the internal hexaquark configurations. These extrema determine regions of metastability for the mixed states near the critical point. We use this chemical potential with the chemical potential modified TOV equations to investigate the properties of hexaquark formation in cold compact stellar cores in beta equilibrium. We find thresholds for the hexaquark layers and changes in the maximum mass values that are consistent with observations from high mass compact stellar objects such as PSR 09043 + 10 and GW 190814. In general, we find that the VDW-TOV model has an upper stability mass and radius bound for a chemical potential of 1340 MeV with a compactness C~0.2.