Phenomenological QCD equations of state for neutron stars

TL;DR

This paper constructs neutron star equations of state based on QCD principles across a range of baryon densities, revealing that strong, non-perturbative gluonic interactions persist even at high densities.

Contribution

It introduces a three-window model for QCD matter in neutron stars, interpolating between nuclear and quark matter, and analyzes the interaction strength needed to match observations.

Findings

Interactions remain as strong as in the QCD vacuum at high densities

Gluons stay non-perturbative at baryon densities 1-10 n_0

Model satisfies neutron star mass-radius constraints

Abstract

We delineate the properties of QCD matter at baryon density n_B=1-10n_0 (n_0: nuclear saturation density), through the construction of neutron star equations of state that satisfy the neutron star mass-radius constraints as well as physical conditions on the speed of sound. The QCD matter is described in the 3-window modeling: at n_B < 2n_0 purely nuclear matter; at n_B > 5n_0 percolated quark matter; and at 2n_0 < n_B < 5n_0 matter intermediate between these two which are constructed by interpolation. Using a schematic quark model with effective interactions inspired from hadron and nuclear physics, we analyze the strength of interactions necessary to describe observed neutron star properties. Our finding is that the interactions should remain as strong as in the QCD vacuum, indicating that gluons at n_B =1-10 n_0 remain non-perturbative even after quark matter formation.