Cold quark matter with heavy quarks and the stability of charm stars

TL;DR

This paper examines how heavy quarks, especially charm quarks, influence the properties and stability of cold, dense quark matter and explores the potential existence of charm stars, concluding they are unstable.

Contribution

It provides a perturbative QCD analysis of heavy quark effects on the equation of state and assesses the stability of hypothetical charm stars.

Findings

Heavy quarks significantly affect the equation of state.

Charm stars are unstable under radial oscillations.

Perturbative QCD is applicable at relevant densities.

Abstract

We study the effects of heavy quarks on the equation of state for cold and dense quark matter obtained from perturbative QCD, yielding observables parametrized only by the renormalization scale. We investigate the thermodynamics of charm quark matter under the constraints of $\beta$ equilibrium and electric charge neutrality in a region of densities where perturbative QCD is, in principle, much more reliable. We also analyze the stability of charm stars, which might be realized as a new branch of ultradense hybrid compact stars, and find that such quark stars are unstable under radial oscillations.