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Title: Do the heaviest neutron stars have quark-matter cores?
Plain: At the centre of the heaviest neutron stars, protons and neutrons may dissolve into free quarks. Whether this happens is not known.
Precise: For a neutron star near $M_{\mathrm{TOV}}$, determine whether the central density exceeds the onset of deconfined quark matter, diagnosed by the polytropic index $\gamma=d\ln P/d\ln\epsilon$ approaching its conformal value 1 and the normalized trace anomaly $(\epsilon-3P)/(3\epsilon)$ approaching 0, where $\epsilon$ is energy density. Answer: yes or no, with posterior probability given all astrophysical data and perturbative QCD limits.
Settled by: Precise radii for two-solar-mass stars together with post-merger gravitational-wave frequencies sensitive to a phase transition.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: contested
Status note: Annala et al. (Nature Physics 2020; Nature Communications 2023) inferred near-conformal matter in maximal-mass cores with high probability, but the conclusion depends on how the hadronic and quark phases are defined.
Posed since: (empty)