Existence of a hadron–quark phase transition in neutron star cores

Determine whether dense matter in the cores of neutron stars undergoes a phase transition from hadronic matter to deconfined quark matter.

Background

Understanding the microphysical composition of matter at supranuclear densities is central to neutron star physics. Ab initio theory provides constraints only at relatively low densities via chiral effective field theory and at very high densities via perturbative QCD, leaving the densities realized in neutron star interiors largely unconstrained by first principles. Observational inferences from masses, radii, and tidal deformabilities are thus crucial.

Multiple scenarios are considered plausible for the behavior of matter at these densities, including a smooth crossover to quark matter, a first-order phase transition that may destabilize the star, or more exotic possibilities. This work performs a Bayesian inference over a broad, model-agnostic ensemble of equations of state to compare evidences for these scenarios, but the fundamental question of whether a hadron–quark phase change actually occurs inside neutron stars remains unresolved.