Impact of soft versus hard equations of state on hybrid stars
Phys. Rev. C 114, 045808 – Published 19 October, 2026
DOI: https://doi.org/10.1103/vxhx-gw7q
Abstract
The nuclear stiffness as a dominant contribution of nuclear symmetry energy is analyzed in the context of the properties of compact stars, considering constraints from nuclear physics and astrophysics. A compact star can be a neutron star composed only of nuclear matter or a hybrid star with a quark core. Two typical models (soft and stiff) are considered for the nuclear equation of state and for the hybrid equation of state, and a parametrized first-order phase-transition approach completed with a linear quark-matter equation of state is implemented. We show that the phase transition reduces the tension between GW170817 and NICER observations, and we illustrate how the nuclear stiffness affects the understanding of the nature of the binary system in GW170817. The implication for nuclear symmetry energy is also discussed. We also confirm our previous findings that the GW170817 waveform is best described as a binary hybrid star with a low-density onset of stiff quark matter. This could also be interpreted as a quarkyonic crossover.
