Constraints on the symmetry energy from PREX-II in the multimessenger era

The neutron skin thickness Δ r_np of heavy nuclei is essentially determined by the symmetry energy density slope L (ρ ) at ρ_c=0.11 fm⁻³≈2 /3 ρ₀ (ρ₀ is nuclear saturation density), roughly corresponding to the average density of finite nuclei. The PREX collaboration recently reported a model-independent extraction of Δ r_np²⁰⁸=0.283 ±0.071 fm for the Δ r_np of ²⁰⁸Pb, suggesting a rather stiff symmetry energy E_sym(ρ ) with L (ρ_c)≥52 MeV. We show that the E_sym(ρ ) cannot be too stiff and L (ρ_c)≤73 MeV is necessary to be compatible with (1) the ground-state properties and giant monopole resonances of finite nuclei, (2) the constraints on the equation of state of symmetric nuclear matter at suprasaturation densities from flow data in heavy-ion collisions, (3) the largest neutron star (NS) mass reported so far for PSR J0740 +6620 , (4) the NS tidal deformability extracted from gravitational wave signal GW170817, and (5) the mass-radius of PSR J0030 +045 measured simultaneously by NICER. This allows us to obtain 52 ≤L (ρ_c)≤73 MeV and 0.212 ≤Δ r_np²⁰⁸≤0.271 fm and further E_sym(ρ₀) =34.3 ±1.7 MeV, L (ρ₀)=83.1 ±24.7 MeV, and E_sym(2 ρ₀ ) =62.8 ±15.9 MeV. A number of critical implications on nuclear physics and astrophysics are discussed.