While the equation of state ( EOS ) of symmetric nuclear matter ( SNM ) at suprasaturation densities has been relatively well constrained from heavy-ion collisions , the EOS of high-density neutron-rich matter is still largely uncertain due to the poorly known high-density behavior of the symmetry energy .
Using the constraints on the EOS of SNM at suprasaturation densities from heavy-ion collisions together with the data of finite nuclei and the existence of 2 M _ { \odot } neutron stars from electromagnetic ( EM ) observations , we show that the high-density symmetry energy can not be too soft , which leads to lower bounds on dimensionless tidal deformability of \Lambda _ { 1.4 } \geq 193 and radius of R _ { 1.4 } \geq 11.1 km for 1.4 M _ { \odot } neutron star .
Furthermore , we find that the recent constraint of \Lambda _ { 1.4 } \leq 580 from the gravitational wave signal GW170817 detected from the binary neutron star merger by the LIGO and Virgo Collaborations rules out too stiff high-density symmetry energy , leading to an upper limit of R _ { 1.4 } \leq 13.3 km .
All these terrestrial nuclear experiments and astrophysical observations based on strong , EM and gravitational measurements together put stringent constraints on the high-density symmetry energy and the EOS of SNM , pure neutron matter and neutron star matter .