# Equation of state of dense matter in the multimessenger era

## TL;DR

This paper combines nuclear physics experiments and astrophysical observations to tightly constrain the high-density symmetry energy and the equation of state of dense matter, impacting neutron star properties and gravitational wave signals.

## Contribution

It provides new bounds on neutron star radius and tidal deformability by integrating diverse multimessenger data and nuclear constraints.

## Key findings

- Lower bound on neutron star radius: R_{1.4} ≥ 11.1 km
- Lower bound on tidal deformability: Λ_{1.4} ≥ 193
- Upper bound on radius from GW data: R_{1.4} ≤ 13.3 km

## Abstract

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 $2M_\odot$ neutron stars from electromagnetic (EM) observations, we show that the high-density symmetry energy cannot be too soft, which leads to lower bounds on dimensionless tidal deformability of $\Lambda_{1.4} \ge 193$ and radius of $R_{1.4} \ge 11.1$ km for $1.4M_\odot$ neutron star. Furthermore, we find that the recent constraint of $\Lambda_{1.4} \le 580$ 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 $R_{1.4} \le 13.3$ 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.