Symmetry energy constraints from GW170817 and laboratory experiments

Understand

The LIGO-Virgo collaboration detection of the binary neutron-star merger event, GW170817, has expanded efforts to understand the Equation of State (EoS) of nuclear matter.

• These measurements provide new constraints on the overall pressure, but do not elucidate its origins, by not distinguishing the contribution to the pressure from symmetry energy which governs much of the internal structure of a neutron star.
• By combining the neutron star EoS extracted from the GW170817 event and the EoS of symmetric matter from nucleus-nucleus collision experiments, we extract the symmetry pressure, which is the difference in pressure between neutron and nuclear matter over the density region from 1.2$\rho_{0}$ to $4.5\rho_{0}$.
• While the uncertainties in the symmetry pressure are large, they can be reduced with new experimental and astrophysical results.