# Constraint to chiral invariant masses of nucleons from GW170817 in an extended parity doublet model

## TL;DR

This paper constrains the chiral invariant masses of nucleons using nuclear matter properties and gravitational wave data from GW170817, finding masses larger than about 600 MeV and predicting high-density symmetry energy parameters.

## Contribution

It introduces an extended parity doublet model with four light nucleons and constrains their chiral invariant masses using nuclear matter saturation and neutron star merger observations.

## Key findings

- Chiral invariant masses are constrained to be above 600 MeV.
- Tidal deformability from GW170817 further restricts nucleon masses.
- Predictions made for symmetry energy and slope parameters at high densities.

## Abstract

We construct nuclear matter based on an extended parity doublet model including four light nucleons $N(939)$, $N(1440)$, $N(1535)$, and $N(1650)$. We exclude some values of the chiral invariant masses by requiring the saturation properties of normal nuclear matter; saturation density, binding energy, incompressibility, and symmetry energy. We find further constraint to the chiral invariant masses from the tidal deformability determined by the observation of the gravitational waves from neutron star merger GW170817. Our result shows that the chiral invariant masses are larger than about $600\,$MeV. We also give some predictions on the symmetry energy and the slope parameters in the high density region, which will be measured in future experiments.