# Impact of chiral hyperonic three-body forces on neutron stars

## TL;DR

This paper investigates how chiral hyperonic three-body forces influence neutron star properties, demonstrating that including these forces results in a stiffer equation of state compatible with observed massive neutron stars.

## Contribution

The study introduces the impact of chiral effective field theory derived NNΛ three-body forces on neutron star equations of state and hypernuclei, enhancing previous models.

## Key findings

- Neutron star maximum mass reaches ~2 solar masses with NNΛ forces.
- Equation of state becomes stiffer, aligning with observed massive neutron stars.
- Improved agreement with hypernuclei separation energies, especially in heavier hypernuclei.

## Abstract

We study the effect of the nucleon-nucleon-lambda (NN$\Lambda$) three-body force on neutron stars. In particular, we consider the NN$\Lambda$ force recently derived by the J\"{u}lich--Bonn--Munich group within the framework of chiral effective field theory at next-to-next-to-leading order. This force, together with realistic nucleon-nucleon, nucleon-nucleon-nucleon and nucleon-hyperon interactions, is used to calculate the equation of state and the structure of neutron stars within the many-body non-relativistic Brueckner-Hartree-Fock approach. Our results show that the inclusion of the NN$\Lambda$ force leads to an equation of state stiff enough such that the resulting neutron star maximum mass is compatible with the largest currently measured ($\sim 2\ M_\odot$) neutron star masses. Using a perturbative many-body approach we calculate also the separation energy of the $\Lambda$ in some hypernuclei finding that the agreement with the experimental data improves for the heavier ones when the effect of the NN$\Lambda$ force is taken into account.