Hyperonic Interactions in Neutron Stars

The matter of neutron stars is characterised by the density of the order of typical nuclear densities; hence, it can be described with methods of nuclear physics. However, at high densities, some effects that are absent in nuclear and hypernuclear physics can appear, and this makes neutron stars a good place for studying the properties of baryonic interactions. In the present work, we consider neutron stars consisting of nucleons, leptons and $\mathrm{\Lambda }$ hyperons with Skyrme baryonic forces. We study the character of the $\mathrm{\Lambda }N$ interactions taking place in neutron stars at high densities. In particular, we show the difference between three-body $\mathrm{\Lambda }NN$ and density-dependent $\mathrm{\Lambda }N$ forces. We also demonstrate that the Skyrme $\mathrm{\Lambda }N$ forces proportional to nuclear density are better suited for the modelling of neutron stars than the forces proportional to fractional powers of density. Finally, we emphasize the importance of the point of appearance of hyperons in a further search for parameterizations which are suitable for describing neutron stars.