The role of hyperonic interactions in proto neutron stars

Abstract

In this paper, how the hyperonic interaction affect the properties of proto neutron stars (PNSs) is studied with relativistic mean field theory. Corresponding to the same baryon density, in consideration of the hyperonic interaction, the $\sigma$-meson field strength increases, whereas the $\omega$- and $\rho$-meson field strengths, chemical potentials of neutrons and electrons, energy density and pressure all decrease. The influence of the interaction between hyperons on the center field strengths of mesons $\sigma$, $\omega$ and $\rho$, the central chemical potential of neutrons and electrons, the central energy density and the central pressure increases with the increase of the PNS’s mass. As the hyperonic interaction is considered, the PNS’s mass $M$ decreases with respect to the same radius $R$, and the larger the PNS’s mass, the larger the radius reduction. Our results show that inside PNSs, ${\mathrm{\Sigma }}^{+}$ hyperons do not appear, but baryons $n$, $p$, $\mathrm{\Lambda }$, ${\mathrm{\Sigma }}^0$, ${\mathrm{\Sigma }}^{-}$, ${\mathrm{\Xi }}^0$ and ${\mathrm{\Xi }}^{-}$ do, whether the hyperonic interaction is considered or not. In consideration of the hyperonic interaction, the relative density of neutrons decreases, while those of hyperons $\mathrm{\Lambda }$, ${\mathrm{\Sigma }}^0$, ${\mathrm{\Sigma }}^{-}$, ${\mathrm{\Xi }}^0$ and ${\mathrm{\Xi }}^{-}$ increase. The effect of hyperonic interaction on the center relative density of baryons increases as the PNS’s mass increases.