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We determine the coupling constants of $��$ hyperon with mesons in relativistic mean field (RMF) models using $��^-$ atomic shift data and examine the effects of $��$ on the neutron star maximum mass. We find that we need to reduce the vector-isovector meson coupling with $��$ ($g_{����}$) from the value constrained by the SU(3)v symmetry in order to explain the $��^-$ atomic shifts for light symmetric and heavy asymmetric nuclei simultaneously. With the atomic shift fit value of $g_{����}$, $��^-$ can emerge in neutron star matter overcoming the repulsive isoscalar potential for $��$ hyperons. Admixture of $��^-$ in neutron stars is found to reduce the neutron star maximum mass slightly., 9 pages, 9 figures

We develop a chiral SU(3) symmetric relativistic mean field (RMF) model with a logarithmic potential of scalar condensates. Experimental and empirical data of symmetric nuclear matter saturation properties, bulk properties of normal nuclei, and separation energies of single- and double-$\Lambda$ hypernuclei are well explained. The nuclear matter equation of state (EOS) is found to be softened by $\sigma\zeta$ mixing which comes from determinant interaction. The neutron star matter EOS is further softened by $\Lambda$ hyperons., Comment: 15 pages, 12 figures

We examine possibilities of pion condensation with zero momentum (s-wave condensation) in neutron stars by using the pion-nucleus optical potential U and the relativistic mean field (RMF) models. We use low-density phenomenological optical potentials parameterized to fit deeply bound pionic atoms or pion-nucleus elastic scatterings. Proton fraction (Y_p) and electron chemical potential (mu_e) in neutron star matter are evaluated in RMF models. We find that the s-wave pion condensation hardly takes place in neutron stars and especially has no chance if hyperons appear in neutron star matter and/or b_1 parameter in U has density dependence., 4 pages, 3 figures, REVTeX

We determine the coupling constants of $\Sigma$ hyperon with mesons in relativistic mean field (RMF) models using $\Sigma^-$ atomic shift data and examine the effects of $\Sigma$ on the neutron star maximum mass. We find that we need to reduce the vector-isovector meson coupling with $\Sigma$ ($g_{\rho\Sigma}$) from the value constrained by the SU(3)v symmetry in order to explain the $\Sigma^-$ atomic shifts for light symmetric and heavy asymmetric nuclei simultaneously. With the atomic shift fit value of $g_{\rho\Sigma}$, $\Sigma^-$ can emerge in neutron star matter overcoming the repulsive isoscalar potential for $\Sigma$ hyperons. Admixture of $\Sigma^-$ in neutron stars is found to reduce the neutron star maximum mass slightly., Comment: 9 pages, 9 figures