Quark-meson coupling model with the cloudy bag and its application to nuclear and neutron-star properties

Using the volume coupling version of the cloudy bag model, the quark-meson coupling model is extended to study the role of pion and kaon fields in a baryon. The hyperfine interaction due to the gluon exchange as well as that due to the pion and kaon clouds is taken into account, and the baryon mass spectra are well reproduced in vacuum. The extended model then applies to the nuclear matter calculations at the quark-mean field level. In particular, we investigate the effect of the gluon, pion, kaon exchanges on hyperons in matter. In addition, the extension of SU(6) spin-flavor symmetry to SU(3) flavor symmetry is examined in determining the couplings of the vector mesons to the octet baryons, introducing the strange vector mesons. We also present the equation of state for neutron stars, which can support the two-scalar mass neutron stars and the recent neutron-star merger event.