Kaon condensation during the thermal evolution of protoneutron stars and the possibility of low-mass block hola

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l) Possibility of the delayed collapse of protoneutron stars due to Kaon condensationWe have presented a new formulation of kaon condensation in the presence of neutrinos and temperature and derived the equation of state (EOS), based on chiral symmetry. Using this EOS, we have systematically examined the equilibrium structure of protoneutron stars and discussed its properties in detail as functions of entropy and lepton number. Then we have discussed the possibility of the delayed collapse of protoneutron stars due to the occurrennce of kaon condensation and the large softening of EOS during their thermal evolution. As a result we have shown the importance of the neutrino trapping effect, which has not benn emphasized yet. We have also clarified the specific features of the chiral model by comparing our results with those given in other papers. Our results have been published in the journals and also reported in the international conferences.2) Hyperonic matter and hyperon superfluidit … More yUsing the realistic hyperon-hyperon and -nucleon interactions obtained from the studies for hypernuclei, we have studied the problem of hyperon mixing in high density nuclear matter and the possibility of hyperon superfluidity. As a result we have suggested that there should be additional repulsive effects in hyperonic matter by considering the drastic softening of EOS and the observational mass of neutron stars. As for the hyperon superfluidity, we have concluded that hyperons such as Λ, Σ^-, Ξ^- should show superfluidity.3) Ferromagnetism of quark matterWe have studied the possibility of ferromagnetism of nuclear matter and quark matter as an origin of magnetic field in compact stars, triggered by the observation of magnetars, a new type of "neutron stars" with the superstrong magnetic field. We have shown that there should be a spontaneous magnetization at low densities in quark matter, and indicated that we can explain the superstrong magnetic field if we can regard magnetars as quark stars. We have also emphasized the relativistic aspects of quark ferromagnetism by considering the non-perturbative effects. Less