Thermal Evolution of Neutron Stars and Hadronic Condensations

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1. Pion condensation and thermal evolution of neutron stars : Taking into account the rapid cooling due to pion condensate and nucleon superfluidity, we have shown that gross feature of observation can be explained. We have also shown that axions, if really exist, bring about the peculiar T^4 dependense of the emissivity, and competes with the photon one in old neutron stars.2. Properties of proto-neutron stars just born : We have first constructed a theoretical framework to treat the supernova-matter, and then presented its chemical composition and equation of state (EOS). Based on these results, we have also given new constraints on the radius and rotational velocity of initial neutron stars.3. Kaon condensation and neutron stars : We have studied kaon condensed phase on the basis of chiral symmetry. Subsequently we have presented a most realistic equation of state, by incorporating the relativistic mean-field theory which supress the condensation at high-density region. Using this EOS we have discussed the bulk properties and dynamical processes of neutron stars ; some implications on the gamma-ray bursts and mini black-hole scenario are also discussed.4. Kaon condensation and the thermal evolution of neutron stars : We have shown that the direct URCA process is not necessarily possible in the kaon condensed phase and works only in the limited density region. We have also examined the possibility of nucleon superfluidity in the condensed phase, and found that it is unlikely.In addition we have pointed out and corrected an error of factor 2 through the previous studies about the neutrino emissivity under the meson condensates.