Pion condensations and neutron star phenomena

Properties of three pion condensations (neutral (π0), charged (πc) and combined (π0-πc) ones) and their consequences on the neutron star phenomena, e.g., the cooling, are discussed with a realistic treatment, in which we consider the isobar Δ(1232) degrees of freedom, baryon-baryon short-range correlations described in terms of the Landau-Migdal parameter g', and form factors in the π-baryon vertices. Special attention is paid for the discussion of combined π0-πc condensation, and then the equation of state and thermal properties such as the neutrino emission or the neutrino transport are considered in a unified way. The combined π0-πc condensation appears at relatively low densities (3 ∼ 5)ρ0 (ρ0 = 0.17 fm-3 is the nuclear density) dependent on g' and strongly softens the equation of state. As for the thermal properties, the neutrino emissivity and opacity are calculated and their results are compared with those given by other calculations. Furthermore their implications on the cooling of neutron stars are briefly discussed. (author)