Neutral pion condensation and Alternating Layer Spin model including isobar Δ(1232) in hot symmetric nuclear matter

Neutral pion condensation in the symmetric nuclear matter at finite temperature T is investigated with use of the Alternating Layer Spin model including explicitly the isobar Δ(1232) degree of freedom. The free energy F is calculated in the Hartree-Fock approximation with an extended effective baryon-baryon interaction based on the G-0 forces. It is shown that the neutral-pion condensed phase is realized as a first-order phase transition with a broad coexistence region of density, for example, from 2.5 ρ0 to 4.3 ρ0 at T=30 MeV, ρ0 being the normal density. Implications of the results in high-energy heavy ion collisions are also discussed on the basis of a simple fluid dynamical model. (author)