Pion Condensation in Superdense Nuclear Matter

Previous work, based on the interaction of only one mode of the pion field with nucleons, indicated the possibility that the ground state of nuclear matter at densities above some onset density would consist of a coherent mixture of protons, neutrons, and pions, the latter condensed in a plane-wave state of momentum ≈ 170 MeV/c. The model is now made more realistic by inclusion of ordinary nuclear forces, emission and absorption of noncondensed pion modes, $S$-wave pion-nucleon interactions, and pion-pion interactions. A pion condensation is again predicted, with onset between $\rho =0.5\mathrm{}$ baryons/${\mathrm{F}}^3$ and $\rho =1\mathrm{}$ baryon/${\mathrm{F}}^3$. Some possible consequences for neutron stars are discussed.