Dispersion relation of the pion in the Nambu–Jona-Lasinio model

Abstract
The propagation of a pionic wave in the NambuJona-Lasinio model is reexamined in the framework of the time-dependent Hartree-Fock theory. It is found that the trial generator of the vacuum fluctuations should be consistent with the chosen configuration space of single-particle states (spanned by occupied negative-energy states and by empty valence states).