Comparison of the extended linear σ model and chiral perturbation theory

The pion-nucleon-scattering amplitudes are calculated in tree approximation with the use of the extended linear sigma model (ELSM) as well as heavy-baryon chiral perturbation theory (HBχPT), and the nonrelativistic forms of the ELSM results are compared with those of HBχPT. We find that the amplitudes obtained in ELSM do not agree with those derived from the more fundamental effective approach, HBχPT.