The Role of Scalar Mesons in Extended Perturbation Scheme for Effective Field Theory.

We argue how it is possible to apply the general scheme of the effective scattering theory (EST) to the description of the hadronic processes. The results of the numerical tests of sum rules for πN spectrum parameters that follow from the bootstrap system allow us to claim the consistency of the predictions obtained in the framework of our approach with the known phenomenology. We also demonstrate that the tree-level low energy expansion coefficients computed in the framework of our approach show nice agreement with known experimental data. [ABSTRACT FROM AUTHOR]