The quark-composites approach to QCD: The nucleon-pion interaction

We derive the pion-nucleon interaction in the framework of a new perturbative approach to QCD, based on the use of quark composites as fundamental variables. The composites with the quantum numbers of the nucleons are assumed as new integration variables in the Berezin integral which defines the partition function, while the composites with the quantum numbers of the chiral mesons are replaced by auxiliary bosonic fields. The action is modified by the addition of irrelevant operators which provide the kinetic terms for these composites, and the quark action is treated as a perturbation. The resulting expansion has the quark confinement built in. To first order we get the pion-nucleon interaction of the Yukawa model.