Large N-c in chiral perturbation theory

The construction of the effective Lagrangian relevant for the mesonic secto r of QCD in the large N-c limit meets with a few rather subtle problems. We thoroughly examine these and show that, if the variables of the effective theory are chosen suitable, the known large N-c counting rules of QCD can u nambiguously be translated into corresponding counting rules for the effect ive coupling constants. As an application, we demonstrate that the Kaplan-M anohar transformation is in conflict with these rules and is suppressed to all orders in 1/N-c. The anomalous dimension of the axial singlet current g enerates an additional complication: The corresponding external field under goes nonmultiplicative renormalization. As a consequence, the Wess-Zumino-W itten term, which accounts for the U(3)(R) x U(3)(L) anomalies in the frame worth of the effective theory, contains pieces that depend on the running s cale of QCD. The effect only shows up at nonleading order in 1/N-c, but req uires specific unnatural parity contributions in the effective Lagrangian t hat restore renormalization group invariance.