On the large Nf limit of chiral perturbation-theory

Abstract

In this letter we show how it is possible to obtain the large N(f) limit of chiral perturbation theory (chi-PT) in the chiral limit. In particular, we compute explicitly the Nambu-Goldstone boson (NGB) elastic scattering amplitude to leading order in 1/N (N being the number of NGB fields) to all powers in the external momenta. This amplitude is unitary to order 1/N and it can incorporate resonant behavior. The price to pay is the introduction of an infinite set of renormalized coupling constants that can be summarized in a single generating function. Playing with these constants, it is possible to simulate the linear sigma model and many others in the same large N limit.