On the Limits of Chiral Perturbation Theory

Abstract

We consider the relation between the breakdown scale of chiral perturbation theory, $Λ_χ$, for large values of $N$ (flavor), and the scale associated with ``new" physical thresholds. This question is addressed using both the linear $σ$ model and an asymptotically-free gauge theory to describe the high energy dynamics. It is suggested that the massive physical threshold could be well above $Λ_χ$.