Chiral Lagrangians and the QCD string

Abstract

We propose a method to derive the low-energy effective action of QCD assuming that the long-distance properties of strong interactions can be described by a string theory. We bypass the usual problems related to the existence of the tachyon and absence of the adequate Adler zero by using a sigma model approach where excitations above the correct (chirally non-invariant) QCD vacuum are included. Two-dimensional conformal invariance then implies the vanishing of the O(p(4)) effective lagrangian coefficients. We interpret this result and discuss ways to go beyond this limit.