Relationship between the quark condensate and low-energy Pi-Pi observables beyond O(p^4)

Abstract

The two-flavor Gell-Mann-Oakes-Renner ratio is expressed in terms of low-energy pi-pi observables including the O(p^6) double chiral logarithms, computed in Generalized Chiral Perturbation Theory. It is found that their contribution is important and tends to compensate the one from the single chiral logarithms.

Comments: contribution to LNF Spring School, Frascati, 15-20 May, 2000