2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/45249In this work we present a strong chiral meson Lagrangian up to and including $O(p^6)$ in the momentum expansion. It is derived from the Nambu--Jona-Lasinio (NJL) model using the heat-kernel method. Identities related to the properties of covariant derivatives of the chiral matrix $U$ as well as field transformations have been used to obtain a minimal set of linearly independent terms.20 pagesHigh Energy Physics - Phenomenologytext