2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/79352We construct a minimax selector for eventually quadratic hamiltonians on cotangent bundles. We use it to give a relation between Hofer's energy and Mather's action minimizing function. We also study the local flatness of the set of twist maps.Corrected version. 17 pagesSymplectic GeometryDynamical Systems58F05text