2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/105979After reviewing briefly the classical examples of duality in four dimensional field theory we present a generalisation to arbitrary dimensions and to p-form fields. Then we explain how U-duality may become part of a larger non abelian V-symmetry in superstring/supergravity theories. And finally we discuss two new results for 4d gravity theory with a cosmological constant: a new exact gravitational instanton equation and a surprizing linearized classical duality around de Sitter space.Chern Conference, Nankai, DGMTP 2005. 6 pHigh Energy Physics - Theorytext