2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/40930This lecture, directed to an broad audience including non-specialists, presents a short review of the problem of strong CP symmetry maintenance. The problem is defined and the possible solutions briefly reviewed. I discuss the way in which Roberto Peccei and I came up with one solution, generally known as Peccei-Quinn symmetry.Dirac Medal Lecture, July 2001High Energy Physics - Phenomenologytext