2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/77772For any $N \geq 5$ nonformal simply connected symplectic manifolds of dimension $2N$ are constructed. This disproves the formality conjecture for simply connected symplectic manifolds which was introduced by Lupton and Oprea.20 pages, LaTeX; the short announcement see in math.SG/9810065; a revised versionSymplectic Geometrytext