2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55471We suggest that compactifications on Anti-de-Sitter (AdS) spaces of type IIA, IIB, heterotic strings and eleven dimensional vacuua of M-theory are related by a combination of $T$ and strong/weak dualities. Maldacena conjecture relates then all these vacuua to a conformal theory on the boundaries. Furthermore acting with discrete groups on part of the internal spaces of these theories will lead to further dual theories with less or no supersymmetry.6 pages, latexHigh Energy Physics - Theorytext