2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/54947We apply the techniques of the ``universal string theory'' to the ``manifold'' paradigm for superstring/M-theory and come up with a candidate manifold: the manifold of F-theory vacua, defined in conformal field theoretical terms. It contains the five known superstring theories as particular vacua; although the natural vacua are (10+2)-dimensional. As a byproduct, a natural explanation emerges for the compactness of the extra two coordinates in F-theory.11 pagesHigh Energy Physics - Theorytext