2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/56202We study the duality between M-theory compactified on Calabi-Yau fourfolds and the heterotic string compactified on Calabi-Yau threefolds times a circle. Our analysis is based on a comparison of the low energy effective actions in three dimensions.5 pages, no figures, uses cargese.cls; changed some references and the discussion of the moduli space on the M-Theory sideHigh Energy Physics - Theorytext