2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/119277We prove a decomposition theorem for the cd-index of a Gorenstein* poset analogous to the decomposition theorem for the intersection cohomology of a toric variety. From this we settle a conjecture of Stanley that the cd-index of Gorenstein* lattices is minimized on Boolean algebras.22 pages, submitted to Journal of Algebraic CombinatoricsCombinatoricsAlgebraic Geometry52C07; 52B05; 14F43text