2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/150013We show that minimal symplectic 4--manifolds with $b_2^+ >1$ and with residually finite fundamental groups are irreducible. We also give examples of irreducible orientable four--manifolds with indefinite intersection forms which are not almost complex with respect to either orientation.AMSLaTeXAlgebraic Geometry57R55,57R57,53C15text