2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/6324Perturbations in a universe with matter and cosmological constant are computed in terms of the primordial scalar perturbation up to second order. The calculation is easy -- a generalization of the spherical dust solution. Our expression might allow accurate measurements of the primordial non-Gaussianity.8 pagesAstrophysicstext