2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/63637We determine the cone of nef divisors on the Igusa and Voronoi compactifications of the moduli space of principally polarised abelian 4-folds. We also show that the canonical bundle on the Igusa compactification of A_4(n) is ample for n at least 3. Analogous results for A_2 and A_3 were earlier obtained by the first author but the case of A_4 is far less simple.54 pages, 4 figuresAlgebraic Geometry14K10text