2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/58537We describe birational models and decide the rationality/unirationality of moduli spaces AA_{d} (and AA^{lev}_{d}) of (1,d)-polarized abelian surfaces (with canonical level structure, respectively) for small values of d. The projective lines identified in the rational/unirational moduli spaces correspond to pencils of abelian surfaces traced on nodal threefolds living naturally in the corresponding ambient projective spaces, and whose small resolutions are new Calabi-Yau threefolds with Euler characteristic zero.56 pages, 2 figures, plain TeX, uses diagrams.tex and epsf.texAlgebraic GeometryHigh Energy Physics - Theorytext