2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/209995We prove that the moduli space of stable sheaves of rank 2 with a certain Chern classes on a smooth quadric $Q$ in $\PP_3$, is isomorphic to $\PP_3$. Using this identification, we give a new proof that a certain Brill-Noether locus on a non-hyperelliptic curve of genus 4, is isomorphic to the Donagi-Izadi cubic threefold.9 pages, any comments are welcomeAlgebraic Geometry14D20, 14E05text