2025/07/09 by Sam Frengley, Frengley, Sam, Sameera Vemulapalli +1
Mathematics · #14H10 #14H51 #Advanced Algebra and Geometry #Algebraic Geometry (math.AG) #Algebraic Geometry and Number Theory #Analytic Number Theory Research #FOS: Mathematics
paper · pdf · doi:10.48550/arxiv.2507.06942
openalex publication_date 2025/07/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A degree d genus g cover of the complex projective line by a smooth irreducible curve C yields a vector bundle on the projective line by pushforward of the structure sheaf. We classify the bundles that arise this way when d = 5. Equivalently, we classify which ℙ3-bundles over ℙ1 contain smooth irreducible degree 5 covers of ℙ1. Our main contribution is proving the existence of smooth covers whose structure sheaf has the desired pushforward. We do this by showing that the substack of singular curves has positive codimension in the moduli stack of finite flat covers with desired pushforward. To compute the dimension of the space of singular curves, we prove a (relative) ``minimization theorem'', which is the geometric analogue of Bhargava's sieving argument when computing the densities of discriminants of quintic number fields.