2023/06/14 by Cesar Hilario, Hilario, Cesar, Karl-Otto Stöhr +1
Arts and Humanities · Mathematics · Medicine · #14D06 #14E05 #14G17 #14H05 #14H45 #Algebraic Geometry (math.AG) #Algebraic Geometry and Number Theory #FOS: Mathematics #Magnolia and Illicium research #North African History and Literature
paper · pdf · doi:10.48550/arxiv.2306.08579
openalex publication_date 2023/06/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/03
We classify fibrations by integral plane projective rational quartic curves whose generic fibre is regular but admits a non-smooth point that is a canonical divisor. These fibrations can only exist in characteristic two. The geometric generic fibre, which determines the generic behaviour of the special fibres, is an integral plane projective rational quartic curve over the algebraic closure of the function field of the base. It has the remarkable property that the tangent lines at the non-singular points are either all bitangents or all non-ordinary inflection tangents; moreover it is strange, that is, all the tangent lines meet in a common point. We construct two fibrations that are universal in the sense that any other fibration with the aforementioned properties can be obtained from one of them by a base extension. Furthermore, among these fibrations we choose a pencil of plane quartic curves and study in detail its geometry. We determine the corresponding minimal regular model and we describe it as a purely inseparable double covering of a quasi-elliptic fibration.