Tetragonal intermediate modular curves

Autorzy

Dane publikacji

  • DOI: 10.4064/aa240831-22-3

  • Tom 220

  • Zeszyt 3

  • Czasopismo: Acta Arithmetica

  • Strony: 263-288

  • Data publikacji online: 14.09.2025

Liczba wyświetleń: 0

Liczba pobrań: 0

Abstrakt

For every group $\{\pm 1\}\subseteq \Delta \subseteq (\mathbb {Z}/N\mathbb {Z})^\times $, there exists an intermediate modular curve $X_\Delta (N)$. We determine all curves $X_\Delta (N)$ whose $\mathbb {Q}$-gonality is equal to $4$, all curves $X_\Delta (N)$ whose $\mathbb {C}$-gonality is equal to $4$, and all curves $X_\Delta (N)$ whose $\mathbb {Q}$-gonality is equal to $5$. We also determine the $\mathbb {Q}$-gonality of all curves $X_\Delta (N)$ for $N\leq 40$ and $\{\pm 1\}\subsetneq \Delta \subsetneq (\mathbb {Z}/N\mathbb {Z})^\times $.