Tetragonal modular quotients $X_0^+(N)$
Volume 217 / 2025
Acta Arithmetica 217 (2025), 261-275
MSC: Primary 14H51; Secondary 11G18, 11G30, 14H30
DOI: 10.4064/aa231121-16-7
Published online: 13 January 2025
Abstract
We determine all quotient curves $X_0^+(N)$ whose $\mathbb Q$ or $\mathbb C$-gonality is equal to $4$. As a consequence, we find several new cases where the modular curve $X_0(N)$ has $\mathbb Q$-gonality equal to $8$.
