Automorphisms

CanonicalInvolution(X): CrvMod -> MapSch

AtkinLehnerInvolution(X, N): CrvMod, RngIntElt -> MapSch

Given a projective modular curve \(X = X_0(N)\), the function returns the Atkin-Lehner involution of the modular curve as a map of schemes. Currently, the only Atkin-Lehner involution returned is that for \(N\) equal to the level of \(X\).