Modular curves Curves Points Pairs (E, α) X(N)  where α : (Z/NZ)2 ' E[N] and eN(α(1, 0), α(0, 1)) = ζN Pairs (E, P) X1(N)  where P ∈ E has exact order N X(1) Elliptic curves E where ζN is a fixed primitive N-th root of 1. Nicolas Mascot p-adic computation of Galois representations