Algebraic modular forms Definition An algebraic modular form of weight k for X(N) over R is a rule f assigning a value to pairs (E/R, α), such that f (E0 , α) = uk f (E, α) for all u ∈ R× . Examples E 7→ A is a modular form of weight 4. E 7→ ∆ := −64A3 − 432B2 is a modular form of weight 12. by (x, y) 7→ (u2 x, u3 y), A0 = u4 A, B0 = u6 B, ω0 = u−1 ω. Nicolas Mascot p-adic computation of Galois representations