gamma group

The group Γ of all Möbius transformations of the form τ' = (a τ + b)/(c τ + d), where a, b, c, and d are integers with a d - b c = 1. The group can be represented by the 2×2 matrix A = [a | b c | d], where det(A) = 1.

Klein's absolute invariant | modular group Γ_0 | modular group Λ | Möbius transformation | unimodular transformation