The Group Structure of the Normalizer of Γ 0 (n )
نویسنده
چکیده
We determine the group structure of the normalizer of Γ0(N) in SL2(R) modulo Γ0(N). These results correct the Atkin-Lehner statement [1, Theorem 8].
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WN ′ = W (N) N ′ denotes the corresponding Atkin–Lehner involution defined for Γ0(N). (If N ′ = 1, W1 means the identity operator.) Then we define the modular group Γ ∗ 0 (N) to be Γ ∗ 0 (N) = 〈Γ0(N) ∪ {WN ′}N ′ ‖N 〉, i.e., Γ ∗ 0 (N) is generated by Γ0(N) and {WN ′}N ′ ‖N . Then Γ ∗ 0 (N) is a normalizer of Γ0(N) in GL + 2 (Q) = {A ∈M2(Q) | detA > 0}. The factor group Γ ∗ 0 (N)/Γ0(N) is abelian...
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