ScalingStacks

Proof. [03DB]

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Proof.

Observe that ⟨vi,wj⟩=1,i,j=0,1\langle v_{i},w_{j}\rangle=1,\ i,j=0,1. Hence, if n∈ℤv0dn\in\mathbb{Z}^{d}_{v_{0}}, then n+⟨v1,n⟩​(w1−w0)∈ℤv0dn+\langle v_{1},n\rangle(w_{1}-w_{0})\in\mathbb{Z}^{d}_{v_{0}}. Now put n′:=n−⟨v1,n⟩​w0∈ℤv1dn^{\prime}:=n-\langle v_{1},n\rangle w_{0}\in\mathbb{Z}^{d}_{v_{1}}. Then n′≡nmodw0n^{\prime}\equiv n\mod w_{0} together with n′≡n+⟨v1,n⟩​(w1−w0)modw1n^{\prime}\equiv n+\langle v_{1},n\rangle(w_{1}-w_{0})\mod w_{1} imply the desired formula. ∎

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