ScalingStacks

Proof. [01ZW]

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Proof.

The proof is the same as that of Theorem 1.4, except for the second fundamental form estimate on the boundary. To see this estimate, we use T0δ​(p)=0T^{\delta}_{0}(p)=0 and Theorem 8.3 to find a diffeomorphism Φ:A1/2,2​(0)→B1​(p)\Phi:A_{1/2,2}(0)\to B_{1}(p) onto its image, such that if gi​j=Φ∗​gg_{ij}=\Phi^{*}g is the pullback metric then

‖gi​j−δi​j‖C0+‖∂kgi​j‖C0<ϵ.\displaystyle||g_{ij}-\delta_{ij}||_{C^{0}}+||\partial_{k}g_{ij}||_{C^{0}}<\epsilon\,. (8.65)

In particular, we can choose UU so that its boundary is ∂U=∂B3/2​(0)\partial U=\partial B_{3/2}(0) in these coordinates. The C1C^{1} estimates on gg give rise to the appropriate second fundamental form estimates on ∂U\partial U. ∎

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