ScalingStacks

Lemma 4.10 . [02HE]

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Lemma 4.10.

As ϵ→0\epsilon\rightarrow 0 the harmonic function hϵh_{\epsilon} converges to the constant function 11. The convergence is in Ck,αC^{k,\alpha} on the complement of the union of balls of radius ϵβ\epsilon^{\beta} around the punctures, where β>0\beta>0 is any number such that β−1>k+1+α\beta^{-1}>k+1+\alpha. In particular, MϵghM^{\textup{gh}}_{\epsilon} collapses to the flat orbifold 𝕋/τ\mathbb{T}/\tau with bounded curvature away from the punctures.

Proof.

The first statement is a simple application of Lemma 4.7, since close to each puncture we have

ρk​|∇k(hϵ−1)|≤C​ϵ​ρ−1,\rho^{k}|\nabla^{k}(h_{\epsilon}-1)|\leq C\epsilon\rho^{-1},

where ρ\rho is the distance from the puncture. It follows that away from the punctures gϵghg^{\textup{gh}}_{\epsilon} is Cl​o​ck,αC^{k,\alpha}_{loc}–close to the ℤ2\mathbb{Z}_{2} quotient of g𝕋+ϵ2​θ2g_{\mathbb{T}}+\epsilon^{2}\theta^{2} for any k≥0k\geq 0 and ϵ\epsilon sufficiently small. ∎

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