ScalingStacks

Proof. [0313]

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Proof.

First of all notice that after replacing UU with a slightly smaller open set, the semi-flat metric ω0+ωS​F\omega_{0}+\omega_{SF} is uniformly equivalent to ωM\omega_{M}, which implies that

(4.4) C−1​(ω0+t​ωS​F)⩽ω0+t​ωM⩽C⁡(ω0+t​ωS​F),C^{-1}(\omega_{0}+t\omega_{SF})\leqslant\omega_{0}+t\omega_{M}\leqslant C(\omega_{0}+t\omega_{SF}),

for all small t>0t>0. Thanks to Lemma 4.1 on UU we have that

C−1​(ω0+t​T−σ∗​ωM)⩽T−σ∗​ω~t⩽C⁡(ω0+t​T−σ∗​ωM),C^{-1}(\omega_{0}+tT_{-\sigma}^{*}\omega_{M})\leqslant T_{-\sigma}^{*}\tilde{\omega}_{t}\leqslant C(\omega_{0}+tT_{-\sigma}^{*}\omega_{M}),

and since T−σ∗​ωMT_{-\sigma}^{*}\omega_{M} is uniformly equivalent to ωM\omega_{M} we also have that

(4.5) C−1​(ω0+t​ωM)⩽T−σ∗​ω~t⩽C⁡(ω0+t​ωM),C^{-1}(\omega_{0}+t\omega_{M})\leqslant T_{-\sigma}^{*}\tilde{\omega}_{t}\leqslant C(\omega_{0}+t\omega_{M}),

and combining (4.4) and (4.5) we get

(4.6) C−1​(ω0+t​ωS​F)⩽T−σ∗​ω~t⩽C⁡(ω0+t​ωS​F),C^{-1}(\omega_{0}+t\omega_{SF})\leqslant T_{-\sigma}^{*}\tilde{\omega}_{t}\leqslant C(\omega_{0}+t\omega_{SF}),

on UU. If we pull back (4.6) by p∘λtp\circ\lambda_{t} we get

(4.7) C−1​(p∗​ω0+t​λt∗​p∗​ωS​F)⩽λt∗​p∗​T−σ∗​ω~t⩽C⁡(p∗​ω0+t​λt∗​p∗​ωS​F),C^{-1}(p^{*}\omega_{0}+t\lambda_{t}^{*}p^{*}\omega_{SF})\leqslant\lambda_{t}^{*}p^{*}T_{-\sigma}^{*}\tilde{\omega}_{t}\leqslant C(p^{*}\omega_{0}+t\lambda_{t}^{*}p^{*}\omega_{SF}),

on all of B×ℂn−mB\times\mathbb{C}^{n-m}. We claim that on the whole of B×ℂn−mB\times\mathbb{C}^{n-m} we have that

(4.8) t​λt∗​p∗​ωS​F=p∗​ωS​F.t\lambda_{t}^{*}p^{*}\omega_{SF}=p^{*}\omega_{SF}.

In fact, the construction of ωS​F\omega_{SF} in section 3 gives that p∗​ωS​F=−1​∂∂¯​η,p^{*}\omega_{SF}=\sqrt{-1}\partial\overline{\partial}\eta, for a function η\eta on B×ℂn−mB\times\mathbb{C}^{n-m} that satisfies

(4.9) η∘λt​(y,z)=η⁡(y,zt)=1t​η​(y,z),\eta\circ\lambda_{t}(y,z)=\eta\left(y,\frac{z}{\sqrt{t}}\right)=\frac{1}{t}\eta(y,z),

for all (y,z)(y,z) in B×ℂn−mB\times\mathbb{C}^{n-m} and any t>0t>0. It follows then that

(4.10) t​λt∗​p∗​ωS​F=t​λt∗​−1​∂∂¯​η=t​−1​∂∂¯​(η∘λt)=−1​∂∂¯​η=p∗​ωS​F,t\lambda_{t}^{*}p^{*}\omega_{SF}=t\lambda_{t}^{*}\sqrt{-1}\partial\overline{\partial}\eta=t\sqrt{-1}\partial\overline{\partial}(\eta\circ\lambda_{t})=\sqrt{-1}\partial\overline{\partial}\eta=p^{*}\omega_{SF},

as claimed. Combining (4.7) and (4.8) we get the bound (4.3). ∎

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