3.7.1. Relative Gibbons-Hawking potential [043L]
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3.7.1. Relative Gibbons-Hawking potential
We plan to exhibit a -bundle preserving diffeomorphism between the Taub-NUT type and the positive vertex space over the common base , with good estimates on the deviations between both Kähler structures.
Since , the -periodic copies of such punctured discs do not overlap.
The topology of the -bundle structures on both spaces agree by construction. The remaining degrees of freedom in defining amounts to a gauge choice, which is the same as a prescription of .
As a general guideline, the corresponding quantities on and have the same singularity, so their difference are smooth quantities. We use superscripts for quantities on to disambiguate from quantities on .
Lemma 3.25.
Over the region ,
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Proof.
The absolute estimate follows from Lemma 3.2. The higher order estimate follows from -harmonicity.
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Lemma 3.26.
Over the disc
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Proof.
The absolute estimate is contained in Lemma 3.7. The higher order estimates follow from the differential relations between and , vis-a-vis and (cf. Lemma 2.7).
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Corollary 3.27.
There is a real-valued relative Gibbons-Hawking potential on the disc , such that its second derivatives are given by
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We can demand the estimates in :
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Proof.
The existence of with presecribed second order derivatives is a consequence of integrability, notably Lemma 2.7 and its counterpart for . If we impose that and its first order derivatives vanish at the origin, then the estimates follow immediately from the Lemmas above and Proposition 3.23.
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