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arXiv 2109.06340math.DG
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$\mathrm{Spin}(7)$-结构的调和流

Harmonic flow of $\mathrm{Spin}(7)$-structures

Shubham Dwivedi, Eric Loubeau, Henrique N. Sá Earp

AI总结:

本文研究紧致8维流形上Spin(7)-结构的调和流,建立Shi型估计、单调性公式与ε-正则性定理,证明紧性定理并刻画Type-I奇点,同时给出基于旋量平方的Bryant型描述。

摘要:

我们提出并研究了紧致8维流形上$\mathrm{Spin}(7)$-结构的等距流,将其作为几何结构调和流的一个实例。从一般视角出发,我们建立了Shi型估计,并证明了任意$H$-结构等距流的调和孤子与自相似解之间的对应关系。随后我们专门研究$H=\mathrm{Spin}(7)\subset\mathrm{SO}(8)$的情形,通过沿流的单调性公式获得长时间存在性条件,该公式实际上导出了一个$\varepsilon$-正则性定理。此外,我们证明了调和流解的Cheeger--Gromov型和Hamilton型紧性定理,并刻画了Type-$\mathrm{I}$奇点,证明其以收缩孤子为模型。我们还基于旋量的平方建立了等距$\mathrm{Spin}(7)$-结构的Bryant型描述,这一结果可能具有独立的研究价值。

英文摘要:

We formulate and study the isometric flow of $\mathrm{Spin}(7)$-structures on compact $8$-manifolds, as an instance of the harmonic flow of geometric structures. Starting from a general perspective, we establish Shi-type estimates and a correspondence between harmonic solitons and self-similar solutions for arbitrary isometric flows of $H$-structures. We then specialise to $H=\mathrm{Spin}(7)\subset\mathrm{SO}(8)$, obtaining conditions for long-time existence, via a monotonicity formula along the flow, which actually leads to an $\varepsilon$-regularity theorem. Moreover, we prove Cheeger--Gromov and Hamilton-type compactness theorems for the solutions of the harmonic flow, and we characterise Type-$\mathrm{I}$ singularities as being modelled on shrinking solitons.We also establish a Bryant-type description of isometric $\mathrm{Spin}(7)$-structures, based on squares of spinors, which may be of independent interest.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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