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arXiv 2012.01713math.DGmath.MG

流形的留数

Residues of manifolds

Jun O'Hara

AI总结:

本文定义并研究流形 Riesz 能量解析延拓后的留数,证明其 Möbius 不变性,引入相对、加权和局部留数以表达曲率与 Euler 示性数,并说明其独立于已知渐近几何量。

摘要:

流形 X 的 Riesz z-能量是两点间距离的 z 次幂在乘积空间 X×X 上的积分。把它视为复变量 z 的函数时,可通过解析延拓推广为亚纯函数,我们称之为 X 的亚纯能量函数。它仅在某些负整数处具有单极点。流形 X 的留数就是该亚纯能量函数的留数。例如,R³ 中曲面的体积和 Willmore 能量都可作为留数得到。本文中,我们首先证明欧几里得空间中闭子流形或紧体在 z=-2 dim X 处留数的 Möbius 不变性。我们引入紧体的相对留数和加权留数,并证明维数小于 4 的紧体的标量曲率、平均曲率以及 Euler 示性数都可用留数和局部留数表示。当 X 是欧几里得空间中的闭子流形时,我们研究为获得(全局)留数而对 X 的局部定义函数所需的微分阶数。我们还证明了容斥原理。留数看起来类似于通过渐近展开得到的量,例如内蕴体积(Lipschitz-Killing 曲率)、Laplacian 谱以及 Graham-Witten 能量。我们证明留数独立于这些量。最后,我们为 R⁵ 中的 4 维超曲面引入一种 Möbius 不变主曲率能量,并将 Graham-Witten 能量用留数、Weyl 张量以及这种 Möbius 不变主曲率能量表示。

英文摘要:

The Riesz $z$-energy of a manifold $X$ is the integration of the distance between two points to the power $z$ over the product space $X\times X$. Considered as a function of a complex variable $z$, it can be generalized to a meromorphic function by analytic continuation, which we will call the meromorphic energy function of $X$. It has only simple poles at some negative integers. The residues of a manifold $X$ are the residues of the meromorphic energy function. For example, the volume and the Willmore energy for surfaces in $\mathbb{R}^3$ can be obtained as residues. In this paper we first show the Möbius invariance of the residue at $z=-2\dim X$ of a closed submanifold or a compact body in a Euclidean space. We introduce the relative residues for compact bodies and weighted residues, and show that the scalar curvature and the mean curvature as well as the Euler characteristic of compact bodies of dimension less than $4$ can be expressed in terms of residues and local residues. We study the order of differentiaion of a local defining function of $X$ that is necessary to obtain the (global) residues when $X$ is a closed submanifold of a Euclidean space. We also show the inclusion-exclusion principle. Residues appear to be similar to quantities obtained by asymptotic expansion such as intrinsic volumes (Lipschitz-Killing curvatures), spectra of Laplacian, and the Graham-Witten energy. We show that residues are independent from them. Finally we introduce a \M invariant principal curvature energy for $4$-dimensional hypersurfaces in $\mathbb{R}^5$, and express the Graham-Witten energy in terms of the residues, Weyl tensor, and this Möbius invariant principal curvature energy.

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