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arXiv 1511.08093math.DG
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分层空间的一个Obata奇异性定理

An Obata singular theorem for stratified spaces

Ilaria Mondello

摘要:

考虑一个在正则集上具有正Ricci下界且锥角不大于2 $π$的分层空间。对于这样的分层空间,我们知道拉普拉斯算子的第一个非零特征值大于或等于维数。我们在这里证明了一个Obata刚性的结果时,达到的平等:下界的频谱达到当且仅当分层空间是等距的球形悬浮。此外,我们还证明了直径至多等于$π$,并且直径等于$π$和拉普拉斯算子的第一非零特征值等于维数是等价的.最后给出了这些结果与Yamabe问题相关的一个结果。考虑一个锥角不大于2 $π$的爱因斯坦分层空间:如果存在一个与爱因斯坦度量共形且具有常数数量曲率的度量,那么它也是一个爱因斯坦度量。此外,如果它的共形因子不是常数,那么空间是等距的球形悬架。

英文摘要:

Consider a stratified space with a positive Ricci lower bound on the regular set and no cone angle larger than 2$π$. For such stratified space we know that the first non-zero eigenvalue of the Laplacian is larger than or equal to the dimension. We prove here an Obata rigidity result when the equality is attained: the lower bound of the spectrum is attained if and only if the stratified space is isometric to a spherical suspension. Moreover, we show that the diameter is at most equal to $π$, and it is equivalent for the diameter to be equal to $π$ and for the first non-zero eigenvalue of the Laplacian to be equal to the dimension. We finally give a consequence of these results related to the Yamabe problem. Consider an Einstein stratified space without cone angles larger than 2$π$: if there is a metric conformal to the Einstein metric and with constant scalar curvature, then it is an Einstein metric as well. Furthermore, if its conformal factor is not a constant, then the space is isometric to a spherical suspension.

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