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arXiv 2003.13105math.GTmath.DG
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Weil-Petersson完备化的层分离和长度函数的梯度估计

Strata Separation for the Weil-Petersson Completion and Gradient Estimates for Length Functions

Martin Bridgeman, Kenneth Bromberg

摘要:

一般来说,很难在Teichmüller空间上用Weil-Petersson度量距离。这里我们考虑有限型曲面Teichmüller空间的Weil-Petersson完备化中的层间距离。Wolpert表明,地层的封闭不相交,有一个明确的分离独立的拓扑结构的表面。我们证明了这个最小分离的最优值是一个常数$δ_{1,1}$,并表明它是实现的节点相交一次的地层。我们也给了一个几乎尖锐的估计$δ_{1,1}$和$δ_{1,1}$和其他距离之间的差距的大小给出了一个下界。一个主要组成部分的文件是一个有效的版本Wolpert的上界$ \langle \nabla \ell_α,\nabla \ell_β\rangle$,内积的威尔-彼得森梯度的长度函数。我们进一步用曲面收缩期的长度来限定双曲曲面到Teichmüller空间边界的距离。我们还获得了新的下界收缩的Weil-Petersson度量的模空间的穿孔环面。

英文摘要:

In general, it is difficult to measure distances in the Weil-Petersson metric on Teichmüller space. Here we consider the distance between strata in the Weil-Petersson completion of Teichmüller space of a surface of finite type. Wolpert showed that for strata whose closures do not intersect, there is a definite separation independent of the topology of the surface. We prove that the optimal value for this minimal separation is a constant $δ_{1,1}$ and show that it is realized exactly by strata whose nodes intersect once. We also give a nearly sharp estimate for $δ_{1,1}$ and give a lower bound on the size of the gap between $δ_{1,1}$ and the other distances. A major component of the paper is an effective version of Wolpert's upper bound on $ \langle \nabla \ell_α,\nabla \ell_β\rangle$, the inner product of the Weil-Petersson gradient of length functions. We further bound the distance to the boundary of Teichmüller space of a hyperbolic surface in terms of the length of the systole of the surface. We also obtain new lower bounds on the systole for the Weil-Petersson metric on the moduli space of a punctured torus.

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