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Xin Nie
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Reference request: flat surfaces

When writing a paper, I feel like to point out exact references to the following seemly easy facts concerning flat structures on a closed surface $\Sigma$ with negative Euler characteristic:

  1. The universal cover $\widetilde{\Sigma}$ equipped with the pullback of any flat metric with conic singularity is quasi-isometric to the hyperbolic plane.
  2. Define two flat metrics $g_1$ and $g_2$ by means of holomorphic $n$-differentials $U_1$ and $U_2$. Then the pullbacks of $g_1$ and $g_2$ to $\widetilde{\Sigma}$ are quasi-isometric and the ratio of quasi-isometry can be controlled by $\|U_1-U_2\|$.

Please either give me a reference or a simple proof/explanation. Any help is appreciated!

Xin Nie
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  • 11
  • 24