English

On the hyperbolic distance of $n$-times punctured spheres

Complex Variables 2017-07-19 v1

Abstract

The length of the shortest closed geodesic in a hyperbolic surface XX is called the systole of X.X. When XX is an nn-times punctured sphere C^A\hat{ \mathbb{C}} \setminus A where AC^A \subset \hat{\mathbb{C}} is a finite set of cardinality n4,n\ge4, we define a quantity Q(A)Q(A) in terms of cross ratios of quadruples in AA so that Q(A)Q(A) is quantitatively comparable with the systole of X.X. We next propose a method to construct a distance function dXd_X on a punctured sphere XX which is Lipschitz equivalent to the hyperbolic distance hXh_X on X.X. In particular, when the construction is based on a modified quasihyperbolic metric, dXd_X is Lipschitz equivalent to hXh_X with Lipschitz constant depending only on Q(A).Q(A).

Keywords

Cite

@article{arxiv.1707.05773,
  title  = {On the hyperbolic distance of $n$-times punctured spheres},
  author = {Toshiyuki Sugawa and Matti Vuorinen and Tanran Zhang},
  journal= {arXiv preprint arXiv:1707.05773},
  year   = {2017}
}

Comments

20 pages, 1 figure