# Möbius characterization of the boundary at infinity of rank one symmetric spaces

Buyalo, Sergei; Schroeder, Viktor (2013). Möbius characterization of the boundary at infinity of rank one symmetric spaces. Geometriae Dedicata, 172(1):1-45.

## Abstract

Möbius structure (on a set X ) is a class of metrics having the same cross-ratios. A Möbius structure is Ptolemaic if it is invariant under inversion operations. The boundary at infinity of a CAT(−1) space is in a natural way a Möbius space, which is Ptolemaic. We give a free of classification proof of the following result that characterizes the rank one symmetric spaces of noncompact type purely in terms of their Möbius geometry: Let X be a compact Ptolemy space which contains a Ptolemy circle and allows many space inversions. Then X is Möbius equivalent to the boundary at infinity of a rank one symmetric space.

Möbius structure (on a set X ) is a class of metrics having the same cross-ratios. A Möbius structure is Ptolemaic if it is invariant under inversion operations. The boundary at infinity of a CAT(−1) space is in a natural way a Möbius space, which is Ptolemaic. We give a free of classification proof of the following result that characterizes the rank one symmetric spaces of noncompact type purely in terms of their Möbius geometry: Let X be a compact Ptolemy space which contains a Ptolemy circle and allows many space inversions. Then X is Möbius equivalent to the boundary at infinity of a rank one symmetric space.

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Item Type: Journal Article, refereed, original work 07 Faculty of Science > Institute of Mathematics 510 Mathematics English August 2013 27 Dec 2013 13:20 05 Apr 2016 17:17 Springer 0046-5755 https://doi.org/10.1007/s10711-013-9906-6
Permanent URL: https://doi.org/10.5167/uzh-87103