The unstabilized canonical Heegaard splitting of a mapping torus

Zou, Yanqing

doi:10.2140/agt.2017.17.3435

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The unstabilized canonical Heegaard splitting of a mapping torus

Yanqing Zou

Algebraic & Geometric Topology 17 (2017) 3435–3448

DOI: 10.2140/agt.2017.17.3435

Abstract

Let $S$ be a closed orientable surface of genus at least $2$ . The action of an automorphism $f$ on the curve complex of $S$ is an isometry. Via this isometric action on the curve complex, a translation length is defined on $f$ . The geometry of the mapping torus $M_{f}$ depends on $f$ . As it turns out, the structure of the minimal-genus Heegaard splitting also depends on $f$ : the canonical Heegaard splitting of $M_{f}$ , constructed from two parallel copies of $S$ , is sometimes stabilized and sometimes unstabilized. We give an example of an infinite family of automorphisms for which the canonical Heegaard splitting of the mapping torus is stabilized. Interestingly, complexity bounds on $f$ provide insight into the stability of the canonical Heegaard splitting of $M_{f}$ . Using combinatorial techniques developed on $3$ –manifolds, we prove that if the translation length of $f$ is at least $8$ , then the canonical Heegaard splitting of $M_{f}$ is unstabilized.

Keywords

Heegaard splitting, stabilization, mapping torus, translation length

Mathematical Subject Classification 2010

Primary: 57M27

Secondary: 57M50

References

Publication

Received: 23 April 2016

Revised: 14 May 2017

Accepted: 25 May 2017

Published: 4 October 2017

Authors

Yanqing Zou
Department of Mathematics Dalian Minzu University Dalian China

Volume 17, issue 6 (2017)