Minimal pseudo-Anosov stretch factors on nonoriented surfaces

Livio Liechti; Balázs Strenner

doi:10.2140/agt.2020.20.451

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arXiv · 1806.00033

Minimal pseudo-Anosov stretch factors on nonoriented surfaces

Livio Liechti·Balázs Strenner

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Abstract

We determine the smallest stretch factor among pseudo-Anosov maps with an orientable invariant foliation on the closed nonorientable surfaces of genus 4, 5, 6, 7, 8, 10, 12, 14, 16, 18 and 20. We also determine the smallest stretch factor of an orientation-reversing pseudo-Anosov map with orientable invariant foliations on the closed orientable surfaces of genus 1, 3, 5, 7, 9 and 11. As a byproduct, we obtain that the stretch factor of a pseudo-Anosov map on a nonorientable surface or an orientation-reversing pseudo-Anosov map on an orientable surface does not have Galois conjugates on the unit circle. This shows that the techniques that were used to disprove Penner's conjecture on orientable surfaces are ineffective in the nonorientable cases.

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Livio Liechti, Balázs Strenner. 2018-05-31. Minimal pseudo-Anosov stretch factors on nonoriented surfaces. https://doi.org/10.2140/agt.2020.20.451

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