Genus 9 and 11 minimal stretch factor conjecture for nonorientable surfaces

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Let NgN_g be the closed nonorientable surface of genus gg, and let δ+(Ng)\delta^+(N_g) be the minimal stretch factor among pseudo-Anosov homeomorphisms of NgN_g with an orientable invariant foliation. The singularity type records the prong numbers of the singularities of a minimizing pseudo-Anosov map.

Genus 9 and 11 minimal stretch factor conjecture. The minimal stretch factors and minimal polynomials are predicted to be

gδ+(Ng)≈Minimal polynomial of δ+(Ng)singularity type91.35680x8−x5−x4−x3−1(16)111.22262x12−x7−x6−x5−1x2+x+1(8,8,8)\begin{array}{c|c|c|c} g & \delta^+(N_g)\approx & \text{Minimal polynomial of }\delta^+(N_g) & \text{singularity type}\\ \hline 9 & 1.35680 & x^8-x^5-x^4-x^3-1 & (16)\\ 11 & 1.22262 & \dfrac{x^{12}-x^7-x^6-x^5-1}{x^2+x+1} & (8,8,8) \end{array}

These predictions concern the cases not settled by the paper's elimination tests: the authors state that the remaining candidate polynomials should be eliminable and that their constructed examples should be minimal. The conjecture is open in the source.

References

Primary source

Livio Liechti and Balázs Strenner, “Minimal pseudo-Anosov stretch factors on nonoriented surfaces”, arXiv:1806.00033 (2020).

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