English

Comparing $h$-genera, Bridge-1 genera and Heegaard genera of knots

Geometric Topology 2025-04-29 v1

Abstract

Let h(K)h(K), gH(K)g_H(K), g1(K)g_1(K), t(K)t(K) be the hh-genus, Heegaard genus, bridge-1 genus, tunnel number of a knot KK in the 33-sphere S3S^3, respectively. It is known that gH(K)1=t(K)g1(K)h(K)gH(K)g_H(K)-1=t(K)\leq g_1(K)\leq h(K)\leq g_H(K). A natural question arises: when do these invariants become equal? We provide the necessary and sufficient conditions for equality and use these to show that for each integer n1n\geq 1, the following three families of knots are infinite: \begin{eqnarray} A_{n}=\{K\mid t(K)=n<g_1(K)\}, B_{n}=\{K\mid g_1(K)=n<h(K)\}, C_{n}=\{K\mid h(K)=n<g_H(K)\}. \end{eqnarray} This result resolves a conjecture in \cite{Mo2}, confirming that each of these families is infinite.

Keywords

Cite

@article{arxiv.2504.19118,
  title  = {Comparing $h$-genera, Bridge-1 genera and Heegaard genera of knots},
  author = {Ruifeng Qiu and Chao Wang and Yanqing Zou},
  journal= {arXiv preprint arXiv:2504.19118},
  year   = {2025}
}

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