English

Small Heegaard genus and SU(2)

Geometric Topology 2025-08-20 v3

Abstract

Let YY be a closed, orientable 3-manifold with Heegaard genus 2. We prove that if H1(Y;Z)H_1(Y;\mathbb{Z}) has order 11, 33, or 55, then there is a representation π1(Y)SU(2)\pi_1(Y) \to \mathrm{SU}(2) with non-abelian image. Similarly, if H1(Y;Z)H_1(Y;\mathbb{Z}) has order 22 then we find a non-abelian representation π1(Y)SO(3)\pi_1(Y) \to \mathrm{SO}(3). We also prove that a knot KK in S3S^3 is a trefoil if and only if there is a unique conjugacy class of irreducible representations π1(S3K)SU(2)\pi_1(S^3\setminus K) \to \mathrm{SU}(2) sending a fixed meridian to (i00i)\left(\begin{smallmatrix}i&0\\0&-i\end{smallmatrix}\right).

Keywords

Cite

@article{arxiv.2309.09780,
  title  = {Small Heegaard genus and SU(2)},
  author = {John A. Baldwin and Steven Sivek},
  journal= {arXiv preprint arXiv:2309.09780},
  year   = {2025}
}

Comments

19 pages; v2: added another example to the introduction; v3: minor changes, accepted version

R2 v1 2026-06-28T12:24:49.566Z