Small Heegaard genus and SU(2)

Abstract

Let $Y$ be a closed, orientable 3-manifold with Heegaard genus 2. We prove that if $H_1(Y;\mathbb{Z})$ has order $1$, $3$, or $5$, then there is a representation ${\pi }_1(Y)\to \mathrm{SU}(2)$ with non-abelian image. Similarly, if $H_1(Y;\mathbb{Z})$ has order $2$ then we find a non-abelian representation ${\pi }_1(Y)\to \mathrm{SO}(3)$. We also prove that a knot $K$ in $S^3$ is a trefoil if and only if there is a unique conjugacy class of irreducible representations ${\pi }_1(S^3\setminus K)\to \mathrm{SU}(2)$ sending a fixed meridian to $\left(\begin{array}{cc}i& 0\\ 0& -i\end{array}\right)$.

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

References in corpus (3)

• Instanton L-spaces and splicing
• Small Dehn surgery and SU(2)
• Fixed-point-free pseudo-Anosov homeomorphisms, knot Floer homology and the cinquefoil