English

Singular instanton homology of dual knots

Geometric Topology 2025-11-26 v1

Abstract

We establish a dimension formula for the unreduced singular instanton homology of dual knots K~p/qSp/q3(K)\widetilde{K}_{p/q}\subset S^3_{p/q}(K) for a knot KS3K\subset S^3: dimI(Sp/q3(K),K~p/q,ω;K)=2qrK(K)+2pqνK(K) for p/qνK(K), \dim I^\sharp(S^3_{p/q}(K),\widetilde{K}_{p/q},\omega; \mathbb{K}) = 2q \cdot r_{\mathbb{K}}(K) + 2|p - q \cdot \nu^\sharp_{\mathbb{K}}(K)|~\mathrm{for}~p/q\neq \nu^\sharp_{\mathbb{K}}(K), where ωS3\K\omega\subset S^3\backslash K is any unoriented 11-submanifold as the bundle set, rK(K)r_{\mathbb{K}}(K) and νK(K)\nu^\sharp_{\mathbb{K}}(K) are integers from the dimension formula of I(Sp/q3(K);K)I^\sharp(S^3_{p/q}(K);\mathbb{K}) for a field K\mathbb{K} defined by Li and the author. In particular, when K\mathbb{K} is the two-element field F2\mathbb{F}_2, the reduced singular instanton homology satisfiesdimI(Sp/q3(K),K~p/q,ω;F2)=dimI(Sp/q3(K);F2) for p/qνF2(K).\dim I^\natural(S^3_{p/q}(K),\widetilde{K}_{p/q},\omega;\mathbb{F}_2)=\dim I^\sharp(S^3_{p/q}(K);\mathbb{F}_2)~\mathrm{for}~p/q\neq \nu^\sharp_{\mathbb{F}_2}(K).As an application, for a determinant-one knot KS3K\subset S^3 other than the unknot and the torus knots T2,3,T2,5T_{2,3},T_{2,5} and a rational p/q(0,6)p/q\in (0,6) with pp odd prime power, the surgery manifold Y^p/2q(K^)\widehat{Y}_{p/2q}(\widehat{K}) is not SU(2)SU(2)-abelian for the double branched cover Y^=Σ(S3,K)\widehat{Y}=\Sigma(S^3,K) and the preimage K^Y^\widehat{K}\subset \widehat{Y} of KK. We also obtain non-abelian results for SU(2)SU(2) representations of the knot complement that send the curves of some fixed slope in (0,6)(0,6) to traceless elements.

Keywords

Cite

@article{arxiv.2511.19883,
  title  = {Singular instanton homology of dual knots},
  author = {Fan Ye},
  journal= {arXiv preprint arXiv:2511.19883},
  year   = {2025}
}

Comments

15 pages, no figures; Comments are welcome