English

$SU(2)$-representations of Branched Covers

Geometric Topology 2025-08-28 v1

Abstract

We study the existence of irreducible SU(2)SU(2)-representations for cyclic branched covers of knots in S3S^3. Our main result establishes that if KK is a non-trivial prime knot and dd is an integer such that d2d \geq 2 and Σd(K)\Sigma_d(K) is an integer homology sphere, then π1(Σd(K))\pi_1(\Sigma_d(K)) admits an irreducible SU(2)SU(2)-representation, whenever KK satisfies one of two conditions: either KK is 22-periodic, or KK can be represented as the closure of a tangle adapted to a d×dd\times d SICUP matrix. The first condition leverages a commuting trick for covering spaces to realize higher-degree branched covers as 2-fold covers, allowing us to apply recent results of Kronheimer-Mrowka and others. The second condition uses equivariant surgery descriptions and the ν\nu^\sharp invariant from instanton Floer homology. As applications, we provide new infinite families of hyperbolic integer homology spheres admitting irreducible representations, including examples where previously known criteria fail.

Keywords

Cite

@article{arxiv.2508.19669,
  title  = {$SU(2)$-representations of Branched Covers},
  author = {Sudipta Ghosh and Zhenkun Li and Juanita Pinzón-Caicedo},
  journal= {arXiv preprint arXiv:2508.19669},
  year   = {2025}
}

Comments

21 pages, 7 figures, comments are welcome