English

Boundary slopes (nearly) bound exceptional slopes

Geometric Topology 2025-06-24 v2

Abstract

For a hyperbolic knot in S3S^3, Dehn surgery along slope r\Q{10}r \in \Q \cup \{\frac10\} is {\em exceptional} if it results in a non-hyperbolic manifold. We say meridional surgery, r=10r = \frac10, is {\em trivial} as it recovers the manifold S3S^3. We provide evidence in support of two conjectures. The first (inspired by a question of Professor Motegi) states that there are boundary slopes b1<b2b_1 < b_2 such that all non-trivial exceptional surgeries occur, as rational numbers, in the interval [b1,b2][b_1,b_2]. We say a boundary slope is {\em NIT} if it is non-integral or toroidal. Second, when there are non-trivial exceptional surgeries, we conjecture there are NIT boundary slopes b1b2b_1 \leq b_2 so that the exceptional surgeries lie in [\floorb1,\ceilb2][\floor{b_1},\ceil{b_2}]. Moreover, if \ceilb1\floorb2\ceil{b_1} \leq \floor{b_2}, the integers in the interval [\ceilb1,\floorb2][ \ceil{b_1}, \floor{b_2} ] are all exceptional surgeries.

Keywords

Cite

@article{arxiv.2309.09918,
  title  = {Boundary slopes (nearly) bound exceptional slopes},
  author = {Kazuhiro Ichihara and Thomas W. Mattman},
  journal= {arXiv preprint arXiv:2309.09918},
  year   = {2025}
}

Comments

(v1): 17 pages, 3 figures (v2): minor edits, 18 pages, 3 figures

R2 v1 2026-06-28T12:25:03.777Z