English

A knot without a nonorientable essential spanning surface

Geometric Topology 2017-09-15 v2

Abstract

This note gives the first example of a hyperbolic knot in the 3-sphere that lacks a nonorientable essential spanning surface; this disproves the Strong Neuwirth Conjecture formulated by Ozawa and Rubinstein. Moreover, this knot has no even strict boundary slopes, disproving the Even Boundary Slope Conjecture of the same authors. The proof is a rigorous calculation using Thurston's spun-normal surfaces in the spirit of Haken's original normal surface algorithms.

Keywords

Cite

@article{arxiv.1509.06653,
  title  = {A knot without a nonorientable essential spanning surface},
  author = {Nathan M. Dunfield},
  journal= {arXiv preprint arXiv:1509.06653},
  year   = {2017}
}

Comments

6 pages, 1 figure. V2: Minor edits, to appear in Illinois J. Math

R2 v1 2026-06-22T11:02:49.396Z