English

Fundamental group in the projective knot theory

Geometric Topology 2020-06-09 v1

Abstract

In this paper, properties of a link LL in the projective space RP3\mathbb R P^3 are related to properties of its group π1(RP3L)\pi_1(\mathbb R P^3\smallsetminus L): LL is isotopic to a projective line if and only if π1(RP3L)=Z\pi_1(\mathbb R P^3\smallsetminus L)=\mathbb Z. LL is isotopic to an affine circle if and only if π1(RP3L)=ZZ/2\pi_1(\mathbb R P^3\smallsetminus L)=\mathbb Z*\mathbb Z_{/2}. LL is isotopic to a link disjoint from a projective plane if and only if π1(RP3L)\pi_1(\mathbb R P^3\smallsetminus L) contains a non-trivial element of order two. A simple algorithm which finds a system of generators and relations for π1(RP3L)\pi_1(\mathbb R P^3\smallsetminus L) in terms of a link diagram of LL is provided.

Cite

@article{arxiv.2006.04032,
  title  = {Fundamental group in the projective knot theory},
  author = {Julia Viro and Oleg Viro},
  journal= {arXiv preprint arXiv:2006.04032},
  year   = {2020}
}

Comments

21 pages. This is an expanded version of a preprint arXiv:1901.07686 [math.GT] of the second author

R2 v1 2026-06-23T16:07:11.451Z