English

Geometric realisation over aspherical groups

Algebraic Topology 2023-12-06 v1 Group Theory Geometric Topology Rings and Algebras

Abstract

We prove that the direct sums of extensions of scalars of relation modules are geometrically realisable as the second homotopy group of a finite 2-complex. We use this to exhibit a finite 2-complex with fundamental group the (10,15)(10,15) torus knot group and non-free π2\pi_2, yielding exotic presentations of a group for which no such examples had previously been known. We conclude by constructing stably free non-free modules over an infinite family of Baumslag-Solitar groups; it remains to determine whether these modules are geometrically realisable by finite 2-complexes.

Keywords

Cite

@article{arxiv.2312.02948,
  title  = {Geometric realisation over aspherical groups},
  author = {William Thomas},
  journal= {arXiv preprint arXiv:2312.02948},
  year   = {2023}
}

Comments

18 pages. Comments welcome

R2 v1 2026-06-28T13:41:57.238Z