English

Twin groups representations

Representation Theory 2026-04-06 v3 Group Theory

Abstract

We construct two representations of the twin group Tn,n2T_n, n\geq 2, namely η1:TnAut(Fn)\eta_1: T_n \rightarrow \text{Aut}(\mathbb{F}_n) and η2:TnGLn(Z[t±1])\eta_2: T_n \rightarrow \text{GL}_n(\mathbb{Z}[t^{\pm 1}]), where Fn\mathbb{F}_n is a free group with nn generators and tt is indeterminate. We then analyze some characteristics of these two representations, such as irreducibility and faithfulness. Moreover, we prove that both representations can be extended to the virtual twin group VTnVT_n in the 22-local extension way, for n2n\geq 2, and we find their 22-local extensions. On the other hand, we obtain a different result for the welded twin group WTnWT_n. More deeply, we show that η1\eta_1 cannot be extended to WTnWT_n in the 22-local extension way, for n3n\geq 3, while η2\eta_2 can be extended to WTnWT_n in the 22-local extension way, for n2n\geq 2, and we find its 22-local extensions.

Cite

@article{arxiv.2507.15005,
  title  = {Twin groups representations},
  author = {Mohamad N. Nasser},
  journal= {arXiv preprint arXiv:2507.15005},
  year   = {2026}
}
R2 v1 2026-07-01T04:10:01.896Z