English

Reidemeister classes in lamplighter type groups

Group Theory 2017-11-28 v1 Representation Theory

Abstract

We prove that for any automorphism ϕ\phi of the restricted wreath product Z2wrZk\mathbb{Z}_2 \mathrm{wr} \mathbb{Z}^k and Z3wrZ2d\mathbb{Z}_3 \mathrm{wr} \mathbb{Z}^{2d} the Reidemeister number R(ϕ)R(\phi) is infinite, i.e. these groups have the property RR_\infty. For Z3wrZ2d+1\mathbb{Z}_3 \mathrm{wr} \mathbb{Z}^{2d+1} and ZpwrZk\mathbb{Z}_p \mathrm{wr} \mathbb{Z}^k, where p>3p>3 is prime, we give examples of automorphisms with finite Reidemeister numbers. So these groups do not have the property RR_\infty. For these groups and ZmwrZ\mathbb{Z}_m \mathrm{wr} \mathbb{Z}, where mm is relatively prime to 66, we prove the twisted Burnside-Frobenius theorem (TBFTf_f): if R(ϕ)<R(\phi)<\infty, then it is equal to the number of equivalence classes of finite-dimensional irreducible unitary representations fixed by the action [ρ][ρϕ][\rho]\mapsto [\rho\circ\phi].

Keywords

Cite

@article{arxiv.1711.09371,
  title  = {Reidemeister classes in lamplighter type groups},
  author = {Evgenij Troitsky},
  journal= {arXiv preprint arXiv:1711.09371},
  year   = {2017}
}

Comments

11 pages

R2 v1 2026-06-22T22:57:04.962Z