English

Virtual retracts in groups acting on rooted trees

Group Theory 2026-01-26 v1

Abstract

We study virtual retracts in groups acting on rooted trees. We show that finitely generated branch groups do not have the local retraction (LR) property. Furthermore, we specialize to iterated monodromy groups of post-critically finite quadratic complex polynomials and show that the (LR) property characterizes, among post-critically finite quadratic complex polynomials, those with a euclidean orbifold, i.e. the powering map and the Chebyshev polynomial. Lastly, we show that periodic quadratic complex polynomials provide new examples of pro-22 groups with complete finitely generated Hausdorff spectrum.

Keywords

Cite

@article{arxiv.2601.16869,
  title  = {Virtual retracts in groups acting on rooted trees},
  author = {Jorge Fariña-Asategui and Jon Merladet Urigüen},
  journal= {arXiv preprint arXiv:2601.16869},
  year   = {2026}
}

Comments

17 pages

R2 v1 2026-07-01T09:17:34.785Z