English

Forest Diagrams and Lengths for the Generalised Thompson's Group $F(n)$

Group Theory 2026-05-11 v1

Abstract

We extend the concept of two-way forest diagrams, introduced by Belk and Brown in 2003, to represent elements of F(n)F(n) as a pair of infinite, bounded nn-ary forests together with an order-preserving bijection of the leaves. This representation allows us to develop an alternative way to compute the length of an element of F(n)F(n), distinct from the formula established by Fordham and Cleary in 2009. As an application of our length formula, we re-prove the existence of dead end elements in F(n)F(n) and show that their depth is always two, first proved by Wladis in 2009.

Keywords

Cite

@article{arxiv.2605.06739,
  title  = {Forest Diagrams and Lengths for the Generalised Thompson's Group $F(n)$},
  author = {Martín Gómez Reynolds},
  journal= {arXiv preprint arXiv:2605.06739},
  year   = {2026}
}

Comments

20 pages, 23 figures