English

The "spread" of Thompson's group $F$

Group Theory 2024-03-01 v1

Abstract

Recall that a group GG is said to be 32\frac{3}{2}-generated if every non-trivial element gGg\in G has a co-generator in GG (i.e., an element which together with gg generates GG). Thompson's group VV was proved to be 32\frac{3}{2}-generated by Donoven and Harper in 2019. It was the first example of an infinite finitely presented non-cyclic 32\frac{3}{2}-generated group. In 2022, Bleak, Harper and Skipper proved that Thompson's group TT is also 32\frac{3}{2}-generated. Since the abelianization of Thompson's group FF is Z\mathbb{Z}, it cannot be 32\frac{3}{2}-generated. However, we recently proved that Thompson's group FF is "almost" 32\frac{3}{2}-generated in the sense that every element of FF whose image in the abelianization forms part of a generating pair of Z2\mathbb{Z}^2 is part of a generating pair of FF. A natural generalization of 32\frac{3}{2}-generation is the notion of spread. Recall that the spread of a group GG is the supremum over all integers kk such that every kk non-trivial elements of GG have a common co-generator in GG. The uniform spread of a group GG is the supremum over all integers kk for which there exists a conjugacy class CGC\subseteq G such that every kk non-trivial elements of GG have a common co-generator which belongs to CC. In this paper we study modified versions of these notions for Thompson's group FF.

Keywords

Cite

@article{arxiv.2402.19444,
  title  = {The "spread" of Thompson's group $F$},
  author = {Gili Golan},
  journal= {arXiv preprint arXiv:2402.19444},
  year   = {2024}
}

Comments

21 pages, 1 figure. arXiv admin note: text overlap with arXiv:2210.03564