English

Simple totally disconnected locally compact groups separated by finiteness properties

Group Theory 2026-03-23 v3

Abstract

We construct a sequence of simple non-discrete totally disconnected locally compact (tdlc) groups separated by finiteness properties; that is, for every positive integer nn there exists a simple non-discrete tdlc group that is of type Fn1F_{n-1} but not of type FnF_n. This generalizes a result for discrete groups of Skipper--Witzel--Zaremsky. Furthermore, we construct a simple non-discrete tdlc group that is of type FP2FP_2 over Z\mathbb{Z} but not compactly presented. Our examples arise as Smith universal groups U(M,N)\mathcal{U}(M, N) associated to permutation groups MM and NN. We generalize a theorem of Haglund--Wise to tdlc groups and show that under mild conditions on MM and NN the finiteness properties of U(M,N)\mathcal{U}(M, N) reflect those of its local actions MM and NN.

Keywords

Cite

@article{arxiv.2509.05101,
  title  = {Simple totally disconnected locally compact groups separated by finiteness properties},
  author = {Laura Bonn and Sebastian Giersbach},
  journal= {arXiv preprint arXiv:2509.05101},
  year   = {2026}
}

Comments

15 pages, 1 figure; v2: The main theorem now holds more generally for finite graphs of groups instead of finite trees of groups; v3: Added reference, fixed hyperlinks and typos

R2 v1 2026-07-01T05:23:07.771Z