English

The generating graph of a profinite group

Group Theory 2020-02-18 v1

Abstract

Let GG be 2-generated group. The generating graph Γ(G)\Gamma(G) of GG is the graph whose vertices are the elements of GG and where two vertices gg and hh are adjacent if G=g,h.G = \langle g, h \rangle. This definition can be extended to a 2-generated profinite group G,G, considering in this case topological generation. We prove that the set V(G)V(G) of non-isolated vertices of Γ(G)\Gamma(G) is closed in GG and that, if GG is prosoluble, then the graph Δ(G)\Delta(G) obtained from Γ(G)\Gamma(G) by removing its isolated vertices is connected with diameter at most 3. However we construct an example of a 2-generated profinite group GG with the property that Δ(G)\Delta(G) has 202^{\aleph_0} connected components. This implies that the so called "swap conjecture" does not hold for finitely generated profinite groups. We also prove that if an element of V(G)V(G) has finite degree in the graph Γ(G),\Gamma(G), then GG is finite.

Keywords

Cite

@article{arxiv.2002.06384,
  title  = {The generating graph of a profinite group},
  author = {Andrea Lucchini},
  journal= {arXiv preprint arXiv:2002.06384},
  year   = {2020}
}
R2 v1 2026-06-23T13:42:42.664Z