Studying Stein's Groups as Topological Full Groups

Owen Tanner

Published 2023-12-12Version 1

We include a class of generalisations of Thompson's group $V$ introduced by Melanie Stein into the growing framework of topological full groups. Like $V$, Stein's groups can be described as certain piecewise linear maps with prescribed slopes and nondifferentiable points. Stein's groups include the class of groups where the group of slopes is generated by multiple integers (which we call Stein's integral groups) and when the group of slopes is generated by a single irrational number, such as Cleary's group, (which we call irrational slope Thompson's groups). We give a unifying dynamical proof that whenever the group of slopes is finitely generated, the derived subgroup of the associated Stein's groups is simple and finitely generated. We then study the homology of Stein's groups, building on the work of others. This line of inquiry allows us to compute the abelianisations and rational homology concretely for many examples.