16 citations · 41 across the 4 of their papers we have counts for
4 papers
Wreath products of cocommutative Hopf algebras
Laurent Bartholdi, Olivier Siegenthaler, Todd Trimble
We define wreath products of cocommutative Hopf algebras, and show that they enjoy a universal property for coalgebra-split extensions, analogous to the Kaloujnine-Krasner theorem…
The Twisted Twin of the Grigorchuk Group
Laurent Bartholdi, Olivier Siegenthaler
We study a twisted version of Grigorchuk's first group, and stress its similarities and differences to its model. In particular, we show that it admits a finite endomorphic present…
The congruence subgroup problem for branch groups
Laurent Bartholdi, Olivier Siegenthaler, Pavel Zalesskii
We state and study the congruence subgroup problem for groups acting on rooted tree, and for branch groups in particular. The problem is reduced to the computation of the congruenc…
Hausdorff dimension of some groups acting on the binary tree
Olivier Siegenthaler
Based on the work of Abercrombie, Barnea and Shalev gave an explicit formula for the Hausdorff dimension of a group acting on a rooted tree. We focus here on the binary tree T. Abe…