Asymptotically rigid mapping class groups I: Finiteness properties of braided Thompson's and Houghton's groups

Abstract

This article is dedicated to the study of asymptotically rigid mapping class groups of infinitely-punctured surfaces obtained by thickening planar trees. Such groups include the braided Ptolemy-Thompson groups $T^{♯},T^{\ast }$ introduced by Funar and Kapoudjian, and the braided Houghton groups $\mathrm{br}{H}_n$ introduced by Degenhardt. We present an elementary construction of a contractible cube complex, on which these groups act with cube-stabilisers isomorphic to finite extensions of braid groups. As an application, we prove Funar-Kapoudjian's and Degenhardt's conjectures by showing that $T^{♯},T^{\ast }$ are of type $F_{\infty }$ and that $\mathrm{br}{H}_n$ is of type $F_{n-1}$ but not of type $F_n$.

36 pages, 11 figures. Comments are welcome!