Finite subgroups of the birational automorphism group are `almost' nilpotent

Abstract

We call a group $G$ nilpotently Jordan of class at most $c$ $(c\in \mathbb{N})$ if there exists a constant $J\in {\mathbb{Z}}^{+}$ such that every finite subgroup $H\leqq G$ contains a nilpotent subgroup $K\leqq H$ of class at most $c$ and index at most $J$. We show that the birational automorphism group of a $d$ dimensional variety over a field of characteristic zero is nilpotently Jordan of class at most $d$.