Ring-theoretic properties of Iwasawa algebras: a survey.
R-trees and the Bieri-Neumann-Strebel invariant.
Let G be a finitely generated group. We give a new characterization of its Bieri-Neumann-Strebel invariant Σ(G), in terms of geometric abelian actions on R-trees. We provide a proof of Brown's characterization of Σ(G) by exceptional abelian actions of G, using geometric methods.