Alexander and Thurston norms, and the Bieri–Neumann–Strebel invariants for free-by-cyclic groups
Alexander and Thurston norms, and the Bieri–Neumann–Strebel invariants for free-by-cyclic groups
We investigate Friedl and Lück's universal L 2 -torsion for descending HNN extensions of finitely generated free groups, and so in particular for F n -by-Z groups.This invariant induces a seminorm on the first cohomology of the group which is an analogue of the Thurston norm for 3-manifold groups.We prove …