Rank gradients of infinite cyclic covers of Kaehler manifolds

Abstract

Given a Kaehler group $G$ and a primitive class $\varphi \in H^1(G;Z)$, we show that the rank gradient of $(G;\varphi )$ is zero if and only if Ker $\varphi$ is finitely generated. Using this approach, we give a quick proof of the fact (originally due to Napier and Ramachandran) that Kaehler groups are not properly ascending or descending HNN extensions. Further investigation of the properties of Bieri-Neumann-Strebel invariants of Kaehler groups allows us to show that a large class of groups of orientation-preserving PL homeomorphisms of an interval, which generalize Thompson's group $F$, are not Kaehler.

arXiv comment16 pages, to appear in J. Group Theory