香蕉视频

Title: Whitehead Graphs and Irreducible Half-clean HNN Extensions

Abstract: We would describe given an irreducible half-clean HNN extension $H$ of a finitely generated free group, how we can construct an ascending irreducible half-clean HNN extension $G$ such that $H$ is a subgroup of $G$. We first introduce the Whitehead automorphisms on free groups, followed by stating Stalling's theorem (1996) on Whitehead graphs. Then, we describe how to construct $G$ by Stalling's theorem.