Hyperbolic groups that are not commensurably coHopfian
arXiv:1812.07799
Abstract
Sela proved every torsion-free one-ended hyperbolic group is coHopfian. We prove that there exist torsion-free one-ended hyperbolic groups that are not commensurably coHopfian. In particular, we show that the fundamental group of every simple surface amalgam is not commensurably coHopfian.
v3: 14 pages, 4 figures; minor changes. To appear in International Mathematics Research Notices