“I believe in everything until it’s disproved. So I believe in fairies, the myths, dragons.” — John Lennon
Our tour of subgroups of non–positively curved groups has reached its end.
What did we miss? Probably lots — apologies to any aggrieved authors out there.
Here are a couple of corners of the landscape that we are conscious of having failed to explore.
- Simplicial non–positive curvature. This page by Tomasz Elsner gives an introduction and many references.
- The recent work of Daniel Wise and his collaborators on special cube complexes. This includes the papers —
- The structure of groups with a quasi–convex hierarchy, and
- Cubulating small-cancellation groups (with Frederic Haglund).
Most likely, there are many more.