# A handle-holding approach to Wall-type stabilization problems

## Location

In dimension four, the differences between continuous and differential topology are vast but fundamentally unstable, disappearing when manifolds are enlarged in various ways. I will discuss Wall's stabilization problem and some of its variants, all of which aim to quantify this instability. In particular, I'll outline a simple "atomic" approach to these problems and, as a proof of concept, use it to produce exotic pairs of knotted surfaces (with boundary) in the 4-ball that remain exotic after one "internal stabilization". The key obstruction comes from the universal version of Khovanov homology. Time permitting, I will speculate on some potential connections to Floer homology.