# Mathematical Field Notes

## Kronheimer’s argument: Small resolutions and Dehn twists

I want to amplify an expository argument I gave in a recent lecture which shows that the squared Dehn twist on a symplectic 4-manifold is smoothly isotopic to the identity map. This is an old argument of Kronheimer and I only managed to sketch it hurriedly in the lecture. A few people have asked me to explain this to them in the past, so here’s an explanation to which I can point people in future.

Written by Jonny Evans

January 27, 2013 at 5:53 pm