Mathematical Research Letters
Volume 27 (2020)
The Dehn twist on a sum of two $K3$ surfaces
Pages: 1767 – 1783
Ruberman gave the first examples of self-diffeomorphisms of four-manifolds that are isotopic to the identity in the topological category but not smoothly so. We give another example of this phenomenon, using the Dehn twist along a $3$-sphere in the connected sum of two $K3$ surfaces.
The work of the first-named author was supported by the National Science Foundation through NSF grant DMS-1707924.
The work of the second-named author was supported by the National Science Foundation through NSF grant DMS-1808794.
Received 30 January 2020
Accepted 7 April 2020
Published 17 February 2021