Exotic iterated Dehn twists

Paul Seidel
2014 Algebraic and Geometric Topology  
Consider cotangent bundles of exotic spheres, with their canonical symplectic structure. They admit automorphisms which preserve the part at infinity of one fibre, and which are analogous to the square of a Dehn twist. Pursuing that analogy, we show that they have infinite order up to isotopy (inside the group of all automorphisms with the same behaviour).
doi:10.2140/agt.2014.14.3305 fatcat:ka7sbhvdjje6fh5fltb6uzo7uy