Speaker: Juan Muñoz-Echániz (Simons Center for Geometry and Physics)
Time: 15:00-16:00, Jun 19, 2025
Room: VooV Meeting: 297 573 110, no password
A 4-manifold with boundary on a Seifert-fibered space admits a 'boundary Dehn twist' diffeomorphism, obtained by a fibered version of the classical 2-dimensional Dehn twist. This diffeomorphism arises naturally as (a power of) the monodromy of Milnor fibrations of surface singularities. In this talk I will discuss non-triviality results for boundary Dehn twists on symplectic fillings of Seifert-fibered spaces, using tools from Seiberg—Witten theory. Some applications include:
- The ADE singularities are the only weighted-homogeneous isolated hypersurface singularities in complex dimension 2 whose monodromy has finite order in the smooth mapping class group.
- There are exotic R^4's which admit exotic (compactly-supported) diffeomorphisms.
Joint with Hokuto Konno, Jianfeng Lin and Anubhav Mukherjee.
