Title: Forty years of Four Manifolds
Abstract: Since the twin breakthroughs in 1982-83 by Freedman and Donaldson the study of four manifolds has been developing rapidly. Freedman’s resolution of the 4d topological Poincaré conjecture and refinements combined with Donaldson’s surprising applications of the Yang-Mills equations to show that the situation for smooth structures in dimension 4 was more complicated than in higher dimensions. Since then new theories including Seiberg-Witten equations, Ozsvath and Szabó’s Heegaard Floer theory, and Embedded Contact Homology and have led to surprising applications to questions in 3 and 4 dimensional topology. This talk will survey some of these developments.