Gauge Theory and Topology Seminar: Pseudo-isotopy, finger/Whitney systems and diffeomorphisms of 4-manifolds

We discuss a method, going essentially back to Cerf, Hatcher – Wagoner and Quinn of constructing diffeomorphisms of 4-manifolds from finger/Whitney systems.  Through finger/Whitney systems David Gay, Daniel Hartman and I defined an invariant of Hatcher – Wagoner families, unchanged under 1-parameter families of Hatcher – Wagoner families.  We will explain how invariance extends to a wider class of 2-parameter families connecting Hatcher – Wagoner families.  Joint work with David Gay and Daniel Hartman.