Freedman CMSA Seminar

*Note: via Zoom only*

2:00-3:30 pm ET

Speaker: Michael Freedman, Harvard CMSA

Title: Some questions and theorems about closed 3 manifolds embedded in S^4

Abstract: Much is unknown about smooth embeddings of 3-manifolds in S^4; the Schoenflies problem  (Is there only one smoothly embedded 3-sphere in S^4 up to isotopy?) is the best-known example. There has long been a hope that 3-manifold reasoning applied to level-sets will be helpful.  I’ll mention some successes and failures of this method and revisit a classical theorem of Hantzsche in this light. (Hantzsche: If a 3-manifold embeds in S^4 its linking form is hyperbolic.)

3:30-4:00 pm ET

Break/Discussion

4:00-5:30 pm ET

Speaker: Slava Krushkal, University of Virginia

Title: A higher order torsion linking form for 3-manifolds

Abstract: This talk is based on a joint work with Mike Freedman defining a triple linking form for rational homology spheres, assuming that the classical torsion linking pairing of three classes pairwise vanishes. I will discuss its vanishing for 3-manifolds in S^4, and its relation to the Matsumoto triple intersection form on 4-manifolds.