In my latest preprint with Georgios Dimitroglou Rizell, we use the topology of diffeomorphism groups of high-dimensional spheres to produce interesting examples of nontrivial topology in symplectomorphism groups of cotangent bundles. 485 more words

## Tags » Homotopy Sphere

#### 285G, Lecture 5: Finite time extinction of the third homotopy group, I

In the previous lecture, we saw that Ricci flow with surgery ensures that the second homotopy group became extinct in finite time (assuming, as stated in the above erratum, that there is no embedded with trivial normal bundle). 2,100 more words