Quasimorphisms and area-preserving homeomorphisms of the sphere

Date: 2022-06-29

Time: 09:45 - 10:45

Zoom link: https://kva-se.zoom.us/j/9217561880


Sobhan Seyfaddini


I will discuss a recent work constructing quasimorphisms on the group of area and orientation preserving homeomorphisms of the two-sphere. The existence of these quasimorphisms answers a question of Entov, Polterovich, and Py. As an immediate corollary, we learn that the commutator length is unbounded, sharply contrasting a result of Tsuboi regarding the group of homeomorphisms that do not preserve area. A key role is played by a new family of spectral invariants, called “link spectral invariants”, associated to certain Lagrangian links in the sphere.