Speaker
Sobhan Seyfaddini
Abstract
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.