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Special Topic Seminar
 
14:00 - 15:00, August 15, 2023 (Tuesday)
Room 509, Cosmology Building, NTU
(臺灣大學次震宇宙館 509研討室)
Lagrangian Link Quasimorphisms and the Non-simplicity of Hameomorphism Group of Surfaces
Cheuk Yu Mak (University of Southampton)

Abstract

In this talk, we will explain the construction of a sequence of homogeneous quasi-morphisms of the area-preserving homeomorphism group of the sphere using Lagrangian Floer theory for links. This sequence of quasi-morphisms has asymptotically vanishing defects, so it is asymptotically a homomorphism. It enables us to show that the Hameomorphism group is not the smallest normal subgroup of the area-preserving homeomorphism group. If time permits, we will explain how to generalize it to all positive genus surfaces even though we no longer have quasi-morphisms. The case of the sphere is joint work with Daniel Cristofaro-Gardiner, Vincent Humilière, Sobhan Seyfaddini, and Ivan Smith. The case of positive genus surfaces is joint work with Ibrahim Trifa.


 

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