November 2017 December 2017 |

4:00 pm Wednesday, February 7, 2018 Geometry-Analysis: Horospheres in Teichmüller space and mapping class groupby Weixu Su (Fudan University) in HBH 227- We study the geometry of horospheres in Teichmuller space of Riemann surfaces of genus g with n punctures, where 3g−3+n≥2. We show that every C^1-diffeomorphism of Teichmuller space to itself that preserves horospheres is an element of the extended mapping class group. Using the relation between horospheres and metric balls, we obtain a new proof of Royden's Theorem that the isometry group of the Teichmuller metric is the extended mapping class group. The work is joint with Dong Tan.
Submitted by mwolf@rice.edu |