Hello everyone,
This week we have Hannah Turner in town. She will be speaking at 3:30 tomorrow on Generalizing the (fractional) Dehn twist coefficient.
The title and abstract are below.
Also, next week Eric Sedgwick is in town. There is a slight conflict with the 3:30 time slot next week, so I wanted to check with everyone to see what conflicts
would arise if the October 4 talk was moved to 2:30. Let me know if you can make that adjusted time on October 4th or if you have a conflict.
Title: Generalizing the (fractional) Dehn twist coefficient.
Speaker: Hannah Turner, Georgia Tech
Date: Sep 27, 2022
Time: 3:30 PM
Room: MSCS 445
Abstract: The fractional Dehn twist coefficient (FDTC) is a rational number associated to a mapping class on a (finite-type) surface with boundary. This 2-dimensional invariant has many applications to 3-manifold topology and contact geometry. One way to think
of the FDTC is as a real-valued function on the mapping class group of a surface with many nice properties. In this talk, we will give sufficient conditions on a more general group to admit a function which behaves like the FDTC. In particular, we use this
to generalize the FDTC to infinite-type surfaces (with boundary); in this setting, we show that the ”fractional” Dehn twist coefficient need not be rational. This is joint work with Peter Feller and Diana Hubbard.
______________________
Neil R. Hoffman
Assistant Professor
Department of Mathematics
523 Math Science Building
Oklahoma State University
Stillwater, OK 74078-1058
405-744-7791