Departmental PhD Thesis Exam

Event Information On Braidors: An Analogue of the Theory of Drinfel'd Associators for Braids in an Annulus
13:00 on Wednesday February 19, 2020
14:00 on Wednesday February 19, 2020
BA1210, Bahen Center, 40 St. George St.
Travis Ens
University of Toronto

PhD Advisor: Dror Bar-Natan


We develop the theory of braidors, an analogue of Drinfel'd's theory of associators in which braids in an annulus are considered rather than braids in a disk. After defining braidors and showing they exist, we prove that a braidor is defined by a single equation, an analogue of a well-known theorem of Furusho [Furusho (2010)] in the case of associators. Next some progress towards an analogue of another key theorem, due to Drinfel'd [Drinfel'd (1991)] in the case of associators, is presented. The desired result in the annular case is that braidors can be constructed degree be degree. Integral to these results are annular versions $\textbf{GT}_a$ and $\textbf{GRT}_a$ of the Grothendieck-Teichm\"uller groups $\textbf{GT}$ and $\textbf{GRT}$ which act faithfully and transitively on the space of braidors.

We conclude by providing surprising computational evidence that there is a bijection between the space of braidors and associators and that the annular versions of the Grothendieck-Teichm\"uller groups are in fact isomorphic to the usual versions potentially providing a new and in some ways simpler description of these important groups, although these computations rely on the unproven result to be meaningful.