USask PIMS Geometry and Physics (GAP) Seminar: Dan Douglas

  • Date: 02/17/2022
Dr. Dan Douglas, Yale University



Tropical Fock-Goncharov coordinates for SL3 webs on surfaces


For a finite-type surface , we study a preferred basis for the commutative algebra of regular functions on the -character variety, introduced by Sikora-Westbury. These basis elements come from the trace functions associated to certain tri-valent graphs embedded in the surface . We show that this basis can be naturally indexed by positive integer coordinates, defined by Knutson-Tao rhombus inequalities and modulo 3 congruence conditions. These coordinates are related, by the geometric theory of Fock-Goncharov, to the tropical points at infinity of the dual version of the character variety. This is joint work with Zhe Sun.

Other Information: 

This seminar is available via Zoom. See website for details or email Alex Weekes,


Time: 2:00pm PST / 4:00 pm CST