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Tuesday, March 25, 2025

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4:00pm
Truncated braid groups [3]
03/25/2025 - 4:00pm

In the 1950s, Coxeter considered the quotients of braid groups given by adding the relation that all half Dehn twist generators have some fixed, finite order. He found a remarkable formula for the order of these groups in terms of some related Platonic solids. Despite the inspiring apparent connection between these objects, Coxeter's proof boils down to a finite case check that reveals nothing about the structure present. I'll explain recent work that gives an interpretation of the truncated 3-strand braid group that makes the connection with Platonic solids clear, using down-to-earth geometric and algebraic topological tools. This is joint work with Tahsin Saffat.

Location:
KT 207
 
Quantum Category O and Categorification of Periodic Hecke Module, Lecture 1 [4]
03/25/2025 - 4:00pm to 6:00pm

The BGG category O plays an important role in the study of representations of semisimple Lie algebras. Its connection to the Hecke category is a starting point of Geometric Representation Theory. In this lecture, I will introduce a version of category O for quantum groups at roots of unity. I will explain a derived equivalence from (the principal block of) quantum category O to the affine Hecke category. Under the equivalence, the highest weight structure of quantum category O provides a categorification of the “periodic Hecke module”.

In the first lecture, I will briefly review the classical story for BGG category O. Then I will give an introduction to the quantum category O with motivations.

Location:
KT 801
 
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[1] https://calendar.math.yale.edu/calendar/grid/day/2025-03-24 [2] https://calendar.math.yale.edu/calendar/grid/day/2025-03-26 [3] https://calendar.math.yale.edu/event/truncated-braid-groups [4] https://calendar.math.yale.edu/event/quantum-category-o-and-categorification-periodic-hecke-module-lecture-1 [5] https://calendar.math.yale.edu/print/list/calendar/grid/day/2025-03-25 [6] webcal://calendar.math.yale.edu/calendar/export.ics