Algebra Seminar: Yacobi -- Normalisers of parabolic subgroups and hyperplane arrangements

Oded Yacobi (University of Sydney) will be speaking in the algebra seminar.  We will go
out for lunch after the talk---all are welcome to join! 

When: 12-1pm Friday November 14 

Where: SMRI Seminar Room (Macleay Building A12 Room 301) [ROOM CHANGE DUE TO BOARD TALK] 

Title: Normalisers of parabolic subgroups and hyperplane arrangements 

Abstract: Consider a Coxeter group and its associated reflection representation.  The
group elements which act by reflections define an arrangement of hyperplanes which is
important in the general theory.  For instance, the associated Artin-Tits group, i.e.
generalised braid group, can be recovered from the topology of the arrangement.  We’ll
review this classical story and then describe a new parabolic version of it in the case
when is finite, which recovers normalisers of parabolic subgroups of Artin-Tits groups
from a hyperplane arrangement recently introduced in works of Iyama and Wemyss.  This is
based on joint work with Owen Garnier, Ed Heng and Tony Licata: Consider a Coxeter group
and its associated reflection representation.  The group elements which act by
reflections define an arrangement of hyperplanes which is important in the general
theory.  For instance, the associated Artin-Tits group, i.e.  generalised braid group,
can be recovered from the topology of the arrangement.  We’ll review this classical
story and then describe a new parabolic version of it in the case when is finite, which
recovers normalisers of parabolic subgroups of Artin-Tits groups from a hyperplane
arrangement recently introduced in works of Iyama and Wemyss.  This is based on joint
work with Owen Garnier, Ed Heng and Tony Licata: https://arxiv.org/abs/2509.21915