Categorical actions and derived equivalences for finite odd-dimensional orthogonal groups

TL;DR

This paper proves Broué's abelian defect group conjecture for finite odd-dimensional orthogonal groups by constructing categorical actions of Kac-Moody algebras and establishing derived equivalences of blocks.

Contribution

It introduces a categorical action of a Kac-Moody algebra on quadratic unipotent representations and constructs derived equivalences for blocks of orthogonal groups.

Findings

Proof of Broué's conjecture for SO_{2n+1}(q) at linear primes

Construction of categorical Kac-Moody actions on representation categories

Establishment of derived equivalences for isolated RoCK blocks

Abstract

In this paper we prove that Brou\'{e}'s abelian defect group conjecture is true for the finite odd-dimensional orthogonal groups $\SO_{2n+1}(q)$ at linear primes with $q$ odd. We first make use of the reduction theorem of Bonnaf\'{e}-Dat-Rouquier to reduce the problem to isolated blocks. Then we construct a categorical action of a Kac-Moody algebra on the category of quadratic unipotent representations of the various groups $\SO_{2n+1}(q)$ in non-defining characteristic, by generalizing the corresponding work of Dudas-Varagnolo-Vasserot for unipotent representations. This is one of the main ingredients of our work which may be of independent interest. To obtain derived equivalences of blocks and their Brauer correspondents, we define and investigate isolated RoCK blocks. Finally, we establish the desired derived equivalence based on the work of Chuang-Rouquier that categorical actions provide derived equivalences between certain weight spaces.