Tilting representations of finite groups of Lie type

TL;DR

This paper introduces a new category called Deligne--Lusztig category  and constructs tilting representations of finite groups of Lie type, computing their characters and confirming a conjecture by Dudas and Malle.

Contribution

It defines the Deligne--Lusztig category , constructs tilting representations, and relates their characters to previous work, confirming a conjecture.

Findings

Constructed tilting representations of 

Computed characters of these representations

Confirmed the Dudas--Malle conjecture

Abstract

Let $\mathbf{G}$ be a connected reductive group over a finite field $\mathbb{F}_q$ of characteristic $p > 0$. In this paper, we study a category which we call Deligne--Lusztig category $\mathcal{O}$ and whose definition is similar to category $\mathcal{O}$. We use this to construct a collection of representations of $\mathbf{G}(\mathbb{F}_q)$ which we call the tilting representations. They form a generating collection of integral projective representations of $\mathbf{G}(\mathbb{F}_q)$. Finally we compute the character of these representations and relate their expression to previous calculations of Lusztig and we then use this to establish a conjecture of Dudas--Malle.