Tilting representations of finite groups of Lie type

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.