Tilting modules and highest weight theory for reduced enveloping algebras

Abstract

Let $G$ be a reductive algebraic group over an algebraically closed field of characteristic $p>0$, and let ${\mathfrak g}$ be its Lie algebra. Given $\chi\in{\mathfrak g}^{*}$ in standard Levi form, we study a category ${\mathscr C}_\chi$ of graded representations of the reduced enveloping algebra $U_\chi({\mathfrak g})$. Specifically, we study the effect of translation functors and wall-crossing functors on various highest-weight-theoretic objects in ${\mathscr C}_\chi$, including tilting modules. We also develop the theory of canonical $\Delta$-flags and $\overline{\nabla}$-sections of $\Delta$-flags, in analogy with similar concepts for algebraic groups studied by Riche and Williamson.