2015/06/19 by Paul Sobaje, Sobaje, Paul
Mathematics · #FOS: Mathematics #Representation Theory (math.RT) #math.RT
paper · pdf · doi:10.48550/arxiv.1506.06115
13 pages, v2. comments very welcome
arxiv created 2015/07/17 · arxiv updated 2015/07/20
Let G be a simple simply connected algebraic group over an algebraically closed field k of characteristic p, with Frobenius kernel G(1). It is known that when p≥ 2h-2, where h is the Coxeter number of G, the projective indecomposable G(1)-modules (PIMs) lift to G, and this has been conjectured to hold in all characteristics. In this paper, we explore the lifting problem via extensions of algebraic groups, following the work of Parshall and Scott who in turn build upon ideas due to Donkin. We prove various results which augment this approach, and as an application demonstrate that the PIMs lift to G(1)H, for particular closed subgroups H ≤ G which contain a maximal torus of G.