The induced PBW filtration, Frobenius splitting of double flag varieties, and Wahl's conjecture

Abstract

Let G be a semisimple algebraic group over an algebraically closed field of positive characteristic p. Generalizing the construction of the PBW filtration on Weyl modules for G we construct a G-stable filtration on tensor products of Weyl modules which we call the induced PBW filtration. We use this filtration to give some purely representation-theoretic conditions which are equivalent to the existence of a Frobenius splitting of the double flag variety $G/B\times G/B$ that maximally compatibly splits the diagonal. In particular, this gives a sufficient condition for Wahl's conjecture to hold for G and we use this criterion to prove that Wahl's conjecture holds in type G2 for p at least 11.

25 pages; comments welcome. This version: bug fixes; removed an incorrect remark

References in corpus (3)

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