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Modular perverse sheaves on flag varieties. II: Koszul duality and formality. (English) Zbl 1375.14162

The paper continues the study of modular perverse sheaves on flag varieties begun in [the authors, Ann. Sci. Éc. Norm. Supér. (4) 49, No. 2, 325–370 (2016; Zbl 1386.14178)] (with a joint appendix with Geordie Williamson). For varieties equipped with a stratification by affine spaces, the authors develop a formalism of “mixed modular perverse sheaves”. Two applications are given: (1) a “Koszul-type” derived equivalence relating a given flag variety to the Langlands dual flag variety, (2) a formality theorem for the modular derived category of a flag variety.

MSC:

14M15 Grassmannians, Schubert varieties, flag manifolds
14F05 Sheaves, derived categories of sheaves, etc. (MSC2010)
20G40 Linear algebraic groups over finite fields

Citations:

Zbl 1386.14178
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References:

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