engleski

BGG complexes in singular blocks of category O

Using translation from the regular block, we construct and analyze properties of BGG complexes in singular blocks of BGG category O. We provide criteria, in terms of the Kazhdan-Lusztig-Vogan polynomials, for such complexes to be exact. In the Koszul dual picture, exactness of BGG complexes is expressed as a certain condition on a generalized Verma flag of an indecomposable projective object in the corresponding block of parabolic category O. In the second part of the paper, we construct BGG complexes in a more general setting of balanced quasi- hereditary algebras and show how our results for singular blocks can be used to construct BGG resolutions of simple modules in S-subcategories in O.

Category O ; BGG complexes ; Kazhdan-Lusztig polynomials ; Balanced quasi-hereditary algebras ; S-subcategories in O

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