Andersen Filtration and Hard Lefschetz
arXiv:math/0604590 · doi:10.1007/s00039-007-0640-9
Abstract
On the space of homomorphisms from a Verma module to an indecomposable tilting module of the BGG-category O we define a natural filtration following Andersen and establish a formula expressing the dimensions of the filtration steps in terms of coefficients of Kazhdan-Lusztig polynomials.
English version of math.RT/0604589, v3 revised translation