Cohomology of tilting modules over quantum groups and t-structures on derived categories of coherent sheaves |
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Authors: | Roman Bezrukavnikov |
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Institution: | (1) Department of Mathematics, MIT, 77 Massachusetts ave, Cambridge, MA 02139, USA |
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Abstract: | The paper is concerned with cohomology of the small quantum group at a root of unity, and of its upper triangular subalgebra,
with coefficients in a tilting module. It turns out to be related to irreducible objects in the heart of a certain t-structure on the derived category of equivariant coherent sheaves on the Springer resolution, and to equivariant coherent
IC sheaves on the nil-cone. The support of the cohomology is described in terms of cells in affine Weyl groups. The basis
in the Grothendieck group provided by the cohomology modules is shown to coincide with the Kazhdan-Lusztig basis, as predicted
by J. Humphreys and V. Ostrik.
The proof is based on the results of ABG ], AB] and B], which allow us to reduce the question to purity of IC sheaves on
affine flag varieties.
To the memory of my father |
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