184 research outputs found
Perverse sheaves, Koszul IC-modules, and the quiver for the category O
For a stratified topological space we introduce the category of IC-modules,
which are linear algebra devices with the relations described by the equation
d^2=0. We prove that the category of (mixed) IC-modules is equivalent to the
category of (mixed) perverse sheaves for flag varieties. As an application, we
describe an algorithm calculating the quiver underlying the BGG category O for
arbitrary simple Lie algebra, thus answering a question which goes back to I.
M. Gelfand.Comment: NEW: final version to appear in Inventiones Mathematicae. Some
exposition revisions. Quiver computed explicitly for A_2 in the appendix. 29
page
Quiver varieties, affine Lie algebras, algebras of BPS states, and semicanonical basis
We suggest a (conjectural) construction of a basis in the plus part of the
affine Lie algebra of type ADE indexed by irreducible components of certain
quiver varieties. This construction is closely related to a string-theoretic
construction of a Lie algebra of BPS states. We then study the new
combinatorial questions about the (classical) root systems naturally arising
from our constructions and Lusztig's semicanonical basis.Comment: 16 page
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