Kazhdan–Lusztig polynomials and subexpressions

Abstract

We refine an idea of Deodhar, whose goal is a counting formula for Kazhdan–Lusztig polynomials. This is a consequence of a simple observation that one can use the solution of Soergel's conjecture to make ambiguities involved in defining certain morphisms between Soergel bimodules in characteristic zero (double leaves) disappear.