Soergel bimodules for universal Coxeter groups

Abstract

We produce an explicit recursive formula which computes the idempotent projecting to any indecomposable Soergel bimodule for a universal Coxeter system. This gives the exact set of primes for which the positive characteristic analogue of Soergel's conjecture holds. Along the way, we introduce the multicolored Temperley-Lieb algebra. An appendix by Ben Webster gives a precise condition on the base ring for a Jones-Wenzl projector to exist.