Hypercube Richardson varieties from magic words

Abstract

Inspired by the recent preprint of Ellenberg, Libedinsky, Plaza, Simental, and Williamson, we study the geometry of Richardson varieties whose associated Bruhat intervals are boolean posets. We define magic words for a Bruhat interval and prove that for intervals with magic words the associated Richardson variety is a tower of ${\mathbb{P}}^1$-s. We also prove that the Bruhat intervals consisting of the dyadically well-distributed permutations all have magic words. This gives a new proof that they form a boolean poset.

arXiv comment12 pages