Affine Deligne-Lusztig Varieties and Quantum Bruhat Graph

Abstract

In this paper, we consider affine Deligne-Lusztig varieties $X_w(b)$ and their certain union $X(\mu,b)$ inside the affine flag variety of a reductive group. Several important results in the study of affine Deligne-Lusztig varieties have been established under the so-called superregularity hypothesis. Such results include a description of generic Newton points in Iwahori double cosets of loop groups, covering relation in associated Iwahori-Weyl group and dimension formula for $X(\mu,b)$. We show that one can considerably weaken the superregularity hypothesis and sometimes completely eliminate it, thus strengthening these existing results.