Affine Deligne-Lusztig varieties and folded galleries governed by chimneys

Abstract

We characterize the nonemptiness and dimension problems for an affine Deligne-Lusztig variety $X_x(b)$ in the affine flag variety in terms of galleries that are positively folded with respect to a chimney. If the parabolic subgroup associated to the Newton point of b has rank 1, we then prove nonemptiness for a certain class of Iwahori-Weyl group elements x by explicitly constructing such galleries.

54 pages, 14 figures best viewed in color; final version to appear in Ann. Inst. Fourier