Cohen-Macaulayness of Local Models via Shellability of the Admissible Set

Xuhua He, Felix Schremmer, Qingchao Yu

We prove that for any dominant cocharacter $\hat{I}¼$ and any parahoric level $K$, the augmented admissible set $\widehat{\Adm(μ)^K}$ in the Iwahori-Weyl group is dual EL-shellable. Thi…