The \mu-ordinary locus for Shimura varieties of Hodge type

Abstract

We review the Newton stratification and Ekedahl-Oort stratification on the special fiber of a smooth integral model for a Shimura variety of Hodge type at a prime of good reduction. We show that the \mu-ordinary locus coincides with the generic Ekedahl-Oort stratum, and that for any two geometric points in the \mu-ordinary locus there is an isomorphism of the attached Dieudonne modules with additional structure. As a consequence, we proof that the \mu-ordinary locus is open and dense, thus generalizing the results which were already known in the PEL-case. To prove our results we provide a method which allows to reduce the equality of strata to a group theoretic statement.