Boundary structures of integral models of Hodge-type Shimura Varieties

Abstract

We compute the level groups associated with mixed Shimura varieties that appear at the boundaries of compactifications of Shimura varieties and show that the boundaries of minimal compactifications of Pappas-Rapoport integral models are finite quotients of smaller Pappas-Rapoport integral models. Additionally, we prove that the compactifications of integral models of Hodge-type Shimura varieties with quasi-parahoric level structures are independent of the choice of Siegel embedding, and use this to construct and analyze the change-of-parahoric morphisms on these compactifications.