English

Arithmetic compactifications of integral models of Shimura varieties of abelian type

Number Theory 2025-11-26 v2 Algebraic Geometry

Abstract

In this paper, we construct good toroidal and minimal compactifications in the sense of Lan-Stroh for integral models of abelian-type Shimura varieties. We start with finding suitable types of cusp labels and cone decompositions which are compatible with those of the associated Hodge-type Shimura varieties. We then study the action of Q\mathbb{Q}-points of the adjoint group on boundary charts and toroidal compactifications of Hodge-type integral models. In particular, we extend the twisting construction of Kisin and Pappas to boundary charts. Finally, up to taking refinements of cone decompositions, we construct an abelian-type toroidal compactification as an open and closed algebraic subspace of a quotient from a disjoint union of Hodge-type toroidal compactifications and construct minimal compactifications with a similar method. Furthermore, we show results on nearby cycles of these compactifications and verify Pink's formula when the level at pp is an intersection of nn quasi-parahoric subgroups.

Keywords

Cite

@article{arxiv.2505.09135,
  title  = {Arithmetic compactifications of integral models of Shimura varieties of abelian type},
  author = {Peihang Wu},
  journal= {arXiv preprint arXiv:2505.09135},
  year   = {2025}
}

Comments

v2: 151 pages. minor changes on typos. Added: A workflow diagram; Section 5.5 on nearby cycles