The almost product structure of Newton strata in the Deformation space of a Barsotti-Tate group with crystalline Tate tensors

TL;DR

This paper develops an almost product structure for Newton strata in deformation spaces of Barsotti-Tate groups with crystalline Tate tensors, enabling detailed geometric analysis and confirming a generalized Grothendieck conjecture.

Contribution

It introduces a new almost product structure for Newton strata, extending previous constructions to a broader context and applications.

Findings

Dimension and closure relations of Newton strata determined.

Nonemptiness of Newton strata established, confirming a generalized Grothendieck conjecture.

Proved equidimensionality of Rapoport-Zink spaces of Hodge type.

Abstract

In this paper, we construct the almost product structure of the minimal Newton stratum in deformation spaces of Barsotti-Tate groups with crystalline Tate tensors, similar to Oort's and Mantovan's construction for Shimura varieties of PEL-type. It allows us to describe the geometry of the Newton stratum in terms of the geometry of two simpler objects, the central leaf and the isogeny leaf. This yields the dimension and the closure relations of the Newton strata in the deformation space. In particular, their nonemptiness shows that a generalisation of Grothendieck's conjecture of deformations of Barsotti-Tate groups with given Newton polygon holds. As an application, we determine analogous geometric properties of the Newton stratification of Shimura varieties of Hodge type and prove the equidimensionality of Rapoport-Zink spaces of Hodge type.