Integral canonical models and period maps
Geometry over non-closed fields, Schloss Elmau, August 2024.
Abstract.
Work of Chai--Faltings, Milne, Moonen, Kisin, and Kottwitz constructs
integral canonical models for abelian type Shimura varieties, but as
the construction relies on the modular interpretation of the moduli
space of abelian varieties, it does not apply to exceptional Shimura
varieties. In joint work with A. Shankar and J. Tsimerman, we
construct integral canonical models for all Shimura varieties at
sufficiently large primes, as well as for the image of any period map
arising from geometry. Our method passes through finite
characteristic and relies on a partial generalization of the work of
Ogus--Vologodsky. As applications, in the context of exceptional
Shimura varieties we prove analogs of Tate semisimplicity in finite
characteristic, CM lifting theorems for ordinary points, and the Tate
isogeny theorem for ordinary points.