English

$p$-adic hyperbolicity for Shimura varieties and period images

Number Theory 2026-04-07 v2

Abstract

We prove that Shimura varieties and geometric period images satisfy a pp-adic extension property for large enough primes pp. More precisely, let D×D\mathsf{D}^{\times}\subset \mathsf{D} denote the inclusion of the closed punctured unit disc in the closed unit disc. Let XX be either a Shimura variety or a geometric period image with torsion-free level structure. Let FF be a discretely valued pp-adic field containing the number field of definition of XX, where pp is a large enough prime. Then, any rigid-analytic map f:(D×)a×DbXFanf: (\mathsf{D}^{\times})^a \times \mathsf{D}^b \rightarrow X_F^{\textrm{an}} defined over FF whose image intersects the good reduction locus of XFanX_F^{\textrm{an}} (with respect to an integral canonical model) extends to a map Da+bXFan\mathsf{D}^{a+b}\rightarrow X_F^{\textrm{an}}. We note that this hypothesis is vacuous if XX is proper. We also deduce an application to algebraicity of rigid-analytic maps. Our methods also apply to the more general situation of the rigid generic fiber of formal schemes admitting Fontaine-Laffaile modules which satisfy certain positivity conditions.

Keywords

Cite

@article{arxiv.2509.25461,
  title  = {$p$-adic hyperbolicity for Shimura varieties and period images},
  author = {Benjamin Bakker and Abhishek Oswal and Ananth N. Shankar and Zijian Yao},
  journal= {arXiv preprint arXiv:2509.25461},
  year   = {2026}
}

Comments

We have now removed a good-reduction hypothesis for Shimura varieties