English

Picard rank jumps for K3 surfaces with bad reduction

Number Theory 2024-12-11 v2 Algebraic Geometry

Abstract

Let XX be a K3 surface over a number field. We prove that XX has infinitely many specializations where its Picard rank jumps, hence extending our previous work with Shankar--Shankar--Tang to the case where XX might have potentially bad reduction. We prove a similar result for generically ordinary non-isotrivial families of K3 surfaces over curves over Fp\overline{\mathbb{F}}_p which extends previous work of Maulik--Shankar--Tang. As a consequence, we give a new proof of the ordinary Hecke orbit conjecture for orthogonal and unitary Shimura varieties.

Keywords

Cite

@article{arxiv.2203.09559,
  title  = {Picard rank jumps for K3 surfaces with bad reduction},
  author = {Salim Tayou},
  journal= {arXiv preprint arXiv:2203.09559},
  year   = {2024}
}

Comments

Minor revisions. To appear in Algebra & Number Theory