English

Perfect points of abelian varieties

Number Theory 2023-09-20 v3 Algebraic Geometry

Abstract

Let kk be an algebraic extension of Fp\mathbb F_p and K/kK/k a regular extension of fields (e.g. Fp(T)/Fp\mathbb F_p(T)/\mathbb F_p). Let AA be a KK-abelian variety such that all the isogeny factors are neither isotrivial nor of pp-rank zero. We give a necessary and sufficient condition for the finite generation of A(Kperf)A(K^{perf}) in terms of the action of End(A)QpEnd(A)\otimes \mathbb Q_p on the pp-divisible group A[p]A[p^{\infty}] of AA. In particular we prove that if End(A)QpEnd(A)\otimes \mathbb Q_p is a division algebra then A(Kperf)A(K^{perf}) is finitely generated. This implies the "full" Mordell-Lang conjecture for these abelian varieties. In addition we prove that all the infinitely pp-divisible elements in A(Kperf)A(K^{perf}) are torsion. These reprove and extend previous results to the non ordinary case. One of the main technical intermediate result is an overconvergence theorem for the Dieudonn\'e module of certain semiabelian schemes over smooth varieties.

Keywords

Cite

@article{arxiv.2103.16568,
  title  = {Perfect points of abelian varieties},
  author = {Emiliano Ambrosi},
  journal= {arXiv preprint arXiv:2103.16568},
  year   = {2023}
}

Comments

v3: 16 pages, shortened and final version. To appear in Compositio Mathematica. Some of the results in Part II will appear elsewhere. v2: minor edits. v1:37 pages, comments are very welcome

R2 v1 2026-06-24T00:42:19.733Z