English

Computing Crystalline Cohomology and p-Divisible Groups for Curves over Finite Fields

Number Theory 2026-01-21 v1 Algebraic Geometry

Abstract

Let XX be a smooth projective curve over a finite field of characteristic pp. We describe and implement a practical algorithm for computing the pp-divisible group Jac(X)[p]Jac(X)[p^\infty] via computing its Dieudonn\'{e} module, or equivalently computing the Frobenius and Verschiebung operators on the first crystalline cohomology of XX. We build on Tuitman's pp-adic point counting algorithm, which computes the rigid cohomology of XX and requires a ``nice'' lift of XX to be provided.

Keywords

Cite

@article{arxiv.2601.14006,
  title  = {Computing Crystalline Cohomology and p-Divisible Groups for Curves over Finite Fields},
  author = {Jeremy Booher},
  journal= {arXiv preprint arXiv:2601.14006},
  year   = {2026}
}

Comments

20 pages, implementation at https://github.com/jeremybooher/crystallinecohomology