English

Comparison between admissible and de Jong coverings of rigid analytic spaces in mixed characteristic

Algebraic Geometry 2022-01-21 v1

Abstract

If kk is a complete non-archimedean field and XX an adic space locally of finite type over Spa(k)\mathrm{Spa}(k), let CovXoc\textbf{Cov}_{X}^{\mathrm{oc}} (resp. CovXadm\textbf{Cov}_{X}^{\mathrm{adm}}) be the category of \'etale coverings of XX that are locally for the Berkovich overconvergent topology (resp. for the admissible topology) disjoint union of finite \'etale coverings. There is a natural inclusion CovXocCovXadm\textbf{Cov}_{X}^{\mathrm{oc}}\subseteq \textbf{Cov}_{X}^{\mathrm{adm}}. Whether or not this inclusion is strict is a question initially asked by de Jong. Some partial answers have been given in the recents works of Achinger, Lara and Youcis in the finite or equal characteristic 00 cases. The purpose of this note is to show that this inclusion can be strict when kk is of mixed characteristic (0,p)(0,p) and pp-closed. As a consequence, following the work of Achinger, Lara and Youcis, the natural morphism of Noohi groups π1dJ,adm(X)π1dJ,oc(X)\pi_1^{\mathrm{dJ, \, adm}}(X)\to \pi_1^{\mathrm{dJ, \,oc}}(X) is not an isomorphism in general.

Keywords

Cite

@article{arxiv.2201.08065,
  title  = {Comparison between admissible and de Jong coverings of rigid analytic spaces in mixed characteristic},
  author = {Sylvain Gaulhiac},
  journal= {arXiv preprint arXiv:2201.08065},
  year   = {2022}
}

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