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arXiv · 2211.16067

Extending torsors under quasi-finite flat group schemes

Sara Mehidi
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Abstract

Let $R$ be a discrete valuation ring of field of fractions $K$ and of residue field $k$ of characteristic $p > 0$. In an earlier work, we studied the question of extending torsors on $K$-curves into torsors over $R$-regular models of the curves in the case when the structural $K$-group scheme of the torsor admits a finite flat model over $R$. In this paper, we first give a simpler description of the problem in the case where the curve is semistable. Secondly, if $R$ is assumed to be Henselian and Japanese, we solve the problem of extending torsors even if the structural group does not admit a finite flat $R$-model.

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Sara Mehidi. 2022-11-29. Extending torsors under quasi-finite flat group schemes. https://doi.org/10.1017/nmj.2024.19

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