---
abstract: 'Given a Henselian and Japanese discrete valuation ring $A$ and a flat and projective $A$-scheme $X$, we follow the approach of [@biswas-dos_santos11] to introduce a [*full subcategory*]{} of coherent modules on $X$ which is then shown to be Tannakian. We then prove that, under normality of the generic fibre, the associated affine and flat group is pro-finite in a strong sense (so that its ring of functions is a Mittag-Leffler $A$-module) and that it classifies finite torsors $Q\to X$. This establishes an analogy to Nori’s theory of the essentially finite fundamental group. In addition, we compare our theory with the ones recently developed by Mehta-Subramanian and Antei-Emsalem-Gasbarri. Using the comparison with the former, we show that any quasi-finite torsor $Q\to X$ has a reduction of structure group to a finite one.'
address:
- 'Institute of Mathematics, Vietnam Academy of Science and Technology, Hanoi, Vietnam'
- 'Institut de Mathématiques de Jussieu – Paris Rive Gauche, 4 place Jussieu, Case 247, 75252 Paris Cedex 5, France'
author:
- Phùng Hô Hai
- João Pedro dos Santos
title: Finite torsors on projective schemes defined over a discrete valuation ring 
---

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Introduction
