Effective models and extension of torsors over a discrete valuation ring of unequal characteristic
Language
en
Article de revue
This item was published in
International Mathematics Research Notices. 2008, vol. 2008, p. 68
Oxford University Press (OUP)
English Abstract
Let R be a discrete valuation ring of unequal characteristic with fraction field K which contains a primitive p^2-th root of unity. Let X be a faithfully flat R-scheme and G be a finite abstract group. Let us consider a ...Read more >
Let R be a discrete valuation ring of unequal characteristic with fraction field K which contains a primitive p^2-th root of unity. Let X be a faithfully flat R-scheme and G be a finite abstract group. Let us consider a G-torsor Y_K\to X_K and let Y be the normalization of X_K in Y. If G=Z/p^n Z, n<3, under some hypothesis on X, we attach some invariants to Y_K \to X_K. If p>2, we determine, through these invariants, when Y\to X has a structure of torsor which extends that of Y_K\to X_K. Moreover we explicitly calculate the effective model (defined by Romagny) of the action of G on Y.Read less <
Keywords
torseurs
schémas en groupes
Origin
Hal imported