Effective models and extension of torsors over a discrete valuation ring of unequal characteristic
Idioma
en
Article de revue
Este ítem está publicado en
International Mathematics Research Notices. 2008, vol. 2008, p. 68
Oxford University Press (OUP)
Resumen en inglés
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 ...Leer más >
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.< Leer menos
Palabras clave
torseurs
schémas en groupes
Orígen
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