Φ-MODULES AND COEFFICIENT SPACES
Φ-MODULES AND COEFFICIENT SPACES
复制标题
Φ-模和系数空间
DOI:
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发表时间:
2008
期刊:
影响因子:
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通讯作者:
M. Rapoport
中科院分区:
文献类型:
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作者:
G. Pappas;M. Rapoport
This paper is inspired by Kisin’s article [Ki1], in which he studies deformations of Galois representations of a local p-adic field which are defined by finite flat group schemes. The result of Kisin most relevant to our paper is his construction of a kind of resolution of the formal deformation space of the given Galois representation, by constructing a scheme which classifies all finite flat group schemes giving rise to the deformed Galois representation. Our purpose here is to globalize Kisin’s construction. Let K be a finite extension of Qp, with residue field k. Let K0 be the maximal unramified extension of Qp contained in K. Then K0 is the fraction field of the ring of Witt vectors W = W (k). Let π be a uniformizer of K and E(u) ∈ W [u] the Eisenstein polynomial that π satisfies. Let GK = Gal(K/K) be the absolute Galois group of K. Set S for the ring of formal power series W [[u]]. Let φ : S → S be such that φ|W is the Frobenius automorphism and with φ(u) = up. Kisin’s construction is based on the existence of a fully faithful exact functor from a suitable category of S-modules M equipped with a φ-linear endomorphism Φ to the category of finite flat (commutative) group schemes of p-power rank over Spec (OK). This in turn was inspired by work of Breuil [Br] who gave a similar but more complicated description of such group schemes. A variant of this functor also works with coefficients: if R is a Zpalgebra with finitely many elements, then there is a similar functor from a suitable category of S ⊗Zp R-modules M with φ-linear endomorphism Φ to the category of finite flat group schemes of p-power rank with R-action over SpecOK . Let K∞/K be the extension obtained by adjoining a compatible system of pn-power roots of π, and let GK∞ = Gal(K/K∞) be its absolute Galois group. Let OE be the p-adic completion of S[1/u], a complete discrete valuation ring, with uniformizer p and residue field k((u)) = k[[u]][1/u]. Then there exists an equivalence of categories between the category of finitely generated OE -modules M equipped with an isomorphism Φ : φ∗(M) → M and the category of continuous representations of GK∞ in Zp-modules, and this is compatible with the previous functor via the restriction functor from GK-representations to GK∞representations. Again there is also a variant for representations with values in a finite coefficient Zp-algebra R.