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On the de Rham homology and cohomology of a complete local ring in equicharacteristic zero
Published online by Cambridge University Press: 07 August 2017
Abstract
Let $A$ be a complete local ring with a coefficient field
$k$ of characteristic zero, and let
$Y$ be its spectrum. The de Rham homology and cohomology of
$Y$ have been defined by R. Hartshorne using a choice of surjection
$R\rightarrow A$ where
$R$ is a complete regular local
$k$-algebra: the resulting objects are independent of the chosen surjection. We prove that the Hodge–de Rham spectral sequences abutting to the de Rham homology and cohomology of
$Y$, beginning with their
$E_{2}$-terms, are independent of the chosen surjection (up to a degree shift in the homology case) and consist of finite-dimensional
$k$-spaces. These
$E_{2}$-terms therefore provide invariants of
$A$ analogous to the Lyubeznik numbers. As part of our proofs we develop a theory of Matlis duality in relation to
${\mathcal{D}}$-modules that is of independent interest. Some of the highlights of this theory are that if
$R$ is a complete regular local ring containing
$k$ and
${\mathcal{D}}={\mathcal{D}}(R,k)$ is the ring of
$k$-linear differential operators on
$R$, then the Matlis dual
$D(M)$ of any left
${\mathcal{D}}$-module
$M$ can again be given a structure of left
${\mathcal{D}}$-module, and if
$M$ is a holonomic
${\mathcal{D}}$-module, then the de Rham cohomology spaces of
$D(M)$ are
$k$-dual to those of
$M$.
MSC classification
- Type
- Research Article
- Information
- Copyright
- © The Author 2017
References
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