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On Special Fiber Rings of Modules
Published online by Cambridge University Press: 09 January 2019
Abstract
We prove results concerning the multiplicity as well as the Cohen–Macaulay and Gorenstein properties of the special fiber ring $\mathscr{F}(E)$ of a finitely generated
$R$-module
$E\subsetneq R^{e}$ over a Noetherian local ring
$R$ with infinite residue field. Assuming that
$R$ is Cohen–Macaulay of dimension 1 and that
$E$ has finite colength in
$R^{e}$, our main result establishes an asymptotic length formula for the multiplicity of
$\mathscr{F}(E)$, which, in addition to being of independent interest, allows us to derive a Cohen–Macaulayness criterion and to detect a curious relation to the Buchsbaum–Rim multiplicity of
$E$ in this setting. Further, we provide a Gorensteinness characterization for
$\mathscr{F}(E)$ in the more general situation where
$R$ is Cohen–Macaulay of arbitrary dimension and
$E$ is not necessarily of finite colength, and we notice a constraint in terms of the second analytic deviation of the module
$E$ if its reduction number is at least three.
Keywords
MSC classification
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- © Canadian Mathematical Society 2018
Footnotes
The author was partially supported by CAPES-Brazil (grant 88881.121012/2016-01), and by CNPq-Brazil (grant 421440/2016-3).
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