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THE DIMENSION OF A SUBCATEGORY OF MODULES

Part of: Abelian categories Theory of modules and ideals Representation theory of rings and algebras

Published online by Cambridge University Press:  09 October 2015

HAILONG DAO  and
RYO TAKAHASHI
HAILONG DAO
Affiliation:
Department of Mathematics, University of Kansas, Lawrence, KS 66045-7523, USA; hdao@ku.edu
RYO TAKAHASHI
Affiliation:
Graduate School of Mathematics, Nagoya University, Furocho, Chikusaku, Nagoya 464-8602, Japan Department of Mathematics, University of Nebraska, Lincoln, NE 68588-0130, USA; takahashi@math.nagoya-u.ac.jp

Abstract

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Let $R$ be a commutative noetherian local ring. As an analog of the notion of the dimension of a triangulated category defined by Rouquier, the notion of the dimension of a subcategory of finitely generated $R$-modules is introduced in this paper. We found evidence that certain categories over nice singularities have small dimensions. When $R$ is Cohen–Macaulay, under a mild assumption it is proved that finiteness of the dimension of the full subcategory consisting of maximal Cohen–Macaulay modules which are locally free on the punctured spectrum is equivalent to saying that $R$ is an isolated singularity. As an application, the celebrated theorem of Auslander, Huneke, Leuschke, and Wiegand is not only recovered but also improved. The dimensions of stable categories of maximal Cohen–Macaulay modules as triangulated categories are also investigated in the case where $R$ is Gorenstein, and special cases of the recent results of Aihara and Takahashi, and Oppermann and Št́ovíček are recovered and improved. Our key technique involves a careful study of annihilators and supports of $\mathsf{Tor}$, $\mathsf{Ext}$, and $\underline{\mathsf{Hom}}$ between two subcategories.

MSC classification

Primary: 13C60: Module categories
Secondary: 13C14: Cohen-Macaulay modules 16G60: Representation type (finite, tame, wild, etc.) 18E30: Derived categories, triangulated categories
Type
Research Article
Information
Forum of Mathematics, Sigma , Volume 3 , 2015 , e19
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Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
© The Author(s) 2015

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