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Fitting ideals and finite projective dimension

Published online by Cambridge University Press:  03 February 2005

CRAIG HUNEKE
Affiliation:
Department of Mathematics, University of Kansas, Lawrence, KS 66045, U.S.A. e-mail: [email protected], [email protected]
DAVID A. JORGENSEN
Affiliation:
Department of Mathematics, University of Texas at Arlington, Arlington, TX 76019, U.S.A. e-mail: [email protected]
DANIEL KATZ
Affiliation:
Department of Mathematics, University of Kansas, Lawrence, KS 66045, U.S.A. e-mail: [email protected], [email protected]

Abstract

Throughout we let ($T,{\frak m},k$) denote a commutative Noetherian local ring with maximal ideal ${\frak m}$ and residue field $k$. We let $I\,{\subseteq}\,T$ be an ideal generated by a regular sequence of length $c$ and set $R\,{\colonequal}\,T/I$. In the important paper [1], Avramov addresses the following question. Given a finitely generated $R$-module $M$, when does $M$ have finite projective dimension over a ring of the form $T/J$, where $J$ is generated by part (or all) of a set of minimal generators for $I$? He gives a fairly complete answer to this question that is expressed in terms of the geometry of varieties in affine space defined by annihilators of certain graded modules derived from resolutions over $R$. In an attempt to understand these ideas more fully, we became interested in the idea that one might answer the question at hand by using data about $M$ (orits syzygies) coming from $T$, in particular, information gleaned from various Fitting ideals defined over $T$. The following theorem from Section 3 is one of our main results. We use $\Fitt_T(M)$ to denote the Fitting ideal of $M$.

Type
Research Article
Copyright
2005 Cambridge Philosophical Society

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