Abstract
The Koszul homology H.(y,N) which is constructed with respect to a sequencey and a maximal Cohen-Macaulay (CM) module N over a local CM ring A admitting a canonical module ωA will be compared with the Koszul homology H. (y, HomA(N, ωA)).
If R:=A/I with I=(y) is a CM ring, then the canonical module ωR of R exists and we will mainly show the existence of a natural isomorphism H. (y, HomA(N, ωA)≃HomR(H. (y, N), ωR, if H. (y, N) is a maximal CM module over R. This generalizes a result of Herzog in [2]. Using this isomorphism we are able to compute the graded canonical module of the graded ring grI (A) in a certain case.
In the last part of this paper we define a polynominal UN (y,x) associated with the Koszul homology H. (y, N) similar to Huneke in [7]. Huneke proved that Hj (y, N) is CM, if j<minding UN (y,x). We will proceed to show that Hj (y, N) is CM if j>deg UN (y,x).
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The material presented in this paper constitutes part of the author's thesis submitted to Universität Essen.
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Sanders, H. Cohen-Macaulay properties of the Koszul homology. Manuscripta Math 55, 343–357 (1986). https://doi.org/10.1007/BF01186650
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DOI: https://doi.org/10.1007/BF01186650