Mathematical Research Letters

Volume 8, Issue 3, May 2001 pp. 347-359.

Unstable Cohen--Macaulay Algebras

Authors: Mara D. Neusel
Author institution: University of Notre Dame

Summary: We characterize Cohen--Macaulay algebras in the category ${\Cal K_{fg}}$ of unstable Noetherian algebras over the Steenrod algebra via the depth of the $\steenrod^*$-invariant ideals. This allows us to transfer the Cohen--Macaulay property to suitable subalgebras. We apply this to rings of invariants of finite groups and to the $\steenrod^*$-inseparable closure.

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