Mathematical Research Letters

Volume 8 (2001)

Number 3

Unstable Cohen–Macaulay Algebras

Pages: 347 – 359



Mara D. Neusel (University of Notre Dame)


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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