Lemma 47.20.2. Let (A, \mathfrak m, \kappa ) be a Noetherian local ring with normalized dualizing complex \omega _ A^\bullet and dualizing module \omega _ A = H^{-\dim (A)}(\omega _ A^\bullet ). The following are equivalent
A is Cohen-Macaulay,
\omega _ A^\bullet is concentrated in a single degree, and
\omega _ A^\bullet = \omega _ A[\dim (A)].
In this case \omega _ A is a maximal Cohen-Macaulay module.
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