Solution

ID: past-exam-of-the-commutative-algebra-course-of-the-university-of-oxford/2023/1/b/ii/solution

In the terminology of a minimal primary decomposition, an associated prime of a primary decomposition of is a prime ideal occurring as in such a decomposition. The first uniqueness theorem for primary decomposition says that this collection is independent of the chosen minimal primary decomposition. Among these prime ideals, an isolated prime of a primary decomposition is minimal under inclusion, equivalently a minimal prime over an ideal ; an embedded prime ideal strictly contains another member of the collection. Thus
When is a Noetherian ring, these are precisely the associated primes of a module . In that case the equivalent definition is
where is a colon ideal. The decomposition terminology applies when a minimal primary decomposition exists; a general ring need not provide one for every ideal.

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