Domain with a nonzero idempotent maximal ideal

ID: domain-with-a-nonzero-idempotent-maximal-ideal

Let
This ring consists of finite sums of rational multiples of nonnegative dyadic rational powers of , interpreted as functions on . Every pair of elements lies in one polynomial ring , so is an integral domain. The constant term defines a surjective ring homomorphism . Its kernel of a ring homomorphism is nonzero and is a maximal ideal, by the maximal ideal quotient criterion.
Every has the form for some and some polynomial . The identity
expresses it as a product of two elements of . Therefore , and for all . This shows that strict descent of powers of an ideal can fail in an integral domain, even for a nonzero maximal ideal. By the determinant trick, such an ideal cannot be finitely generated, so this ring is not a Noetherian ring.

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