I want to find a semi-constructive example of a unitary commutative ring without any maximal ideals assuming that axiom of choice is incorrect and/or a model of ZF where we have such a concrete ring.
This question is similar to the questions Vector space bases without axiom of choice and A confusion about Axiom of Choice and existence of maximal ideals..
What I tried is to use R as a Q vector space without a basis and try to construct some chains of ideals on a related ring and try to show that a maximal ideal corresponds to a basis but didn't achieve much.
Thank you in advance!
Answer
Let k be a field, let I⊂kN be the ideal of sequences that are eventually zero, and let S=kN/I. Then maximal ideals in S are in bijection with nonprincipal ultrafilters on N. In particular, in any model of ZF in which there are no nonprincipal ultrafilters on N, there will be no maximal ideals in S.
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