On Chains of Intermediate Rings Resulting from the Juxtaposition of Minimal Ring Extensions
نویسندگان
چکیده
Let R ⊂ S and S ⊂ T be minimal ring extensions of (commutative) rings. If (i) each of these extensions is integral or (ii) each of these extensions is integrally closed or (iii) R ⊂ S is integral while S ⊂ T is integrally closed, then each chain of rings between R and T is finite. Examples are given of minimal extensionsR ⊂ S and S ⊂ T such thatR ⊂ S is integrally closed, S ⊂ T is any of the three possible kinds of integral minimal extensions, and there exists (resp., does not exist) an infinite chain of intermediate rings between R and T .
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