Abstract
Our main result states that for a commutative ring R and a finite abelian group G the following conditions are equivalent: (a) Gal(R,G)=Gal (R[X],G), i.e. every commutative Galois extension of R[X]with Galois group G is extended from R. (b) The order of G is a non-zero-divisor in R/Nil(R). The proof uses lifting properties of Galois extensions over Hensel pairs and a “Milnor-type” patching theorem.
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Greither, C., Haggenmüller, R. Abelsche Galoiserweiterungen von R[X]. Manuscripta Math 38, 239–256 (1982). https://doi.org/10.1007/BF01168593
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DOI: https://doi.org/10.1007/BF01168593