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A cohomological approach to the Brauer-Long group and the groups of Galois extensions and strongly graded rings


Authors: S. Caenepeel and M. Beattie
Journal: Trans. Amer. Math. Soc. 324 (1991), 747-775
MSC: Primary 16H05; Secondary 13A20
DOI: https://doi.org/10.1090/S0002-9947-1991-0987160-8
MathSciNet review: 987160
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Abstract: Let $ G$ be a finite abelian group, and $ R$ a commutative ring. The Brauer-Long group $ \operatorname{BD} (R,G)$ is described by an exact sequence

$\displaystyle 1 \to {\operatorname{BD} ^s}(R,G) \to \operatorname{BD} (R,G)\xrightarrow{\beta }\operatorname{Aut} (G \times {G^{\ast}})(R)$

where $ {\operatorname{BD} ^s}(R,G)$ is a product of étale cohomology groups, and Im $ \beta $ is a kind of orthogonal subgroup of $ \operatorname{Aut} (G \times {G^{\ast}})(R)$. This sequence generalizes some other well-known exact sequences, and restricts to two split exact sequences describing Galois extensions and strongly graded rings.

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Additional Information

DOI: https://doi.org/10.1090/S0002-9947-1991-0987160-8
Keywords: Brauer group, Azumaya algebra, Galois extension, étale cohomology, strongly graded ring, dimodule algebra
Article copyright: © Copyright 1991 American Mathematical Society

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