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Inverse images of block varieties

Linckelmann, M. (2023). Inverse images of block varieties. Communications in Algebra, 52(5), pp. 2086-2100. doi: 10.1080/00927872.2023.2281600


We extend a result due to Kawai on block varieties for blocks with abelian defect groups to blocks with arbitrary defect groups. Kawai’s result is a tool to calculate the cohomology variety of a module in a block B of a finite group algebra kG restricted to subgroups of a defect group P , provided that P is abelian. Kawai’s result coincides with a Theorem of Avrunin and Scott specialised to modules in the principal block and their restrictions to p-subgroups. J. Rickard raised the question whether Kawai’s result can be extended to modules in blocks with arbitrary defect groups. We show that this is indeed the case for modules whose corresponding module over some almost source algebra is fusion stable. We show that this fusion stability hypothesis is automatically satisfied for principal blocks and blocks with abelian defect groups.

Publication Type: Article
Additional Information: © 2023 The Author(s). Published with license by Taylor & Francis Group, LLC This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (, which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent.
Publisher Keywords: Finite groups, blocks, cohomology varieties
Subjects: Q Science > QA Mathematics
Departments: School of Science & Technology > Mathematics
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