A Characterization of Biregular Group Rings
Canadian mathematical bulletin, Tome 21 (1978) no. 1, pp. 119-120
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In this note biregular group rings are characterized and an example is given to show that Renault′s conjecture is false.A ring A with 1 is biregular if for all a∈A, AaA is generated by a central idempotent Equivalently, A is biregular iff all the stalks of its Pierce sheaf are simple.In [1] Bovdi and Mihovski showed that for a ring A, if the group ring AG is biregular then: (*) A is biregular and G is locally normal with the order of each finite normal sub-group of G invertible in A. A proof is found in Renault [7]. In [6] Renault showed that (*) is necessary and sufficient in case A is a finitely generated module over its centre or if A is right self-injective. He conjectured that (*) is necessary and sufficient in general. In fact (*) is not sufficient as the example below shows. Some familiarity with Pierce sheaf techniques is assumed (see [5] or [2]).
Burgess, W. D. A Characterization of Biregular Group Rings. Canadian mathematical bulletin, Tome 21 (1978) no. 1, pp. 119-120. doi: 10.4153/CMB-1978-020-8
@article{10_4153_CMB_1978_020_8,
author = {Burgess, W. D.},
title = {A {Characterization} of {Biregular} {Group} {Rings}},
journal = {Canadian mathematical bulletin},
pages = {119--120},
year = {1978},
volume = {21},
number = {1},
doi = {10.4153/CMB-1978-020-8},
url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1978-020-8/}
}
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