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May 5, 2019 at 0:11 vote accept Dave Shulman
May 4, 2019 at 20:23 comment added user131654 Thanks for your comment. I edited the answer to make remove that ambiguity.
May 4, 2019 at 20:20 history edited user131654 CC BY-SA 4.0
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May 4, 2019 at 15:17 comment added Yemon Choi It is worth pointing out (I'm sure you know this, but the phrasing above is potentially ambiguous) that the "open problem" is about characterising when the group ring is a domain. If one merely wants to get examples of ${\bf C}[\Gamma]$ with non-trivial idempotents then every non-trivial torsion element of $\Gamma$ gives rise to such an idempotent
May 4, 2019 at 9:40 history answered user131654 CC BY-SA 4.0