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# Trichotomy theorem

In mathematical finite group theory, the trichotomy theorem divides the simple groups of characteristic 2 type and rank at least 3 into three classes. It was proved by Aschbacher (1981, 1983) for rank 3 and by Gorenstein & Lyons (1983) for rank at least 4. The three classes are groups of GF(2) type (classified by Timmesfeld and others), groups of "standard type" for some odd prime (classified by the Gilman–Griess theorem and work by several others), and groups of uniqueness type, where Aschbacher proved that there are no simple groups.

References

Aschbacher, Michael (1981), "Finite groups of rank 3. I", Inventiones Mathematicae 63 (3): 357–402, doi:10.1007/BF01389061, ISSN 0020-9910, MR 620676

Aschbacher, Michael (1983), "Finite groups of rank 3. II", Inventiones Mathematicae 71 (1): 51–163, doi:10.1007/BF01393339, ISSN 0020-9910, MR 688262

Gorenstein, D.; Lyons, Richard (1983), "The local structure of finite groups of characteristic 2 type", Memoirs of the American Mathematical Society 42 (276): vii+731, ISBN 978-0-8218-2276-0, ISSN 0065-9266, MR 690900

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