Higman group

In mathematics, the Higman group, introduced by Graham Higman (1951), was the first example of an infinite finitely presented group with no nontrivial finite quotients. The quotient by the maximal proper normal subgroup is a finitely generated infinite simple group. Higman (1974) later found some finitely presented infinite groups $G n, r$ that are simple if $n$ is even and have a simple subgroup of index 2 if $n$ is odd, one of which is one of the Thompson groups.

Higman's group is generated by 4 elements $a, b, c, d$ with the relations

a^{-1}ba=b^{2},\quad b^{-1}cb=c^{2},\quad c^{-1}dc=d^{2},\quad d^{-1}ad=a^{2}.

References

Higman, Graham (1951), "A finitely generated infinite simple group", Journal of the London Mathematical Society, Second Series, 26 (1): 61–64, doi:10.1112/jlms/s1-26.1.61, ISSN 0024-6107, MR 0038348
Higman, Graham (1974), Finitely presented infinite simple groups, Notes on Pure Mathematics, vol. 8, Department of Pure Mathematics, Department of Mathematics, I.A.S. Australian National University, Canberra, ISBN 978-0-7081-0300-5, MR 0376874

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