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Tarski Monster


A Tarski monster is an infinite finitely generated noncyclic group whose proper nontrivial subgroups are all cyclic. In the prime-exponent form, every proper nontrivial subgroup has the same prime order p. Such groups exist for sufficiently large primes p (Ol'shanskii 1991). In a torsion-free Tarski monster every proper nontrivial subgroup is infinite cyclic.

Ersoy (2026, Theorems A and B) reports nonsofic Tarski monsters of every sufficiently large prime exponent, and torsion-free nonsofic examples. The torsion-free examples include continuum many pairwise non-quasi-isometric simple groups. The argument combines quotient theorems with the Sandhu-Thom construction of a hyperbolic group having no nontrivial sofic group quotient. Independent verification of that complete construction has not been established here, so the inherited qualification remains.


See also

Cyclic Group, Simple Group, Sofic Group

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References

Ersoy, K. "Non-Sofic Tarski Monsters." 30 Oct 2026. https://arxiv.org/abs/2610.42140v1.Ol'shanskii, A. Yu. "An Infinite Group with Subgroups of Prime Orders." Math. USSR-Izv. 16, 279-289, 1981. https://doi.org/10.1070/IM1981v016n02ABEH001307.Ol'shanskii, A. Yu. Geometry of Defining Relations in Groups. Dordrecht, Netherlands: Kluwer, 1991. https://doi.org/10.1007/978-94-011-3618-1.

Cite this as:

Weisstein, Eric W. "Tarski Monster." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/TarskiMonster.html

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