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Uniform Turán Density


A 3-uniform hypergraph G on N vertices is uniformly (d,eta)-dense if every subset U of its vertex set satisfies

 e_G(U)>=d(|U|; 3)-etaN^3,

where e_G(U) is the number of hyperedges contained in U. The uniform Turán density pi_u(F) of a 3-uniform hypergraph F is the supremum of the real numbers d such that for every eta>0, there are arbitrarily large F-free uniformly (d,eta)-dense 3-uniform hypergraphs. Erdős and Sós (1982) introduced this parameter.

The tetrahedron is the complete 3-uniform hypergraph K_4^((3)). Bucić (2026) and Kielak et al. (2026) independently proved

 pi_u(K_4^((3)))=1/2.

Bucić (2026) reports that ChatGPT-6 supplied a tensor projection identity used in his otherwise human-developed argument, and that the formal verifier Aristotle checked the identity. As of Sep. 22, 2026, external specialist review of the two papers had not been reported.


See also

Hypergraph, Turán's Theorem

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References

Bucić, M. "The Uniform Turán Density of the Tetrahedron." 10 Sep 2026. https://arxiv.org/abs/2609.11802.Erdős, P. and Sós, V. T. "On Ramsey-Turán Type Theorems for Hypergraphs." Combinatorica 2, 289-295, 1982.Kielak, B.; Kráł, D.; Lamaison, A.; Liu, H.; Shu, X.; and Wu, Z. "Solution of Uniform Turán's Tetrahedron Problem." 8 Sep 2026. https://arxiv.org/abs/2609.08336.

Cite this as:

Weisstein, Eric W. "Uniform Turán Density." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/UniformTuranDensity.html

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