The refined threshold conjecture for expanded cliques with bounded matching number

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Let Kℓ+1(r)+K_{\ell+1}^{(r)+} be the rr-uniform expansion of the complete graph on ℓ+1\ell+1 vertices, let Ms+1(r)+M_{s+1}^{(r)+} be an rr-uniform matching with s+1s+1 edges, and let tr(n,ℓ−1)t_r(n,\ell-1) denote the number of edges in the complete balanced (ℓ−1)(\ell-1)-partite rr-graph on nn vertices. Refined threshold conjecture. For integers ℓ≥r≥3\ell\geq r\geq3, there is a constant s1=s1(r,ℓ)≥ℓ22s_1=s_1(r,\ell)\geq \frac{\ell^2}{2} such that, for sufficiently large nn, when (ℓ2)≤s<s1\binom{\ell}{2}\le s<s_1,

exr(n,{Kℓ+1(r)+,Ms+1(r)+})=(ℓ2)⋅(n−(ℓ2)r−1),{\mathrm{ex}}_r(n,\{K_{\ell+1}^{(r)+},M_{s+1}^{(r)+}\})=\binom{\ell}{2}\cdot \binom{n-\binom{\ell}{2}}{r-1},

and when s≥s1s\geq s_1,

exr(n,{Kℓ+1(r)+,Ms+1(r)+})=s⋅tr(n,ℓ−1).{\mathrm{ex}}_r(n,\{K_{\ell+1}^{(r)+},M_{s+1}^{(r)+}\})=s\cdot t_r(n,\ell-1).

This refines the preceding conjecture by proposing a second asymptotic regime below a threshold s1s_1; the supplied text gives no resolution.

References

Primary source

Xiamiao Zhao, Yuanpei Wang and Junpeng Zhou, “Hypergraph extensions of the Alon–Frankl Theorem and rainbow Turán problems”, arXiv:2605.01768 (2026).

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