Conjecture on the matching-restricted Turán number of Berge cliques

Let H+1rH_{\ell+1}^r be the Berge clique appearing in the source, let Ms+1rM_{s+1}^r denote a matching of size s+1s+1, and let G(n,,s,r)\mathcal{G}(n,\ell,s,r) be the hypergraph defined earlier in the paper. For integers satisfying

r3,s(2),\ell \ge r \ge 3,\qquad s \ge \binom{\ell}{2},

and for sufficiently large nn, consider rr-graphs avoiding both H+1rH_{\ell+1}^r and Ms+1rM_{s+1}^r.

The matching-restricted Berge-clique conjecture.

exr(n,{H+1r,Ms+1r})=str1(ns,1).\operatorname{ex}_r(n, \{H_{\ell+1}^r, M_{s+1}^r\})=s\cdot t_{r-1}(n-s,\ell-1).

In particular, G(n,,s,r)\mathcal{G}(n,\ell,s,r) is the unique extremal hypergraph.

The conjecture extends matching-restricted Turán problems for hypergraphs and proposes that, once s(2)s\ge\binom{\ell}{2}, the previously defined construction remains extremal. The supplied text gives a counterexample to this construction in the range 1s(2)1\ell-1\le s\le\binom{\ell}{2}-1, but does not report a resolution of the stated conjecture.

Sources & referencesView supporting material

Primary source

Caihong Yang, Jiasheng Zeng and Xiao-Dong Zhang, “A hypergraph analogue of Alon-Frankl Theorem”, arXiv:2511.21096 (2025).

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