The conjecture on the local maxima of the inducibility profile of K2,2,1K_{2,2,1}

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Let IK2,2,1(e)I_{K_{2,2,1}}(e) denote the inducibility profile of the complete 33-partite graph K2,2,1K_{2,2,1}. For k≥3k\geq 3, set

a=k+(1−e)k2−ekk2+k.a=\frac{k+\sqrt{(1-e)k^2-ek}}{k^2+k}.

The conjectured profile of K2,2,1K_{2,2,1}. The function is conjectured to satisfy

IK2,2,1(e)={25/24⋅e2.5if e∈[0,2/3],[15a5(k−2)+30(ak−1)2a3−15(ak−1)a4](k−1)kif e∈[k−1k,kk+1].I_{K_{2,2,1}}(e)=\begin{cases} \sqrt{25/24}\cdot e^{2.5} & \text{if }e\in[0,2/3],\\[6pt] [15a^5(k-2)+30(ak-1)^2a^3-15(ak-1)a^4](k-1)k & \text{if }e\in\left[\frac{k-1}{k},\frac{k}{k+1}\right]. \end{cases}

The proposed description concerns the shape of the inducibility profile, which is continuous but appears not to be differentiable at edge densities of the form (k−1)/k(k-1)/k. Experiments with other multipartite graphs suggest that sharper peaks may produce additional local maxima.

References

Primary source

József Balogh, Bernard Lidický and Haoran Luo, “Local maximum of inducibility profiles”, arXiv:2605.15021 (2026).

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