Li–Peng square-root booksize conjecture for Nosal graphs

Let GG be an mm-edge graph with spectral radius ρ(G)>m\rho(G)>\sqrt{m}. Such a graph is called Nosal, and let bk(G)bk(G) denote the maximum number of triangles sharing a common edge in GG.

Li–Peng conjecture. For every mm-edge Nosal graph GG,

bk(G)=Ω(m).bk(G)=\Omega(\sqrt{m}).

Nikiforov had previously shown the weaker bound bk(G)>112m4bk(G)>\frac{1}{12}\sqrt[4]{m}. The conjecture was confirmed by Li, Liu and Zhang, who proved bk(G)>124mbk(G)>\frac{1}{24}\sqrt{m} and showed that the order m\sqrt{m} is best possible.

Sources & referencesView supporting material

Primary source

Xinghui Zhao, Lihua You, Jing Zeng and Xiaoxue Zhang, “Two problems on booksize and triangular edges in Nosal graphs”, arXiv:2607.15071 (2026).

Additional references

3 papers in this index state this conjecture (2025–2026). The statement above is taken from the most recent of them; the others are arXiv:2601.10163, arXiv:2508.14366.

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