Ebrahimi–Mohar–Nikiforov–Ahmady conjecture on the spectral sum of graphs

Let GG be any graph of order nn, and let λ1(G)\lambda_1(G) and λ2(G)\lambda_2(G) denote its two largest adjacency eigenvalues. Ebrahimi–Mohar–Nikiforov–Ahmady conjecture. The spectral sum satisfies

λ1(G)+λ2(G)≤8n7.\lambda_1(G)+\lambda_2(G)\leq \frac{8n}{7}.

The conjecture extends the extremal spectral-sum question from trees to arbitrary graphs. The supplied context states that analogous questions for graphs remain open and gives no resolution of this bound.

References

Primary source

Hitesh Kumar, Bojan Mohar, Shivaramakrishna Pragada and Hanmeng Zhan, “Convex combination of first and second eigenvalues of trees”, arXiv:2601.10036 (2026).

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