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

From papers

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.

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Sources & referencesView supporting material

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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