Maximum spectral sum of graphs

Fuente: arXiv
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Autores principales: Kumar, Hitesh, Liu, Lele, Monterde, Hermie, Pragada, Shivaramakrishna, Tait, Michael
Formato: Preprint
Publicado: 2026
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author Kumar, Hitesh
Liu, Lele
Monterde, Hermie
Pragada, Shivaramakrishna
Tait, Michael
author_facet Kumar, Hitesh
Liu, Lele
Monterde, Hermie
Pragada, Shivaramakrishna
Tait, Michael
contents For a graph $G$ of order $n$, the spectral sum of $G$ is defined to be the sum $λ_1(G) + λ_2(G)$, where $λ_1(G)$ (resp. $λ_2(G)$) is the largest (resp. second largest) adjacency eigenvalue of $G$. Ebrahimi, Mohar, Nikiforov and Ahmady (2008) conjectured that the spectral sum \[ λ_1(G) + λ_2(G)\le \frac{8}{7}n \] for any graph $G$. We prove this conjecture by combining tools from the theory of graph limits, convex geometry, exterior algebra and convex optimization. The techniques developed are of independent interest.
format Preprint
id arxiv_https___arxiv_org_abs_2604_00512
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Maximum spectral sum of graphs
Kumar, Hitesh
Liu, Lele
Monterde, Hermie
Pragada, Shivaramakrishna
Tait, Michael
Combinatorics
05C50, 15A18, 15A60, 52A38, 15A75, 15A39
For a graph $G$ of order $n$, the spectral sum of $G$ is defined to be the sum $λ_1(G) + λ_2(G)$, where $λ_1(G)$ (resp. $λ_2(G)$) is the largest (resp. second largest) adjacency eigenvalue of $G$. Ebrahimi, Mohar, Nikiforov and Ahmady (2008) conjectured that the spectral sum \[ λ_1(G) + λ_2(G)\le \frac{8}{7}n \] for any graph $G$. We prove this conjecture by combining tools from the theory of graph limits, convex geometry, exterior algebra and convex optimization. The techniques developed are of independent interest.
title Maximum spectral sum of graphs
topic Combinatorics
05C50, 15A18, 15A60, 52A38, 15A75, 15A39
url https://arxiv.org/abs/2604.00512