Asymptotic Spectral Bounds under Odd-Girth Constraints
Abstract
Odd girth and the sum of the largest and smallest adjacency eigenvalues are two common indicators of how close a graph is to being bipartite. This paper investigates the asymptotic behavior of this eigenvalue sum under odd-girth constraints. We study the associated abstract moment problem over finite real lists satisfying the vanishing odd-moment identities imposed by odd girth at least g and the standard second-moment bound for graph spectra. We prove that the supremum of (λ1+λn)/n over these lists lies between (1−o(1))(log g)2/g3 and (10/7+o(1))(log g)2/g3 as g→∞ through the odd integers. The upper bound applies in particular to graphs of odd girth at least g. For regular graphs of odd girth g≥5, we obtain a stronger bound (λ1+λn)/n ≤ 12/((g−1)(g−2)(g−3)), which is optimal up to a constant factor.
Related
- Optimal Spectral Lower Bounds and Nonradial Nonlinear Asymptotic Stability of a Family of Three-Dimensional Keller--Segel Self-Similar Blow-Up Solutions
- Optimal girth-dependent bounds for the Bethe approximation of the permanent
- Whither quantum advantage? New classical lower bounds for Max-Cut on large-girth 3-regular graphs
- A Spectral Local-to-Global Principle for Spin Systems on Graphs with Girth At Least Five
- Integral of Scalar Curvature: Sharp Asymptotic Bounds and Rigidity
BibTeX
@misc{wang2026asymptotic,
title = {{Asymptotic Spectral Bounds under Odd-Girth Constraints}},
author = {Chen Wang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.05172},
eprint = {2610.05172},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.05172},
}
RIS
TY - UNPB
TI - Asymptotic Spectral Bounds under Odd-Girth Constraints
AU - Chen Wang
PY - 2026
DA - 2026/10/04
PB - arXiv
DO - 10.48550/arxiv.2610.05172
UR - https://arxiv.org/abs/2610.05172
AB - Odd girth and the sum of the largest and smallest adjacency eigenvalues are two common indicators of how close a graph is to being bipartite. This paper investigates the asymptotic behavior of this eigenvalue sum under odd-girth constraints. We study the associated abstract moment problem over finite real lists satisfying the vanishing odd-moment identities imposed by odd girth at least g and the standard second-moment bound for graph spectra. We prove that the supremum of (λ_1+λ_n)/n over these lists lies between (1−o(1))(log g)^2/g^3 and (10/7+o(1))(log g)^2/g^3 as g→∞ through the odd integers. The upper bound applies in particular to graphs of odd girth at least g. For regular graphs of odd girth g≥5, we obtain a stronger bound (λ_1+λ_n)/n ≤ 12/((g−1)(g−2)(g−3)), which is optimal up to a constant factor.
ER -