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arXiv · 2606.16369

On the minimum spectral radius of unicyclic graphs with a given matching number

Joyentanuj Das·Debabrota Mondal
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Abstract

A matching $M$ in a graph $G = (V, E)$ is a set of edges such that no two edges in $M$ share a common vertex. A matching with maximum cardinality is called a maximum matching and its cardinality is the matching number $\gamma(G)$. The spectral radius of $G$ is the maximum absolute eigenvalue of its adjacency matrix. This article addresses the Brualdi-Solheid problem--the determination of extremal spectral radii within specific graph classes--for the class $\mathcal{U}_{n,\gamma}$ of simple connected unicyclic graphs on $n$ vertices with matching number $\gamma$. We specifically characterize all graphs that achieve the minimum spectral radius in $\mathcal{U}_{n,\gamma}$ for matching numbers $\gamma \in \left\{ 1, 2, 3, \lfloor \frac{n}{2} \rfloor \right\}$.

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Joyentanuj Das, Debabrota Mondal. 2026-06-15. On the minimum spectral radius of unicyclic graphs with a given matching number. https://arxiv.org/abs/2606.16369

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