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arXiv · 2611.00817

Maxima of the Q-index: Forbidden an odd wheel

Hongyu Wang·Yue Ma
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Abstract

In 2013, Freitas, Nikiforov and Patuzzi (EJLA, 2013) proposed the problem of determining the maximum signless Laplacian spectral radius of an $n$-vertex $F$-free graph. Recently, Yuan, Zhai and Zhang (LAA, 2026) determined the maximum signless Laplacian spectral radius of graphs without wheels of sufficiently large order. In this paper, we consider the problem of forbidding a single wheel $W_{2k+1}=K_1\vee C_{2k}$. We show that, for every fixed integer $k\ge 3$ and sufficiently large $n$, the unique extremal graph maximizing the signless Laplacian spectral radius among all $n$-vertex $W_{2k+1}$-free graphs is $K_k\vee(K_2\cup(n-k-2)K_1)$.

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Hongyu Wang, Yue Ma. 2026-10-31. Maxima of the Q-index: Forbidden an odd wheel. https://arxiv.org/abs/2611.00817

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