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具有规定平均度的图的谱半径的新下界

A New Lower Bound on the Spectral Radius of Graphs with Prescribed Average Degree

Sonny Ben-Shimon, Idan Eisner, Shlomo Hoory

arXiv 2607.17895首次发表:更新:

AI 中文总结

研究给定平均度的图的谱半径下界,通过问题分数松弛的精确解得到改进下界,肯定了Hong的猜想,刻画了离散实现条件,证明固定顶点数时有效边配置数量至少线性增长,平均渐近阶为Θ(n log n)。

AI 中文摘要

这项工作为给定平均度的图的谱半径建立了一个改进的下界。新的界来自于该问题分数松弛的精确解。我们的发现对Hong(1993)关于具有特定平均度的图的猜想给出了肯定答案,因为达到我们界的极值图被证明其最小度和最大度相差至多为1。此外,我们精确刻画了允许这种离散实现的条件。我们证明,对于固定数量的顶点n,有效边配置的数量至少随n线性增长,平均渐近阶为Θ(n log n)。

英文摘要

This work establishes an improved lower bound for the spectral radius of a graph given its average degree. The new bound follows from an exact solution of the fractional relaxation of the problem. Our findings lead to an affirmative answer to a conjecture by Hong (1993) for graphs with specific average degrees -- as the extremal graphs that meet our bound are proven to have a minimal and maximal degree that differ by at most one. Furthermore, we provide an exact characterization of the conditions that permit such discrete realizations. We prove that for a fixed number of vertices $n$, the number of valid edge configurations grows at least linearly with $n$, achieving an average asymptotic order of $Θ(n\log n)$.

Comments25 pages, 3 figures

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