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arXiv · 2407.02535

Eccentricity and algebraic connectivity of graphs

B. Afshari·M. Afshari
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Abstract

Let $G$ be a graph on $n$ nodes with algebraic connectivity $\lambda_{2}$. The eccentricity of a node is defined as the length of a longest shortest path starting at that node. If $s_\ell$ denotes the number of nodes of eccentricity at most $\ell$, then for $\ell \ge 2$, $$\lambda_{2} \ge \frac{ 4 \, s_\ell }{ (\ell-2+\frac{4}{n}) \, n^2 }.$$ As a corollary, if $d$ denotes the diameter of $G$, then $$\lambda_{2} \ge \frac{ 4 }{ (d-2+\frac{4}{n}) \, n }.$$ It is also shown that $$\lambda_{2} \ge \frac{ s_\ell }{ 1+ \ell \left(e(G^{\ell})-m\right) },$$ where $m$ and $e(G^\ell)$ denote the number of edges in $G$ and in the $\ell$-th power of $ G $, respectively.

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B. Afshari, M. Afshari. 2024-07-01. Eccentricity and algebraic connectivity of graphs. https://arxiv.org/abs/2407.02535

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