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arXiv · 1708.01916

On the Mean Connected Induced Subgraph Order of Cographs

Matthew E. Kroeker·Lucas Mol·Ortrud R. Oellermann
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Abstract

In this article the extremal structures for the mean order of connected induced subgraphs of cographs are determined. It is shown that among all connected cographs of order $n \ge 7$, the star $K_{1,n-1}$ has maximum mean connected induced subgraph order, and for $n \ge 3$, the $n$-skillet, $K_1+(K_1 \cup K_{n-2})$, has minimum mean connected induced subgraph order. It is deduced that the density for connected cographs (i.e. the ratio of the mean to the order of the graph) is asymptotically $1/2$. The mean order of all connected induced subgraphs containing a given vertex $v$ of a cograph $G$, called the local mean of $G$ at $v$, is shown to be at least as large as the mean order of all connected induced subgraphs of $G$, called the global mean of $G$.

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Matthew E. Kroeker, Lucas Mol, Ortrud R. Oellermann. 2017-08-06. On the Mean Connected Induced Subgraph Order of Cographs. https://arxiv.org/abs/1708.01916

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