$\lambda$-Core Distance Partitions

Abstract

The $\lambda$-core vertices of a graph correspond to the non-zero entries of some eigenvector of $\lambda$ for a universal adjacency matrix $\mathbf{U}$ of the graph. We define a partition of the vertex set $V$ based on the $\lambda$-core vertex set and its neighbourhoods at a distance $r$, and give a number of results relating the structure of the graph to this partition. For such partitions, we also define an entropic measure for the information content of a graph, related to every distinct eigenvalue $\lambda$ of $\mathbf{U}$, and discuss its properties and potential applications.

8 pages, 2 figures. Linear Algebra Appl. (2021)