Abstract

If the inverse of a non-singular real symmetric matrix that represents an edge-weighted graph with no loops has zero diagonal, then the inverse itself is the matrix of a loopless graph. Here we show that such graphs having non--zero weight on each edge always exist if their number of vertices is at least 6.

Highlights

  • Since the discovery of fullerenes in 1985, an intimate relationship has matured between these carbon molecules and mathematics

  • For a graph not to be a NSSD for any associated adjacency matrix, it suffices to show that it has a non–singular vertex–deleted subgraph

  • We have shown that complete NSSDs exist for all positive integers at least six

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Summary

Introduction

Since the discovery of fullerenes in 1985, an intimate relationship has matured between these carbon molecules and mathematics. Over the years, non–traditional fullerenes composed of cycles of other sizes, which are general 3–regular polyhedra, have been studied, especially for their regularity properties. This current work is motivated mainly by the beauty of these structures, coupled with the elegance of the interplay between combinatorics, graph theory and algebra. This family of graphs has remarkable properties as explored in [2] and [8] It is the purpose of this work to determine the existence of complete NSSDs. In [8], a characterisation of a graph G which is G–nutful is given. Some of these G–nutful graphs turn out to be complete, in which case both G and the graph of G−1 are nutful

Preliminaries
Complete Graphs On Less Than 5 Vertices
Complete Graphs On 5 Vertices
Complete Graphs on at Least Six Vertices
The Characteristic Polynomial of Circulant Matrices
The Construction of Complete NSSDs
Existence of Complete NSSDs on at least Nine Vertices
Conclusion
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