There are many ways of calculating a graphs characteristic polynomial; a lesser known method is a formula called the figure equation. The figure equation provides a direct link between a graphs structure and the coefficients of its characteristic polynomial. This method does not use determinants, but calculates the characteristic polynomial of any graph by counting cycles. We give a complete combinatorial analysis of four increasingly complex graph families, which yields closed formulae for their characteristic polynomial. In this paper, we introduce the figure equation, prove formulae for the line, cyclic, ladder, and dihedral graphs, and examine connections among these graph families including isospectrality and graph covering maps.
Terremce Bisson, Department of Mathematics and Statistics, Canisius College firstname.lastname@example.org
"Combinatorics of the Figure Equation on Directed Graphs,"
Rose-Hulman Undergraduate Mathematics Journal: Vol. 7
, Article 17.
Available at: http://scholar.rose-hulman.edu/rhumj/vol7/iss2/17