Equivalent characterizations of the spectra of graphs and applications to measures of distance-regularity

V. Diego, J. Fàbrega, M. A. Fiol

As it is well known, the spectrum $\mathrm{sp}\Gamma$ (of the adjacency matrix $A$) of a graph $\Gamma$, with $d$ distinct eigenvalues other than its spectral radius ${\lambda }_0$, usually provides…