AMS classifications: 05E30; 51E20; 94B05;

AMS classification: 05C50;

In [E.R. van Dam and W.H. Haemers, Which graphs are determined by their spectrum?, Linear Algebra Appl. 373 (2003), 241-272] we gave a survey of answers to the question of which graphs are determined by the spectrum of some matrix associated to the graph. In particular, the usual adjacency...

AMS Subject Classification: 05C50

Abstract: For a graph Γ with adjacency matrix A, we consider a switching operation that takes Γ into a graph Γ' with adjacency matrix A', defined by A' = QtAQ, where Q is a regular orthogonal matrix of level 2 (that is, QtQ = I, Q1 = 1, 2Q is integral, and Q is not a permutation matrix). If...

AMS Subject Classification: 05B20, 05C50.

AMS Subject Classification: 05B05, 05E30, 05C50.

AMS Subject Classification: 05C50, 15A42.