On adjacency and Laplacian cospectral non-isomorphic signed graphs

Abstract

Let Γ = (G,σ) be a signed graph, where σ is the sign function on the edges of G. In this paper, we use the operation of partial transpose to obtain non-isomorphic Laplacian cospectral signed graphs. We will introduce two new operations on signed graphs. These operations will establish a relationship between the adjacency spectrum of one signed graph with the Laplacian spectrum of another signed graph. As an application, these new operations will be utilized to construct several pairs of cospectral non-isomorphic signed graphs. Finally, we construct integral signed graphs.