
Let G be a simple graph of order n and A(G) be its adjacency matrix. The nullity of a graph G, denoted by η(G), is the multiplicity of the eigenvalue zero in the spectrum of A(G). Denote by Ck and Lk the set of all connected graphs with k induced cycles and the set of line graphs of all graphs in Ck, respectively. In 1998, Sciriha [I. Sciriha, On singular line graphs of trees, Congr. Numer. 135 (1998) 73-91] show that the order of every tree whose line graph is singular is even. Then Gutman and Sciriha [I. Gutman, I. Sciriha, On the nullity of line graphs of trees, Discrete Math. 232 (2001) 35-45] show that the nullity set of L0 is {0,1}. In this paper, we investigate the nullity of graphs with cut-points and deduce some concise formulas. Then we generalize Scirihas' result, showing that the order of every graph G is even if such a graph G satisfies that G∈Ck and η(L(G))=k+1, and the nullity set of Lk is {0,1,…,k,k+1} for any given k, where L(G) denotes the line graph of the graph G.
Numerical Analysis, Eigenvalues, singular values, and eigenvectors, Algebra and Number Theory, Singularity, Graphs and linear algebra (matrices, eigenvalues, etc.), Adjacency matrix, Line graph, Article, Matching, Discrete Mathematics and Combinatorics, Geometry and Topology, Nullity, Cut-point
Numerical Analysis, Eigenvalues, singular values, and eigenvectors, Algebra and Number Theory, Singularity, Graphs and linear algebra (matrices, eigenvalues, etc.), Adjacency matrix, Line graph, Article, Matching, Discrete Mathematics and Combinatorics, Geometry and Topology, Nullity, Cut-point
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