We determine the graph with the largest signless Laplacian spectral radius among all unicyclic graphs with fixed matching number.

In this paper, we will describe some algorithms and give their complexity as following: (1) The algorithm for finding a dominating set of radius r in a vertex-weighted graph with small number of spanning tress. The complexity of this algorithm for the unicyclic graph is O(m.n). (2) The algorithm for finding an absolute and vertex p-center of a vertex-weighted graph with small number of spanning...

The Balaban index of a connected graph G is defined as J(G) = |E(G)| μ+ 1 ∑ e=uv∈E(G) 1 √ DG(u)DG(v) , and the Sum-Balaban index is defined as SJ(G) = |E(G)| μ+ 1 ∑ e=uv∈E(G) 1 √ DG(u)+DG(v) , where DG(u) = ∑ w∈V (G) dG(u,w), and μ is the cyclomatic number of G. In this paper, the unicyclic graphs with the maximum Balaban index and the maximum Sum-Balaban index among all unicyclic graphs on n v...

The hyper-Kirchhoff index is introduced when the hyper-Wiener operator is applied to the resistance-distance matrix of a connected graph. We give lower and upper bounds for the hyper-Kirchhoff index, and determine the n-vertex unicyclic graphs with the smallest, the second and the third smallest as well as the largest, the second and the third largest hyper-Kirchhoff indices for n ≥ 5. We also ...

*Correspondence: [email protected] 2School of Science, Zhejiang A&F University, Hangzhou, 311300, China Full list of author information is available at the end of the article Abstract Let S(G ) be the skew-adjacency matrix of an oriented graph G with n vertices, and let λ1,λ2, . . . ,λn be all eigenvalues of S(G ). The skew-spectral radius ρs(G ) of G is defined as max{|λ1|, |λ2|, . . . , |λn|}....

In this paper, the signed graphs with one positive eigenvalue are characterized, and the signed graphs with pendant vertices having exactly two positive eigenvalues are determined. As a consequence, the signed trees, the signed unicyclic graphs and the signed bicyclic graphs having one or two positive eigenvalues are characterized.

If G is a connected graph with vertex set V (G), then the eccentric connectivity index of G, denoted by ξc(G), is defined as ∑ v∈V (G) deg(v)ec(v), where deg(v) is the degree of a vertex v and ec(v) is its eccentricity. Morgan et al. [5] investigated the eccentric connectivity index of trees. In this paper, we investigate the eccentric connectivity index of unicyclic graphs. Upper bound is obta...

For n ≥ 11, we determine all the unicyclic graphs on n vertices whose signless Laplacian spectral radius is at least n− 2. There are exactly sixteen such graphs and they are ordered according to their signless Laplacian spectral radii.