The signless Laplacian coefficients and the incidence energy of unicyclic graphs with given pendent vertices


Wen-Huan Wang, Lei Zhong




Let U r n be the set of unicyclic graphs with n vertices and r pendent vertices (namely, r leaves), where n ≥ 4 and r ≥ 1. We consider the signless Laplacian coefficients (SLCs) and the incidence energy (IE) in U r n. Firstly, among a subset of U r n in which each graph has a fixed odd girth ≥ 3, where n ≥ + 1 and r ≥ 1, we characterize a unique extremal graph which has the minimum SLCs and the minimum IE. Secondly, if G ∈ U r n and G has odd girth ≥ 5, where n ≥ 7 and r ≥ 1, then we prove that a unique extremal graph L n ∈ U r n with girth 4 satisfies that both the SLCs and the IE of G are more than the counterparts of L n