Title of article :
A note on the re-defined third Zagreb index of trees
Author/Authors :
Dehgardi ، Nasrin Department of Mathematics and Computer Science - Sirjan University of Technology
Abstract :
For a graph $\Gamma$, the re-defined third Zagreb index is defined as $$ReZG_3(\Gamma)=\sum_{ab\in E(\Gamma)}\deg_\Gamma(a) \deg_\Gamma(b)\Big(\deg_\Gamma(a)+\deg_\Gamma(b)\Big),$$where $\deg_\Gamma(a)$ is the degree of vertex $a$. We prove for any tree $T$ with $n$ vertices and maximum degree $\Delta$, $ReZG_3(T)\geq16n+\Delta^3+2\Delta^2-13\Delta-26$ when $\Delta n-1$ and $ReZG_3(T)=n\Delta^2+n\Delta-\Delta^2-\Delta$ when $\Delta=n-1$. Also we determine the corresponding extremal trees.
Keywords :
Zagreb indices , re-defined third Zagreb index , trees
Journal title :
Communications in Combinatorics and Optimization
Journal title :
Communications in Combinatorics and Optimization