TY - JOUR
ID - 14584
TI - On graphs with integer sombor indices
JO - Communications in Combinatorics and Optimization
JA - CCO
LA - en
SN - 2538-2128
AU - Sepehr, Marzie
AU - Jafari Rad, Nader
AD - Department of Mathematics, Shahed University, Tehran, Iran
Y1 - 2024
PY - 2024
VL - 9
IS - 4
SP - 693
EP - 705
KW - Integer Sombor index
KW - Bipartite graphs
KW - $r$-degree&lrm
DO - 10.22049/cco.2023.28334.1510
N2 - â€ŽSombor index of a graph $G$ is defined by $SO(G) = \sum_{uv \in E(G)} \sqrt{d^2_G(u)+d^2_G(v)}$, where $d_G(v)$ is the degree of the vertex $v$ of $G$. An $r$-degree graph is a graph whose degree sequence includes exactly $r$ distinctive numbers. In this article, we study $r$-degree connected graphs with integer Sombor index for $r \in \{5, 6, 7\}$. We show that: if $G$ is a 5-degree connected graph of order $n$ with integer Sombor index then $n \geq 50$ and the equality occurs if only if $G$ is a bipartite graph of size 420 with $SO(G) = 14830$; if $G$ is a 6-degree connected graph of order $n$ with integer Sombor index then $n \geq 75$ and the equality is established only for the bipartite graph of size $1080$; and if $G$ is a 7-degree connected graph of order $n$ with integer Sombor index then $n \geq 101$ and the equality is established only for the bipartite graph of size $1680$.
UR - https://comb-opt.azaruniv.ac.ir/article_14584.html
L1 - https://comb-opt.azaruniv.ac.ir/article_14584_8d0ef76fd228409214f2430caf9898bf.pdf
ER -