# A note on the extended total graph of commutative rings

Document Type: Research Paper

Authors

1 University of Tehran

2 Department of Mathematics, University of Guilan, Rasht, Iran

Abstract

Let $R$ be a commutative ring and $H$ a nonempty proper subset of $R$.
In this paper, the extended total graph, denoted by $ET_{H}(R)$ is presented, where $H$ is a
multiplicative-prime subset of $R$. It is the graph with all elements of $R$ as vertices, and for distinct $p,q\in R$, the vertices $p$ and $q$ are adjacent if and only if $rp+sq\in H$ for some $r,s\in R\setminus H$. We also study the two (induced) subgraphs $ET_{H}(H)$ and $ET_{H}(R\setminus H)$, with vertices $H$ and $R\setminus H$, respectively. Among other things, the diameter and the girth of $ET_{H}(R)$ are also studied.

Keywords