The enhanced quotient graph of the quotient of a finite group

Abstract

For a finite group $G$ with a normal subgroup $H$, the enhanced quotient graph of $G/H$, denoted by $\mathcal{G}_{H}(G),$ is the graph with vertex set $V=(G\backslash H)\cup \{e\}$ and two vertices $x$ and $y$ are edge connected if $xH = yH$ or $xH,yH\in \langle zH\rangle$ for some $z\in G$. In this article, we characterize the enhanced quotient graph of $G/H$. The graph $\mathcal{G}_{H}(G)$ is complete if and only if $G/H$ is cyclic, and $\mathcal{G}_{H}(G)$ is Eulerian if and only if $|G/H|$ is odd. We show some relation between the graph $\mathcal{G}_{H}(G)$ and the enhanced power graph $\mathcal{G}(G/H)$ that was introduced by Sudip Bera and A.K. Bhuniya (2016). The graph $\mathcal{G}_H(G)$ is complete if and only if $G/H$ is cyclic if and only if $\mathcal{G}(G/H)$ is complete. The graph $\mathcal{G}_H(G)$ is Eulerian if and only if $|G|$ is odd if and only if $\mathcal{G}(G)$ is Eulerian, i.e., the property of being Eulerian does not depend on the normal subgroup $H$.