Inclusion graph of subgroups of a group

Abstract

For a finite group $G$, we define the inclusion graph of subgroups of $G$, denoted by $\mathcal I(G)$, is a graph having all the proper subgroups of $G$ as its vertices and two distinct vertices $H$ and $K$ in $\mathcal I(G)$ are adjacent if and only if either $H \subset K$ or $K \subset H$. In this paper, we classify the finite groups whose inclusion graph of subgroups is one of complete, bipartite, tree, star, path, cycle, disconnected, claw-free. Also we classify the finite abelian groups whose inclusion graph of subgroups is planar. For any given finite group, we estimate the clique number, chromatic number, girth of its inclusion graph of subgroups and for a finite abelian group, we estimate the diameter of its inclusion graph of subgroups. Among the other results, we show that some groups can be determined by their inclusion graph of subgroups