On the deep commuting graph of a finite group
Sumana Hatui, Sanjay Mukherjee, Kamal Lochan Patra
TL;DR
The paper advances the study of the deep commuting graph $Δ_D(G)$, defined via commuting preimages in a Schur cover, and shows it is independent of the chosen cover. It establishes fundamental structural results, including the criterion that $Δ_D(G)$ is complete iff $G$ is cyclic, and develops a broad classification of when $Δ_D(G)$ is perfect, tying this to the perfectness of the Schur cover’s commuting graph. The authors also explore universality, Eulerian properties, and reduced-graph connectivity, with detailed analyses across finite abelian and several non-abelian groups (dihedral, quaternion, Heisenberg, symmetric, and alternating). They show how $Δ_D(G)$ interacts with classical notions like the enhanced power graph and the Schur and Bogomolov multipliers, yielding precise results for large families and proposing open directions for a complete classification and fine-grained graph invariants. Overall, the work deepens the connection between group cohomology and graph-theoretic properties of group-derived graphs, with potential implications for understanding commuting structures in finite groups.
Abstract
Let $G$ be a finite group and let $\tilde{G}$ be a Schur cover of $G$. The deep commuting graph $Δ_D(G)$ of $G$ is a simple graph with vertex set $G$, where two distinct vertices are adjacent if their pre-images commute in $\tilde{G}$. The deep commuting graph of a finite group was first introduced in [P. J. Cameron and B. Kuzma, Between the enhanced power graph and the commuting graph, {\it J. Graph Theory} {\bf 102} (2023), no. 2, 295--303], where the authors have shown that $Δ_D(G)$ is fixed irrespective of the choice of the Schur cover $\tilde{G}$. In this paper, we first prove that $Δ_D(G)$ is complete if and only if $G$ is cyclic. Also, we classify finite simple groups, symmetric groups and alternating groups, for which $Δ_D(G)$ is perfect. In addition, explore several other properties of $Δ_D(G)$ like Eulerianess, universality and connectedness of reduced deep commuting graphs. Next, we classify the finite abelian groups for which deep commuting graphs coincide with enhance power graphs. We also characterize the dominant vertices for the deep commuting graphs of finite abelian groups and examine the connectedness of the associated reduced deep commuting graphs. These properties of the deep commuting graphs for the non abelian groups like symmetric groups, alternating groups, dihedral groups, generalized quaternion group and Heisenberg groups are also discussed.