On commensurating graphs of pro-$\mathcal{C}$ groups

Abstract: We study commensurations of pro-$\mathcal{C}$ groups, where $\mathcal{C}$ is an extension-closed variety of finite groups. We characterize those commensurations of pro-$\mathcal{C}$ groups that can be extended to embeddings into a common overgroup, obtaining a pro-$\mathcal{C}$ analog of a recent theorem by Touikan. We also consider obtain a structural result on virtual retracts of pro-$\mathcal{C}$ groups.