The Rhodes semilattice of a biased graph

Abstract

We reinterpret the Rhodes semilattices \(R_n({\mathfrak {G}})\) of a group \({\mathfrak {G}}\) in terms of gain graphs and generalize them to all gain graphs, both as sets of partition-potential pairs and as sets of subgraphs, and for the latter, further to biased graphs. Based on this we propose four different natural lattices in which the Rhodes semilattices and its generalizations are order ideals.