While they did not overlap, Arc and Google+ share a common theme in tech analysis:
Because, according to an internal design memo leaked to TechCrunch (and later confirmed by Arc’s then-CPO), Google+ represented a forgotten model of “spatial sociality” — content organized by (asymmetric follow relationships) and Communities (topic-first grouping) rather than algorithmic feeds.
If you are looking for information on "Arc on G+," you may be referring to one of the following: