Graph theory MOC Graph automorphism Let be a general graph. A graph automorphism is a bijection which leaves the adjacency matrix of fully invariant, #m/def/graph i.e. for all . Clearly forms a group under composition, which in addition to an action on has an action on . A digraph is called vertex-transitive iff acts transitively on ; arc-transitive iff acts transitively on . Results Every arc-transitive digraph is an orbital digraph #state/tidy | #lang/en | #SemBr