Infinite highly arc transitive digraphs and universal covering digraphs (Q1316644)

A digraph \(D\) is said to be \(s\)-arc transitive if its automorphism group is transitive on the set of \(s\)-arcs, and \(D\) is said to be highly arc transitive if it is \(s\)-arc transitive for all finite \(s\geq 0\). The authors give a few methods for obtaining new highly arc transitive digraphs from a given one. They attempt to characterize highly arc transitive digraphs in several ways, and they also study certain properties of these digraphs.