Maximal Line Digraphs
Quentin Japhet, Dimitri Watel, Dominique Barth, Marc-Antoine Weisser · Journal of Graph Theory · 2026
ABSTRACT A line digraph is the digraph constructed from the digraph such that there is an arc in if the terminal node of in is the initial node of . The maximum number of arcs in a line digraph with nodes is if is even, and otherwise. For , there is only one line digraph with as many arcs if is even, and if is odd, there are two line digraphs, each being the transpose of the other.