Iterated line digraphs are asymptotically dense

© 2017. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/We show that the line digraph technique, when iterated, provides dense digraphs, that is, with asymptotically large order for a given diameter (or with small diameter for a given order). This is a well- known result for regular digraphs. In this note we prove that this is also true for non-regular digraphsPostprint (author's final draft