The second out-neighbourhood for local tournaments
Combinatorics
2018-12-06 v1
Abstract
Sullivan stated the conjectures: (1) every oriented graph has a vertex such that ; (2) every oriented graph has a vertex such that . In this paper, we prove that these conjectures hold for local tournaments. In particular, for a local tournament , we prove that has at least two vertices satisfying if has no vertex of in-degree zero. And, for a local tournament , we prove that either there exist two vertices satisfying or there exists a vertex satisfying if has no vertex of in-degree zero.
Cite
@article{arxiv.1812.01800,
title = {The second out-neighbourhood for local tournaments},
author = {Ruijuan Li and Juanjuan Liang},
journal= {arXiv preprint arXiv:1812.01800},
year = {2018}
}