pith. sign in

arxiv: 1812.01800 · v1 · pith:XQAQQIK2new · submitted 2018-12-05 · 🧮 math.CO

The second out-neighbourhood for local tournaments

classification 🧮 math.CO
keywords vertexlocalprovesatisfyingconjectureseverygraphin-degree
0
0 comments X
read the original abstract

Sullivan stated the conjectures: (1) every oriented graph $D$ has a vertex $x$ such that $d^{++}(x)\geq d^{-}(x)$; (2) every oriented graph $D$ has a vertex $x$ such that $d^{++}(x)+d^{+}(x)\geq 2d^{-}(x)$. In this paper, we prove that these conjectures hold for local tournaments. In particular, for a local tournament $D$, we prove that $D$ has at least two vertices satisfying $(1)$ if $D$ has no vertex of in-degree zero. And, for a local tournament $D$, we prove that either there exist two vertices satisfying $(2)$ or there exists a vertex $v$ satisfying $d^{++}(v)+d^{+}(v)\geq 2d^{-}(v)+2$ if $D$ has no vertex of in-degree zero.

This paper has not been read by Pith yet.

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.