Quasi-Carousel Tournaments

Abstract

A tournament is called locally transitive if the outneighbourhood and the inneighbourhood of every vertex are transitive. Equivalently, a tournament is locally transitive if it avoids the tournaments $W_4$ and $L_4$, which are the only tournaments up to isomorphism on four vertices containing a unique $3$-cycle. On the other hand, a sequence of tournaments $(T_n{)}_{n\in \mathbb{N}}$ with $|V(T_n)|=n$ is called almost balanced if all but $o(n)$ vertices of $T_n$ have outdegree $(1/2+o(1))n$. In the same spirit of quasi-random properties, we present several characterizations of tournament sequences that are both almost balanced and asymptotically locally transitive in the sense that the density of $W_4$ and $L_4$ in $T_n$ goes to zero as $n$ goes to infinity.

arXiv comment26 pages, 5 figures; corrected proofs of Lemma 3.2 and Proposition 4.1