Bounds and constructions for n-e.c. tournaments

Abstract. Few families of tournaments satisfying the n-e.c. adjacency property are known. We supply a new random construction for generating infinite families of vertex-transitive n-e.c. tournaments by considering circulant tournaments. Switching is used to generate new n-e.c. tournaments of certain orders. With aid of a computer search, we demonstrate that there is a unique minimum order 3-e.c. tournament of order 19, and there are no 3-e.c. tournaments of orders 20, 21, and 22. We show that there are no 4-e.c. tournaments of orders 47 and 48 improving the lower bound for the minimum order of such a tournament. 1