Nonexistence of Almost Moore Digraphs of Diameter Four

[摘要] Regular digraphs of degree $d>1$, diameter $k>1$ and order $N(d,k) = d+\cdots +d^k$ will be called almost Moore $(d,k)$-digraphs. So far, the problem of their existence has only been solved when $d=2, 3$ or $k = 2, 3$. In this paper we prove that al

[学科分类] 离散数学和组合数学

[关键词] Almost Moore digraph;characteristic polynomial;cyclotomic polynomial