1
Department of Mathematics, South China Normal University, and Faculty of Applied Mathematics, Guangdong University of Technology
2
Department of Mathematics, South China Normal University, Guangzhou 510631, P. R. China
Abstract
It is known that the directed cycle of order $n$ uniquely achieves the minimum spectral
radius among all strongly connected digraphs of order $n\ge 3$.
In this paper, among others, we determine the digraphs which achieve the second, the third
and the fourth minimum spectral radii respectively among strongly connected
digraphs of order $n\ge 4$.
