A note on nonisomorphic cospectral digraphs
β Scribed by V Krishnamoorthy; K.R Parthasarathy
- Publisher
- Elsevier Science
- Year
- 1974
- Tongue
- English
- Weight
- 75 KB
- Volume
- 17
- Category
- Article
- ISSN
- 0095-8956
No coin nor oath required. For personal study only.
π SIMILAR VOLUMES
A necessary and sufficient condition is given for two Cayley digraphs X 1 = Cay(G 1 , S 1 ) and X 2 = Cay(G 2 , S 2 ) to be isomorphic, where the groups G i are nonisomorphic abelian 2-groups, and the digraphs X i have a regular cyclic group of automorphisms. Our result extends that of Morris [J Gra
In this paper we characterize all digraphs each one of which is cospectral with its line digraph and both the digraph and its line digraph are connected. Some related enumeration problems are also considered. From these results we can see that there are arbitrarily large sets of cospectral digraphs.
In his survey article [3] Nash Williams gives a list of unsolved problems. The last problem is the following. Let an (n, ~>q)-digraph denote a digraph without loops and parallel directed edges on a set of n vertices such that the outdegree of every vertex is at least q. If D is an (m + n, >~q + r)-