Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4648973 | Discrete Mathematics | 2010 | 5 Pages |
Abstract
Let ΓΓ denote a distance-regular graph with a strongly closed regular subgraph YY. Hosoya and Suzuki [R. Hosoya, H. Suzuki, Tight distance-regular graphs with respect to subsets, European J. Combin. 28 (2007) 61–74] showed an inequality for the second largest and least eigenvalues of ΓΓ in the case YY is of diameter 2. In this paper, we study the case when ΓΓ is bipartite and YY is of diameter 3, and obtain an inequality for the second largest eigenvalue of ΓΓ. Moreover, we characterize the distance-regular graphs with a completely regular strongly closed subgraph H(3,2)H(3,2).
Keywords
Related Topics
Physical Sciences and Engineering
Mathematics
Discrete Mathematics and Combinatorics
Authors
Qian Kong, Kaishun Wang,