Journal of Inequalities and Applications
Volume 2010 (2010), Article ID 591758, 10 pages
Research Article

Ordering Unicyclic Graphs in Terms of Their Smaller Least Eigenvalues

Department of Applied Mathematics, Zhejiang A&F University, Hangzhou 311300, China

Received 15 July 2010; Accepted 2 December 2010

Academic Editor: Józef Banaś

Copyright © 2010 Guang-Hui Xu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Let 𝐺 be a simple graph with 𝑛 vertices, and let 𝜆 𝑛 ( 𝐺 ) be the least eigenvalue of 𝐺 . The connected graphs in which the number of edges equals the number of vertices are called unicyclic graphs. In this paper, the first five unicyclic graphs on order 𝑛 in terms of their smaller least eigenvalues are determined.