摘要

Let B(n, k) be the set of bicyclic graphs with n vertices and k pendant vertices. In this paper, we determine the unique graph with minimal least eigenvalue among all graphs in B(n, k). This extremal graph is the same as that on the Laplacian spectral radius as done by Ji-Ming Guo[The Laplacian spectral radius of bicyclic graphs with n vertices and k pendant vertices, Science China Mathematics, 53(8)(2010)2135-2142]. Moreover, the minimal least eigenvalue is a decreasing function on k.

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