Unicyclic Graphs with Minimal Energy

If G is a graph and λ1,λ2,...,λn are its eigenvalues, then the energy of G is defined as E(G)=|λ1|+|λ2|+⋅⋅⋅+|λn|. Let Sn3 be the graph obtained from the star graph with n vertices by adding an edge. In this paper we prove that Sn3 is the unique minimal energy graph among all unicyclic graphs with n vertices (n≥6).