Let G be a graph, A(G) be the adjacency matrix of G, and λ(G) the least eigenvalue of A(G). Information is given about the following three quantities: $\lambda_R(G ...

This is a survey paper on the second largest eigenvalue λ₂ of the adjacency matrix of a graph. Among the topics presented are the graphs with small λ₂, bounds for λ₂, algebraic connectivity, graphs ...