On the α-index of minimally 2-connected graphs with given order or size

For any real α∈[0,1], Nikiforov defined the A_α-matrix of a graph G as A_α(G)=αD(G)+(1−α)A(G), where A(G) and D(G) are the adjacency matrix and the diagonal matrix of vertex degrees of G, respectively. The largest eigenvalue of A_α(G) is called the α-index or the A_α-spectral radius of G. A graph is minimally k-connected if it is k-connected and deleting any arbitrary chosen edge always leaves a graph which is not k-connected. In this paper, we characterize the extremal graphs with the maximum α-index for [Formula presented] among all minimally 2-connected graphs with given order or size, respectively.