Line graph of combinations of generalized Bethe trees: Eigenvalues and energy

Abstract: We characterize the eigenvalues and energy of the line graph whenever is (i) a generalized Bethe tree, (ii) a Bethe tree, (iii) a tree defined by generalized Bethe trees attached to a path, (iv) a tree defined by generalized Bethe trees having a common root, (v) a graph defined by copies of a generalized Bethe tree attached to a cycle and (vi) a graph defined by copies of a star attached to a cycle; in this case, explicit formulas for the eigenvalues and energy of are derived. [Copyright &y& Elsevier]