Maxima of the Q-index: forbidden 4-cycle and 5-cycle

Maria Aguieiras A. de Freitas, Vladimir Nikiforov, Laura Patuzzi

This paper gives tight upper bounds on the largest eigenvalue q(G) of the signless Laplacian of graphs with no 4-cycle and no 5-cycle. If n is odd, let F_{n} be the friendship grap…