Evolutionary games on scale-free networks with tunable degree distribution

We study evolutionary games on scale-free networks with tunable degree distribution. The heterogeneity of networks is controlled by the exponent of power-law degree distribution. It is found that there exists an optimal value of the exponent, for which the level of cooperation becomes highest. This phenomenon indicates that, although degree heterogeneity plays an important role in maintaining cooperation, too strong heterogeneity may counterintuitively encourage defection. We observe that, for strong heterogeneity, large-degree nodes are no longer certainly occupied by cooperators. Our results yield insights into the effect of degree heterogeneity on cooperation.