  Dynamics of evolutionary games strongly depend on underlying networks. We
study the coevolutionary prisoner's dilemma in which players change their local
networks as well as strategies (i.e., cooperate or defect). This topic has been
increasingly explored by many researchers. On the basis of active linking
dynamics [J. M. Pacheco et al., J. Theor. Biol. 243, 437 (2006), J. M. Pacheco
et al., Phys. Rev. Lett. 97, 258103 (2006)], we show that cooperation is
enhanced fairly robustly. In particular, cooperation evolves when the payoff of
the player is normalized by the number of neighbors; this is not the case in
the evolutionary prisoner's dilemma on static networks.
