The state equation of Yang Mills field dark energy models

In this paper, we study the possibility of building Yang Mills (YM) field dark energy models with equation of state (EoS) crossing -1, and find that it cannot be realized by the single YM field models, no matter what kind of Lagrangian or initial condition. But the states of -1 < ω < 0 and ω < -1 all can be naturally got in this kind of model. The former is like a quintessence field, and the latter is like a phantom field. This states that one can build a model with two YM fields, one with the initial state of -1 < ω < 0, and the other with ω < -1. We give an example model of this kind, and find that its EoS is larger than -1 in the past and less than -1 at the present time. We also find that this change must be from ω > -1 to <-1, and it will go to the critical state of ω = -1 with the expansion of the universe, which character is the same as the single YM field models, and the big rip is naturally avoided.